Symposium Organizers
William Yu, Louisiana State University Shreveport
Vicki Colvin, Brown University
Yu Zhang, Jilin University
Symposium Support
MilliporeSigma (Sigma-Aldrich Materials Science)
NM02.01: Session I
Session Chairs
Monday PM, November 27, 2017
Hynes, Level 3, Room 302
8:15 AM - *NM02.01.01
Nanosize and Nanostructure Effect of Molecularly Functionalized Graphene Sheet Deposit Films on Supercapacitor and Membrane Performance
Michael Hu 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractFilms consisted of surface functionalized graphene sheet particles on electrode contact are developed to serve as electrodes for next-generation supercapacitors. On the other hand, the cross-linked graphene oxide layers deposited on nanoporous supports can serve as membranes for molecule/ion separations. This talk will discuss the effect of graphene size (i.e., 2D sheet dimension) and microstructural orientation of molecularly interspaced graphene stacks in particulate film deposits. Nano-sized graphene oxide flake particles were grafted with ligand molecules (2,5-diamino-1,4-dihydroxylbenzene dihydrochloride, DDDC) and was then reduced to form ligand-grafted reduced nano-GOs (nano-DDDC-rGO). DDDC serves as an interlayer spacer prohibiting stacking/aggregation and provide hydrophilicity, resulting in well dispersed slurry that is suitable for deposit uniform thin films on a circular disc substrate of carbon fiber paper (as current collector). The surface-modified graphene sheets enhanced surface usability and diffusion and accessibility of electrolyte ions by shortening transport paths (compared with horizontally stacked tenth micron size graphene sheets). By controlling the graphene size and surface property, nano-DDDC-rGO film electrodes showed enhancement in electrochemical performance (i.e., higher specific capacitance, faster electron and ion transport kinetics, better contact between current collector and active material), compared to the baseline films of micro-DDDC-rGO consisting of larger sized (tens of micrometers) graphene flake particles. For example, with a large molecule sized organic electrolyte (e.g., 1M tetraethylammonium tetrafluoroborate in acetonitrile), the size control enhancement was more effectively achieved by ~4.2 times higher capacitance, 4.0 times lower IR drops and order of magnitude enhanced mass transport. Furthermore, we present an electrical field orientation method to align the molecularly interspaced rGO sheets in perpendicular to the surface of current collector substrate, and thus leading to the enhanced performance, e.g., ~1.6 times higher values in capacitance (430 F/g at 0.5 A/g) and ~67% reduction in equivalent series resistance.
8:45 AM - NM02.01.02
Solution-Controlled Fabrication of Wrinkled Graphene for Chemical and Mechanical Detection
Wenjun Chen 1 , Xuchun Gui 1 , Zikang Tang 1 2
1 State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou China, 2 Institute of Applied Physics and Materials Engineering, University of Macau, Macau China
Show AbstractGraphene wrinkles induce many excellent properties, which facilitate its sensing applications for chemical and mechanical detection. In this conference, we will report the controllable fabrication of large-area wrinkled graphene (WG) with homogeneous wrinkles by a liquid-phase shrink method. It is facile to control the roughness of WG by modifying the category and concentration of organic solutions, essentially the lateral surface tension and interface interactions. Furthermore, based on the Rayleigh-Bénard convection, which plays an important role in the self-assembly of graphene wrinkles on the solution surface, we also can change the temperature difference and height between surface and bottom of the certain solution to modulate the morphology of the WG. The as-prepared WG can withstand 100% tensile strain and 720° torsion strain.
Accordingly, we devised a highly-stretchable surface-enhanced Raman scattering (SERS) substrate based on WG and gold nanoparticles, the synergy of which enables its stable detection for low-concentration (10-9 M) molecules even under 50% tensile strain. What's more, for analysis of multiple analytes, corresponding identifiability is changeable by stretching the SERS substrate. Then, sensors based on the stack of two-layer of WG are able to detect low torsion strain (more than 50% resistance change under 5° twist). In addition, the insert of an isolation layer of anodic aluminum oxide membrane between two layers of conductive WG endows the based piezoresistive sensors an energy-saving device (no energy consumption in off state) and a high sensitivity (6.92 kPa-1) with a distinguished operating mechanism. We believe that the solution-processed WG has great potential to be applied in flexible electronics.
9:00 AM - NM02.01.03
Performance Improvement of Carbon Nanotube Thin-Film Transistors and Application in Flexible CMOS Logic Circuits
Qunqing Li 1
1 , Tsinghua University, Beijing China
Show AbstractSingle Wall Carbon Nanotube (SWNT) random networks are suitable for fabricating thin-film transistors (TFTs) on flexible substrates. To achieve low static power consumption and high noise margin, both p-type and n-type transistor are needed to make complementary logic circuits. However, the single carbon nanotube field-effect transistors is usually observed as p-type conduction. Fabrication of air-stable n-type devices by methods compatible with standard photolithography on flexible substrates is challenging. We demonstrated that by using a bilayer dielectric structure of MgO and atomic layer deposited (ALD) Al2O3 or HfO2， air-stable n-type devices can be obtained. The mechanism for conduction type conversion was elucidated and attributed to hole depletion in SWNT, the decrease of the trap state density by MgO assimilating adsorbed water molecule in the vicinity of SWNT, and the energy band bending because of positive fixed charges in the ALD layer. The key advantage of the method is the relatively low temperature required here for the ALD process because we need not employing this step to totally remove the absorbates on the SWNTs.
Large current hysteresis has been observed in CNT transistors and usually shows as a positive threshold voltage shift when the gate sweeping direction changes from positive to negative. We found inverse hysteresis of CNT-TFTs can be observed using magnetron sputtered oxide as a dielectric. Stacking of the sputtered dielectric with dielectrics deposited by other methods, such as atomic layer deposition, can effectively reduce or even eliminate the hysteresis. This can be explained as a combination of the effects of surface and interface trapped charges. Additionally, this hysteresis reduction method is widely compatible with various CNT-TFT structures and types, and is even suitable for MoS2 TFTs.
We also proposed and fabricated stable and repeatable, flexible, CNT-TFT complementary metal oxide semiconductor (CMOS) integrated circuits based on a three-dimensional (3D) structure. Two layers of CNT-TFT devices were stacked, where one layer served as n-type devices and the other one served as p-type devices. Based on this method, it is able to save at least half of the area required to construct an inverter, and make large-scale and high-density integrated CMOS circuits easier to design and manufacture. The 3D flexible CMOS inverter gain can be as high as 40, and the total noise margin is more than 95%. Moreover, the input and output voltage of the inverter are exactly matched for cascading. 3D flexible CMOS NOR, NAND logic gates, and 15-stage ring oscillators were fabricated on PI substrates with high performance as well. Stable electrical properties shows that such a 3D structure is a reliable architecture and suitable for carbon nanotube electrical applications in complex flexible and wearable electronic devices.
9:15 AM - NM02.01.04
Large-Scale Preparation of Printable High-Performance Semiconducting Single-Walled Carbon Nanotube (sc-SWCNT) Inks and Application in Flexible Printed Logic Gates and Circuits
Tingting Liu 1 , Jianwen Zhao 1 , Zheng Xin 1 , Zheng Cui 1
1 , Suzhou Institute of Nanotech and Nanobionics, CAS, Suzhou China
Show AbstractPrinted thin film transistors (TFTs) are the key components to construct printed driving circuits for displays, printed logic gates and circuits, biologic and chemical sensors, and wearable electronics. Electrical properties of printed TFTs are largely dependent of performance of printable inks, especially semiconductor inks. Semiconducting single-walled carbon nanotubes (sc-SWCNTs) have been regarded as one of promising semiconductors for flexible printed TFTs because of their excellent electrical properties, solubility, flexibility, high chemical and physical stability, and process temperatures compatible with flexible substrates. In this talk, I will present a valid approach to large-scale production of printable sc-SWCNT inks from commercial arc discharge SWCNTs using conjugated organic compound wrapping methods along with the aid of high pressure homogenizer. High-performance printed SWCNT TFTs, CMOS inverters, diode-transistor logic (DTL) circuits and 3-stage ring oscillators were achieved on PET substrates. Resulted printed p and n-type TFTs showed high on/off ratio of 106, effective mobility up to 30 cm2V-1s-1, small hysteresis and small subthreshold swing (90~140 mV dec-1). The voltage gains of printed CMOS inverters and the frequency of printed 3-stage oscillators were up to 30 and 3.3 kHz at Vdd of 1 V, respectively. Furthermore, DTL circuits exhibited high dark-to-photo current ratios (105) and on currents at Vdd of 1V and it can be acted as the driving circuits to drive the external QLEDs.
9:30 AM - NM02.01.05
Copper-Graphene Composite Foils via DC Electro-Deposition
Gongsheng Song 1 , Chunxu Pan 1
1 , Wuhan University, Wuhan China
Show AbstractDirect current (DC) electrodeposited copper foils are important raw materials in manufacturing copper-clad laminate (CCL), printed circuit board (PCB) and the negative current collector of lithium ion battery, where the copper foil not only serve as the carrier of the cathode active material but also play a role in collecting and conducting electrons. Graphene (Gr), as a new carbon material with a one-atom thick 2D layer structure, has been recognized as an attractive reinforcing phase due to its unique and excellent physical, chemical and mechanical properties. In past few years, preparation of the Cu-Gr composite foils via electrochemical deposition has been concerned by several groups, and we also made the following two researches.
1) It is well-known that the amount of Gr in a composite plays a key role in enhancing the performance of the composite. In general, an indirect method, namely, by adjusting the concentration of Gr or graphene oxide(GO) in electrolyte, is used to study the influence of the Gr content on the properties of Cu-Gr composite foil. Here, we firstly propose a direct and accurate approach, that is, by using an instrumental carbon and sulfur analyzer, to determine the amount of Gr in the DC electrodeposited Cu–Gr composite foil, and also obtain the relationship between the amount of Gr in the composite foil and the concentration of GO in the electrolyte. Further, mechanical property measurements reveal that: (1) the variations in the mechanical properties of the Cu-Gr foils along with the concentration of GO in the electrolyte exhibit similar tendencies to that of the Gr content in the Cu–Gr foils. (2) In our work, the optimal values of the mechanical properties and the amount of Gr in the foils appears at GO concentration of 0.5g/L in the electrolyte. (3) When the GO concentration is less than 0.5g/L, the values of the mechanical properties and the amount of Gr in the foils present an approximately linear relationship; and beyond 0.5g/L, agglomeration of excess GO in the electrolyte would make it difficult to be co-deposited into the foil.
2) It is well established that many factors, such as concentration of electrolyte, additives, applied current density, bath temperature and agitation, etc., will affect the quality of the electrolytic Cu foils, especially for the thin Cu foils which is more sensitive to electrodeposited parameters. In our work, according to the process for industrial Cu foil production by using DC electro-deposition, we prepared the Cu-Gr composite thin foils with a thickness of 20μm, and studied systematically the effect of the key factors, involving GO concentration in electrolyte, applied current density and temperature on the foils' mechanical properties. Results showed that, the optimized conditions was as follows, 0.5g/L GO concentration, 10-20A/dm2 applied current density and 25-40°C temperature. It is expected that the results provide a important reference to the practical industrial productions.
10:15 AM - *NM02.01.06
Preparation of Bio-Inspired Single-Walled Carbon Nanotubes for Ultra-High Mechanical Property and Its Sensor Applications
Chengzhi Luo 1 2 , Qiang Fu 2 , Chunxu Pan 1 2
1 Shenzhen Research Institute, Wuhan University, Shenzhen, Guangdong, China, 2 School of Physics and Technology, Wuhan University, Wuhan, Hubei, China
Show AbstractIt is well-known that the natural spider silk features exceptional mechanical property due to its constituent molecules and the hierarchical assembly into silk. In this work, we imitate a unique structure of natural spider silk and directly prepare a kind of the bio-inspired spider silk single-walled carbon nanotube (BISS-SWCNT) film via a strong magnetic-filed-assisted CVD system. The film is composed of pure SWCNTs as skeleton, embedded Fe nanoparticles and a amorphous carbon layer. The carbon layer not only form the spider silk featured “skin-core” structure with SWCNTs, but also make the tube junction tougher. The embedded Fe nanoparticles act as glue spots of the spider silk that prevent interfacial slippages between the BISS-SWCNTs and reinforced matrix. With only 2.1 wt% BISS-SWCNTs adding, the tensile strength and Young’s modulus of the BISS-SWCNTs/PMMA composites have been improved by 300%. More importantly, the BISS-SWCNTs also retain the high conductivity and transmittance of pristine SWCNT film.
Sensitivity, durability, and multifunction are the essential requirements for a high- performance wearable sensor in monitoring human health. we report a novel sensor with high-performance involving high sensitivity, high durability and multifunction by using the buckled BISS-SWCNTs film as the conducting network and the Au film as a sensitive transducer. Its working principle is that: when it is stretched, the Au film fractures into micro-cracks that make the resistance varies exponentially and sensitively, while the buckled BISS-SWCNTs film with mechanical robustness keeps the composite film integrated for a long durable life. The experimental results reveal that: 1) This sensor exhibits a high sensitivity to a small strain, i.e., when the strains reduce from 20% to 1%, the sensitivity increase from 10 to 70. 2) This sensor also is of a sensitive response to temperature. 3) This sensor possesses combined superiority of fast response (<60 ms) and high durability (>10000 cycles). The proposed quantum tunneling model is consistent with experimental data. We fabricate a wearable device for monitoring various human health indicators, including pulse, respiration, joint motion, and body temperature fluctuation. It is expect that this composite film sensor will have wide potential applications in intelligent devices and human–machine interfacing.
10:45 AM - NM02.01.07
Influence of Graphene Transfer Methods on Remote Epitaxial Growth
Chanyeol Choi 1 , Yunjo Kim 1 , Jeehwan Kim 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThe severe obstacle for applications of graphene results from the fact that a band gap does not exist. Alternatively, we use single layer graphene for cutting down the cost of expensive III-IV semiconductor by introducing remote epitaxial growth. The remote epitaxy is achieved through graphene and as a form of GaAs-graphene-GaAs. Graphene plays an important role in the remote epitaxy due to its weak van der Waals potential which cannot screen the potential field from the bottom substrates. Furthermore, the weakness of van der Waals interaction enables us to release semiconductor films at the surface between graphene and grown semiconductor. When it comes to computational model, plane-wave pseudopotential GaAs(001) shows high charge density up to ~ 9 Å from GaAs(001) substrate. Accordingly, how closely the graphene was transferred on the substrate influences the epitaxial growth significantly. We explore the effect of graphene transfer methods by using poly(methyl-methacrylate) (PMMA) and ethylene-vinyl acetate (EVA). Firstly, chemical vapor deposition (CVD) graphene was synthesized on a Cu foil with low pressure CVD. In turn, we use both PMMA and EVA to handle the graphene. It is worth saying that EVA shows better transfer surface, which we attribute to less contact stiffness and small elastic modulus of EVA. Also, polymer residues, which is inevitable during wet transfer methods, are minimized in case of EVA. We confirm that epitaxial growth on top of EVA-transferred graphene shows highly aligned crystallinity along with the bottom substrate by electron backscatter diffraction (EBSD). This results from spatial proximity between graphene and substrate and less polymer residue. In conclusion, we demonstrate two different methods for graphene transfer. Our improved transfer method will enhance the homo-epitaxy and save the cost of non-silicon substrates by reusing the substrates after film release process.
11:00 AM - NM02.01.08
Observation of the Marcus Inverted Region of Electron Transfer from Asymmetric Chemical Doping of Pristine (n, m) Single-Walled Carbon Nanotubes
Albert Liu 1 , Yuichiro Kunai 1 , Anton Cottrill 1 , Michael Strano 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThe concept of electrical energy generation based on asymmetric chemical doping (ACD) of single-walled carbon nanotube (SWNT) papers is presented. We explore 27 small, organic, electron-acceptor molecules that are shown to tune the output open circuit voltage (VOC) across three types of pristine SWNT papers with varying (n, m) chirality distributions. A considerable enhancement in the observed VOC, from 80 to 440 mV, is observed for SWNT/molecule acceptor pairs that have molecular volume below 120 Å3 and lowest unoccupied molecular orbital (LUMO) energies centered around -0.8 eV. The electron transfer (ET) rate constants driving the VOC generation are shown to vary with the chirality-associated Marcus theory, suggesting that the energy gaps between SWNT and the LUMO of acceptor molecules dictate the ET process. When the ET rate constants and the maximum VOC are plotted versus the LUMO energy of the acceptor organic molecule, volcano-shaped dependencies, characteristic of the Marcus inverted region, are apparent for three distinct sources of SWNT papers with modes in diameter distributions of 0.95 nm, 0.83 nm, and 0.75 nm. This observation, where the ET driving force exceeds reorganization energies, allows for an estimation of the outer-sphere reorganization energies with values as low as 100 meV for the (8,7) SWNT, consistent with a proposed image-charge modified Born energy model. These results expand the fundamental understanding of ET transfer processes in SWNT and allow for an accurate calculation of energy generation through asymmetric doping for device applications.
11:15 AM - NM02.01.09
Theoretical Estimation of the Desalination Performance of Graphene Membranes using Molecular Dynamics Simulations
Rahul Prasanna Misra 1 , Daniel Blankschtein 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractWater scarcity is a major problem facing humanity, with one in ten individuals worldwide currently lacking access to clean drinking water. Seawater, which is too salty for our needs, can be converted into potable water through seawater desalination. Several previous studies have predicted extraordinarily high water flow rates through nanopores in two-dimensional materials like graphene, owing to their atomic thickness. The observed high water permeabilities through graphene has, in turn, generated tremendous hope for use of graphene as potential membranes for seawater desalination. Graphene membranes are expected to sterically block salt ions when their pore sizes approach the size of the hydration shell of the salt ions. However, for smaller diameter graphene membranes, cations can block water flow through these membranes due to strong interaction between the cations and the electron clouds of carbon atoms in graphene. In this talk, we discuss our formulation of a new atomistic molecular dynamics force field derived from ab-initio calculations to model the interaction of salt ions with the carbon atoms in graphene. We also present results showing the effect of dielectric polarization of carbon atoms on the nanoscale interfacial friction of water in contact with graphene, and provide theoretical estimates for the desalination performance of graphene membranes with varying pore sizes. We hope that our simulation results will guide future experimental studies on water and ion transport through graphene membranes.
11:30 AM - NM02.01.10
Nanoparticle Activated and Directed Assembly of Graphene Nanoscrolls
Karteek Bejagam 1 , Samrendra Singh 1 , Sanket Deshmukh 1
1 Department of Chemical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, United States
Show AbstractGraphene nanoscrolls (GNS) have obtained a tremendous interest in recent years (1-3) due to their potential applications in tribology, nanotechnology, and bioengineering. Recently, GNS have been utilized to obtain superlubricity- a state with almost zero friction (4). In our work, we have employed the metal/non-metal nanoparticles to activate and facilitate the formation of GNS. Reactive molecular dynamics (RMD) simulations of diamond, nickel, platinum and gold nanoparticles (NPs) placed on the 2-D graphene sheet were performed. Our simulations suggest that the surface chemistry and interactions between nanoparticles and graphene play a crucial in determining the mechanism of scroll formation and the nature of the GNS. Experiments also shed light on the nanoparticles activated graphene nanoscrolls. Our studies provide a systematic pathway to design GNS for a wide range of properties. Mechanical properties of NP encapsulated GNS are significantly improved as compared to bare NPs.
References:
Viculis, L.M., Mack,J.J. and Kaner,R.B. Science, 2003, 299, 1361
Xie,X., Ju,L., Feng,X.F. et al. Nano Letters, 2009, 9, 2565-2570
Shioyama,H. and Akita,T. Carbon, 2003, 41, 179-181
Berman D. et al. Science, 2015, 6239, 1118-1122
NM02.02: Session II
Session Chairs
Carlo Casari
Pradip Kumar
Monday PM, November 27, 2017
Hynes, Level 3, Room 302
1:30 PM - *NM02.02.01
Graphene, h-BN, Clusters—Adhesion, Alignment, Friction, Pinning, Thermophoresis
Erio Tosatti 1
1 , SISSA and ICTP, Trieste Italy
Show Abstract
The nanocontact mechanics between graphene and other 2D sheet materials or adsorbed clusters presents, in theory and simulation, a host of surprises.(*) I will review here an equilibrium and a non-equilibrium case.
The equilibrium bilayer contact adhesion between two 2D lattices should, according to standard theory, involve a slight misalignment angle, with important consequences including frictional changes. We show, using graphene/h-BN substrate as an example, that the spontaneous onset of graphene corrugation and the accompanying h-BN strain pattern, both non-standard but inevitable elements, act to discourage and in the specific case eliminate the misalignment, with consequences on the substrate anchoring. [1] Additional examples of the effects of an applied squeezing pressure on a bilayer contact will be discussed if there will be time. [2]
The non-equilibrium thermophoretic drift of physisorbed clusters or molecules on a 2D sheet subject to an in-plane temperature imbalance is a phenomenon observed in simulation but not well understood. By simulating a gold cluster adsorbed on suspended graphene sheet of size L up to 150 nm we find that the cluster is pushed from hot to cold by a phoretic whose magnitude is proportional to the temperature imbalance but, surprisingly at first, independent of L -- the force is independent of temperature gradient, contrary to conventional wisdom. Analysis shows that at this scale thermophoresis is not diffusive but ballistic, caused by the ballistic transport of the graphene flexural phonons that drive it. The subtle mechanisms by which this phonon flux can impress to the cluster a real positive momentum as opposed to just crystal momentum are uncovered [3] These results may be of considerable potential importance in nanomanipulation and transport of matter using thermal gradients.
(*) Projects in collaboration with Y. Crespo, A, Fasolino, L. Gigli, R. Guerra, E. Panizon, M. van Wijk, A. Vanossi
[1] R. Guerra, M. van Wijk, A. Vanossi, A. Fasolino, E. Tosatti, Nanoscale, DOI: 10.1039/c7nr02352a, (2017)
[2] Y. Crespo, E. Tosatti, in preparation (2017)
[3] E. Panizon, R. Guerra, E. Tosatti, submitted to PNAS (2017).
2:00 PM - NM02.02.02
Formation of Networks of Graphene Nanoribbons and Nanosheets in Metals by the Electrocharging Assisted Process
Lourdes Salamanca-Riba 1 , Xiaoxiao Ge 1 , Romaine Isaacs 1 , Daniel Cole 2 , Manfred Wuttig 1 , Karen Gaskell 3 , Oded Rabin 1 4 , Balu Balachandran 5
1 Materials Science and Engineering Department, University of Maryland, College Park, Maryland, United States, 2 , U.S. Army Research Laboratory, Aberdeen, Maryland, United States, 3 Chemistry and Biochemistry, University of Maryland, College Park, Maryland, United States, 4 Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland, United States, 5 , Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractThe incorporation of carbon nanostructures such as graphene and carbon nanotubes in the lattice of metals is desirable to take advantage of the superior mechanical and electrical properties of these graphitic nanostructures and the high density of electrons in metals. For this purpose, attempts to create composites of carbon with metals, such as copper and aluminum, have gained a great deal of interest in recent years. We have formed graphene nanoribbons and nanosheets in metals by the application of a high current to a mixture of the liquid metal and particles of activated carbon of ~100 nm. The graphitic structures form in the liquid metal and bond with atoms in the metal making the composite very stable. A current of ~150 A is applied while the mixture of liquid metal and carbon nanoparticles is slowly stirred. It generates a plasma in the liquid metal causing the carbon in the nanoparticles to ionize. The carbon ions bond to each other and form crystalline graphene nanoribbons and sheets even though the activated carbon source is amorphous. Raman scattering, X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS) of the resulting materials, called covetics, reveal the presence of graphitic carbon with mostly sp2 bonding and small amounts of sp3 bonding. Transmission electron microscopy (TEM), in combination with EELS spectrum imaging, indicate that the graphitic regions form graphene nanoribbons and nanosheets of ~20 nm in width which have a preferred orientation with the lattice of the metal. Analysis of the EELS spectrum images by principal component analysis using blind source separation and non-negative matrix factorization present a shift of the C-K edge in localized regions indicating bonding between the metal and the carbon which makes the composite very stable. This technique is very general and can be used to incorporate carbon nanostructures in metals even in cases like silver and copper for which the solubility of C in the metal is in the ppm range. With this method the electrical conductivity of Al covetic with 3 wt % C increased by ~20% and the thermal conductivity of copper with 3 wt % C increased by ~13%. Copper covetic films deposited by pulsed laser deposition and e-beam evaporation show higher resistance to oxidation and higher optical transmission compared to pure copper films making them good candidates for transparent electrodes.
Funded by ANL/DOE subcontract No. 6F-30062
2:15 PM - NM02.02.03
Dynamic Air-Brush Deposition Method for the New Generation of Graphene Based Sueprcapacitors
Paolo Bondavalli 1 , Gregory Pognon 2
1 , Thales Research and Technology, Palaiseau France, 2 Laboratoire de Chimie et de Matériaux Multi-fonctionnels, Thales Research and Technology, Paliaseau France
Show AbstractThis contribution deals with the deposition method developed at Thales Research and Technology to achieve extremely uniform mats of nanomaterials for different applications. The dynamic air-brush deposition method has been firstly developed for gas sensors based on CNTFET[1]. We were able to fabricate large array for sensors using this technique with very good reproductibility. Briefly the nanomaterials in suspensions are sprayed on a substrate that has to be heat at a temperature higher than the boiling point of the solvent. At the same time the nozzles move on the surface. Thanks to that we are able to avoid the coffee ring effect and we obtain an extremely uniform deposition whose thickness is variable from some nm to hundredths of µm. Now we are using this technique to fabricate graphene based supercapacitors that exploit the nanostructuration of layers of graphene and of CNTs or CNFs. Indeed thanks to that we are able to exploit the large surface of graphene (thanks to CNTs that avoid their restacking) and to create an optimized mesoporous distribution inside the electrodes allowing the charge s to enter and to go out quickly (enhancing the power delivered). Recently in collaboration with IIT (Genoa) we were able to obtain supercapacitors with a power of around 100kW/kg[2] which is an extremely interesting results considering the potential implementation of the technique exploiting roll-to-roll fabrication. These supercapacitors were obtained spraying suspensions of graphene and, alternatively of CNTs exploiting more nozzles. After these results, we decided to test water as a solvent in order to reduce the heating temperature and to obtain a green type process without toxic solvents. To achieve stable suspensions we used graphene oxide and oxidized CNTs (to make them hydrophile) before putting them in water. We observed that changing the Graphene Oxide concentrations we obtained different value of capacitance and energy. The best results were obtained with 90% of GO and 10% of CNTs. We obtained a power of 30kW/Kg [3]. The importance of these results is that it is the first time that these performances have been obtained for graphene related materials using an industrial fabrication suitable technique that can be implemented in roll-to-roll production. This technique has also been implemented to fabricate graphene oxide based memories exploiting thin layers (<100nm) of this material.
[1] Selective gas detection using CNTFET arrays fabricated using air-brush technique, with different metal as electrodes, P.Bondavalli, et al., Sensors and Actuators B: Chemical 202, 2014, 1290–1297
[2] High-power graphene-carbon nanotube hybrid supercapacitors, Ansaldo, A., Bondavalli, M., Pellegrini, V., and Bonaccorso, F. et al. (2017), ChemNanoMat
[3 ]P. Bondavalli et al., "Graphene based supercapacitors fabricated using a new dynamic spray-gun deposition technique," 2015 IEEE 15th International Conference on Nanotechnology (IEEE-NANO), Rome, 2015, pp. 564-567
2:45 PM - NM02.02.05
Molecularly-Functionalized Near Infrared Photoluminescence Properties of Single-Walled Carbon Nanotubes
Tomohiro Shiraki 1 2 , Tomonari Shiraishi 1 , Hisashi Onitsuka 1 , Tamehito Shiga 1 , Gergely Juhász 3 , Naotoshi Nakashima 2
1 Department of Applied Chemistry, Kyushu University, Fukuoka Japan, 2 WPI-I2CNER, Kyushu University, Fukuoka Japan, 3 Graduate School of Science, Tokyo Institute of Technology, Tokyo Japan
Show AbstractNear infrared photoluminescence (NIR PL) properties of semiconducting single-walled carbon nanotubes (SWNTs) emerge on the basis of the unique one-dimensional nanostructures. Recently, PL intensity enhancement with wavelength shifts of the SWNTs has been reported through a very limited amount of chemical modification by oxygen atom doping and sp3 defect doping on the sp2 carbon networks of the SWNT walls (local functionalization).[1-3] Thus, the locally-functionalized SWNTs (lf-SWNTs) are expected as novel NIR PL materials because pristine SWNTs typically have low quantum yields (< 1%) and specific PL wavelengths determined by the tube structures defined as chiral indices.
We have been developing NIR PL modulation techniques from a view point of structural design of the modified sites on the lf-SWNTs using functionalized modifiers.[4,5]
For example, bisdiazonium compounds (2Dz) are newly synthesized and we find that the lf-SWNTs modified with 2Dz (SWNT/2Dz) shows new red-shifted PL. Namely, the emission peak appears at 1256 nm which is remarkably red-shifted than those of pristine SWNTs (985 nm) and mono-functionalized SWNTs (SWNT/1Dz, 1129 nm). [4] The present approach providing large spectral changes, therefore, is expected to modulate PL of lf-SWNTs in a wide NIR wavelength range.
Another topic of our achievements is a dynamic wavelength shifting system. For example, a phenylboronic acid-modified lf-SWNTs show selective PL wavelength shift by attachment of saccharide molecules through molecular recognition at the modified sites.[5] The spectral change occurs with clear dependence on the added saccharides, which show a similar tendency to the binding affinity difference between saccharides and a phenylboronic acid itself. The responsiveness would be applicable to a novel detection technique utilizing NIR PL towards future bio-imaging/sensing applications.
The details and progress of these studies will be discussed at the meeting.
References: [1] Weisman, R. B. et al., Science 2010, 330, 1656-1659. [2] Wang, Y. et al., Nat. Chem. 2013, 5, 840-845. [3] Nakashima, N. et al., J. Phys. Chem. C 2016, 120, 15632-15639. [4] Shiraki, T. and Nakashima, N. et al., Sci. Rep. 2016, 6, 28393. [5] Shiraki, T. and Nakashima, N. et al., Chem. Commun. 2016, 52, 12972-12975.
3:30 PM - *NM02.02.06
Freestanding Carbon Composite Film Electrodes for Electrochemical Capacitors
Bin Xu 2 , Mohamed Alhabeb 1 , Katherine Van Aken 1 , Yury Gogotsi 1
2 State Key Laboratory of Organic-Inorganic Composites, Beijing Key Laboratory of Electrochemical Process and Technology for Materials, Beijing University of Chemical Technology, Beijing China, 1 A.J. Drexel Nanomaterials Institute and Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania, United States
Show AbstractCarbon-based electrodes have attracted much attention as electrodes for electrochemical capacitors. However, they are often made into free-standing films with the addition of polymeric binders, a component that adds electrochemically inactive weight to the electrodes. Here, for the first time, we report freestanding supercapacitor electrodes made of highly porous carbide-derived carbon (CDC), highly accessible hierarchical porous carbon, and activated carbon fibers (ACF) all paired with electrochemically active 2D binding materials such as reduced graphene oxide (rGO) or transition metal carbides (MXenes). In these hybrid electrodes, the 2D layered structures hold the nanoparticles together in free-standing films while the carbon nanoparticles sandwiched between the layers prevent stacking and increase accessibility of the active material to the electrolyte ions, which improves electrochemical performance. For example, despite increasing the electrode thickness tenfold, the rGO/CDC hybrid electrode exhibits high capacitance of over 210 F/g, high power density at 100 mV/s and 10 A/g charge/discharge rates, and long stability of over 10,000 cycles in an aqueous electrolyte.1 These hybrid electrode material designs are greatly viable in high-power and high energy applications.
1. Alhabeb, M., Beidaghi, M., Van Aken, K. L., Dyatkin, B. & Gogotsi, Y. High-density freestanding graphene / carbide-derived carbon fi lm electrodes for electrochemical capacitors. Carbon 118, 642–649 (2017).
4:00 PM - NM02.02.07
Anisotropy in Structural and Transport Properties of Amorphous Carbon—A Molecular Dynamics Study
Raghavan Ranganathan 2 , Srujan Rokkam 1 , Tapan Desai 1 , Pawel Keblinski 3
2 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 1 Defense Aerospace, Advanced Cooling Technologies, Inc., Lancaster, Pennsylvania, United States, 3 Materials Science & Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractAmorphous carbon materials have been a subject of research for a spectrum of chemical, mechanical and bio-medical applications. In this work, we discuss a computational approach (the liquid quench method [1]) to generate models of amorphous carbon (a-C) using molecular dynamics simulations with a reactive force field (ReaxFF). Subsequently, we investigate the transport properties (diffusion) and thermal conductivity of the generated a-C model. We demonstrate that a-C can be modeled satisfactorily at a range of densities from 0.5 g/cc to 3.2 g/cc, as a function of their simulation conditions (quench rate, anneal time, and simulation box size). Further, we characterize structural aspects like pore distribution, pore-connectivity and hybridization/graphitization, and find good agreement with models from literature. Interestingly, we observe that at low densities (< 1 g/cc), a-C models exhibit substantial anisotropy in their structure. The geometric/structural anisotropy correlates with the anisotropic gas-diffusion and [2], and thermal conductivity characteristics of a-C, especially in low-density char.
References
1. Ranganathan, R., Rokkam, S., Desai, T. and Keblinski, P., 2017. Generation of amorphous carbon models using liquid quench method: A reactive molecular dynamics study. Carbon, 113, pp.87-99.
2. Ranganathan, R., Rokkam, S., Desai, T., Keblinski, P., Cross, P. and Burnes, R., 2015. Modeling high-temperature diffusion of gases in micro and mesoporous amorphous carbon. The Journal of Chemical Physics, 143(8), p.084701.
4:30 PM - NM02.02.09
Tuning the Structure of Carbon-Atom Wires from Semiconductor to Metal-Like
Carlo Casari 1 , Alberto Milani 1 , Yuri Pensotti 1 , Valentino Barbieri 1 , Matteo Tommasini 2 , Andrea Lucotti 2 , Valeria Russo 1 , Anna Facibeni 1 , Jonathan Marshall 3 , Franco Cataldo 4 , Rik Tykwinski 3
1 Department of Energy, Politecnico Di Milano, Milan Italy, 2 Department of Chemistry, Materials and Chem Eng., Politecnico di Milano, Milano Italy, 3 Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada, 4 , Actinium Chemical Research s.r.l., Rome Italy
Show AbstractCarbon-atom wires are the ultimate 1D systems comprising a chain of sp-hybridized carbon atoms. Recent advances in experimental research have opened new perspectives for understanding the properties and for opening potential nanotechnology applications [1]. The ideal sp-carbon wire is a 1-atom-diameter cable with two possible structural and electronic properties: a single-triple bond sequence leads to a semiconductor (polyyne) while a sequence of double bonds leads to a metal (cumulene). In a finite system the wire length (i.e. number of carbon atoms) and the terminations can affect the overall structure of the wire thus ideally allowing to tune the electronic and optical properties from semiconductor to metal behaviour [1]. However cumulene-like wires are typically less stable and more difficult to synthesize. One possible strategy is based on the increase of pi-conjugation of the endgroups to obtain equalized wires (i.e. cumulenes), as shown in the case of a wire terminated by graphene [2].
Here we discuss carbon-atom wires with different terminations to outline some general strategies to control and tune the structure. In particular, endgroups containing sp2 carbon units are able to provide stability in air thus permitting to fabricate sp-sp2 hybrid carbon films. The effect of length, termination and conjugation on wire structure is investigated by means of a combined experimental and computational approach, based on Raman, surface enhanced Raman scattering (SERS) and density functional theory (DFT) calculations [3]. A charge transfer between wires and metal nanoparticles used for SERS tends to equalize the structure of polyynes pointing to a polyyne-to-cumulene transition which would correspond to a metal-like system. The effect of different sp2 end groups in driving such semiconductor-to-metal transition is investigated on a series of wires terminated with different groups (i.e., phenyl, biphenyl, naphthyl, and coronene, also with oxygen substituents) to highlight the role of aromatic endgroups of increasing size. By means of DFT calculations we show that the increase of the sp2 conjugation in the terminating group is not enough for the full tunability of properties, and we highlight how a wide range tunability can be obtained by controlling charge transfer effects or proper chemical design (i.e oxygen substitution) [4]. As a further example, we report the fabrication and investigation of cumulene-like wires forming needle crystals and nanocrystalline films stable in air and up to moderate temperatures (i.e. 150 °C). These results provide a guideline for the design of novel sp-sp2 hybrid carbon nanosystems with tunable properties, where graphene-like and polyyne-like domains are closely interconnected.
[1] C.S. Casari et al. Nanoscale 8, 4414 (2016)
[2] A. La Torre, et al. Nature Comm. 6, 6636 (2015)
[3] A. Milani et al. Beilstein J. of Nanotech. 6, 480 (2015)
[4] A. Milani et al. J. Phys. Chem. C 121, 10562 (2017)
4:45 PM - NM02.02.10
Polyamide-Carbon Nanotubes Nanocomposite Membranes for Desalination—Synthesis, Performance and Computational Studies
Rodolfo Cruz-Silva 1 2 , Takumi Araki 1 3 , Shigeki Inukai 1 , Josue Ortiz-Medina 1 , Aaron Morelos-Gomez 1 , Syogo Tejima 1 3 , Takuya Hayashi 2 , Toru Noguchi 2 , Kenji Takeuchi 1 2 , Mauricio Terrones 2 4 , Morinobu Endo 1 2
1 Global Aqua Innovation Center, Shinshu University, Nagano Japan, 2 Institute of Carbon Science and Technology, Shinshu University, Nagano Japan, 3 , Research Organization for Information Science and Technology, Tokyo Japan, 4 Department of Physics, Chemistry and Materials Science & Engineering, The Pennsylvania State University, State College, Pennsylvania, United States
Show AbstractCarbon nanotubes-aromatic polyamide nanocomposites have been studied recently as the possible material for the next generation membranes for desalination applications. Many reports indicate that nanocomposite membranes show improved permeation and salt rejection compared to traditional aromatic polyamide reverse osmosis membranes. However, neither the mechanism of water diffusion nor the salt rejection of these membranes containing carbon nanotubes have been completely understood. While several groups have proposed that super flow phenomena through the carbon nanotubes might be the key for the high water permeation, here we show theoretical and experimental evidence that this is not likely the case for the membranes made by interfacial polymerization using multiwalled carbon nanotubes. The main reasons why water flow within the nanotubes should be ruled out from the difussion mechanism is because carbon nanotubes are oriented mainly parallel to the membrane and usually the nanotube cores are occluded. Nevertheless experimental results do show that carbon nanotubes can improve the performance of the membranes, and even positively influence other aspects such as chlorine resistance. Here, we will show a comprehensive experimental-theoretical study of carbon nanotube-polyamide nanocomposite membranes. We proposed an oriented diffusion mechanism that can explain the higher water flux by shortening the diffusion path of water molecules across the membrane in spite of being impermeable to water. We also analyze the possible effects of polymer mobility on operation temperature and chlorine resistance. Compared to previous molecular dynamic models, we have improved the level of description of the membrane model by considering the bond polarizability due to dynamic charge transfer. Regarding the water permeation mechanism, our results support an oriented diffusion effect due to the well dispersed nanotubes, that directs the water flow across the membrane by providing energetically favorable wells distributed across the membrane. On the other hand, the stiffening of the molecular network by the reinforcing nanotubes, results in higher salt rejection and better chlorine resistance. We will also discuss remaining challenges in order to transfer this new material from the laboratory to large-scale membrane preparation.
Symposium Organizers
William Yu, Louisiana State University Shreveport
Vicki Colvin, Brown University
Yu Zhang, Jilin University
Symposium Support
MilliporeSigma (Sigma-Aldrich Materials Science)
NM02.03: Session III
Session Chairs
Tuesday AM, November 28, 2017
Hynes, Level 3, Room 302
8:15 AM - *NM02.03.01
Highly Textured Graphene Films as Stretchable, Breathable Barriers and Growth Templates
Po-Yen Chen 1 , Ruben Spitz Steinberg 1 , Muchun Liu 1 , Ian Wong 1 , Robert Hurt 1
1 , Brown University, Providence, Rhode Island, United States
Show AbstractGraphene oxide (GO) nanosheets can serve as atomically-thin, sheet-like, giant molecular precursors for assembling new carbon material architectures. This talk will give an overview of recent work in our laboratory on complex hierarchical wrinkle and crumple textures in assembled GO multilayer films. First a general texturing method will be described that uses extreme graphene film compression driven by multiple cycles of contraction by underlying thermally responsive polymer substrates. Any compression step can be biaxial (2D) or unidirectional (1D), and a 1D contraction step can be aligned parallel or perpendicular to the previous step, leading to a family tree or “genealogy” of different but related hierarchical wrinkle/crumple textures.
One application for these textured graphene films is as stretchable molecular barriers. Barrier technologies are widely used in food and pharma packaging, personal protective equipment, and environmental toxicant containment. Many applications would benefit from stretchability, but achieving good barrier performance in polymeric elastomers is difficult, since they consist of disordered polymer chains with free volume and high permeability. The ideal graphene layer is known to be impermeable to all molecules, and here we demonstrate that those layers can be assembled into textured multilayer films that can be stretched/relaxed up to 500% by area while maintaining barrier performance against a variety of small-molecule organic liquids. A separate challenge in the field of wearable barrier fabrics is “breathability” - the ability to selectively pass water and allow user perspiration while rejecting inward molecular permeation of external toxicants. Here we show that GO membranes are effective barriers to the environmental toxicant trichloroethylene, both in the presence and absence of simulated perspiration flux. Some limited back-permeation of the toxicant is observed, and a molecular transport model suggests it occurs not by diffusion against the convective perspiration flow in hydrophobic channels, but rather through GO oxidized domains where hydrogen-bonding produces a near-stagnant water phase.
Finally, textured graphene films can be used as templates. We demonstrate a general synthetic route for transcribing the complex wrinkle and crumple topographies in graphene oxide films into textured metal oxides. Intercalation of hydrated metal ions into textured GO multilayer films followed by dehydration, thermal decomposition, and air oxidation produces Zn, Al, Mn, and Cu oxide films with high-fidelity replication of the original GO textures.
8:45 AM - NM02.03.02
Thin-Film Metal Reservoirs as Growth Inhibitor/Enhancers to Modulate the Height of Carbon Nanotubes Forests
Efrat Shawat Avraham 1 , Lior Shani 1 , Vladislav Mor 1 , Olga Girshevitz 1 , Andrew Westover 2 , Cary Pint 2 , Gilbert Nessim 1
1 , Bar Ilan University, Ramat Gan Israel, 2 Department of Mechanical Engineering, Vanderbilt University, Nashville, Tennessee, United States
Show AbstractThree years ago, we pioneered the concept of thin film reservoir where we describe how we doubled the height of carbon nanotube (CNT) forests by using a thin film reservoir of iron positioned below the alumina underlayer.1 We are now submitting a new paper where we show how, by using a copper/silver thin film as a reservoir, we can inhibit CNT growth for the areas positioned above.2 Using this technique, we show how we pattern the thin film reservoir (using lithography and lift-off) to then replicate this pattern on the CNT forest above.
We also present our most recent development where we use a molybdenum thin film reservoir to further enhance CNT growth, up to 4X (manuscript in preparation). What is most remarkable, and different compared to the iron reservoir mentioned above, is that by varying the thickness of the Mo film, we can modulate the CNT height and grow taller CNTs with thicker Mo layers.
By patterning the reservoir, we show how we can grow patterned CNT carpets with varying heights, all from the same catalyst layer. We will discuss the complex mechanisms based on diffusion from the reservoir to the surface and how the reservoir material interacts with the catalyst material to either inhibit or enhance CNT growth. We believe these findings are significant as they provide a simple way to locally control CNT growth on the third dimension (height) with lithographic precision.
1. Shawat, E.; Mor, V.; Oakes, L.; Fleger, Y.; Pint, C. L.; Nessim, G. D., What Is Below the Support Layer Affects Carbon Nanotube Growth: An Iron Catalyst Reservoir Yields Taller Nanotube Carpets. Nanoscale 2014, 6, 1545-1551.
2. Shawat Avraham, E. S., L.; Mor, V.; Girshevitz, O.; Westover, A.; Pint, C. L.; Nessim, G. D., Thin Reservoir Copper-Silver Thin Film as a Growth Inhibitor to Synthesize Lithographically Patterned Carbon Nanotube Forests. Under submission 2016.
9:00 AM - NM02.03.03
Design and High Precision Assembly of Macroscopic Objects from Carbon Nanotubes
Dawid Janas 1
1 , Silesian University of Technology, Gliwice Poland
Show AbstractAlthough individual carbon nanotubes have shown remarkable properties on many fronts, their macroscopic assemblies still cannot match their performance. Besides issues such as imperfect alignment and contact resistance, one of the main underlying problems is the lack of necessary degree of control over their atomic structure. Macroscopic objects such as fibers or thin films are highly heterogeneous and contain a wide range of types of carbon nanotubes. For many applications such as transistors or wires the presence of metallic or semiconducting carbon nanotubes, respectively, is highly unwanted and can be actually considered as contamination. As a consequence, the performance of these devices is often reduced by orders of magnitude.
We have developed a method of formation of highly-defined carbon nanotube macroassemblies, which circumvents the limitations of the present strategies. The process is straightforward, scalable, compatible with any type of nanocarbon feed (including monochiral carbon nanotubes) and does not require specialized equipment. By this approach flexible free-standing thin nanocarbon films of arbitrary size and shape can be created. In this contribution, a range of nanocarbon films of highly-defined structure or tailored properties for a specific application will be presented.
9:15 AM - NM02.03.04
Textile-Based Wearable Wide-Range Stretchable Sensor by Aligned CNT/Elastomer Composites
Yoku Inoue 1 , Takayuki Nakano 1 , Yasuro Okumiya 2 , Koji Yataka 2 , Shingo Sakakibara 2 , Katsunori Suzuki 2
1 , Shizuoka University, Hamamatsu Japan, 2 , Yamaha Corporation, Hamamatsu Japan
Show AbstractIn recent years, a wide variety of wearable device have been developed. We have been working on carbon nanotube (CNT)-based strain sensors to be used as a component of a textile-based wearable sensing system for real time motion detection. In the stretchable sensor, millimeter-long multi-walled CNTs are unidirectionally aligned and sandwiched in between elastomer layers. As for the elastomer, we used urethane resin, which has low elasticity and good affinity for human skin. The aligned CNT layer was formed by stacking CNT webs drawn from a spin-capable CNT forest. The sensor is stretched along the alignment direction so that the stretchable sensor detects displacement by sensing changes in resistance of the CNT/urethane resin composite film. In the expansion process CNT-CNT connections are detached and resistance of sensor increases, and in the contraction process the CNT connections recover with decreasing resistance. Our stretchable sensor can be stretched up to 200 % and shows short sensing delay time less than 20 msec. Resistance-displacement (strain) curve shows high linearity with a gauge factor higher than 10, which means high sensitivity. Moreover, the device is thin and as soft as human skin. Those sensing properties are suitable for a textile-based real-time motion sensing application used on human body surfaces. To integrate the sensor device into a textile and apparel, we newly developed a stretchable conductive knit fabric in which silver coated fibers are interwoven. The sensors are integrated in elbow and ankle supporters to be used for locomotion training, and in a “data glove”. The data glove senses finger patterns of piano playing in real-time. Since the low-elasticity glove does not limit any finger motion for musical instrument performance, it can be used to analyze the fine motions of musical players.
9:30 AM - NM02.03.05
Water/Alcohol Separation in Graphene Oxide Membranes—Insights from Molecular Dynamics and Monte Carlo Simulations
Daiane Damasceno Borges 1 , Cristiano Woellner 1 , Pedro Autreto 2 , Douglas Galvao 1
1 , University of Campinas, Sao Paulo Brazil, 2 , Federal University of ABC, Santo Andre, Sao Paulo, Brazil
Show AbstractRecent studies [1-2] have shown that graphene oxide (GO) membranes can work as effective separation membranes, although the detailed filtration mechanisms remain controversial. In order to gain further insights into these mechanisms, we carried out a series of molecular dynamics and grand canonical Monte Carlo simulations to probe the ethanol/water and methanol/water separation. We considered GO membranes composed of multiple layered graphene-based sheets with different interlayer distances and number of functional groups. Our results [3] show that the size exclusion and membrane affinities are not sufficient to explain the membrane selectivity. It seems that formation of an H-bond network is crucial for an effective separation water/alcohol; the filtration mechanisms are not dominated by affinities with the membrane (enthalpic mechanisms) but rather by the geometry and size factors (entropic mechanisms). Our findings are consistent with the available experimental data and contribute to clarifying important aspects of the separation behavior of confined alcohol/water in GO membranes.
[1] R. R. Nair et. al., Science v335, 442 (2012).
[2] R K. Joshi et. al., Science v343, 752 (2014).
[3] D. D. Borges, C. F. Woellner, P. A. S. Autreto, and D. S. Galvao – submitted.
10:15 AM - *NM02.03.06
Laser-Induced Graphene Growth and Applications
James Tour 1
1 , Rice University, Houston, Texas, United States
Show AbstractDiscussed will be the growth, characerization, properties and use of laser-induced graphene (LIG) for materials and energy applications.
10:45 AM - NM02.03.07
Commensurate Transition at van der Waals Interface in Twisted Bilayer Graphene
Hyobin Yoo 1 , Kuan Zhang 2 , Rebecca Engelke 1 , Paul Cazeaux 2 , Sukhyun Sung 4 , Robert Hovden 4 , Adam Tsen 3 , Takashi Taniguchi 5 , Kenji Watanabe 5 , Gyu-Chul Yi 6 , Miyoung Kim 6 , Mitchell Luskin 2 , Ellad Tadmor 2 , Philip Kim 1
1 , Harvard University, Cambridge, Massachusetts, United States, 2 , University of Minnesota, Minneapolis, Minnesota, United States, 4 , University of Michigan, Ann Arbor, Michigan, United States, 3 , University of Waterloo, Waterloo, Ontario, Canada, 5 , National Institute for Materials Science, Tsukuba Japan, 6 , Seoul National University, Seoul Korea (the Republic of)
Show AbstractStacking different two-dimensional (2-D) van der Waals (vdW) atomic crystals into heterostructures has proved a fruitful way to create novel materials with multifunctionalities. In addition to material selection, adjusting stacking angle or lattice mismatch between the layers can tune the electronic properties of the system. For unrelaxed vdW interface with small twist angle between the lattice, additional quasiperiodicity larger than the original atomic periodic lattice emerge, described by a Moiré pattern. Considering the interaction between the layers, however, the twisted stacking layer can exhibit an atomic scale relaxation. In particular, the interplay between van der Waals interaction energy and elastic energy of each layer causes atomic reconfiguration at the interface to form commensurate domain structures. Accordingly, understanding the microstructures that result from the commensurate transition at the interface and their effect on physical properties is crucial for engineering 2-D heterostructures in various applications.
In this presentation, we exploited transmission electron microscopy (TEM) to investigate the microstructures of twisted bilayer graphene with controlled twist angle. Detailed microstructures including commensurate domain structures as well as the domain boundaries were studied by TEM-based analytical techniques such as electron diffraction and dark field imaging. Furthermore, low-temperature transport properties of the twisted bilayer graphene were investigated to understand the effect of commensurate domain structures on the charge transport behavior.
11:00 AM - NM02.03.08
Mechanism and Prediction of Gas Permeation through Sub-Nanometer Graphene Pores—Comparison of Theory and Simulation
Zhe Yuan 1 , Ananth Govind Rajan 1 , Rahul Prasanna Misra 1 , Lee Drahushuk 1 , Kumar Agrawal 2 , Michael Strano 1 , Daniel Blankschtein 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, Lausanne Switzerland
Show AbstractDue to its atomic thickness, porous graphene with sub-nanometer pore sizes constitutes a promising candidate for gas separation membranes that exhibit ultra-high permeances. While graphene pores can greatly facilitate gas mixture separation, there is currently no validated analytical framework with which one can predict gas permeation through a given graphene pore. In this regard, we simulate the permeation of adsorptive gases, such as CO2 and CH4, through sub-nanometer graphene pores using molecular dynamics simulations. We show that gas permeation can typically be decoupled into two steps: (1) adsorption of gas molecules to the pore mouth, and (2) translocation of gas molecules from the pore mouth on one side of the graphene membrane to the pore mouth on the other side. We find that the translocation rate coefficient can be expressed using an Arrhenius-type equation, where the energy barrier and the pre-exponential factor can be theoretically predicted using the transition state theory for classical barrier crossing events. We propose a relation between the pre-exponential factor and the entropy penalty of a gas molecule crossing the pore. Furthermore, based on the theory, we propose an efficient algorithm to calculate CO2 and CH4 permeances per pore for sub-nanometer graphene pores of any shape. For the CO2/CH4 mixture, the graphene nanopores exhibit a trade-off between the CO2 permeance and the CO2/CH4 separation factor. This upper bound on a Robeson plot of selectivity versus permeance for a given pore density is predicted and described by the theory. Pores with CO2/CH4 separation factors higher than 102 have CO2 permeances per pore lower than 10-22 mol s-1 Pa-1, and pores with separation factors of ~ 10 have CO2 permeances per pore between 10-22 and 10-21 mol s-1 Pa-1. Finally, we show that a pore density of 1014 m-2 is required for a porous graphene membrane to exceed the permeance-selectivity upper bound of polymeric materials. Moreover, we show that a higher pore density can potentially further boost the permeation performance of a porous graphene membrane above all existing membranes. Our findings provide insights into the potential and the limitations of porous graphene membranes for gas separation, and provide an efficient methodology for screening nanopore configurations and sizes for the efficient separation of desired gas mixtures.
11:15 AM - NM02.03.09
Carrier Transport in Bilayer Graphene
Cheng Tan 1 , Lei Wang 1 , Derek Ho 2 , J.I.A. Li 1 , Kenji Watanabe 4 , Takashi Taniguchi 4 , Shaffique Adam 3 , Cory Dean 1 , James Hone 1
1 , Columbia University, New York, New York, United States, 2 Physics, National University of Singapore, Singapore Singapore, 4 , National Institute for Materials Science, Ibaraki Japan, 3 Physics, Yale-NUS College, Singapore Singapore
Show AbstractBilayer graphene has become a material of interest in recent years due to its unique band structure and its similarity to monolayer graphene. Numerous experiments have sought to understand the rich physics enabled by the material, such as the observation of a tunable band gap, fractional quantum hall states, exciton condensation, etc. Much is still to be understood, however, about the properties of bilayer graphene. In this work, we present the electronic properties of bilayer graphene near the charge neutrality point, and showcase how a tunable band structure modifies the charge concentration and the carrier mobility. We also observe the breakdown of the single carrier transport model with thermal excitations, and present the electronic contributions of electron and hole carriers in such a setting.
11:30 AM - NM02.03.10
Synthesis and Luminescence of Graphene–Based Nanocomposites with Lithium Tin Oxide Nanoparticles
Felix del Prado 1 , María Taeño 1 , Borja Martín 1 , David Maestre 1 , Julio Ramirez Castellanos 1 , Ana Cremades 1 , Jose Gonzalez-Calbet 1 , Javier Piqueras 1
1 , Univ Complutense de Madrid, Madrid Spain
Show AbstractThe development of different carbon-based nanocomposites is an increasing research field mainly due to the applications of these composites in energy storage and sensing. The carbon related host can be varied, among others, from graphene and graphene oxide to graphite, whereas the employment of nanoparticles of semiconducting oxides such as TiO2 and SnO2 has been reported for their use in Li ion batteries. However, little is known about properties other than the structural/microstructural of these composites or their behaviour as anode material for batteries. Taking advance of the luminescence properties of the semiconducting nanoparticles, the applicability of these composites can be effectively widen.
In this work, the synthesis of composites using graphene, graphene oxide and grafite as a host and lithium doped SnO2 nanoparticles as a filler is reported. The nanoparticles have been prepared using a liquid-mix (LM) method following a variation of the Pechini method and alternatively a coprecipitation method based on the hydrolisis of the precursors, or a hydrothermal proccess. The graphene and reduced graphene oxide have been prepared by a variation of the Hummer method. In the case of graphite, comercial powders have been used. The composites have been prepared following two routes. The first is based on the mixture and ultrasonication of the previously synthetised counterparts and the second route includes the carbon based precursors during the synthesis of the nanoparticles.
The microstructure and composition of the composites have been characterized by XRD, Raman spectroscopy, HRTEM, and EDS. The nanoparticle sizes are comprised between 11-14 nm for coprecipitation-grown nanoparticles, 9 and 11 nm for hydrothermal nanoparticles, whereas smaller sizes between 4,5 and 10 nm are achieved by the liquid-mix method. The tin oxide nanoparticles show a high crystallization in the rutile structure. The graphene oxide is formed by an average of 4 layers. Quantification of Lithium has been carried out by ICPS, achieving lithium incorporationvery near the nominal composition, specially for the LM synthetised nanoparticles. The luminescence behaviour has been studied by photoluminescence and cathodoluminescence. The luminescence of tin oxide nanoparticles is formed by three emission bands (blue, green and orange) related to different defects, mainly oxygen vacancies, covering the visible spectral range. Due to the lithium incorporation a new emission band in the near infrared is obtained at around 1,5 eV. The luminescence behaviour is tuned by the composite host towards the green emission, introducing another band around 3 eV which is most favored in the case of including graphene oxide as host. Complementary XPS and XAS measurements have been carried out at the Elettra Sincrotrone, in Trieste (Italy), in order to obtain a deeper insight into the properties of these materials.
NM02.04: Session IV
Session Chairs
Tuesday PM, November 28, 2017
Hynes, Level 3, Room 302
1:30 PM - *NM02.04.01
Porous Graphene Oxide Gas Sensors
Raz Jelinek 1 , Nagappa Teradal 1
1 , Ben Gurion University, Beer Sheva Israel
Show AbstractDevelopment of broad-based, readily-implemented, sensitive, and selective gas and volatile organic compounds (VOCs) sensors is a significant challenge in environmental monitoring. We describe new capacitance sensors comprising porous graphene oxide (pGO) for gas sensing. The pGO matrix was synthesized through simple and inexpensive process, providing significant accessible surface area for adsorption of gas molecules. In particular, we show that the capacitance sensing mode endows the sensors with unprecedented sensitivity and dynamic range. Selectivity among VOCs and gases could be achieved using covalent attachment of functional groups or through an array-based approach.
2:00 PM - NM02.04.02
Mechanism and Application of Surface-Enhanced Raman Scattering Based on 3D Graphene-TiO2 Nanocomposites
Tingting Zheng 1
1 , East China Normal University, Shanghai China
Show AbstractWith a burst development of new nanomaterials for plasmon-free surface-enhanced Raman scattering (SERS), the understanding of chemical mechanism and further applications have become more and more attractive. Herein, a novel SERS platform was specially designed through electrochemical deposition of graphene onto TiO2 nanoarrays (EG-TiO2). The developed EG-TiO2 SERS platform possessed remarkable Raman activity with an enhancement factor of ~ 48 using copper phthalocyanine (CuPc) as a probe molecule. XPS measurement revealed that the chemical bond Ti-O-C was formed at the interface between graphene and TiO2 in EG-TiO2 nanocomposites. Both experimental and theoretical results demonstrated that the obvious Raman enhancement was attributed to TiO2-induced Fermi level shift of graphene, resulting in effective charge transfer between EG-TiO2 nanocomposites and molecules. Taking advantage of marked Raman response of CuPc molecule on EG-TiO2 surface as well as specific recognition of CuPc toward multiple telomeric G-quadruplex, EG-TiO2 nanohybrid was tactfully employed as SERS substrate for selective and ultrasensitive determination of telomerase activity with low detection limit down to 2.07×10-16 IU. Interestingly, self-cleaning characteristic of EG-TiO2 nanocomposites under visible light irradiation successfully provided a recycling ability for this plasmon-free EG-TiO2 substrate. The present SERS biosensor with high analytical performance such as high selectivity and sensitivity, has been further explored to determine telomerase activity in stem cells, as well as to count the cell numbers. More importantly, using this useful tool, it was discovered that telomerase activity plays an important role in the proliferation and differentiation from human mesenchymal stem cells (hMSCs) to neural stem cells (NSCs). This work has not only established an approach for gaining fundamental insights into chemical mechanism (CM) of Raman enhancement, but also has opened a new way in investigation of long-term dynamic of stem cell differentiation and clinical drug screening.
2:15 PM - NM02.04.03
Direct Growth of Graphene on Insulator in Carbon Dioxide Atmosphere
Satoru Kaneko 1 3 , Kazuo Satoh 2 , Masahito Kurouchi 1 , Manabu Yasui 1 , Takeshi Rachi 1 , Satomi Tanaka 1 , Chihiro Kato 1 , Akifumi Matsuda 3 , Mamoru Yoshimoto 3
1 , Kanagawa Institute of Industrial Science and Technology, Ebina Japan, 3 , Tokyo Institute of Technology, Yokohama, Kanagawa, Japan, 2 , Osaka Research Institute of Industrial Science and Technology, Izumi, Oska, Japan
Show AbstractSatoru Kaneko1,3, Kazuo Sato2, Masahito Kurouchi1, Manabu Yasui1, Takeshi Rachi1, Satomi Tanaka1, Chihiro Kato1, Akifumi Matsuda3, Mamoru Yoshimoto3
1)Kanagawa Institute of Industrial Science and Technology (KISTEC)
2)Osaka Research Institute of Industrial Science and Technology
3)Tokyo Institute of Technology
After the discovery of graphene prepared by peeling graphite off using scotch tape, many methods are proposed and actually have used to prepare graphene film such as thermal decomposition of silicon carbide (SiC), and chemical vapor deposition (CVD) method. However the CVD method requires metal catalyst (Cu, Ni), and films are required to transfer onto insulating substrates for device fabrications. Another interesting method employs pencils and paper. Paper sheet drown using a lead pencil is irradiated by femtosecond laser, and graphitic materials remain on the paper sheet [1]. In this presentation, yet another method using pulsed laser deposition (PLD) in carbon oxide[2] will be proposed.
Although carbon dioxide (CO2) is product after hydrocarbon combustion in oxygen atmosphere, interestingly, CO2 can be an oxidant in certain situations. We show direct growth of graphene on insulating substrates in 100% CO2 environment, and observed the layer by layer growth on stepped edge of insulating substrate. The direct growth can be a large advantage over other common methods because of excluding the necessary process of transferring the graphene on insulating substrate.
Stepped substrates and carbon target were placed face to face in CO2 atmosphere with the distance of 40 mm in nitrogen, oxygen and carbon dioxides. Carbon films were examined by Raman spectroscopy with the exciting laser wavelength of 785 nm and surface morphology was observed by atomic force microscopy (AFM). Target surface was irradiated with a wavelength of 532 nm generated at the repetition rate of 2 Hz, which was reduced by a slow Q-switched YAG laser system[3].
Carbon film prepared in nitrogen seems to be diamond like carbon (DLC) or amorphous carbon, and often showed ripples on the film surface, which often occurs on preparing DLC film due to an internal stress. Strong oxidizability in oxygen atmosphere did not allow the film growth at high substrate temperature. Oxidizing environment prepared by carbon oxides offers optimal environment for graphene growth. We will show details of AFM and Raman spectra at our presentation.
[1] S. Kaneko, Y. Shimizu, T. Rachi, K. Sato, M. Ushiyama, S. Konuma, Y. Itou, H. Takikawa, G. Tan, A. Matsuda, M. Yoshimoto: Jpn. J. Appl. Phys. 55 (2016) 01AE24.
[2] S. Kaneko, T. Ito, C. Kato, S. Tanaka, S. Yasuhara, A. Matsuda, M. Yoshimoto: ACS Omega 2 (2017) 1523.
[3] S. Kaneko, Y. Shimizu, and S. Ohya, Jpn. J. Appl. Phys. 40 4870 (2001).
2:30 PM - NM02.04.04
Unprecedented Increase of the Lattice Thermal Conductivity of Auxetic Carbon under Tensile Strain
Yang Han 1 , Ming Hu 2
1 , University de Lorraine, Nancy France, 2 , RWTH Aachen University, Aachen Germany
Show AbstractIt is well-known that thermal transport plays a crucial role in many applications, such as heat dissipation and electronic packaging. Tuning thermal conductivity of material for superior performance is one of the most critical factors in electronics design and operation inspired by the working principle of integrated circuits. The strain effect on material's thermal conductivity needs to be well understood for repeatable thermal characterization and the design of electronic devices since materials and devices are always inevitably under compressive or tensile strains in both practical applications and experimental fabrications. On the other hand, as most existing electronic devices are based on rigid technologies, the novel, innovative and rapidly emerging wearable and stretchable electronic devices in their soft form hold the promise for the next-generation novel electronic applications such as implantable display, smart sensors and portable healthcare devices. Mechanical robustness, electrical reliability and high efficient heat dissipation of devices against large deformations such as bending, twisting, folding, crumpling and stretching without performance failure have become the key metrics for the flexible and wearable electronics. Sufficient levels of flexibility and heat dissipation ability are essential to realize the practical comfort against wearing utility of electronic devices. One cannot imagine how terrible it would be when people use a flexible smartphone playing a 3D game but burnt due to its long time running and thus much electric heat generated, but is not dissipated timely and efficiently. In this respect, thermal transport properties of various materials under mechanical deformation have been widely explored, in order to make them effectively and correctly used in electronic devices and thermal transport manipulation. Among many methods to tune thermal transport, mechanical strain (such as compression/tension) is one of the most effective ways to engineer the lattice thermal conductivity (κ) based on its flexibility and easy realization in experiments. Despite mechanical strain has been widely used, only three (out of four) possibilities of κ vs. strain have been found. Herewith, we identified the fourth (and the last) possibility in auxetic carbon crystals which are monoclinic and anisotropic, namely cis-, trans-hinged polydiacetylene, and hinged polyacetylene (cis-C, trans-C and hin-C). Unexpectedly, κ of trans-C (cis-C) increases with tensile strain up to 7% (6%) with maximum k of 7 (5) times larger than the unstrained value. The abnormal strain dependent k are attributed to the dominant role of the enhancement of phonon lifetime under stretching, which can be further explained from the unique atomic structure of the main chain of polydiacetylene in trans-C and cis-C. The reported giant augmentation of κ may inspire intensive research on auxetic carbon crystals as potential materials for emerging nanoelectronic devices.
2:45 PM - NM02.04.05
Heteroatom-Doping into Two-Dimensional Materials by High-Energy Ion Irradiation
Shiro Entani 1 , Masaki Mizuguchi 2 , Hideo Watanabe 3 , Masaru Takizawa 4 , Konstantine Larinov 5 , Liubov Antipina 5 6 , Pavel Sorokin 5 6 , Pavel Avramov 7 , Songtian Li 1 , Hiroshi Naramoto 1 , Seiji Sakai 1
1 , National Institutes for Quantum and Radiological Science and Technology, Tokai Japan, 2 , Tohoku University, Sendai Japan, 3 , Kyushu University, Kasuga Japan, 4 , Ritsumeikan University, Kusatsu Japan, 5 , Technological Institute for Superhard and Novel Carbon Materials, Moscow Russian Federation, 6 , National University of Science and Technology MISiS, Moscow Russian Federation, 7 , Kyungpook National University, Daegu Korea (the Republic of)
Show AbstractTwo-dimensional materials such as graphene and hexagonal boron nitride (h-BN) have attracted wide attention for nanoelectronics and spintronics. The characteristics are strongly affected by atomic-scale local structure of the two-dimensional material. It is expected that the nano-structural control by heteroatom doping leads to tailoring of the electronic and the physical properties of the two-dimensional material. Ion irradiation is one of the effective techniques to introduce these local atomic structures in the two-dimensional material.
In the present work, a new non-chemical method for heteroatom doping into graphene and h-BN was demonstrated by high-energy ion irradiation to the heterostructure of the two-dimensional material layer and the dopant material layer. Graphene and h-BN were synthesized by conventional thermal chemical vapor deposition on a polycrystalline Cu foil. After the graphene and h-BN growths, the specimens were introduced to an ultrahigh vacuum chamber and 100 nm-LiF films were deposited on graphene/Cu and h-BN/Cu, respectively. These specimens prepared were then irradiated with 2.4 MeV 63Cu2+ ions at room temperature using a tandem-type accelerator at the Research Institute for Applied Mechanics (RIAM), Kyushu University. After the ion irradiation, the LiF overlayer was removed by water-rinsing. Raman spectroscopy, near edge X-ray absorption fine structure and X-ray photoelectron spectroscopy revealed that 20%- and 7%-fluorinated graphene and h-BN are obtained superior to the defect formation by the high-energy ion irradiation up to 1014 ions/cm2. It was also shown that the F atoms are chemically adsorbed on graphene by the C-F bonds in a similar manner to the fluorinated graphene synthesized by the purely chemical route. For LiF/h-BN, ion irradiation causes the formation of B-F bonds in h-BN, which is consistent with the theoretical prediction. The atomic rearrangement of h-BN promotes the interatomic interaction between N and Cu.
In the high-energy ion irradiation with the energies more than several MeV, the electronic excitations are dominant compared with the energy transfer by nuclear collisions. It can be considered that the high-energy irradiation to the heterostructure between the two-dimensional material layer and the dopant material layer causes the electronic excitation in both the graphene (h-BN) layer the heteroatom layer. During the relaxation process from the excited states, new chemical bonds are formed between graphene (h-BN) and the heteroatom. We propose that the MeV-energy ion irradiation can be useful as a novel tool for heteroatom doping into the two-dimensional material.
3:30 PM - *NM02.04.06
High Quality Graphene from Solution Exfoliated Graphene Oxide
Manish Chhowalla 1
1 , Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States
Show AbstractEfficient exfoliation of graphite in solutions to obtain high quality graphene flakes is desirable for technologies such as printable electronics, catalysis, energy storage, and composites. Graphite oxide with large lateral dimensions has an exfoliation yield of ~ 100% but it has not been possible to completely remove the oxygen functional groups so that the reduced form of graphene oxide (GO) remains a highly disordered material. Here, we report a simple and quick method to reduce GO (rGO) into pristine graphene using 1 – 2 second pulse of microwaves. The excellent structural properties are translated into mobility values of ~ 1500 cm2-V-1-s-1 in field effect transistors (FETs) with MW-rGO as the channel material and in exceptionally low Tafel slope values of ~ 38 mV/decade for MW-rGO catalyst support for oxygen evolution reaction (OER).
4:00 PM - NM02.04.07
Polymer Cloaking Modulates Carbon Nanotube Surface Chemistry, Optical Properties and Cellular Delivery
Januka Budhathoki-Uprety 1 , Rachel Langenbacher 1 2 , Prakrit Jena 1 , Daniel Roxbury 3 , Jackson Harvey 1 2 , Elizabeth Isaac 2 , Ryan Williams 1 , Thomas Galassi 1 2 , Daniel Heller 1 2
1 , Memorial Sloan Kettering Cancer Center, New York, New York, United States, 2 , Weill Cornell Medical College, New York, New York, United States, 3 Department of Chemical Engineering, University of Rhode Island, Kingston, Rhode Island, United States
Show AbstractUses of single-walled carbon nanotubes (SWCNTs) as near-infrared optical probes, imaging agents, and sensors require the ability to simultaneously modulate nanotube fluorescence and functionally derivatize the nanotube surface. We synthesized amphiphilic helical polycarbodiimide polymers that non-covalently suspended the single-walled carbon nanotubes in aqueous media. The polymer-nanotube assembly is driven by π-π interactions between the graphitic carbon nanotube surface & the phenyl side groups on the polymers and the water solubility is conferred by the hydrophilic side chains. The polymers exhibited ordered surface coverage on the nanotubes and allowed systematic modulation of nanotube optical properties, producing up to 12-fold differences in photoluminescence efficiency. Polymer cloaking of the nanotubes facilitated the first instance of controllable and reversible inter-nanotube exciton energy transfer, allowing kinetic measurements of dynamic self-assembly and disassembly. Using these materials, we found that the functional moieties on the polymer modulated the carbon nanotube protein corona & delivery into cancer cells; with significantly higher uptake of cationic nanotubes into cancer cells compared to the anionic nanotubes and a competitive inhibition of anionic nanotubes by serum proteins in a dose-dependent manner. Polymers also facilitated nanotube delivery into the cell nucleus via a noncanonical importin β nuclear transport pathway and not by the more common importin α/β pathway. Additionally, the nanotube photoluminescence exhibited a distinct emission red-shifting upon entry to the nucleus, functioning as a reporter for the pathway, which may be used as a research tool for the study of nucleus-related pathologies. Our findings have implications for improved engineering of nanomaterials for drug delivery devices, molecular probes, and biosensors.
4:15 PM - NM02.04.08
Design of Catalyst/Support Systems for Highly Efficient Synthesis of Single-Walled Carbon Nanotube Forest with Millimeter Height and Improved Number Density
Shunsuke Sakurai 1 , Takashi Tsuji 1 , Maho Yamada 1 , Kenji Hata 1 , Don Futaba 1
1 , National Institute of Advanced Industrial Science and Technology, Tsukuba Japan
Show AbstractOne of the most essential process in the synthesis of carbon nanotubes (CNTs) forest (i.e. vertically aligned CNTs) is preparing an assembly of metal catalyst nanoparticle with controlled size and high areal density on the substrate [1]. Especially for the synthesis of single-walled CNT (SWNT) forest, small (c.a. 3 nm) iron (Fe) nanoparticle with areal density around 1012 cm−2 is required to be formed in prior to the synthesis of CNT by chemical vapor deposition (CVD) of carbon feedstock (such as ethylene). In order to prepare such catalyst array, as pointed out by previous works [2,3], diffusions of iron atoms (or particles) on the substrate (such as Ostwald ripening) and into the substrate (subsurface diffusion) should be well controlled. Although aluminum oxide (Al2O3) has been used as a support layer in most of the previous works, we recently demonstrated that magnesium oxide (MgO) can also facilitate a highly efficient synthesis of SWCNTs instead of Al2O3 [4].
Here, we report a novel design of catalyst/support system consisting of double-layered support to independently control both Ostwald ripening and subsurface diffusion. Specifically, 40 nm films of various metal oxides (such as hafnium oxide (HfO2)) were prepared as a bottom layer, and then capped with a middle layer of 1 nm thickness Al2O3 and a top layer of 1.8 nm Fe film. Using Fe/Al2O3/HfO2 system improved the efficiency of SWCNT forest (c.a. 1 mm height) synthesis compared with typical Fe/Al2O3 system with improved CNT yield (4.5 vs 0.4 mg/cm2). Atomic force microscope (AFM) observations suggests the formation of highly-dense catalyst particle array by using double-layered support layers. The results using different bottom-layer is shown in the presentation.
[1] K. Hata, D. N. Futaba, K. Mizuno, T. Namai, M. Yumura, and S. Iijima, Science 306, 1362 (2004).
[2] S. Sakurai, H. Nishino, D. N. Futaba, S. Yasuda, T. Yamada, A. Maigne, Y. Matsuo, E. Nakamura, M. Yumura, and K. Hata, J. Am. Chem. Soc. 134, 2148 (2012).
[3] S. Sakurai, M. Inaguma, D. N. Futaba, M. Yumura, and K. Hata, Small 9, 3584 (2013).
[4] T. Tsuji, K. Hata, D. N. Futaba, S. Sakurai, J. Am. Chem. Soc., 138, 16608 (2016).
4:30 PM - NM02.04.09
Chirality Dependent Toughness and Strength in Carbon Nanotube
Fazle Elahi 1 , Md Hossain 1
1 , University of Delaware, Newark, Delaware, United States
Show AbstractCarbon nanotube is a highly appreciated engineering material because of its exceptional mechanical and electronic properties. This work investigates the chirality dependent mechanical properties (stiffness, toughness, and strength) of carbon nanotube for a range of diameters using molecular dynamics simulations with its parameters derived from first-principles calculations. It is found that stiffness has a strong diameter dependence at diameters less than 1 nm, but this diameter dependence is influenced by the chirality of the nanotube. Strength on the other hand varies non-linearly on diameter as well as chirality of the nanotube. However, toughness is independent of the diameter but dependent strongly on the chirality of the nanotube. We considered zigzag (0o) to armchair (30o) orientations of carbon nanotube including the in between angles. Armchair (30o) orientation shows 12% higher maximum strength than Zigzag (0o), whereas other chiral structures exhibit their strengths in between. However, fracture toughness is very sensitive to chiral angle: Armchair configuration possess 50% higher value than zigzag. While the behavior of all these mechanical properties is found to be describable by simpler trigonometric functions, non-linearity in both strength and toughness can only be captured by considering a non-linearly varying chiral angle dependent third-order term. In comparison, our simulation results are in strong agreement with the analytical calculations.
4:45 PM - NM02.04.10
Direct Synthesis of Nanopatterned Vertical-Aligned Carbon Nanotube Metamaterials with Tailored Periodicity
Kehang Cui 1 , Hangbo Zhao 1 , Jinjing Li 1 , A. John Hart 1
1 Department of Mechanical Engineering and Laboratory for Manufacturing and Productivity, MIT, Cambridge, Massachusetts, United States
Show AbstractMetamaterials are periodic subwavelength structures in resonance with corresponding electromagnetic fields, which could selectively enhance photon absorption and thermal emission in a desired wavelength range. However, the manufacturing complexity significantly limits their scalability. The bottom-up nature of carbon nanotubes (CNTs) synthesis process enables geometrically precise nanostructures with high aspect ratios over scalable areas. Moreover, the high melting temperature and surface stability of CNTs could mitigate the structural degradation of metamaterials at high operating temperatures.
We employ nanoscale holographic interferometry for the patterning of catalysts, and engineer the annealing and nucleation conditions to achieve high-density and well-aligned vertical CNT growth which is critical to form desired sub-micrometer features. We fabricate both negative (honeycomb) and positive (cylindrical pillar) nanopatterns over centimeter-scale areas, with tailored diameter and periodicity ranging from 370 nm to 720 nm. The periodicity is designed using ab-initio electromagnetic simulation based on finite-domain time-difference (FDTD) method. The nanopatterned VACNTs are coated with tungsten using atomic-layer deposition to form W-CNT core-shell structures. The nanopatterned W-CNT metamaterials exhibit both excellent spectral and angular selectivity as well as long-term thermal stability. The structural evolution of the metamaterials over long operating time at temperatures high than 900 °C is also studied. We expect our findings here would open up a paradigm for the scalable manufacturing of submicron metamaterials.
NM02.05: Poster Session I
Session Chairs
Wednesday AM, November 29, 2017
Hynes, Level 1, Hall B
8:00 PM - NM02.05.01
Dynamic Encapsulation of Polycyclic Aromatic Hydrocarbons into Carbon Nanotubes
R. Sasaki 1 , Y. Joko 2 , K. Shintani 1
1 Department of Mechanical Engineering and Intelligent Systems, University of Electro-Communications, Chofu, Tokyo, Japan, 2 , C3I Systems Corporation, Minato-ku, Tokyo, Japan
Show AbstractIt was experimentally verified that if carbon nanotubes (CNTs) whose edges are opened are inserted into an atmosphere of polycyclic aromatic hydrocarbons (PAHs), the PAH molecules spontaneously enter the CNTs and form their stacks to yield PAHs-encapsulated CNTs symbolized as PAHs@CNTs. It may happen that the encapsulated PAHs keep their original fluorescence properties; whether it happens or not depends on their stacking morphologies. Such fluorescent PAHs@CNTs could act as diagnostic probes in organisms. Since the host CNTs play a role of protecting containers, these probes are robust against harsh environments, e.g. strong acidity and high temperature. We have already investigated dynamic encapsulation of coronenes and sumanenes into a single-walled CNT (SWCNT) and their morphologies after encapsulation (Mouri and Shintani, Phys. Chem. Chem. Phys. 18, 31043 (2016)). Now, corannulenes and pyrenes are the targets of simulation. Corannulene as well as sumanene is a bowl-shaped π-conjugated molecule which shows a unique dynamic behavior named bowl-to-bowl inversion. Kigure et al. (J. Phys. Soc. Jpn 83, 124709 (2014)) concluded that corannulenes tend to be randomly arranged in a SWCNT. However, their calculation is based on the first-principles energetics of the static configurations of the encapsulated corannulenes, and what kind of morphology the ‘dynamically’ encapsulated corannulenes take remains unresolved. On the other hand, pyrene is a rhombic-shaped flat PAH molecule with blue fluorescence property. Accordingly, if pyrenes are encapsulated into a SWCNT, the resulting hybrids might be fluorescent probes for diseased sites in organisms. In this paper, dynamic encapsulation of corannulenes/pyrenes into a SWCNT is simulated using molecular dynamic (MD) simulation. An atmosphere of either of these molecules is equilibrated at each melting point. If an edge-opened SWCNT is inserted into such an atmosphere and if the system is maintained at the temperature, spontaneous encapsulation of corannulenes/pyrenes into the SWCNT starts and continues until the SWCNT is filled with these molecules. It is revealed that corannulenes tend to form concave-concave dimers which are either stacked tilting against the SWCNT axis or arranged so that their convex surfaces face the concave inner wall of the SWCNT; this tendency stems from the predominance of the van der Waals interactions between the convex surfaces of the corannulenes and the concave inner wall of the host SWCNT in their dynamic encapsulation. On the other hand, pyrenes are deformed to be of the shape of saddles and inevitably form their dimers with their faces parallel to the inner wall of the host SWCNT once they are encapsulated into a SWCNT. After the SWCNT is filled with the dimers, they start to make angles with the SWCNT axis sequentially from the end of the SWCNT where additional pyrenes enter the SWCNT. Such dynamic aspects of encapsulation of corannulenes and pyrenes are investigated by tracking the snapshots in the MD simulations. The tilt angles of the stacked corannulenes/pyrenes are calculated, and their dependences on the SWCNT diameter are expressed by semi-analytical formulas useful for controlling the morphologies of the stacked molecules.
8:00 PM - NM02.05.02
Proximal Modification for Near Infrared Photoluminescence Modulation of Carbon Nanotubes
Tomonari Shiraishi 1 , Tomohiro Shiraki 1 2 , Naotoshi Nakashima 2
1 , Kyushu University, Fukuoka Japan, 2 , WPI-I2CNER, Fukuoka Japan
Show AbstractSingle-walled carbon nanotubes (SWNTs), which consist of a rolled-up single graphene sheet, show attracting optical properties based on their unique one-dimensional nanostructures. In particular, near infrared photoluminescence (PL) appears on the semiconducting SWNTs, which is applicable various applications including bioimaging and telecommunications. The PL of the SWNTs originates from the recombination of an exciton that is, the electron-hole pairs generated by photoexcitation. Recently, locally-functionalized SWNTs (lf-SWNTs) have been reported to emerge red-shifted PL (E11*) through a very limited amount of modification.[1] The shifted peaks are typically observed at longer wavelength regions over 100 nm in comparison to the typical emission (E11) of pristine SWNTs. Moreover, an exciton trapping mechanism at the functionalized sites contributes enhancement of PL quantum yields. Importantly, the chemical functionalization is considered to generate narrow band gaps due to the partial structural changes of the tube structures.
Recently, we have successfully determined the electronic states of lf-SWNTs prepared by oxygen-atom doping[2] and by sp3 defect doping by aryl group modification using diazonium salts[3] through an in situ PL spectroelectrochemical analysis technique. From these results, we come up with the idea of proximal chemical modification that is expected to induce new PL properties of lf-SWNTs owing to structural differences from the reported single-point modification. For example, the lf-SWNTs modified with bisdiazonium compounds showed a largely red-shifted PL peak (E112*) compared to the E11* emission of the conventional modified SWNTs and the E11 emission of the pristine SWNTs.[4] The results indicate that molecular design of modifiers would be a promising approach to modulate the PL properties of the SWNTs. The other structural factors that could affect the PL properties of If-SWNTs are examined and will be discussed at the meeting.
References
[1] Y. Piao, B. Meany, L. R. Powell, N. Valley, H. Kwon, G. C. Schatz and Y. Wang, Nat. Chem., 2013, 5, 840.
[2] T. Shiraishi, G. Juhász, T. Shiraki, N. Akizuki, Y. Miyauchi, K. Matsuda and N. Nakashima, J. Phys. Chem. C, 2016, 120, 15632.
[3] Manuscript in preparation.
[4] T. Shiraki, T. Shiraishi, G. Juhász and N. Nakashima, Sci. Rep., 2016, 6, 28393.
8:00 PM - NM02.05.03
Covalent-Reinforcement of Carbon Nanotube Yarns and Sheets—Approaches for Stronger Carbon-Based Materials
Xavier Lepro 1 , Leonardus Bayu Aji 1 , Chantel Aracne-Ruddle 1 , Daniel Malone 1 , Salmaan Baxamusa 1 , Sergei Kucheyev 1 , Michael Stadermann 1
1 , Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractSince the discovery of carbon nanotubes (CNTs), their inherent anisotropic mechanical and thermal properties have captured the attention of researchers attempting to develop a next generation of high-performance materials. However, translating individual CNT properties into benefits to macroscopic materials has proven to be challenging mostly due to the processing techniques currently available to manufacture composite materials. Polymer-based blends, for example typically require a liquid dispersion of nanotubes and sometimes their exposure to aggressive chemical treatments to improve their interaction with the continuous phase. Techniques such as direct CNT sheet drawing and spinning avoid the need of a supporting material by exploiting a unique self-assembly property of certain vertical CNT arrays with specific morphologies. In those arrays, upon pulling, CNTs orientate parallel to the displacement self-assembling into mechanically strong planar aerogels with volumetric densities similar to air [1]. Such CNT sheets can remain free-standing or be converted into flexible, micrometric-thin yarns by twist insertion thru techniques resembling conventional spinning methods [2] used in the textile industry.
Since mechanical entanglement and other non-covalent interactions such as van der Waals forces are the responsible of CNT self-assembly, material failure is driven by nanotube slippage rather than by the breaking of the covalent carbon-carbon bonds forming individual CNTs. As a result, CNT self-assembled materials while strong, are still weaker than individual nanotubes. Therefore, most techniques aimed to increase the strength of CNT self-assembled materials focus on finding ways to reinforce or strengthen these relative weak interconnection points among adjacent individual nanotubes. Here, we explore the effect of two different liquid-free alternatives to promote covalent bonding between CNTs either by recombination of unstable induced-surface defects or by auxiliary chemical reactions in the gas-phase. Free-standing sheets and yarns retain their morphology after the cross-linking procedure which effectively increases their mechanical properties by at least 40%. Both types of treated structures show diminished elastic behavior upon ball indentation (sheets) and tensile testing (yarns) which is consistent with structural reinforcement induced through covalent crosslinking. We expect that the technologies here described could contribute in the short-term development of strong, light weighted materials that can survive extreme conditions and lead to technological advances in cutting-edge technologies.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-733006.
*email: xnlepro@llnl.gov
1. Zhang, M., et al. Science, 2005. 309(5738): 1215-1219.
2. Zhang, M., K.R. Atkinson, and R.H. Baughman. Science, 2004. 306(5700): 1358-1361.
8:00 PM - NM02.05.04
In Situ XANES Study on Chemical States of Metal Catalysts During SWCNT Growth
Makoto Kumakura 1 , Hoshimitsu Kiribayashi 1 , Takahiro Saida 1 , Shigeya Naritsuka 1 , Takahiro Maruyama 1
1 , Meijo University, Nagoya Japan
Show AbstractSingle-walled carbon nanotubes (SWCNTs) have been anticipated for applications to electronic devices because SWCNTs have superior electrical properties. In general, transition metals such as Fe, Co and Ni are widely used as catalysts for SWCNT growth. However, chemical states of catalyst metals during SWCNT growth have not been clarified and controversial, although the reaction process is essential to control the structure of SWCNTs. In this study, we carried out in situ X-ray absorption near edge structure (XANES) measurements to clarify the chemical states of Co and Ni catalysts during SWCNT growth.
Using Co and Ni catalyst particles on Al2O3/SiO2/Si substrates, we carried out SWCNT growth by alcohol catalytic chemical vapor deposition (ACCVD) in a CVD system for in situ XANES measurement. After heating at 650 °C in a vacuum, ethanol gas was irradiated onto the substrates to start SWCNT growth. The growth temperature, growth time and the ethanol pressure were 650 °C, 60 min and 50 Pa, respectively. During the SWCNT growth, we measured Co and Ni K edge XANES spectra using the fluorescence mode. All XANES measurements were carried out at BL5S1 of Aichi SR, Japan. After XANES measurements, SWCNTs were characterized by Raman spectroscopy [1].
XANES spectra showed that both Co and Ni catalysts were partially oxidized before heating, but they were reduced to metallic states during the heating to 650 °C. In the case of Co catalysts, metallic catalysts changed to carbides, after the ethanol gas was irradiated. On the other hand, Ni catalysts remained metallic even after the SWCNT growth started. These results indicate that, during the SWCNT growth, carbon atoms dissolve into Co particles, while they diffuse in the near-surface region of Ni particles. These show that the growth mechanism of SWCNTs are different between Co and Ni catalysts.
[1] M. Kumakura et al. J. Cryst. Growth 468 (2017) 155.
8:00 PM - NM02.05.05
Low Temperature Synthesis of Single–Wall Carbon Nanotubes from Ru Catalysts by Alcohol Gas Source Method in High Vacuum
Takayuki Fujii 1 , Takuya Okada 1 , Takahiro Saida 1 , Shigeya Naritsuka 1 , Takahiro Maruyama 1
1 , Meijo University, Nagoya Japan
Show AbstractSingle-walled carbon nanotubes (SWCNTs) possess tremendous properties such as a ballistic transport, a high current density and a high thermal conductivity. Therefore, applications to electronics have been anticipated. However, in order to realize SWCNT devices, it is necessary to grow small-diameter SWCNTs at low temperature. So far, we have conducted SWCNT growth using platinum-group metals and succeeded in small-diameter SWCNT growth from Pt and Rh catalysts [1, 2]. However, these metals are one of the most expensive metals, which would be disadvantages for practical use. In this study, we carried out SWCNT growth using Ru catalysts, because the price of Ru is less than one-eighth of that of Pt.
Ru catalysts were deposited on Al2O3/SiO2/Si substrates using a pulsed arc plasma gun, and SWCNT growth was carried out on them. The growth temperature between 450 and 700 °C and the ethanol pressure between 1×10-5 and 1×10-2 Pa. The grown SWCNTs were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. Ru catalysts were analyzed by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).
When the growth temperature was 700 °C, Raman spectra showed peaks corresponding to both a strong G band and the radial breathing mode (RBM), indicating SWCNT growth. SEM observations showed that web-like SWCNTs were grown on the entire substrate surface. As the growth temperature was decreased, the SWCNT yield became smaller, but by optimizing the ethanol pressure in a high vacuum, SWCNTs were grown even at 450 °C. With the reduction of growth temperature, the RBM peaks in Raman spectra shifted to higher wavenumber regions, indicating that the SWCNT diameters became smaller. We also discuss the growth mechanism of SWCNTs from Ru catalysts.
References
[1] T. Maruyama et al., Carbon 96 (2016) 6.
[2] T. Maruyama et al., Carbon 116 (2017) 128.
8:00 PM - NM02.05.06
Combinatorial Screening of Binary Metal Catalyst for Chirality-Selective Growth of Single-Wall Carbon Nanotubes
Michiko Edo 1 , Hisashi Sugime 2 , Suguru Noda 1 3
1 Department of Applied Chemistry, Waseda University, Tokyo Japan, 2 Waseda Institute for Advanced Study, Waseda University, Tokyo Japan, 3 Research Institute for Science and Engineering, Waseda University, Tokyo Japan
Show AbstractStructure of single-wall carbon nanotubes (SWCNTs) can be defined by a pair of chiral index (n, m). Chirality-controlled growth of SWCNTs is desired for many applications, especially optoelectronic devices and transistors. Post-growth chirality separation has been extensively studied, however, direct growth of SWCNTs with single chirality is another attractive option. Chirality-controlled growth of SWCNTs was previously reported using cobalt (Co) and tungsten (W) binary catalyst [1]. If both the amount and the composition of the catalyst are optimized, chiral selectivity and production yield of SWCNTs will be enhanced further.
We applied our combinatorial masked deposition (CMD) method [2] to optimize the Co-W catalyst conditions on a single substrate. By placing a physical shadow mask with slit above the substrate during RF magnetron sputtering, we changed the nominal thickness of both Co (0.014–0.9 nm) and W (0.002–0.8 nm) by >two orders of magnitude on a 15×15 mm2 substrate. Appling this method to x- and y-axes, we made orthogonal thickness/composition profiles of Co and W on SiO2(90 nm)/Si substrates.
In this research, we optimized conditions for catalyst, its annealing by H2, and CNT synthesis. Each sample was analyzed by laser micro-Raman spectroscopy at 10Χ10 points by automated mapping to roughly search catalyst conditions for narrow chirality distributions, which were then analyzed more carefully using three different wavelengths (488, 514, and 633 nm) to search conditions for single radial breathing mode (RBM) peak. Chiral selectivity depended largely on the catalyst composition and thickness, and narrow chiral distribution was achieved at a narrow catalyst window of 0.2–0.7 nm with Co/W volume ratio ~1. We also found that H2 annealing needs be optimized for each catalyst. Finally, uniform samples of the optimum catalyst condition were prepared, which yielded (12, 6) SWCNTs selectively.
[1] F. Yang et al., Nature, 510, 522 (2014).
[2] S. Noda, et al., Carbon 44, 1414 (2006).
Corresponding Author: S. Noda
Tel&Fax: +81-3-5286-2769
E-mail: noda@waseda.jp
8:00 PM - NM02.05.07
Near Infrared Emission Wavelength Modulation Based on Post-Modification Using Imine Bond Formation on Single-Walled Carbon Nanotubes
Tamehito Shiga 1 , Naotoshi Nakashima 2 , Tomohiro Shiraki 1 2
1 , Department of Applied Chemistry, Kyushu University, Fukuoka Japan, 2 , WPI-I2CNER, 744 Motooka Nishiku Fukuoka Japan
Show AbstractIntroduction
Single-walled carbon nanotubes (SWNTs) show photoluminescence (PL) in the near infrared (NIR) region, which is applicable to a wide variety of advanced applications including imaging materials and optoelectronic devices. Moreover, a small amount of chemical modification of SWNTs has recently been reported to create new red-shifted PL with enhanced quantum yields (E11*) in comparison to PL of pristine SWNTs (E11) due to generation of new emissive sites with narrower band gap on the tube structure1. Our group has succeeded in creation of largely red-shifted PL (E112*) than E11* by a proximal modification approach using a bisdiazonium salt derivative2. As another achievement of dynamic PL wavelength shifting, molecular recognition system has been applied to the modified sites of SWNTs, in which saccharide binding on a phenyl boronic acid group selectively induces wavelength shift of E11*3.
In this study, we newly design a dynamic PL wavelength modulation system based on a post-modification method using imine bond formation. The imine bond can be formed by various combination of aldehyde and amine compounds, which allows us to introduce diverse chemical structures on the modified sites. The post-modification method, therefore, is expected to modulate the E11* PL on the basis of the introduced chemical structures and would provide novel functional NIR-PL materials for imaging and sensing nanosystems.
Results and discussion
Chemical modification of SWNTs was conducted by using a synthesized aryldiazonium salt tethering an aldehyde group. The aromatic aldehyde-modified SWNTs (PhCHO-SWNTs) showed a PL peak at 1140 nm (E11*) the intensity of the E11 PL at 980 nm decreased by the chemical modification in comparison to that of the pristine SWNTs. The value of emission wavelength difference between E11* and E11 (ΔE = E11* - E11) was 160 nm. Wang et al. reported correlation between spectral shift values and Hammett substituent constants (σ) of the introduced aryl groups1. The observed ΔE value agreed with the relationship when modification of the aryl aldehyde group (σ = 0.42) is considered.
Interestingly, when p-toluidine or p-bromoaniline were mixed with PhCHO-SWNTs, the emission wavelength of E11* shifted to 1134 and 1143 nm, respectively. The result indicates that the observed wavelength shift shows strong dependence on the chemical structures of the aniline derivatives. The versatility of usable amine compounds, therefore, would enable us to modulate the PL wavelength of E11*.
References
1) Y. Piao, B. Meany, L. R. Powell, N. Valley, H. Kwon, G. C. Schatz, Y. Wang, Nat. Chem. 2013, 5, 840.
2) T. Shiraki, T. Shiraishi, G. Juhasz, N. Nakashima, Sci. Rep. 2016, 6, 28393.
3) T. Shiraki, H. Onitsuka, T. Shiraishi, N. Nakashima, Chem. Commun. 2016, 52, 12972.
8:00 PM - NM02.05.08
Few-Minute Fabrication of Morphology Controlled CNT Field Electron Emitters Partially Embedded in Cu Films
Sae Kitagawa 1 , Hisashi Sugime 2 , Suguru Noda 1 3
1 Department of Applied Chemistry, Waseda University, Tokyo Japan, 2 Waseda Institute for Advanced Study, Waseda University, Tokyo Japan, 3 Research Institute for Science and Engineering, Waseda University, Tokyo Japan
Show AbstractElectron emitters are important for information displays, X-ray tubes and so on. Field emitters (FEs), based on electron tunneling under high electric field, have some advantages such as small power consumption, long lifespan and miniaturization of device compared to conventional thermionic emitters [1]. Carbon nanotubes (CNTs) are suitable materials for FEs due to their high aspect ratio, electric conductivity, thermostability and mechanical strength. Vertical aligned CNTs, grown on substrate by catalytic chemical vapor deposition (CVD) have been extensively researched. It is essential to control CNTs at adequate densities to realize high FE performance and long lifespan. We have reported the morphology controlled CNT-FEs by using e-beam lithography with good FE performances [2,3].
In this work, we propose fabrication of CNTs/Cu electron emitters by CNT-CVD and Cu-rapid vapor deposition (Cu-RVD) method. Tens-μm-tall CNTs are synthesized on textured Si substrate in 1 min, Cu is deposited on CNTs in 1 min, and then the CNTs/Cu self-supporting film is peeled off. In this method, morphology of CNTs reflects the texture of Si substrate. In addition, CNTs have their root embedded in Cu layer, resulting in good adhesion, lower electric resistance and longer lifespan. 4.3 mA/cm2 was extracted at applied voltage of 1000 V in the 100th measurement run, which was stable after 100th runs.
References:
[1] Y. Cheng et al, C. R. Physique 4 (2003).
[2] Y. Shiratori et al, Nanotechnology 20 (2009).
[3] K. Sekiguchi et al, Carbon 50 (2012).
*Corresponding Author: S. Noda
Tel&Fax: +81352862769
Email: noda@waseda.jp
Web: http:www.f.waseda.jp/noda/
8:00 PM - NM02.05.09
Substrate-Independent Synthesis of Big-Inner-Diameter Carbon Nanotube Thin Films and Catalytic Films of the Au Nanoparticle-Carbon Composite Tubular Arrays
Wei Gong 1 , Lei Su 2 , Xueji Zhang 2 , Bunshi Fugetsu 1 , Ichiro Sakata 1
1 , The University of Tokyo, Tokyo Japan, 2 , University of Science and Technology Beijing, Beijing China
Show AbstractIn our study, we introduce a method for large-area and substrate-independent synthesis of the big-inner-diameter carbon nanotube (BIDI-CNT) array films by utilizing polydopamine (PDA) as carbon source and ZnO nanorods (NRs) as sacrificing template. This method is simple and facile, and takes full advantage of the merit of the template-directed carbonization route. ZnO NRs with hexagonal morphology were coated with PDA films via the ammonium persulfate-induced polymerization of dopamine at neutral pH for avoiding the degradation of amphoteric ZnO at alkaline pH needed by the conventional oxygen-induced polymerization of dopamine. After carbonization in N2 atmosphere at 500 oC followed by ZnO removal, the hollow BIDI-CNTs with tuned wall thickness and hexagonal morphology were obtained. In addition, the obtained BIDI-CNTs were found to be N-doped. The large area thin films of the N-doped BIDI-CNTs could be synthesized on various solid substrates, for instance, Al2O3, gold, fluorine-doped tin oxide-coated glass, platinum, silicon, mica, and quartz. This fabrication approach can potentially be developed into a versatile tool for the preparation of hollow carbon nanostructures with more complex morphologies on various solid materials.
Catalytic films comprising the arrayed mesoporous and big-inner-diameter carbon nanotubes (pBIDI-CNTs) embedded with high density Au nanoparticles (NPs) were prepared through a template-directed carbonization route with a simple sputtering approach. As a result, these NPs were collectively and selectively incorporated inside the formed pBIDI-CNTs, forming the arrayed tubular nanoreactor films. After carbonization, the embedded AuNPs were still relatively uniformly distributed and had a high surface density to a level of ~ 9 × 1015 NPs m-2, the average size of the AuNPs was slightly increased to ~ 8.44 nm with a standard deviation (σ) of 2.99 nm. The high density AuNPs were sandwiched in the two-dimensionally confined space formed by the ZnO phase and the carbonized PDA phase, and this unique microstructures surrounding these high density ultrafine AuNPs exert an important stabilizing effect. We have demonstrated the fabrication of catalytic films comprising the catalyst NP-embedded pBIDI-CNT arrays with AuNPs as a model. The obtained catalytic films exhibited good catalytic activity and offered the feasibility and ease of multiple reuse. This approach can be applied to introduce other NPs, regardless of their sizes and chemical compositions, inside the arrayed pBIDI-CNTs to produce catalytic films for NP-catalyzed applications.
8:00 PM - NM02.05.10
Mechanical Properties of Pentagraphene-Based Nanotubes—A Molecular Dynamics Study
Jose de Sousa 2 1 , Acrisio Aguiar 2 , Eduardo Girao 2 , Alexandre Fonseca 1 , Antonio Souza Filho 3 , Douglas Galvao 1
2 , Federal University of Piauí, Teresina Brazil, 1 , State University of Campinas, Campinas-SP Brazil, 3 , Federal University of Ceará, Fortaleza Brazil
Show AbstractRecently, a new carbon allotrope named pentagraphene (PG) [1] was theoretically proposed [1]. PG is similar to graphene, but instead of having hexagonally arranged carbon atoms, it has pentagonal ones. PG exhibits interesting properties, such as intrinsic geometric wrinkles and negative Poison's ratio [1,2]. As carbon nanotubes can be considered as graphene sheets rolled up into cylindrical topology, a natural question is whether PG-based nanotubes (PGT) could exist. A recent work [3] using molecular dynamics methods showed that PGT are stable and under axial deformations present plastic characteristics and structural transitions. However, a detailed and comprehensive PGT study is still needed. In this work we carried out extensive fully atomistic reactive molecular dynamics (MD) simulations to investigate the structural and fracture patterns of different PGT (diameters and chiralities). The MD simulations used the reactive interatomic potential ReaxFF, as implemented in LAMMPS code [4]. Young's modulus values were estimated from the linear regime of the stress-strain curves. The fracture patterns were obtained from MD trajectories and using the von Mises stress tensor. Preliminary results show that armchair PGT have on average an elasticity modulus of 800 GPa and the zigzag ones ~700 GPa. These differences in the elasticity modulus can be explained by edge effects (armchair and zigzag). These values are consistent with the cases available in the literature [3].
[1] S. Zhang et al., PNAS v112, 2372 (2015).
[2] J. M. de Sousa et al., arXiv preprint arXiv:1703.03789 (2017).
[3] M. Chen et al., J. Chem. Phys C v121, 9642 (2017).
[4] http://lammps.sandia.gov
8:00 PM - NM02.05.11
Mechanical Properties of Phagraphene Membranes—A Fully Atomistic Molecular Dynamics Investigation
Jose de Sousa 1 2 , Acrisio Aguiar 2 , Eduardo Girao 2 , Alexandre Fonseca 1 , Antonio Souza Filho 3 , Douglas Galvao 1
1 , State University of Campinas, Campinas-SP Brazil, 2 , Federal University of Piauí, Teresina Brazil, 3 , Federal University of Ceará, Fortaleza Brazil
Show AbstractRecently [1], a new 2D carbon allotrope structure, named phagraphene (PG), was proposed. PG has a densely compacted form of penta-hexa-hepta-graphene carbon rings. PG presents low and anisotropic thermal conductivity [2] and it is believed that this anisotropy resulted from its unusual topology and should be also reflected in its mechanical properties. PG mechanical properties have been investigated [2,3], but a detailed and comprehensive study is still needed and it is one of the objectives of the present work. We have carried out fully atomistic reactive molecular dynamics simulations using the ReaxFF force field, as available in the LAMMPS code [4]. In particular we have investigated the mechanical properties and fracture patterns of PG membranes of different sizes and chiralities. The Young's modulus values of the diverse PG membranes were estimated from the stress-strain curves. Our results show that the stress-strain curves present three distinct regimes: the first one where the membranes still present ripples in their structural forms, followed by an elastic regime where the membranes exhibit fully planar configurations, and finally a plastic region just before mechanical failure (fracture).
[1] Z. Wang et al., Nano letters, v15, 6182 (2015).
[2] L. F. Pereira et al. , RSC Advances, v6, 57773 (2016).
[3] A. L. Podlivaev and L. Arturobich, JETP letters, v103, 185 (2016).
[4] http://lammps.sandia.gov
[5] J. M. de Sousa, A. L. Aguiar, E. C. Girão, A. F. Fonseca, A. G. S. Filho, and D. S. Galvão – submitted.
8:00 PM - NM02.05.12
Role of Functionalized MWCNTs and Micron Size Dispersants in Enhancement of Fracture Toughness of Epoxy Resin
Berhanu Zewde 1 , Praveen Pitliya 1 , Dharmaraj Raghavan 1
1 , Howard University, Washington, District of Columbia, United States
Show AbstractEpoxy resins are widely used as matrix material in composites for use in aerospace and automobiles because of their excellent environmental and dimensional stabilities, and good bulk properties. However, epoxy resins can be brittle and show poor resistance to crack growth due to their high crosslink density and amorphous characteristics. Previously, we have shown that the use of rubber dispersants in epoxy matrix can alleviate the brittle characteristics of epoxy resin but the addition of rubber dispersants to epoxy resin can have a negative effect on the modulus of the resin. In this study, we describe the positive benefits of adding functionalized MWCNTs and rubber dispersants to epoxy resin in improving the overall mechanical properties of the epoxy matrix. Initially, we functionalized MWCNTs by Prato reaction to yield aromatic (phenyl and 2-hydroxy-4-methoxyphenyl) (fCNT1 and fCNT2) and aliphatic (2-ethylbutyl and n-octyl) (fCNT3 and fCNT4) substituted pyrrolidine functionalized CNTs. The functionalization of CNTs was established by TGA, Raman Spectroscopy, and XPS measurements. Optical micrographs showed smaller aggregates for fCNT epoxy mixture compared to pristine CNT epoxy mixture. Mechanical measurements of well dispersed aliphatic chain fCNT/epoxy nanocomposite showed far superior tensile properties compared to poorly dispersed pristine CNT/epoxy nanocomposite . We used the most promising fCNT4 in combination with rubber dispersant to demonstrate the synergistic effect of 0.1 wt% fCNT4 and micron sized rubber particles (15 wt%) in the enhancement of toughness (i.e. 197%) and thermal stability (12oC) of epoxy resin. The findings of this study have broad utility in the field of advanced structural applications.
Acknowledgement : US Army/MIT ISN W911NF-13-D-0001
8:00 PM - NM02.05.13
Thermal Properties of a Graphene/Hexagonal Boron Nitride Heterobilayer with Interlayer Bonds
T. Iwata 1 , K. Shintani 1
1 Department of Mechanical Engineering and Intelligent Systems, University of Electro-Communications, Chofu, Tokyo, Japan
Show AbstractTwo-dimensional (2D) van der Waals heterostructures attract much attention of researchers of nanomaterials because of their novel properties arising from the interactions between the stacked monolayers. A structure of graphene on hexagonal boron nitride (hBN) is among such heterostructures. Graphene and hBN are chemically inert and have nearly the same honeycomb lattice; the lattice constant of hBN is larger than that of graphene only by 1.8 %. hBN layers show a large optical bandgap and high optical transparency. The electron mobility in graphene on hBN is very high. These suggest graphene-on-hBN structures are applicable to nanoelectronic devices. As a limit of graphene on hBN, a graphene/hBN heterobilayer (HBL) is especially focused on because its bandgap and electron mobility can be modulated by tuning the interlayer distance and stacking arrangement (Fan et al., Appl. Phys. Lett. 98, 083103 (2011)). Its use for heat management and thermoelectric conversion naturally comes to mind if we consider the thermal conductivities (TCs ) of bilayer graphene and bilayer hBN are of the order of 102 W/mK at room temperature, and the TC of the former is tunable by adjusting the number of the interlayer bonds which can be created by irradiating electron beam or femtosecond-laser excitation (Rajabpour and Allaei, Appl. Phys. Lett. 101, 053115 (2012)). Since the figure of merit of a thermoelectric conversion device is in inverse proportion to the TC of the employed material, reduction of its TC leads to enhancement of the performance of the device. Accordingly, a graphene/hBN HBL will be fit for use in such thermal devices if its TC is tunable by adjusting the number of interlayer bonds like that of bilayer graphene. In the present paper, the effects of interlayer bonds in a graphene/hBN HBL on its TC are addressed using molecular dynamics (MD) simulation. The TC is estimated by the method of nonequilibrium MD (NEMD). Short-range and long-range interactions between the constituent atoms are calculated using the Tersoff and the Lannard-Jones potentials, respectively. It is shown that the TC of a graphene/hBN HBL sharply decreases if only a few interlayer bonds exist, and continues to gradually decrease with increasing the density of the interlayer bonds up to about 25 %. However, it starts to gradually increase if the density of the interlayer bonds exceeds about 25 %. Namely, there exists a minimum TC of the HBL. The reduction of the TC occurs because the interlayer bonds work as phonon scatterers. On the other hand, its increase occurs because the rigidity of the HBL is enhanced with increasing the number of interlayer bonds. Its minimum is caused by the conflict between the both actions of the interlayer bonds. In order to verify such a physical interpretation, the phonon densities of states (DOSs) in the HBLs with/without interlayer bonds are examined in details.
8:00 PM - NM02.05.14
PdxNi1-x/Reduced Graphene Oxide Nanocomposites as Effective Electromagnetic Interference Shielding Material
Vineeta Shukla 2 , Sanjeev Srivastava 2 , Suneel Srivastava 1
2 Physics, IIT Kharagpur, Kharagpur, West Bengal, India, 1 Chemistry, IIT Kharagpur, Kharagpur, West Bengal, India
Show AbstractElectromagnetic interference (EMI) pollution is a modern kind of pollution that affects the efficiency and lifetime of electronic as well as communication devices. Moreover, serious impedances are concerned with our defensive techniques such as satellite communication, radar surveillance systems, military functions and wireless technology. To prevent the EMI pollution, electromagnetic interference shielding materials play significant role in order to control unnecessary electromagnetic radiations. Recently, carbon-based nano composites have been reported to possess high EMI shielding efficiency (SE). In particular, alloy/carbon based materials shows good EMI shielding effectiveness e.g. Pd-CNT-Cu possess shielding effectiveness (SE) of 35 dB [1], Cu-Ni/graphite shows shielding effectiveness of 35.34 dB [2]. In the same order, we prepared Pd1-xNix nanoparticles anchored on graphene sheet for EMI shielding materials. Pd1-xNi/rGO nanocomposites were synthesized by chemical reflux method [3]. The X-ray diffraction analysis, scanning electron microscopy and high-resolution transmission electron microscope confirms the PdxNi1-x nanoparticles formation on graphene sheet. Particle size was found about 3-10 nm. Selected area diffraction (SEAD) pattern showed good cystallinity of nanocomposites. Presence of all elements in nanocomposites and their chemical states was confirmed by X-ray photo electron (XPS) analysis. Raman spectroscopy showed the presence of defect in alloy/rGO nanocomposites. The EMI shielding effectiveness of the PdxNi1-x/rGO nanocomposites was found between 25 to 34 dB into 2 to 8 GHz frequency range for the sample containing different ratio of Pd and Ni.
References:
[1] A. Kumar, A. P. Singh, S. Kumari, A. K. Srivastava, S. Bathula, S. K. Dhawan, P. K. Duttaand, A. Dhar, E.M. shielding effectiveness of Pd-CNT-Cu nanocomposite buckypaper, J. Mater. Chem. A, 3, (2015) 13986.
[2] S. Kumari, A. Kumar, A. P. Singh, M. Garg, P. K. Dutta, S. K. Dhawan and R. B. Mathur, Cu-Ni alloy decorated graphite layers for EMI suppression, RSC Adv., 4, (2014) 23202-23209.
[3] P. Swain, S. K. Srivastava and S. K. Srivastava, Quantum phase transition and Fermi liquid behaviour in Pd1−xNix nanoalloys, Phys. Rev. B 91, (2015) 045401.
8:00 PM - NM02.05.15
Electrochemical Bath Deposition of Graphene under Hydrothermal Conditions
Shunichi Ishiguro 1 , Takaaki Tomai 1 , Yusuke Okamura 1 , Hiroaki Kobayashi 1 , Itaru Honma 1
1 , Tohoku University, Sendai-shi Japan
Show AbstractGraphene is a two-dimensional carbon sheet with honeycomb structure, and has attracted attention because of its many excellent characteristics, such as high electron mobility and huge specific surface area [1]. Various techniques for the synthesis of graphene via bottom-up process, including the graphitization of silicon carbide surfaces [2] and chemical vapor deposition (CVD) on metal substrates [3], have been developed. However, most of the bottom-up synthesis methods need high-temperature conditions more than 1000 °C. Therefore, the development of the method of graphene synthesis under milder temperature condition is required.
Previously, we demonstrated the novel synthesis method of graphene using the electrolysis method combined with hydrothermal reaction. By applying a small negative potential (–3.5 V) against Pt counter electrode, a mono-layer graphene was formed from carboxylic acid (formic acid or acetic acid) over the surface of Pt working electrode under sub-critical condition (300 °C, 10 MPa). However, the reaction mechanism has not been clarified, and the amount of produced graphene was too small due to the generation of a large amount of by-products such as graphite and amorphous carbon.
In this study, we investigated the reaction mechanism and favorable conditions for the hydrothermal electrolysis of graphene. To study the reaction process, we use alcohols (methanol or ethanol) as carbon source materials instead of carboxylic acids, since alcohols were considered to be formed from carboxylic acids during the cathodic reduction reaction. As a result, graphene was successfully synthesized by adding NaCl for sufficient ionic conductivity. Next, we further investigated the dependency on the surface conditions of Pt working electrode. Raman spectra and electron backscatter diffraction (EBSD) analyses coupled with scanning electron microscopy (SEM) indicated that the plane orientation of Pt substrate affected the generation amount of graphene and that the Pt (110) plane was suitable for graphene deposition. The pre-annealing treatment of Pt working electrode increased the generation amount of graphene, since the proportion and the domain size of Pt (110) plane increased. The amount of the generated graphene increased by surface polish of the Pt working electrode, indicating that the generation amount of graphene also depended on the surface roughness of the electrode.
References:
[1] A. K. Geim, et al., Nat. Mater. 6, 183–199 (2007).
[2] C. Berger, et al., J. Phys. Chem. B 108, 19912–19916 (2004).
[3] A. Reina, et al., Nano Lett. 9, 30–35 (2009).
8:00 PM - NM02.05.16
GaN(0001) as Substrate to Grow Graphene Oxide—A Computational Study
Maria Moreno-Armenta 1 , Jairo Rodriguez 2 , Fabian Herrera 3
1 , Univ Nacional Autonoma de Mexico, La Mesa, California, United States, 2 Fisica, Universidad Nacional de Colombia, Bogota Colombia, 3 , Centro de Investigación Científica y de Educación Superior de Ensenada, Ensenada, Baja California, Mexico
Show AbstractThere are some experimental papers where the interaction between graphene or its oxide with GaN is studied, mainly with the aim to take advantage of the graphene properties in order to improve the performance of devices. They could reduce the operational temperature at which transistors or LED’s works [1], also can be used to develop high potency diodes [2]. The graphene oxide is a very promising material for its own properties and for its use in the production of graphene by reduction. However theoretical papers that describe the underlying physics are scarce. In previous works we estimated the feasibility of a graphene monolayer grew over GaN(0001) surfaces[3]. The results were that the most stable configurations are a 4x4(0001)GaN/3√3×3√3graphene under N rich conditions, and a 2√3×2√3 (0001) GaN Northrup bilayer/√21×√21graphene under Ga rich conditions. These two structures maintain the hexagonal honeycomb lattice with the C-C bonds intact. Dirac cones are maintained in both structures. In this work we will present Density Functional Theory (DFT) calculations, of the surface structure resultant from introduction of oxygen on a monolayer of graphene to obtain a graphene oxide monolayer. The unit cell used was 3√3x3√3graphene/4x4(0001)GaN. First of all we considered the adsorption of a single oxygen atom over the carbon atoms, which are no equivalent due to their interaction with the Ga and N atoms of the substrate. The sites considered are: over Ga or N atoms, between two Gallium atoms, and some other sites. The total energy calculations show that the position between two Ga atoms is the preferred adsorption site. Then we introduce more oxygen atoms up to four by unit cell. The introduction of oxygen favors the match among the surfaces and the system changes its metallic character to a semiconductor one in relation to the oxygen content. Finally we studied the adsorption of hydroxyl groups and different combinations of hydroxyl and oxygen. The results obtained seem to indicate that this could be a good method to fine tuning the gap.
Acknowledgments: DGAPA project IN114817. The authors are grateful to A. Rodriguez for his technical assistance. Calculations were performed at the DGCTIC-UNAM under project LANCAD-UNAM-DGTIC-150.
References:
1. Yan, Z. et. al. Graphene quilts for thermal management of high-power GaN transistors. NATURE COMMUNICATIONS, 3(827):1–8 (2012).
2. Kim, B.-J. et. al. Transparent Conductive graphene electrode in GaN-based ultra-violet light emitting diodes. Optics Express, 18(22):23030–23034 (2010).
3. Espitia-Rico, M. et. al. Graphene monolayers on GaN (0001). Appl. Surf. Sci., 326:7–11 (2014)
8:00 PM - NM02.05.17
Graphene Oxide Membranes on Chemically Stable, Free-Standing CNT Supports for High Flux Organic Solvent Nanofiltration
Seon Joon Kim 1 , Dae Woo Kim 1 , Hee-Tae Jung 1
1 , Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
Show AbstractUtilizing membrane technology in organic solvent systems is especially important because the majority of products in chemical and pharmaceutical industries are handled in organic conditions. For the practical operation in organic solvents, the development of chemically stable membranes is highly important where carbon nanomaterials such as graphene oxide have been recently employed due to their high chemical stability. To achieve high flux, ultrathin selective layers need to be deposited on a nanoporous support, in which the stability of the support in organic solvents is of paramount importance, as a small failure in the support leads to a large defect in the ultrathin selective layer. In this study, we have developed an all-carbon, freestanding membrane where a graphene oxide (GO) laminate was deposited on top of an entangled CNT nanoporous support, fabricated by sequential vacuum filtration. The fabricated CNT support displayed outstanding chemical stability with no signs of swelling or degradation in organic solvents, acids, and bases. The performance of the GO-CNT membranes was demonstrated by observing diffusion rates of molecules with various sizes, dissolved in ethanol. It was shown that the GO-CNT membranes effectively blocked large molecules such as Brilliant blue while displaying high permeation rates for smaller molecules such as naphthalene, due to the very thin nature of the GO layer with a 30 nm thickness. Also, high flux was observed where permeation rates through GO-CNT membranes were up to 50 times faster than that of previously reported graphene paper membranes. GO-CNT membranes well performed in harsh organic solvents such as NMP and DMF over 72 hours of permeation, demonstrating their excellent chemical stability. This work demonstrates that a combination of carbon nanotube supports along with two-dimensional selective layers can be a promising candidate for high-performance membranes in organic solvent nanofiltration.
8:00 PM - NM02.05.18
Preparation and Modification of Fluorographene
Vlastimil Mazanek 1 , Daniel Bouša 1 , Jan Luxa 1 , Zdenek Sofer 1
1 , UCT Prague, Prague Czechia
Show AbstractGraphene is 2D nanomaterial with a lot of excellent properties like extraordinary electric and heat conductivity, optical transparency, mechanical toughness and heterogeneous electron transfer (HET) rate. Despite these excellent properties, graphene has also drawbacks such as zero band-gap energy which limits its possible applications mainly in fields of microelectronics and electrocatalysis. However, band-gap energy can be easily tailored by chemical modification for example by hydrogen or halogens. Fluorinated graphene can be prepared by several approaches including fluorination of graphene by various fluorinating agents (like SF4 or XeF6).
Recently, we published simple synthesis of fluorinated graphene. The first one was by reaction of thermic exfoliated graphene with elemental fluorine and the second one by thermic exfoliation of fluorographite. Depending on the method and parameters used, we can achieve the full range of fluorine content from a few percent up to stoichiometric fluorographene (C1F1). Graphene properties like wettability, electrical conductivity and width of bandgap were dramatically changed with increasing fluorine content.
Very recently, we have shown possible modification of fluorographene by Grignard reagents which were used as bases for the substitution of fluorine. For this purpose, we used ethyl, vinyl, ethynyl and propargyl magnesium bromides. This discovery was quite surprising if we consider the chemical inertness of Teflon (C2F4)n which has very similar composition as fluorographene (C1F1). We have also shown that the most reactive species are fluorographene edges with CF2 and CF3 functional groups. If we consider the key role of edges and defects in electrochemical behaviour of graphene, we can easily prepare electrode material with interesting detection and electrocatalytical activity.
Moreover, fluorographene modified by organic residues with triple bond were used to another modification by so called Click chemistry reaction. This reaction allows incorporation of various biomolecules or organic molecules. Moreover, fluorographene’s high reactivity opened up a wide range of possible modifications in graphene chemistry from simple anions up to complex biomolecules like proteins, DNA, enzymes etc. Therefore, fluorographene can be used as a platform for a broad range of new functional nanomaterials.
8:00 PM - NM02.05.19
Scalable Synthesis of Turbostratic Multilayer Graphene Film from Graphene Oxides by Ultrahigh Temperature Process
Yoshihiro Kobayashi 1 , Shingo Nakamura 1 , Takashi Ishida 1 , Atsuki Ohata 1 , Yuta Nishina 2
1 , Osaka University, Suita Japan, 2 , Okayama University, Okayama Japan
Show AbstractGraphene oxides (GOs) are a hopeful material for large scale applications of graphene because of their mass-production feature due to efficient chemical exfoliation of graphite. However, defects such as adduct of oxygen-containing groups and lattice vacancies in the graphene sheet are formed during their synthesis process and they significantly degrade superior properties of graphene. Therefore, restoration of the defects is a crucial issue for their practical use as the graphene. It has been reported that GO restoration significantly proceeds by heating at high temperature. Structure of multi-layer graphene film obtained from GO by this process, however, becomes the Bernal stacking like graphite, resulting in disappearance of excellent physical properties of monolayer graphene due to strong interaction between graphene layers in the ordered structure. Multi-layer graphene with turbostratic stacking should be a promising candidate to address this issue, since theoretical calculations predict the electronic structure of the turbostratic graphene is very similar to that of the single-layer graphene because of no stacking order between graphene layers. In this study, we investigate the formation of turbostratic multi-layer graphene with very low defect by ultrahigh temperature process under reactive environments [1]. We extend our process to scalable synthesis of turbostratic graphene by using bulky samples with porous sponge-like structures.
Large-area single-layer GO flakes with typical size of several tens microns were synthesized by chemical exfoliation [2]. Porous cm-scale GO blocks produced by freeze-dry process of single-layer GO dispersion were used as samples. The GO samples processed in ethanol at 1800°C at reduced pressure exhibit much better features of D- and G-bands in Raman spectra, indicating superior crystallinity comparable to a CVD-grown graphene. The stacking order of the processed GO was analyzed by 2D-band shapes. The analysis indicates that volume ratio of the Bernal stacking was ≈70 % for the GO processed under inert (Ar) environment at 1800°C. In contrast, GO processed in ethanol environment gave rise to the ratio of ≈30 %. This means that turbostratic structures are preferentially formed in the multi-layer graphene synthesized from GO at ultrahigh temperature in ethanol. Isotope-labelling analysis using 13C-ethanol indicates that C-C exchange reaction was preferentially induced around defect sites due to etching effect of ethanol, and the exchange reaction may dominate the suppression of the GO graphitization even at ultrahigh temperatures. The results in this work indicate that the thermal process of GO films at ultrahigh temperature in ethanol should be promising for scalable production of turbostratic multi-layer graphene and its applications to quasi single-layer electronics/phononics in future studies.
[1] T. Ishida et al., Appl. Phys. Express 9(2016)025103.
[2] N. Morimoto et al., Sci. Rep. 6(2016)21715.
8:00 PM - NM02.05.20
Growth of Single-Layer Graphene on Ge (100) by Low-Pressure Chemical Vapor Deposition
Cesar Diaz Mendoza 1 , Paula Caldas 1 , Fernando Freire Junior 1 , Marcelo Huguenin Maia da costa 1
1 , Pontificia Universidade Católica do Rio de Janeiro, Rio de Janeiro Brazil
Show AbstractGraphene has the potential to play an important role in nanoelectronic devices because of its outstanding properties including carrier mobility, transparency, and one-atom-thick layer dimension [1]. However, for this purpose, graphene must be of the highest quality and produced over a large area at a low cost [2].
There are two different routes to integrate the graphene into devices: the first one is transferring the graphene to the device surface, and the second one is direct growth on the desired surface. The transfer method has some defects, and the residue from the polymer used in the process can degrade the performance of graphene-based devices, [3]; in contrast, the direct growth method has an advantage of providing a better integration between the substrate and the graphene sheet. This integration is essential for nanoelectronic devices.
Growing graphene on Si would normally enable the best compatibility with the dominant technologies today. Nevertheless, it is actually a challenge, because the low carbon diffusivity on the Si surface and high carbon solubility makes the direct growth of graphene on Si substrates difficult [4]. Unlike Si, Ge does not form stable carbide and it is an intrinsic semiconductor material with higher carrier mobility than Si, and its integration with graphene sheets is of high interest for both fundamental materials science and electronic device applications [5].
In this work, we made a comparison between two different processes for the growth of graphene on a Ge (100) wafer synthesised by LPCVD. The main difference between the two processes is the pre-annealing step; this step is an attempt to reduce the Ge oxide at the surface. Under optimal conditions and independent of the process implemented, uniform monolayer graphene can be produced on a Ge (100) wafer. Raman spectroscopy and scanning tunnelling microscopy were employed to the analysis of the samples.
[1] Geim AK, Novoselov KS. The rise of graphene. Nature Mater 2007; 6:183–191.
[2] Bae S, Kim H, Lee Y, Xu X, Park JS, Zheng Y, et al. Roll-to-roll production of 30-inch graphene films for transparent electrodes. Nature Nanotech. 2010; 5:574–578.
[3] Ambrosi A, Pumera M. The CVD graphene transfer procedure introduces metallic impurities which alter the graphene electrochemical properties. Nanoscale 2014; 6:472–476.
[4] Trung PT, Joucken F, Campos-Delgado J, Raskin JP, Hackens B, Sporken R. Direct growth of graphitic carbon on Si(111). Appl. Phys. Lett. 2013; 102:013118.
[5] Claeys C, Simoen E. Germanium based technologies: from materials to devices. 1st ed. Elsevier Science; (2007).
8:00 PM - NM02.05.21
Study of Nucleation Mechanism of Graphene in Direct Precipitation Method
Jumpei Yamada 1 , Yuki Ueda 1 , Daichi Yamamoto 1 , Kyosuke Fujiwara 1 , Takahiro Maruyama 1 , Shigeya Naritsuka 1
1 , Meijo University, Nagoya Japan
Show AbstractBecause of its superior characteristics, graphene is highly expected to apply in various fields, such as electrical wiring in integrated circuits, transparent electrodes of light emitting diodes. In recent years, a direct growth of graphene on a substrate has been attracted much attention as a useful technique in the fabrication of graphene devices because the serious transfer process can be avoided. It is reported a direct growth of multilayer graphene on a sapphire substrate was successfully performed by the precipitation method using W capping layer [1]. The further decrease of the process temperature, for example, less than 600 oC is requested to stop thermal-destruction of the devices. Though the quality of graphene degrades with lowering the temperature, the crystallization of nickel catalyst and slow cooling after annealing are found to be beneficial to improve the quality of graphene [2]. However, there are a lot of unclear points in the mechanism. Therefore, in this study, we investigate it with systematically changing the temperature. The nucleation of graphene are especially focused.
Ni (300 nm), amorphous carbon (a-C) (1 nm) and W (20 nm) layers was deposited on a sapphire (0001) substrate using electron-beam deposition. The samples were annealed between 400 and 900 oC for 30min in vacuum. The catalysts were removed using a diluted aqua regia to characterize the graphene on the substrate.
Raman scattering spectroscopy showed that the graphene started to nucleate at 525 oC. G’ peak was obtained from the 20% area on the sample. On the other hand, G’ peak was observed all over the sample at 600 oC. The narrow G and G’ peaks above 700 oC indicate the precipitation of large grains. The amount of carbons firstly deposited on the sample is an important parameter. If it is too large, a certain part of them may remain as it is and harm the graphene growth. On the other hand, the carbons are consumed not only by the growth but also the formation of the intermediate WC layer. The concentration of carbons in the catalyst and the cooling rate determine the supersaturation of the precipitation. Namely, the graphene nucleation stands on the balance between the carbon income and expense in the catalyst. The existing nuclei also suppress a new nucleation around them. These factors control the nucleation and, consequently, the quality of precipitated graphene.
Acknowledgement: This work was supported in part by JSPS KAKENHI Grant Numbers 2660089, 15H03558, 26105002, 25000011.
References:
[1] J. Yamada et al., Jpn. J. Appl. Phys. 55, 100302 (2016).
[2] J. Yamada et al. 2016 MRS Fall Meeting & Exhibit, (2016) NM3. 7. 40.
8:00 PM - NM02.05.22
Graphane Preparation—Hydrogenated Analog of Graphene
Daniel Bouša 1 , Vlastimil Mazanek 1 , Jan Luxa 1 , Zdenek Sofer 1
1 , UCT Prague, Prague Czechia
Show AbstractGraphene has been attracting great attention due to its unique mechanical, optical, electronic and other properties over the last decade. However, its usage is limited due to the missing band gap. Band gap introduction into graphene electronic structure is very important for its future use in modern electronics, optoelectronics, and electrocatalytic applications. One of many approaches for band gap introduction is a chemical modification.
Hydrogenation is a popular way of graphene modification. It could lead to the graphane, fully hydrogenated analog of graphene with formula (C1H1)n, or to the partially hydrogenated graphene. Hydrogenation leads to change of structure. Graphene planar structure consisting of sp2 hybridized carbon atoms is changed into graphane non-planar structure composed of sp3 hybridized carbon atoms. Graphane or partially hydrogenated graphene exhibits several interesting properties like tunable band gap (according to the degree of hydrogenation), photoluminescence, ferromagnetism and other.
Present work deals with the synthesis of graphane and study of its fundamental properties. Birch reduction was employed as a hydrogenation procedure. Several different starting materials like graphene oxide, carbon fibers, carbon nanotubes or fluorinated carbons were used for the hydrogenation. Resulting materials were characterized in detail by SEM, HRTEM, AFM, XPS, CHN-S, Raman spectroscopy, FT-IR and magnetic properties measurement. Different reaction parameters of Birch reduction were studied in order to identify the best hydrogenation conditions. Potassium as an electron source and water as a proton source were identified as optimal conditions for hydrogenation of graphene oxide by Birch reduction. Hydrogenation of carbon fibers with various shape leads to the almost pure graphane with the composition of (C1H1.14)n. Ferromagnetism together with the longitudinal opening of multiwall carbon nanotubes was observed after hydrogenation by Birch reduction. Hydrogenation of various halogenated (Cl/Br/I) graphenes lead to the exceptionally high hydrogen concentration especially in the case of brominated and iodinated graphene precursors.
8:00 PM - NM02.05.23
Photothermal Reduction of Chemically Exfoliated Graphene Oxides Using Intense Pulsed Light
Hee Jin Jeong 1 , Ho Young Kim 1 , Jae-Won Lee 1 , Seung Yol Jeong 1 , Joong Tark Han 1 , Geon-Woong Lee 1
1 , Korea Electrotechnology Res Inst, Changwon Korea (the Republic of)
Show AbstractAmong the various synthetic approaches for graphene nanosheets, chemical exfoliation and reduction of graphite can be a straightforward manner to continuous process applications, for instance, screen printing, inkjet printing, or spray methods, etc. Despite the recent progress in reduction of graphene oxide (GO) using either chemical agents or high temperature treatment, complete removal of oxygen functional groups on GO has not been possible, resulting in a highly disordered structure of reduced graphene oxide (rGO). Here, we show a simple, chemical-free method to obtain the highly crystalized rGO within a millisecond level by irradiation of the intense pulsed light (IPL). This photothermal effect is efficient to deoxygenate the GO without any damage on both basal plane and edge site. As increasing the light energy, the reduction is gradually enhanced in low energy regime, and from at 14.4 J/cm2, the relative atomic percentage of oxygen functional groups compared to that of carbon is reaching below 7 %, which is comparable to the value of pristine graphene. To verify this photothermal effect-based GO reduction, we measured the surface temperature of the sample during the IPL irradiation, and we discuss this in the presentation.
8:00 PM - NM02.05.24
Graphene-Based 2D Films for Stabilization of SERS-Active Substrates
Andrei Panarin 5 , Goran Isic 2 , Anna Abakshonok 3 , Bahdan Ranishenka 4 , Vitaly Bondarenko 1 , Sergei Terekhov 5
5 , B.I. Stepanov Institute of Physics of NAS of Belarus , Minsk Belarus, 2 , Institute of Physics Belgrade, University of Belgrade, Zemun-Belgrade Serbia, 3 , Institute of Chemistry of New Materials of NAS of Belarus , Minsk Belarus, 4 , Institute of Physical Organic Chemistry of NAS of Belarus , Minsk Belarus, 1 Micro- and Nanoelectronics, Belarusian State University of Informatics and Radioelectronics, Minsk Belarus
Show AbstractSurface-enhanced Raman scattering (SERS) is a current hot topic in the rapidly advancing field of nanooptics and plasmonics since it is an extremely sensitive technique for wide applications in chemistry, physics, environmental monitoring, biology and medical sciences. SERS effect can be observed for analyte molecules adsorbed on the rough metallic surfaces (SERS-active substrates) at spatial domains, so-called “hot spots”, where local light field strength can exceed the incident field by many orders of magnitude. Silver nanostructures are the most widespread materials for SERS because of their superior Raman signal’s enhancement in comparison to other metals when excited in the visible region.
However, the major shortcoming of silver-based substrates is their poor stability and tendency towards SERS intensity degradation, especially under illumination by the laser beam. In particular, for silver nanoparticles deposited on porous silicon, it has been found that the degradation is substantially decreased if the sample is excited in vacuum, indicating that the ambient and oxygen in particular play a deciding role [1]. Thus, one of the ways of substrate’s stabilization is to passivate the silver plasmonic film by covering it with a protective layer. This, however, can lead to a substantial decrease of the SERS enhancement even at thin coverage, i.e. when analyte molecules are a few nanometers away from the silver surface as the electromagnetic fields responsible for the Raman enhancement decreases evanescently with distance from the metal surface. Inert and atomically thin 2D carbon films are promising candidates for silver passivation because they are (i) the thinnest possible spacer between silver and the analyte, (ii) almost transparent allowing light to scatter and create hot spots on the nanostructured metal and (iii) impenetrable for oxygen and other molecules and thus prevent them from reaching and degrading silver.
In the present work, we present results of our study on protective modification of silver plasmonic structures with thin 2D graphene-based films. With this purpose three different types of SERS-active substrates were prepared and investigated: metallic nanostructures formed on the surface of (i) meso-porous and (ii) macro-porous silicon as well as (iii) colloidal silver nanoparticles deposited on the glass plate. Different nanocomposite structures based on various combinations of plasmonic layer, graphene-based 2D structures and analyte molecules were prepared in order to determine the influence graphene has on the SERS performance of such materials. The SERS intensity behaviors are discussed and compared by the detection of cationic water-soluble porphyrin CuTMPyP4 as analyte.
Reference
1. A.Yu. Panarin, I.A. Khodasevich, O.L. Gladkova, S.N. Terekhov, "Determination of Antimony by Surface-Enhanced Raman Spectroscopy," Applied Spectroscopy 68, 297 (2014).
8:00 PM - NM02.05.25
A Study of Stacking Orders in Few-Layer Graphene on Silicon Carbide
Jisun Kim 1 , Yooseok Kim 1 , Kyoung Soon Choi 1 , Seung Youb Lee 1 , Chong-Yun Park 2 , Cheolho Jeon 1
1 Advanced Nano-Surface, Korea Basic Science Institute, Daejeon Korea (the Republic of), 2 Physics, Sungkyunkwan University, Suwon Korea (the Republic of)
Show AbstractSince numbers of studies demonstrate even more interesting properties of a few-layer graphene (FLG) after chemical modifications than graphene itself, FLG has been considered as a basis for the development of graphene-based materials for future applications. In FLG, the stacking order offers an extra degree of freedom. Indeed the electronic structure and the Landau level spectrum differ significantly depending on the stacking order in FLG.
Epitaxial graphene (EG) grown on SiC single crystal can be a good model for FLG study because both bernal and turbostratic stacking orders were found on the Si-face and C-face, respectively. EG has been easily grown by heating the SiC in an ultra-high vacuum or in an inert gas atmosphere. Nowadays growth of graphene by the sublimation method is typically performed in a furnace with an Ar overpressure to improve the uniformity of the EG layer. The surface reconstructions and growth kinetics for Si and C faces are different, resulting in different graphene growth rates, morphologies, and electronic properties. In the transition from graphene to FLG, the addition of each individual graphene layer modifies the electronic structure and produces a different material with unique properties. Therefore, controlled growth of FLG on SiC is of fundamental interest and will provide access to materials with engineered electronic structure.
In this study, abnormal stacking orders of FLG on SiC(0001) grown in Ar atmosphere have been investigated using various experimental techniques including angle-resolved photoemission spectroscopy (ARPES), Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), low energy electron microscopy/diffraction (LEEM/LEED), and transmission electron microscopy (TEM). The 8~10 layers FLG can be grown on SiC(0001) at around 1,800~1,900 K in several minutes with an excellent quality confirmed by Raman spectroscopy, LEED, and ARPES. The Raman signal of SiC crystal observed normally at around G peak from EG on SiC was not appeared, but very sharp G and 2D peaks similar to those observed from monolayer graphene on SiO2 were recorded without considerable D peak intensity. We noted that the SiC signal was easily observed from a thick HOPG layer transferred on SiC(0001) substrate. On the other hand, LEED data exhibited sharp 6r3 spots even though the FLG is thick enough to block the LEED signal of zeroth layer of EG. The interlayer distance measured by TEM was around 0.38 nm which is similar to that of AA stacking graphene. More details including ARPES data and abnormal stacking orders will be discussed on site.
8:00 PM - NM02.05.26
Investigating the Effect of Dielectric Polarization of Graphene in the Wetting Behavior of Graphitic Surfaces by Molecular Dynamics Simulations
Rahul Prasanna Misra 1 , Daniel Blankschtein 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractGraphene, an allotrope of carbon and the two-dimensional form of bulk graphite, consists of only a single layer of carbon atoms arranged in a honeycomb lattice. Owing to its atomic thickness and high mechanical strength, graphene has attracted widespread attention as a potential membrane for seawater desalination, nanopore-based osmotic power harvesting, and DNA sequencing applications, as well as a model system to explore the unique phase behavior of nanoconfined water. However, to realize the full potential of graphene in these applications, it is imperative to develop a deeper, fundamental understanding of the mechanisms governing the wetting of graphene by water. Previous molecular dynamics (MD) simulation studies which investigated the contact angle of a water droplet on graphene, graphite, and on graphene-coated substrates, have assumed that the water molecules interact with graphene solely through weak pair-wise additive dispersion interactions, modeled using a Lennard-Jones potential. However, when graphene comes in contact with a polar liquid like water, it is expected that the permanent dipoles of the water molecules will exert a finite electric field on graphene. The resulting dielectric polarization of graphene arising from the electric field exerted by the water molecules can potentially influence the wetting properties of graphene. However, to the best of our knowledge, many-body polarization effects on the contact angle of a polar solvent like water on a polarizable material like graphene have not been investigated to date. In this talk, using force-field molecular dynamics simulations with parameters determined from first-principles calculations, we discuss the effect of the dielectric polarization of graphene on the contact angle of water on graphene and highly-ordered pyrolytic graphite. Our study, for the first time, reveals that the electric field felt by the carbon atoms in graphene depends on the orientation of water molecules in the interfacial layer, which results in a strong non-linear dependence of the electric field on the static dipole polarizability of graphene. Our results also show that polarization (permanent dipole – induced dipole interactions) has a more pronounced effect on the interfacial entropy of water compared to dispersion (instantaneous dipole – induced dipole interactions). As a result, polarization and dispersion effects contribute differently to the wetting of graphitic surfaces by water. Our theoretical estimation of 63° for the contact angle of water on highly-ordered pyrolytic graphite is in excellent agreement with recent experimental data which report a contact angle value in the range of 61-68°.
8:00 PM - NM02.05.27
Pinhole Defects in Graphene Grown on Ge(100)
Matthew Dodd 1 , Marziyeh Zamiri 1 , Robert Jacobberger 1 , Maja Lazarevic 1 , Michael Arnold 1 , Max Lagally 1 , Susmi Singha Roy 1
1 , University of Wisconsin-Madison, Waukesha, Wisconsin, United States
Show AbstractThe growth of graphene directly on Ge offers intriguing potential for the development of high-speed Ge-based electronics and photonics. Chemical vapor deposition (CVD) is most commonly used to grow continuous graphene sheets directly on Ge(100) substrates. These graphene sheets generally contain grain boundaries and pinhole defects.[i] Their concentration depends on surface cleaning and growth conditions. Pinholes, in particular, can provide entry points for species to attack the Ge surface. Pinholes may also act as scattering centers for charge transport and thus diminish the charge carrier mobility in electronic devices. It is thus of interest to determine the pinhole defect density.
We have grown graphene on Ge(001) and other orientations of Ge, varying growth temperature, time, gas flow rates, and annealing temperature to optimize the growth conditions to produce continuous graphene sheets that effectively passivate germanium with minimal defect sites. We have developed an appropriate etching solution to create pits in the Ge substrate though the pinholes in the graphene to highlight them for quantitative analysis by scanning electron microscopy. We additionally attempt to correlate the rate of oxidation of the Ge, measured by x-ray photoelectron spectroscopy, with the pinhole defect density.
This work is supported by Department of Energy (DOE)
[i] Roy, S. S., Jacobberger, R. M., Wan, C., & Arnold, M. S. (2016). Controlling the density of pinhole defects in monolayer graphene synthesized via chemical vapor deposition on copper. Carbon, 100, 1-6.
8:00 PM - NM02.05.29
Elastomeric Polymer Composite with Carbon Nanomaterial for Tire Efficiency Improvement
Jae Hyeung Park 1 , Georgios Polyzos 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractWe have developed an innovative elastomeric polymer composite with carbon nanomaterial that will reduce the fuel consumption by reducing the tire rolling resistance. The influence of filler materials is significance for the performance of rubber products. In this research, we replaced existing fillers (such as carbon black and silica nanoparticles) with higher performance nanomaterials (graphene and silica nanofibers). The combination of graphene and silica nanofiber synergistically improved the mechanical performance and reduced the hysteretic losses of the tire elastomer at the same time. Incorporated fillers form robust flexible interfaces that will disrupt the mobility of the polymer chain, cause nanoconfinement effect in polymer composite. The combination of nanomaterials developed here can be readily adapted to apply other advanced polymer composite materials.
8:00 PM - NM02.05.30
The Effect of Viscosity and Dielectric Constant on the Fabrication and Rheological Properties of Graphene Dispersions
Matthew Diasio 1 , David Green 2 3 1
1 Materials Science and Engineering, University of Virginia, Charlottesville, Virginia, United States, 2 Chemical Engineering, University of Virginia, Charlottesville, Virginia, United States, 3 Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia, United States
Show AbstractThere has been an explosion of interest in two-dimensional (2-D) nanomaterials, in particular, the carbon allotrope graphene, because of their many outstanding properties. A major limit in the practical use of graphene, and 2-D nanomaterials generally, is the synthesis of large amounts with the desired properties, such as electronic conductivity or nanoparticle size. Size is particularly important for determining the properties that result from incorporating these nanomaterials as fillers in novel polymer nanocomposites. Hence, we seek to innovate the exfoliation of graphene by applying shear forces in liquid. Liquid-phase exfoliation by shear is attractive because it is scalable and potentially size-selective. Shear exfoliation also produces significantly fewer defects than prior methods based on ultrasonication.
Much of this work on liquid-phase exfoliated graphene focuses on optimizing exfoliation by choosing solvents that have surface energies close to that of graphite/graphene. Prior work and our preliminary results suggest that while surface energy matching is useful for exfoliation, it does not necessarily predict dispersion stability. We propose to expand on prior work by studying the effect of solvent viscosity and dielectric constants on the exfoliation process and the rheology of these dispersions. Colloid science shows that long-range attractive forces between particles are more effectively cancelled by matching the polarizability of the particles and the solvent, which corresponds to dispersing the particles in a solution with a matching refractive index or dielectric constant. We propose to study various organic solvents and evaluate their effectiveness both as exfoliation and dispersion media for graphene and compare it to their viscosities and dielectric constants. We hypothesize that more viscous solutions should exfoliate graphene at lower critical shear rates. Rheological flow curves of the dispersions at varying graphene concentrations will provide information about the attractive forces between exfoliated flakes.
8:00 PM - NM02.05.31
Synthesis of Single-Walled Carbon Nanotube Covered with Cross-Linked Polymer Post-Modifiable by Michael Addition Reaction for Cancer Targeting
Yukiko Nagai 1 , Naotoshi Nakashima 2 , Tsuyohiko Fujigaya 1 2 3
1 , Kyushu University, Fukuoka Japan, 2 , WPI-I2CNER, Fukuoka Japan, 3 , JST-PRESTO, Fukuoka Japan
Show AbstractIntroduction
Single-walled carbon nanotube (SWNT) are attracting increasing attention in biological applications because of their unique thermal, physical and optical properties. However, as produced SWNT are not soluble in many solvents and form aggregation due to the strong intertube van der Waals interactions. Since the aggregation of SWNT has a risk of toxicity in vivo, a functionalization of SWNT surfaces is important in biological applications.
We have reported a unique method to functionalize SWNT with cross-linked polymer wrapped by the polymerization in the interior of surfactant micelle encapsulating around SWNT in the presence of cross-linker [1]. Because of cross-linking, polymer layer is coated SWNT surface very stable, which is attractive for biological application. This method has an advantage. It is that we can design the cross-linked polymer layer by changing the monomer. In this study, we used newly designed vinyl monomer having maleimide endo group for SWNT functionalization to post modify thiol-containing target ligand for cancer therapy.
Result and discussion
New vinyl monomer containing maleimide (M1) was synthesized via Mitsumobu reaction of polyethyleneglycol (PEG) methacrylate with furan-protected maleimide. The functionalization of SWNT with M1 was carried out in similar manner reported previously [1] in the presence of PEG methacrylate as a co-monomer. The M1 containing SWNT thus obtained was denoted as M1/PEG/SWNT.
The absorption spectrum of M1/PEG/SWNT solution showed several sharp peaks from the visible to near infrared region ascribable to metallic and semiconducting SWNT. These characteristic spectra suggested that the SWNT remained in an isolated state. We also recognized that the absorption spectrum of M1/PEG/SWNT solution shifted to longer wavelength compared to that of SWNT in SDS aqueous solution. Such a clear shift after the polymerization indicated that SWNT surface was replaced from SDS to polymer network structure. In addition, the observation of the intense photoluminescence (PL) signals from the M1/PEG/SWNT solution also guaranteed the presence of an isolated of SWNT since the PL signals are detected only from the individually isolated SWNT. Deprotection of furan and introduction of thiol groups on M1/PEG/SWNT was carried out and discussed in the presentation.
[1] Y. Tsutsumi et al., RSC Adv., 2014, 4, 6318.
8:00 PM - NM02.05.32
Room Temperature Photo Sensor Based on Carbon Nanotubes/Silicon Interface
Shivani Dhall 1 , Bodh Mehta 1
1 Physics, Indian Institute of Technology, Delhi India
Show AbstractCarbon nanotubes (CNTs) based photo sensor has received great attentions and the performance of such sensor is stretching to both ends of high sensitivity and ultra-fast response. CNTs possess exceptional physical, chemical and electronic properties that make them most promising material for next generation electronic and photo sensor. In the present work, we have adopted simple fabrication steps including hydrofluoric acid (HF) etching of silicon dioxide (SiO2), drop casting of SWCNTs and Pd deposition for contact which makes much simpler as comparison to reported photosensor. To improve photo-sensitivity, pristine SWCNTs was functionalized by hydrogen peroxide and nitric acid at room temperature conditions. It was found that acid infiltration of SWCNTs proved helpful for the removal of impurities such as amhoporous carbon and improved photoresponse at room temperature. The functionalized SWCNTs/Si based photodetector exhibit high responsivity i.e. 57% as compared to pristine CNTs/Si photodetector (46%) at room temperature with 1V. The photoresponse time of pristine CNTs/Si was 30 ms which is quite large as compared to functionalized CNTs/Si device (10ms). The proposed current device structure does not need complicated fabrication process and is fully compatible with the silicon technology.
8:00 PM - NM02.05.33
Biomass-Dreived Nanomaterials and Supercapacitors
Josiah Roberts 1 , Doo Young Kim 1
1 , University of Kentucky, Lexington, Kentucky, United States
Show AbstractMead westwood, high fructose corn syrup (HFCS) and soybean biochars, all prepared through hydrothermal carbonization, are characterized and their electrochemical properties measured and compared against nanodiamond-derived carbon nano-onions (nCNOs). Of specific interest is the surface area, pore size, and capacitance of each sample. Biochars (Mead westwood = 1609 m2/g) are shown to have significantly greater surface areas as compared to the nCNOs (444 m2/g) with significantly smaller pore sizes (3.5 nm vs 14.4 nm) as measured by N2 adsorption-desorption. To determine capacitance, electrodes are prepared by drop-casting an aqueous suspension of the chosen sample with Nafion (as a binder) onto a glassy carbon electrode. Electrochemical measurements are taken in a three-electrode cell with a Pt counter and Ag/AgCl reference electrodes in 0.1 M KHCO3 using both cyclic voltammetry and galvanostatic charge-discharge techniques. For both methods, mead westwood has roughly three times the specific capacitance as nCNOs, while the other biochars exhibit significantly lower specific capacitance than the nCNOs (Mead = 37.537 F/g, HFCS = 0.72 F/g, Soybean = 1.94 F/g, nCNOs = 12.45 F/g all at 50mV/s cyclic voltammetry). All samples are additionally characterized through SEM, XPS, IR, and Raman spectroscopy to determine size, elemental composition, and carbonaceous structure. Once characterized and measured, these samples are modified through oxidation and nitrogen-doping in attempts to improve the above properties and elucidate a structure-function relationship. In the process of oxidizing certain samples, nanoparticles are obtained and characterized as being similar to graphene quantum dots (GQDs). While not direct candidates for supercapacitors, the easy generation of GQDs from a cheap and sustainable source is still of interest.
8:00 PM - NM02.05.34
Detection of PETN Explosive Surrogate Using Peptide Modified SWCNTs—An Experimental and Theoretical Approach
George Kubas 1 , Pedro Cortes 1 , Diana Fagan 1 , Donald Priour 1
1 , Youngstown State University, Youngstown, Ohio, United States
Show AbstractThe present research work has investigated the identification of peptides that exhibit selective binding towards PETNH [a surrogate of the explosive Pentaerythritol tetranitrate (PETN)] as well as their covalent attachment onto single wall carbon nanotubes (SWCNTs) with the purpose to establish a nano-sensing platform. This work has concentrated on the use of a phage display technique and enzyme-linked immunosorbent assays to screen the peptides with affinity toward PETNH. It has been observed that the identified and selected peptides here investigated display similar segments in their amino acid sequences to those observed in PETN reductase (a protein known to interact with explosives such as TNT). The initial testing of the peptide-SWCNTs complexes towards PETNH has been performed in a liquid state, and the results have shown that the identified peptides were able to detect the presence of PETNH (about 1.6x10-4 mmol of PETNH). Additionally, the selectivity of the peptides was investigated, and it was observed that neither TNT, nitrobenzene, sodium nitrate, nor Pentaerythritol compete with the binding process towards PETNH.
The solid-state detection capabilities of these peptide/SWCNTs complex were also modeled in a Field Effect Transistor (FET) platform using Density Functional Tight Binding (DFTB) theory in an oxygen lacking environment. Here, without the presence of PETN, the modeled electrical characteristics of the system appeared to display an n-type semiconductor profile. Similarly, in the presence of the PETN explosive, the peptide-SWCNT system seem to have maintained its n-type character; however, as the negative gate voltage decreased, the electrical current increased when compared against the SWCNT/peptide complex without PETN. It was observed that at a gate voltage of -0.05 V and a bias voltage of -0.1 V, the SWCNT/peptide-PETN interaction displayed an increase of the electrical current change by almost two orders of magnitude (from 10-9 to 10-7 Amps). This suggests that the interaction of PETN with the peptide-SWCNT complex results in a net donation of electrons to the conducting channel. These preliminary results indicate that the operation parameters of a peptide-SWCNT FET sensing platform can be modeled using DFTB theory. Indeed, this modeling could potentially reduce the experimental work required to identify the functional groups that tailor the selective features of SWCNT based sensors.
8:00 PM - NM02.05.35
Graphene and Graphene Oxide Functionalized Using the Photochlorination Technique
Jose Nocua 2 , Frank Mendoza 1 , Gerardo Morell 1 , Brad Weiner 3
2 College of Education, University of Puerto Rico at Río Piedras, San Juan, Puerto Rico, United States, 1 Physics, University of Puerto Rico at Río Piedras, San Juan, Puerto Rico, United States, 3 Chemistry, University of Puerto Rico at Río Piedras, San Juan, Puerto Rico, United States
Show AbstractFunctionalization of graphene and graphene oxide can fundamentally change the properties of these, therefore, the chemically obtained result could be made most adaptable for a wide range of applications. There are many ways in which graphene and the graphene oxide can be functionalized, depending on the desired application, is promising for different chemical and biological applications, such as electrochemical detection of glucose and solution pH sensors. In this research, we achieved functionalized graphene and graphene oxide containing a variety of features with different specificities. For the functionalization of graphene and oxide graphene, manganese chloride molecules were used as precursor and an ultra violet lamp as the light source of the photochlorination process. To identify desirable electrical properties around the sample, we analyze the surface the sheet resistance and level of dopant concentration agent on graphene and graphene oxide surfaces. Other sensitive surface characterization is reported here to demonstrate the molecule interaction and the estimated energy of linkers
8:00 PM - NM02.05.36
Formation of Graphene Phases from Graphite by Non-Standard Route
Oxana Kharissova 1 , Jared Rodríguez 1 , Boris Kharissov 1 , Carlos Luna Criado 1
1 , UANL, Monterrey Mexico
Show AbstractGraphene sheets were formed in water as a result of dispersion and destruction of graphite in mild conditions using a water-soluble cobalt octacarboxyphthalocyanine derivative theraphthal (TP) and ascorbic acid (AA) in ultrasound treatment conditions. The synthesis was carried out using different amounts of graphite, AA and TP, which were ultrasonicated in 30 mL flasks with DI water for 5 h in ultrasonic cleaner. The fact of graphite decomposition in these conditions is out of conventional concepts on classic p-p stacking interactions and/or-bonding between macrocycles and carbon phases. Destruction of graphite forming oxidized graphene is explained by free radical processes in the system TP-AA in strong cavitation conditions. Characterization of samples was made by IR- and Raman spectroscopy and Transmission Electron Microscopy (TEM).
8:00 PM - NM02.05.37
Synthesis and Characterization of 3D Carbon Nanotubes
Oxana Kharissova 1 , Beatriz Ortega Garcia 1 , Patsy Y. Arquieta Guillén 1 , Hugo Galindo Cuevas 1 , Romeo Selvas Aguilar 1
1 , UANL, Monterrey Mexico
Show AbstractMulti-wall carbon nanotubes (MWCNTs) are nanomaterials that attracts attention in various research fields because due to extraordinary mechanical properties, high electrical and thermal conductivity, among others. By this reason, the preparation of three-dimensional (3D) structures on their basis causes an interest in opening up new horizons for the production of materials with novel properties and useful applications. In the present research, the synthesis of 3D carbon nanotubes (nanoforest type), functionalized with nanoparticles of silver, aluminum and iron, was carried out. A 3D structure in the form of aligned microchannels was observed. The functionalization of MWCNTs was performed by the following methods: a) low temperature green chemistry method applying ultrasound (without the use of acids) in order to be less aggressive to the environment; b) functionalization of MWCNTs with nanoparticles of silver, aluminum or iron during the process of synthesis of carbon nanotubes by spray-pyrolysis varying the time of synthesis and concentration of solution. The products were characterized by SEM and TEM microscopy, as well as Raman spectroscopy, revealing novel 3D carbon structures with organization in the nanometer scale.
8:00 PM - NM02.05.38
Structures and Optical Properties of Nanoforest-Like Carbon Nanotubes Decorated with Nanoparticles of Strontium Aluminate Doped with Rare-Earth Elements
Patsy Y. Arquieta Guillén 1 , Alena Borisovna K. 1 , Beatriz Ortega Garcia 1 , Oxana Kharissova 1
1 , UANL, Monterrey Mexico
Show AbstractNowadays, carbon nanotubes have a lot of applications in daily life, being applied in the fabrication of cellphones, computers, nanotransistors, among many others. Currently, their new applications in biotechnology area are in search, in particular in order to find new biosensors with fluorescent properties applying on the basis of multi-wall carbon nanotubes (MWCNTs). In this work, the obtaining of carbon nanoparticles having fluorescent properties via spray pirolysis is presented. Synthesis, properties, structural peculiarities, and applications of nanobuds and related nanostructures are discussed. MWCNTs, decorated with strontium aluminate SrAl12O19 and doped with rare-earth elements, were synthesized from distinct organic precursors and the corresponding metal oxides. The metal oxides used was samarium (Sm), europium (Eu), neodymium (Nd), lanthanum (La), cerium (Ce) and some their combinations.
The synthesis was carried out on the surface of optical fibers to obtain a uniform growth of forest-like MWCNTs, adding to metal oxide nanoparticles to their surface. The preparation of composites was carried out by spray pyrolysis techniques in dry nitrogen atmosphere in the temperature range from 780 to 850oC. The formed products were characterized by XRD, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), FTIR spectroscopy, Raman spectroscopy and UV/visible spectroscopies. The analysis of the obtained data shows that the deposited nanoparticles are in the range of size 20-60 nm being uniformly distributed on the surface of MWCNTs. The samples, obtained at different temperatures and with doping metal oxides added to SrAl12O19, show different fluorescence behavior. The best results were observed with lanthanum oxide as a dopant. Possible applications as persistently luminescent phosphors for the formed MWCNTs-supported luminescent materials are proposed.
8:00 PM - NM02.05.39
Increasing the Electrical Conductivity in Stretchable Graphene Oxide Fibers with Outstanding Mechanical Properties
He Liu 1 , Ana Laura Elias 1 , Nestor Perea Lopez 1 , Yu Lei 1 3 , Cynthia Guerrero-Bermea 1 3 , Rodolfo Cruz-Silva 2 , Morinobu Endo 2 , Mauricio Terrones 1
1 , Pennsylvania State University, University Park, Pennsylvania, United States, 3 , Universidad Autónoma de Coahuila, Nueva Rosita Mexico, 2 , Shinshu University, Nagano Japan
Show AbstractWe have prepared graphene oxide (GO) films and fibers with a very high Young modulus and toughness (1). Their excellent tear resistance and mechanical behavior make them ideal candidates to replace metallic wires in electrical circuits. Reduction of GO fibers has proven to increase their current densities. Here we describe an alternative approach to substantially increase the GO fibers electrical properties by adding carbon nanotube fillers. Avoiding reduction helps preserving the original good mechanical properties of the fibers. The electrical conductivity of pristine and hybrid CNT-GO fibers has been studied along with a careful structural characterization by scanning electron microscopy and Raman spectroscopy.
1. ACS Nano, 2014, 8 (6), pp 5959–5967
8:00 PM - NM02.05.40
Magneto-Optical Conductivity of Strained Graphene
Maurice Oliva Leyva 1 , Chumin Wang 1
1 , Universidad Nacional Autonoma de Mexico, Mexico City Mexico
Show AbstractThe physics of massless Dirac fermions in graphene has been studied by applying an external magnetic field, where a relativistic Landau spectrum has been observed by means of infrared spectroscopy measurements. In these experiments, the light transmittance through unstrained grapheme under magnetic field is in excellent agreement with the theoretical Kubo magneto-optical conductivity [1]. Even in absence of magnetic field the optical properties of graphene are per se unusual. For example, graphene presents a universal transmittance determined by the fine-structure constant. However, due to the large interval of elastic response of grapheme, the mechanical deformations have been proposed as a tool to tune its light absorption [2].
In this work, we report an analytical study on the optical response of strained graphene in the presence of an external magnetic field. From Kubo formalism, the magneto-optical conductivity of strained graphene is obtained within Dirac approximation. Such conductivity results a tensor neither symmetric nor antisymmetric. We analyze the combined effects of strain-induced anisotropy and magnetic field on the transmittance as well as on the Faraday rotation of linearly polarized light after passing through the strained grapheme. Moreover, we provide a generalized expression of the Faraday angle, which allows to identify the strain-induced effects as in comparison to the magnetic effects. Finally, our findings for strained graphene are extended to anisotropic two-dimensional materials with massless Dirac fermions of arbitrary pseduospin.
M.O.L. acknowledges the postdoctoral fellowship from DGAPA-UNAM.
[1] D. N. Basov, et al., “Colloquium: Graphene spectroscopy,” Rev. Mod. Phys. 86, 959 (2014).
[2] M. Oliva-Leyva and C. Wang, “Low-energy theory for strained graphene: an approach up to second-order in the strain tensor,” J. Phys.: Condens. Matter 29, 165301 (2017).
8:00 PM - NM02.05.41
Fabrication of Polyketone Grafted Multi-Walled Carbon Nanotubes by Reactive Extrusion for Their Composites with Polyketone
Jeoung Ung Nam 1 , Somin Lee 1 , Hyejin Park 1 , Chang Keun Kim 1
1 , Chung-Ang University, Seoul Korea (the Republic of)
Show AbstractMulti-walled carbon nanotubes (MWCNTs) functionalized with the Grignard reagents and chemical moieties containing amine group as a chain end group were melt-mixed with polyketone (PK) in a twin extruder to improve physical and electrical properties of PK composite with MWCNT. It has been shown that the alkyl groups of the Grignard reagents and the amine groups on the MWCNTs were reacted with ketone groups in PK during melt extrusion. As a result, PK composites containing PK grafted MWCNTs (PK-g-MWCNTs) were produced. Formation of PK-g-MWCNT were confirmed with FT-IR, XPS, and TEM. Interfacial adhesion energy between PK and PK-g-MWCNT, dispersion of PK-g-MWCNT in the PK matrix, the mechanical and electrical properties of the PK/ PK-g-MWCNT were explored. The interfacial adhesion energy between PK and PK-g-MWCNT was higher than that between PK and pristine MWCNT and the former reached at the highest value that could be obtained with PK and MWCNT. The PK/PK-g-MWCNT composite was also exhibited better MWCNT dispersion than the PK/pristine MWCNT composite. PK/PK-g-MWCNT composites exhibited the best mechanical and electrical properties among the composites examined due to the improved interfacial adhesion
8:00 PM - NM02.05.42
Approaching One Hundred Percent Continuous Graphene Using Copolymer-Assisted Transfer
Arka Karmakar 1 , Farah Vandrevala 1 , Florian Gollier 1 , Luke Zakrajsek 1 , Mahima Ann Philip 1 , Josep Miquel Jornet 1 , Erik Einarsson 1
1 , State University of New York at Buffalo, Buffalo, New York, United States
Show AbstractTransferring graphene from copper foil to a target substrate should ideally be a nondestructive process, but cracks, voids, wrinkles, and contamination are difficult to prevent. Here we report a method in which we use a commercially available copolymer in addition to poly(methylmethacrylate) (PMMA) to obtain centimeter-scale transfer of graphene with very high continuity. Compared to conventional PMMA-only methods, the copolymer-assisted approach not only results in fewer voids, but also effectively eliminates cracks and wrinkles. Our findings are based on characterization using Raman spectroscopy, Raman mapping, quantitative image analysis of optical micrographs, and Terahertz time-domain spectroscopy. We attribute the results to more thorough relaxation of initially deposited PMMA by solvent contained in the thicker copolymer layer, which improves contact at the PMMAgraphene interface before removal of the underlying copper substrate. We then use photolithography and plasma etching to obtained patterned graphene and terahertz nano-antenna applications
8:00 PM - NM02.05.43
Retained Carrier-Mobility and Enhanced Plasmonic-Photovoltaics of Graphene via Ring-Centered η6 Functionalization and Nano-Interfacing
Vikas Berry 1 , Songwei Che 1 , Kabeer Jasuja 2 , Sanjay Behura 1 , T. S. Sreeprasad 3
1 , University of Illinois at Chicago , Chicago, Illinois, United States, 2 , Indian Institute of Technology, Gandhinagar India, 3 , Rice University, Houston, Texas, United States
Show AbstractBinding graphene with auxiliary nanoparticles for plasmonics, photovoltaics, and/or optoelectronics, while retaining the trigonal-planar bonding of sp2 hybridized carbons to maintain its carrier-mobility has remained a challenge. The conventional nanoparticle-incorporation route for graphene is to create nucleation/attachment sites via ‘carbon-centered’ covalent functionalization, which changes the local hybridization of carbon atoms from trigonal-planar sp2 to tetrahedral sp3. This disrupts the lattice planarity of graphene, thus dramatically deteriorating its mobility and innate superior properties. Here, we show large-area, vapor-phase, ‘ring-centered’ hexahapto (h6) functionalization of graphene to create nucleation-sites for silver nanoparticles (AgNPs) without disrupting its sp2 character. This is achieved by the grafting of chromium tricarbonyl [Cr(CO)3] with all six carbon atoms (sigma-bonding) in the benzenoid ring on graphene to form an (h6-graphene)Cr(CO)3 complex. This non-destructive functionalization preserves the lattice continuum with a retention in charge carrier mobility (9% increase at 10 K); and with AgNPs attached on graphene/n-Si solar cells, we report an ~11-fold plasmonic-enhancement in the power conversion efficiency (1.24%).
8:00 PM - NM02.05.44
Layer by Layer Growth of High Quality Graphene on Copper—An Approach beyond Surface Mediated Self-Limited Growth Process
Tej Limbu 2 1 , Frank Mendoza 2 , Jean Hernandez 3 , Rajesh Katiyar 2 , Joshua Razink 4 , Brad Weiner 2 5 , Gerardo Morell 2 1
2 , Institute for functional nanomaterials, San Juan, Puerto Rico, United States, 1 Physics, University of Puerto Rico, Río Piedras, San Juan, Puerto Rico, United States, 3 Biology, University of Puerto Rico, Río Piedras, San Juan, Puerto Rico, United States, 4 , Center for Advanced Materials Characterization at Oregon, Eugene, Oregon, United States, 5 Chemistry, University of Puerto Rico, Río Piedras, San Juan, Puerto Rico, United States
Show AbstractThermal chemical vapor deposition (TCVD) of methane on copper is the most common technique of high quality and large area graphene growth at present days. However, graphene growth by TCVD is limited to monolayer, and hence it is difficult to obtain bilayers and multilayers owing to the surface mediated self-limited graphene growth process. Here, we report the layer number controlled growth of high quality and large area polycrystalline graphene of large grain size on copper foil in the hot filament chemical vapor deposition (HFCVD). We show that suitable combinations of different growth parameters such as substrate to filament distance, substrate heater temperature, temperature of the filaments, methane concentration, deposition time, and process pressure lead to the controlled growth of monolayer, bilayer, and few-layer graphene. We also show that graphene can be grown with controlled grain size from about to as large as . The measured field effect electron mobility of the graphene sheets are about 3500, 2600, and 1400 cm2V-1s-1 for the largest grained monolayer, bilayer, and fewlayer graphene, respectively, which are comparable to the highest mobility values in the previous reports for polycrystalline graphene. The versatility and capability of the HFCVD for facile and inexpensive growth of graphene make it a suitable technique for industrial scale production of high quality and large area graphene for future device applications.
Symposium Organizers
William Yu, Louisiana State University Shreveport
Vicki Colvin, Brown University
Yu Zhang, Jilin University
Symposium Support
MilliporeSigma (Sigma-Aldrich Materials Science)
NM02.06: Session V
Session Chairs
Vikas Berry
Maurizio Prato
Wednesday AM, November 29, 2017
Hynes, Level 3, Room 302
8:15 AM - *NM02.06.01
Multifunctional Hybrid Carbon Interfaces
Maurizio Prato 1 2
1 , Univ di Trieste, Trieste Italy, 2 , CIC biomaGune, San Sebastian Spain
Show AbstractConnecting nanostructured materials to biological compartments is a crucial step in prosthetic applications, where the interfacing surfaces should provide minimal undesired perturbation to the target tissue. Ultimately, the (nano)material of choice has to be biocompatible and promote cellular growth and adhesion with minimal cytotoxicity or dis-regulation of, for example, cellular activity and proliferation.
In this context, carbon nanomaterials, including nanotubes and graphene, are particularly well suited for the design and construction of functional interfaces. This is mainly due to the extraordinary properties of these novel materials, which combine mechanical strength, thermal and electrical conductivity.
Our group has been involved in the organic functionalization of various types of nanocarbons, including carbon nanotubes, fullerenes and, more recently, graphene. The organic functionalization offers the great advantage of producing soluble and easy-to-handle materials. As a consequence, since biocompatibility is expected to improve upon functionalization, many modified carbon nanomaterials may be useful in the field of nanomedicine.
In particular, we have recently shown that carbon nanotubes and graphene can act as active substrates for neuronal growth, a field that has given so far very exciting results. Nanotubes and graphene are compatible with neurons, but, especially, they play a very interesting role in interneuronal communication. Improved synaptic communication is just one example.
In addition, in combination with suitable catalysts, carbon nanotubes can serve as versatile interfaces for the splitting of water molecules to give oxygen, but, especially, molecular hydrogen, ideal for clean energy generation. In combination with catalysts of different nature, carbon nanostructures can serve for many scopes.
During this talk, we will show the latest and most exciting results obtained in our laboratories in these fast developing fields.
8:45 AM - NM02.06.02
In Situ Observations of Catalyst Phase Dynamics During Carbon Nanotube Nucleation and Growth by Environmental TEM
Nicholas Dee 1 , Piran Ravichandran Kidambi 1 , Dmitri Zakharov 2 , Jinjing Li 1 , Eric Stach 2 , A. John Hart 1
1 Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 , Brookhaven National Laboratory, Upton, New York, United States
Show AbstractVertically-aligned carbon nanotubes (CNTs) are readily synthesized by catalytic chemical vapor deposition (CVD). While significant progress has been achieved by optimization of CVD parameters, the complex interplay between the catalyst and the growing nanostructure during CVD limits rational engineering advances. In this work, we perform in situ investigations of the CNT growth process by CVD using environmental transmission electron microscopy (ETEM). Using real-time, high-resolution imaging coupled with complementary diffraction mapping and EELS spectroscopy, we study the kinetics of catalyst formation and phase evolution during CNT nucleation and growth, starting from a sputtered thin film of Fe. We report the influence of the the annealing environment, including the reducing agent and transient carbon species, on the development of the catalyst phase and the resulting CNT yield. Finally, we relate these observations to our ability to grow ultra-dense CNT forests by introducing trace amounts of carbon during annealing.
9:00 AM - NM02.06.03
Control of Carbon Nanotube Emission for Applications in Cancer Research
Daniel Heller 1 2 , Januka Budhathoki-Uprety 1 , Thomas Galassi 1 2 , Rune Frederiksen 1 , Jackson Harvey 1 2 , Christopher Horoszko 1 2 , Prakrit Jena 1 , Rachel Langenbacher 1 2 , Daniel Roxbury 3 , Ryan Williams 1
1 , Memorial Sloan-Kettering Cancer Center, New York, New York, United States, 2 , Weill Cornell Medical College, Cornell University, New York, New York, United States, 3 , University of Rhode Island, Kingston, Rhode Island, United States
Show AbstractThe real-time detection of biomarkers and drugs in live cells and animals would allow for more effective studies of the dynamics of cancer and drug pharmacokinetics. Toward these ends, single-walled carbon nanotubes suspended have suitable optical properties for application towards sensors for use in live cells and in vivo, such as near-infrared emission and sensitivity to the local environment via solvatochromic responses. Currently, solvatochromic changes of such sensors have been limited by the chemical nature of the analyte, making it impossible to control the direction of energy emission changes. Here, we describe a new approach to control the direction and magnitude of solvatochromic responses of carbon nanotubes. We found a method to exacerbate the nanotube emission response to produce large differences (> 14 nm) upon the binding of cancer biomarkers and chemotherapeutic drugs. The technique surprisingly exacerbated differences in the nanotube response among analytes upon binding. The ability to control carbon nanotube solvatochromism may improve sensitivity and selectivity and potentially expand the application of nanotube-based optical sensors to new analyte classes.
9:15 AM - NM02.06.04
Efficient Sorting of High-Purity Semiconducting Carbon Nanotubes for High-Performance TFT Devices
Qingwen Li 1
1 , Suzhou Inst, Suzhou China
Show AbstractSemiconducting single-walled carbon nanotubes (s-SWCNTs) with tunable bandgap and high mobility show great promise in field-effect transistors (FET), IC chips, IR-based detectors, and flexible sensors etc. In particular, application of high-purity s-SWCNTs in thin-film transistors (TFTs) has gained intense interest recently on account of growing requirement for low-cost and flexible thin film display techniques for smart phones and TVs, etc. Rational and scalable fabrication of s-SWCNT assemblies between electrodes with high purity, uniformity and controlled density is crucial for achieving large-area and high-performance TFT-based arrays and circuits. In my talk, I will review our recent attempts in molecular design for sorting high-purity s-SWCNTs, uniform film deposition and transferring on wafer scale substrates and TFT device fabrication.
9:30 AM - NM02.06.05
Pulse-Driven Lab-on-a-Chip Capacitive Lead Ion Detection with Single Layer Reduced Graphene Oxide Field-Effect Transistor (FET)
Xiaoyu Sui 1 , Arnab Maity 1 , Chad Tarman 1 , Haihui Pu 1 , Jingbo Chang 1 , Guihua Zhou 1 , Ren Ren 1 , Shun Mao 2 , Junhong Chen 1
1 , University of Wisconsin, Milwaukee, Wisconsin, United States, 2 College of Environmental Science and Engineering, State Key Laboratory of Pollution Control and Resource Reuse, Shanghai, Shanghai, China
Show AbstractRapid and real time detection of heavy metals in water with a portable micro-system is a growing demand in the field of environmental monitoring, food safety and future cyber-physical infrastructure and cybernetic organism. Here, we present a novel ultrasensitive pulse-driven capacitance-based lead ion sensor using alumina gated reduced graphene oxide (rGO) field-effect transistor (GFET). Single layer graphene oxide (SLGO) as a channel material is achieved through electrostatic interaction of positively charged cysteamine (AET) functionalized gold electrodes and negatively charged GO flakes. Later the deposited GO is thermally reduced (reduced graphene oxide, rGO), followed by deposition of an alumina thin film on the top of the device. A layer of gold nanoparticles (Au NPs) is sputtered on the alumina in conjunction with functionalization of glutathione for serving as active sites to attract lead ions. Using a pre-programmed microcontroller, chemo-capacitance based detection of lead ions has been demonstrated using this FET sensor. A rapid response (~ 1 s) and a significant change in source-drain capacitance are observed in the presence of lead ion solutions with a good selectivity. This pulse-driven capacitance measurement technology shows significant potential for onsite quick testing of real water quality. The sensing performance is interpreted through modeling the FET structure and understanding the change in equivalent RC time constant of the FET device.
10:15 AM - *NM02.06.06
Carbon Nanomaterials of Different Dimensions—From Sheets to Dots and from Energy Conversion to Bioimaging and Bactericidal Functions
Ya-Ping Sun 1
1 , Clemson University, Clemson, South Carolina, United States
Show AbstractNanoscale carbon materials including tubes, sheets, and dots have interesting and, in many cases, unique optical, electronic, and thermal properties. We have been exploring these nanomaterials for various technologies, from bulk-separated metallic/semiconducting single-walled carbon nanotubes for electrical/electronic devices to carbon nanosheets for thermal and mechanical composites and carbon-based photoluminescent nanoparticles (“carbon dots”) as effective imaging-sensing agents and photocatalysts. In this talk, some interesting and representative recent results from our research will be highlighted.
10:45 AM - *NM02.06.07
Confined, Oriented and Electrically Anisotropic Graphene Wrinkles on Bacteria
Shikai Deng 1 , Enlai Gao 2 , Soumyo Sen 1 , Sreeprasad Sreenivasan 1 , Sanjay Behura 1 , Petr Kral 1 , Zhiping Xu 2 , Vikas Berry 1
1 , University of Illinois at Chicago , Chicago, Illinois, United States, 2 , Tsinghua University, Beijing China
Show AbstractCurvature induced dipole moment and orbital rehybridization in graphene wrinkles modify its electrical properties and induces transport-anisotropy. Current wrinkling processes are based on contraction of the entire substrate, and do not produce confined or directed wrinkles. Here we show that selective desiccation of bacterium under impermeable and flexible graphene via a flap-valve operation produces axially-aligned graphene-wrinkles of wavelength 32.4 – 34.3 nm, consistent with modified Föppl-von Kármán mechanics (confinement ~0.7 X 4 mm2). Further, electrophoretically-oriented bacterial device with confined wrinkles aligned with van der Pauw electrodes were fabricated and exhibited anisotropic transport barrier (ΔE = 1.69 meV). Theoretical models were developed to describe the wrinkle formation mechanism. The results obtained here show bio-cellular desiccation via flap-valve to produce confined, well-oriented and electrically anisotropic graphene wrinkles, which can be applied for electronics, bioelectromechanics and strain-patterning.
11:15 AM - NM02.06.08
Facile Fabrication of Large Area ZnO—Graphite Composite Thin Films for Ultraviolet Photodetection
Rachel Meyen 1 , Kerri Houghton 1 , Medini Padmanabhan 1
1 , Rhode Island College, Providence, Rhode Island, United States
Show AbstractWe use the technique of interface exfoliation to incorporate ZnO particles into thin films of multi-layer graphene. Two-point electrical characterization of these films reveal very low dark current values. In the presence of UV illumination from a hand-held flashlight, the current rises by up to three orders of magnitude. We study the variation of the strength and response time of this photodetector as a function of the relative ratio between carbon and ZnO. This one-pot synthesis method is cost-effective, scalable and can be used to functionalize graphene films with light absorbing entities.
11:30 AM - NM02.06.09
Strong Graphene Adhesion Enables Glue Application and Assembly of Suspended Wrinkles
Liusi Yang 1 , Anyuan Cao 1
1 , Peking University, Beijing China
Show AbstractSince its discovery in 2004, graphene has stimulated tremendous interest in the field of materials and nanotechnology, with applications in electronic devices, sensors, energy conversion and storage. However, several interesting properties have not been explored or utilized thoroughly. In particular, graphene has a two-dimensional (2D) planar structure with high flexibility, which leads to conformal contact and strong adhesion when transferred or deposited onto surfaces or substrates. Here, we utilize the strong adhesion generated between solution precipitated graphene oxide (GO) sheets and selected substrates, to explore two novel applications: 1) a conductive non-penetrating GO glue for making functional vertical architectures, and 2) assembly of suspended GO wrinkles with high pre-tension and elastic properties.
In the first application, we show that a GO solution can glue 3D porous carbon nanotube (CNT) sponges and their composites onto rigid or flexible substrates (e.g. Si wafer, Cu foil). Mechanical tests and theoretical calculation based on van deer Waals interaction reveal high adhesion strengths at the GO-CNT and GO-SiO2 interfaces, respectively. Taking the reduced GO (rGO) glue as a thin layer electrode, we utilize the rGO-fixed CNT sponge as a porous template to fabricate polymer-reinforced, vertical composite columns, which exhibit high conductivity, super-elastic behavior and reversible resistance change under large-strain compression for 1000 cycles. Compared with conventional polymer-based glues, our GO glue-electrode is pure, ultra-thin, non-penetrating and high temperature-resistant.
In addition to solid substrates, we further utilize a liquid TiO2 gel to modify the local structure of GO films and create suspended, aligned wrinkles with tailored wavelength, which are strongly clamped at the edge of cracked TiO2 islands. In particular, those GO wrinkles are subjected to a high pre-tension, which is important for making stable suspended configurations, as confirmed by theoretical calculations based on the wrinkle geometry and measured spring constants, respectively. As a result, in situ atomic force microscope indentation reveals tunable elastic deformation depending on the gap width, and rGO wrinkles show enhanced spring constants and reversible behavior after 1000 indentation cycles. These suspended wrinkles have potential applications in many areas such as sensors, actuators, and micro/nano electromechanical systems.
The strong adhesion of graphene could be utilized to fabricate various 1D-2D and 2D-3D composite structures and functional devices, which is an interesting phenomenon that deserves further study on the fundamental mechanism and practical applications.
11:45 AM - NM02.06.10
PEEK-Graphene Nanocomposites—Understanding Energy Transfer
Stephen Bartolucci 1 , Thierry Tsafack 1 , Andrew Littlefield 1 , Joshua Maurer 1
1 , U.S. Army ARDEC, Watervliet, New York, United States
Show AbstractGraphene has been studied extensively as a filler in polymer nanocomposites for enhancing mechanical, electrical and thermal properties. In many cases, energy transfer from the graphene to the surrounding matrix is an important consideration in how the composite behaves. The transfer of heat, for example, from the graphene to the polymer is important in heat conduction applications. In other applications, radiative energy absorbed by the graphene is then transferred to the matrix. In this study, we examine the transfer of energy in the form of heat from graphene to a matrix of polyetheretherketone (PEEK) using molecular dynamics simulations. We explore the effect of the number of graphene layers on the transfer of energy to the polymer and specifically look at how the orientation of the PEEK molecules to the graphene plays a role in heat transfer. This work provides insight for designing composites for improved heat conduction and absorptive processes, such as microwave absorption and heating.
NM02.07: Session VI
Session Chairs
Alireza Khanaki
Ester Vazquez
Wednesday PM, November 29, 2017
Hynes, Level 3, Room 302
1:30 PM - *NM02.07.01
Harvesting, Storing, and Converting Energy Using Fibers, Yarns, and Textiles
Ray Baughman 1
1 , University of Texas at Dallas, Richardson, Texas, United States
Show AbstractOur evolving and new technology platforms for harvesting, storing, and converting energy using carbon nanotubes, graphene, and other materials will be described, and related to product needs in such diverse areas as robotics, electronic textiles, and self-powered sensors for the human body. Various types of powerful artificial muscles will be discussed, which can be used to harvest waste thermal and chemical energy as electrical energy, to provide comfort adjusting textiles, and for robotic applications. Our biscrolling technology, which traps multifunctional powders inside nanofiber yarns, is used to make superconducting yarns, textile batteries and supercapacitors, fuel cell textiles, and superelastic electronic yarns. Performance realized, versus application needs, as well as advances in theoretical understanding will also discussed. Collaborations between colleagues at the University of Texas at Dallas, Hanyang University, and the University of Wollongong were especially important for realizing the described results.
2:00 PM - NM02.07.02
Precipitation Growth of Graphene under Exfoliated Hexagonal Boron Nitride to Form Heterostructures on Cobalt Substrate by Molecular Beam Epitaxy
Renjing Zheng 1 , Alireza Khanaki 1 , Hao Tian 1 , Yanwei He 1 , Yongtao Cui 1 , Zhongguang Xu 1
1 , University of California, Riverside, Riverside, California, United States
Show AbstractGraphene and hexagonal boron nitride (h-BN) are van der Waals (vdW) materials, and they share the same layered crystal structure and hexagonal symmetry, with a small lattice mismatch of only ~1.7%. Graphene/h-BN heterostructures have a great deal of potential applications in diverse areas, including photo-electricity, catalysts, and transistors. These advantages have attracted widespread interest of the growth and properties study of the heterostructures containing graphene and h-BN. Much work has been reported about the preparation of the heterostructures by employing different growth methods on different substrates. However, the realization of epitaxial heterostructure (graphene on h-BN or h-BN on graphene) remains challenging. Because of the stability of boron and nitrogen molecules under inert conditions, the reaction to form h-BN usually requires high growth temperature (>900 C) and long growth duration (several hours). Additionally, due to the weak vdW interaction, it is difficult for boron and nitrogen atoms to stick onto the surface of the deposited film, thus hindering the growth of h-BN films with controllable thickness for dielectric materials and barriers.
In this presentation, we demonstrate graphene/h-BN heterostructures by growing graphene onto the substrates which consist of exfoliated h-BN on Co thin film using molecular beam epitaxy. The heterostructure samples grown at different temperature and growth time were characterized by Raman, optical microscopy, atomic force microscopy, microwave impedance microscopy and scanning tunneling microscopy. It is found that the graphene/h-BN heterostructures were formed by the formation of graphene underneath rather than on top of the h-BN flakes. The growth mechanism is discussed.
This growth method provides a convenient path to produce graphene/h-BN heterostructures, which avoids high temperature and long duration needed for BN growth.
2:15 PM - NM02.07.03
The Intrinsic Water Wettability of Graphitic Carbons and Its Implications
Lei Li 1 , Haitao Liu 1
1 , University of Pittsburgh, Pittsburgh, Pennsylvania, United States
Show AbstractGraphitic carbons are long regarded as model hydrophobic materials. However, recent works in our labs have shown that graphite and graphene are much more hydrophilic than previously thought. [1] Since the water-graphitic interface is critical to many important applications including electrodes, adsorbents, catalyst support, and solid lubricants, this unexpected finding could completely change the way graphitic materials are made, modeled and modified. This presentation aims to summarize our recent works [1-3] on the intrinsic water wettability of graphitic carbons and discuss its implications. First, historical perspective will be provided highlighting the long accepted concept that graphite is hydrophobic. Next, our recent contact angle, XPS, ATR-FTIR and ellipsometry results will be presented showing that pristine graphene and graphite are mildly hydrophilic and airborne hydrocarbons adsorb onto the clean surfaces thus rendering them hydrophobic. These results are further rationalized by analyzing the change in surface energy of the graphitic surfaces before and after hydrocarbon contamination. Facile methods to remove hydrocarbons from a contaminated surface will be discussed along with a convenient water treatment method we developed to inhibit hydrocarbon adsorption onto a pristine graphitic surface. Implications of contamination will be illustrated through comparing the electrochemical activity and adsorption property of pristine and contaminated graphite. Lastly, consequences of these findings and future research directions to address a few important unanswered questions will be discussed.
References:
1. Li, Z.; Wang, Y.; Kozbial, A.; Shenoy, G.; Zhou, F.; McGinley, R.; Ireland, P.; Morganstein, B.; Kunkel, A.; Surwade, S. P.; Li, L. and Liu, H. “Effect of airborne contaminants on the wettability of supported graphene and graphite”, Nature Mater., 2013, 12, 925-931
2. Li, Z.; Kozbial, A.; Nioradze, N.; Parobek, D.; Shenoy, G. J.; Salim, M.; Amemiya, S.; Li, L.; Liu, H. Water Protects Graphitic Surface from Airborne Hydrocarbon Contamination. ACS Nano 2016, 10, 349-359
3. Kozbial, A.; Zhou, F.; Li, Z.; Liu, H. and Li, L. “Are graphitic surfaces hydrophobic”, Acc. Chem. Res., 2016, 49(12), 2765-2773
3:30 PM - NM02.07.04
Structural and Electron Diffraction Scaling of Twisted Graphene Bilayers
Kuan Zhang 1 , Ellad Tadmor 1
1 , University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractA novel continuum-atomistic framework is used to simulate the mechanics of twisted graphene bilayers. The results show an incommensurate to commensurate transformation to a structure consisting primarily of low energy AB and BA domains separated by SP solitons surrounding a high-energy AA domain. The system minimizes the size of AA domains through an additional uniform local twisting. We find that the local twisting at the AA domain scales with the initial rotation between the layers. Two regimes are observed. For small initial rotation, the twist angle is constant; for large initial rotation this value scales linearly with the applied rotation. The relaxation pattern at small initial rotation is associated with a novel electron diffraction pattern involving the appearance of weak satellite peaks. This pattern can be directly related to the scaling of the local twisting at the AA domain, and can be explained using a simple Gaussian rotation model. The angle-dependent scaling of the local twist at the AA domain and the complex diffraction patterns are both in quantitative agreement with experimental observations.
3:45 PM - NM02.07.05
Graphene Oxide Hydrogels and Aerogels with Tailored Morphology for Conductive 3D Networks
Dorsa Parviz 1 , Morgan Odom 2 , Smit Shah 2 , Micah Green 2
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 , Texas A&M University, College Station, Texas, United States
Show AbstractPorous 3D networks of graphene have potential applications in battery electrodes, chemical sensors, oil adsorption and catalysis. These networks exhibit high surface area and unique mechanical and electrical properties, depending on their preparation method, chemical composition, and morphology. In this work, a low temperature sol-gel technique was used to prepare graphene aerogels from graphene oxide (GO) nanosheets. Through this method, GO nanosheets simultaneously undergo reduction and crosslinking in presence of ammonia to form a hydrogel. The Critical point drying was performed on the hydrogels, and they were annealed at higher temperatures to produce graphene aerogels. Our studies indicated that the GO/ammonia ratio affects the reduction pathway and crosslinking of the nanosheets, which in turn determine the packing density and pore size distribution in the final aerogels. The nature of the covalent bonds and the inter-sheet “bridges” observed in the SEM images were investigated using various spectroscopic techniques. These aerogels possessed considerably high surface areas in the range of 900-1500 m2/g and electrical conductivities comparable to those of copper and silver.
Nanosheets morphology and aspect ratio is another factor that determines the morphology and properties of GO aerogels. To study the effect of theses parameters, we have used semi-spherical crumpled graphene oxide (cGO) particles as the precursor for aerogel preparation. cGO particles were produced by spray drying aqueous GO dispersions. During this process, the 2D nanosheets are crumpled into 3D semispherical particles. Usage of these cGO particles instead of flat GO nanosheets led to a higher degree of crosslinking and packing density in a 100% cGO aerogel. A slight increase in the surface area (1600 m2/g) was also observed in this sample. The synergistic effects of mixed GO/cGO precursors on the structure and properties of aerogels were also explored and characterized.
4:00 PM - *NM02.07.06
Biomass-Derived Activated Carbon Scaffolds for Electrochemical Energy Storage
Xiaodong Li 1
1 , University of Virginia, Charlottesville, Virginia, United States
Show AbstractWe converted cotton, banana, recycled paper, and wheat flour into highly porous, conductive activated carbon scaffolds for advanced energy storage applications via a low-cost and high throughput manufacturing process. The activated carbon scaffolds were coated with highly dense carbon nanotubes and/or graphene. Biomass-derived carbons are effective in improving supercapacitor’s energy density and in blocking the dissolution of reaction intermediates in lithium sulfur batteries. In addition, biomass derived carbons provide scaffolds for depositing active materials such as metal oxides for supercapacitors, and for hosting sulfur in lithium sulfur batteries to manipulate the “shuttle effects” of polysulfides and improve the utilization of sulfur. Using biomasses is definitely the right track towards making renewable carbon materials for future energy storage devices.
4:30 PM - NM02.07.07
Doping and Reduction of Graphene Oxide Using Chitosan-Derived Volatile N-Heterocyclic Compounds for Metal-Free Oxygen Reduction Reaction
Subodh Kumar 1 , Gilbert Daniel Nessim 1
1 , Bar Ilan University, Ramat Gan Israel
Show AbstractWe developed a fast, simple, scalable and safe method for the metal-free reduction and nitrogen-doping of graphene oxide (GO) using volatile nitrogen-containing heterocyclic compounds. In this method, chitosan and graphene oxide were simultaneously annealed without making any physical contact between them under a flow of argon using chemical vapor deposition (CVD). Based on the established knowledge of chitosan thermal decomposition, in-situ formed volatile nitrogen-containing heterocyclic compounds interact with graphene oxide to produce N-doped reduced graphene oxide (NrGO). In order to study the effect of temperature on the nitrogen content distribution and on the carbon/oxygen ratio, we annealed the graphene oxide and chitosan at 300, 450 and 600 °C. We fully characterized the synthesized materials (NrGOs) by XPS, Raman, FT-IR, HR-SEM, AFM, XRD and UV–Vis techniques. On the basis of XPS analysis, we achieved the highest nitrogen-doping level at 4.3 atom % at 450 °C with an atomic ratio of C/O as high as 16, which, to our knowledge, is the highest value reported so far at this temperature. Electrochemical characterizations demonstrate electrocatalytic activity of this NrGO towards the oxygen reduction reaction (ORR) in alkaline electrolytes, with a high reaction onset potential of 0.78 V vs. RHE.
4:45 PM - NM02.07.08
Improving Graphene-Metal Contacts—Thermal Induced Polishing
Eliezer Oliveira 1 , Ricardo Santos 2 , Pedro Autreto 3 , Stanislav Moshkalev 1 , Douglas Galvao 1
1 , State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil, 2 Physics, University of São Paulo State (UNESP), Rio Claro, São Paulo, Brazil, 3 , Federal University of ABC (UFABC), Santo André, São Paulo, Brazil
Show AbstractGraphene is a very promising material for nanoelectronics applications due to its unique and remarkable electronic and thermal properties. However, when deposited on metallic electrodes the overall thermal conductivity is significantly decreased. This phenomenon has been attributed to the mismatch of the interfaces and contact thermal resistance. Experimentally, one way to improve the graphene/metal contact is thorough high-temperature annealing. Recently [1], excellent results for improving thermal conduction were achieved using laser heating, but the detailed mechanisms behind these processes remain unclear. In order to address these questions, we carried out fully atomistic reactive molecular dynamics simulations (MD) using the REAX force field, as available in the LAMMPS [2] package. We investigated the interactions between multi-layer graphene and metallic electrodes (nickel) under (thermal) annealing. Our results [3] show that the annealing induces an upward-downward movement of the graphene layers, causing a pile-driver-like effect over the metallic surface. This graphene induced movements cause a planarization (polishing-like effect) of the metallic surface. In this way, the effective graphene/metal contact area is increased, which can explain the experimentally observed improvements of the thermal and electric conductivities [1].
[1] V. A. Ermakov et al., Nanotechnology 24 (2013) 155301.
[2] http://lammps.sandiv.gov.
[3] R. Paupitz, E. F. Oliveira, P. A. S. Autreto, S. Moshkalev, D. S. Galvão - Submitted
NM02.08: Poster Session II
Session Chairs
Thursday AM, November 30, 2017
Hynes, Level 1, Hall B
8:00 PM - NM02.08.01
Fluorescent Single Wall Carbon Nanotube Microarray for Label-Free, Real-Time Biomolecular Detection and Binding Kinetic Analysis
Juyao Dong 1 , Michael Strano 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractA label-free, real-time, multiplexed detection method is desired for biomolecular sensing for their high sensitivity, the capacity for kinetic analysis and the short processing time. We present here an optical microarray platform based on fluorescent single wall carbon nanotubes that has integrated all these features. The microarray constructed are made of carbon nanotubes dispersed on the glass substrates and has a spot density of ~300 spots/cm2. The nanotubes are non-covalently modified with a chelating group to immobilize Cu2+ ions and subsequently the histidine-tagged molecular recognition sites, in order to perform specific detection. As a proof-of-concept, a group of immunoglobulin-binding proteins is integrated as capture proteins and the sensor responses towards the antibody analytes are recorded in real-time. Not only does the microarray quantitatively respond to the analyte with various concentrations, it also provides rich binding kinetics of the analyte, using a few micro liter of sample. Moreover, when sensors modified with different capture proteins are integrated into the same microarray, they demonstrated specific recognition of the target analyte based on the interaction kinetics. We envision this platform will open a new path to examine multiple biomolecules with interaction kinetics, for bioanalytical applications such as pharmaceutical quality control and biomarker detections.
8:00 PM - NM02.08.02
Template-Assisted Macroscopic Patterning of Au Nanoparticle-Decorated Reduced Graphene Oxide by Controlled Dynamic Self-Assembly
Seok Hee Kang 1 , Suck Won Hong 1
1 , Pusan National University, Busan Korea (the Republic of)
Show AbstractOne-dimensional (1DW) and two-dimensional (2D) carbon nanomaterials such as single-walled carbon nanotubes (SWNTs) and graphene have received great attention due to their remarkable electrical and physical properties. The demonstration of synthesizing these carbon nanomaterials has been progressed by chemical vapor deposition (CVD) process on metallic surfaces which is an inexpensive and robust way to produce high quality of carbon nanotubes and sheets of graphene. In addition, besides of this technique, the exfoliation of graphite with strong oxidants has been explored to prepare a suspension of individual two-dimensional (2D) graphene oxide (GO) nanosheets dispersed in various types of solvents. Thus, this colloidal suspension can readily be employed in a wide range of promising potential applications such as transparent electrodes, solar cells, optoelectronic devices and biological sensors. One major challenge is to assemble such individual nanosheets on defined areas of surfaces forming specific structures. Thus far, a variety of techniques such as Langmuir-Blodgett assembly, vacuum filtration, dip-coating, spraying, and spin casting process have been developed to allow the formation of carbon nanostructures at the micro and nanoscale.
Here, we describe a simple and facile one-step process to achieve patterned arrays of chemically reduced graphene oxide (rGO) on a substrate with precisely controllable manner over large areas. By confining a drop of rGO solution in a restricted geometry composed of a moving-roll on a flat substrate, the self-organized rGO patterns were fabricated on a SiO2/Si substrate through the combination process of coffee-ring effect and cyclic stick-slip motions. In addition, a simple modification of rGO with Au nanoparticles by in-situ synthesis process functionalized a patterned rGO array into the biologically activated surfaces for the spontaneous assembly of thiolated DNA molecules. Finally, we successfully demonstrated hierarchically well-ordered structures composed of rGO using a self-assembly process and the patterned arrays of DNA were prepared for bio-sensing applications. This suggests that graphene-based substrates decorated with a unique nanomaterial i.e., the nanoparticle can be used as functional biomaterials for sensors or other biomimetic applications.
8:00 PM - NM02.08.03
Graphene Oxide Local Reduction by Laser Irradiation for Temperature Sensor Application
Vladislav Kondrashov 1 , Nikolay Struchkov 2 , Vladimir Nevolin 2 , Albert Nasibulin 1 3
1 Center of Photonics and Quantum Materials, Skolkovo Institute of Science and Technology, Skolkovo Village Russian Federation, 2 Department of Electronics and Computer Technologies , National Research University of Electronic Technology (MIET), Zelenograd Russian Federation, 3 Department of Applied Physics, Aalto University, Espoo Finland
Show AbstractReduced graphene oxide (rGO) is a promising material for optical and electrical applications including sensors and wearable electronic. Here, we demonstrate fast and cheap ready-made technology for temperature sensor device manufacturing with a minimum number of operations, where a solid-state laser is used to create a thermistor chip - an electronic device on a dielectric substrate. This method allows easily to isolate conductive pathway and to manufacture conductive, resistive and semiconducting elements in one technological step as well as to create a thermistors matrix. Moreover, our method allows to control the GO reduction qality by varying the processing parameters and thus controlling the material properties critical for thermistors such as resistance and temperature coefficient of resistance.
We use the Ar/O2 mixture for the background environment during the reduction process. The Hammers method was used for prepare graphene oxide suspension. Graphene oxide thick films (up to 1 um) were obtained by drop-casting on different substrates such as Si/SiO2, glass, PET and PDMS. We use 445 nm solid-state laser with controllable output power by pulse weight modulation of diode pump solid state laser current for local reduction. Reduced graphene oxide quality was determined by Raman spectroscopy (relative intensity of the Raman peaks ID ~1350 cm-1 I2D ~2700 cm-1) and sheet resistance measurements. We have obtained experimental dependences of rGO quality as functions of Ar/O2 partial pressure ratio and laser irradiation energy density in the range from 0.2 to 20 kJ/cm2. Optimization of process parameters allowed us to obtain rGO traces with ~0.4 μm thickness and 200 Ohm/sq sheet resistance.
We found the temperature dependence of the reduced GO film resistance. Fabricated thermistor have temperature coefficient of resistance (TCR) about -7.82×10-4 K-1. The change in resistance of the resulting structure was -9.7 Ohm/K, in range from 0 to 90 °C this dependence has a linear form. We also study the TCR dependence on the rGO quality. The number of the functional groups left in the rGO influences to the structure temperature sensitivity. In this case, it is possible to obtain different thermistors in a single process with controlled TCR parameters.
This work was supported by Skoltech NGP Program (Skoltech-MIT joint project).
8:00 PM - NM02.08.04
Simple Two-Step Preparation of Reduced Graphene Oxide and Their Application in Organic Solar Cells as Interfacial Layer
Jong-Jin Park 1 , Minji Kang 1 , Sehyun Lee 1 , Youn-Jung Heo 1 , Dongseong Yang 1 , Dong-Yu Kim 1
1 , Gwangju Institute of Science and Technology, Gwangju Korea (the Republic of)
Show AbstractGraphene-based materials have been tremendous interest due to their excellent mechanical and electrical properties. Among them, graphene oxide (GO), which chemically exfoliated from graphite, is possible to solution process in aqueous solutions owing to having oxygen-containing functional groups (ketone, carboxyl, epoxide, and hydroxyl) on its basal plane and edges. Moreover, they are active site for reduction of GO and covalent functionalization of GO with small organic molecules or inorganic nanomaterials. For these reasons, GO have been researched in many applications such as polymer composites, biomedical, and energy-related materials. In particular, reduced graphene oxide (rGO) reduced by functionalized hydrazine from GO is promising alterative material to poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as an interfacial layer in solar cells because it allowed the controllability of electronic properties through versatile functionalization and can improve the long-term stability of solar cells. However, rGO has limitation of selecting solvent for dispersion because of very low dispersibility to organic solvent, so it is restricted applying at solar cells of various structure as an interfacial layer. Therefore, more extensive research is required about controlling the dispersibility of rGO in order that rGO apply to various types of solar cells. In this study, we introduce two different functional groups on the rGO surface via using a simple two-step reduction method in order to control the dispersibility of rGO while maintaining their electrical properties. rGO synthesized by two-step method (TSrGO) is well dispersed in common organic solvents such as chlorobenzene and butanone. The structural, optical, and thermal properties of TSrGO was characterized by Infrared spectroscopy, EA, XPS, UV-vis spectroscopy and TGA and their work function was estimated by UPS. Finally, we investigated the effect of TSrGO on device performance and long-term stability through applying TSrGO to various types of solar cells.
8:00 PM - NM02.08.05
Field-Effect Transistor-Based Carbon Nanotube Chemical Sensors
Vera Schroeder 1 , Suchol Savagatrup 1 , Timothy Swager 1
1 Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractVera Schroeder, Suchol Savagatrup, and Timothy M. Swager
Carbon nanotube-based chemical sensors are a promising alternative to established analytical methods for monitoring the concentration of toxic gases. These sensors are highly selective, inexpensive, functional under low power with real-time detection, and modifiable to target specific analytes. Herein, we describe the development of a platform for voltage-activated chemiresistive gas detection based on covalently functionalized single-walled carbon nanotubes (SWCNTs) decorated with voltage-responsive chemical selectors. The selectivity arises from the recognition of CO by an iron-metalloporphyrin anchored to the pyridyl-functionalized SWCNTs. We demonstrate that the sensor is highly selective towards CO over oxygen, nitrogen, and carbon dioxide and that it is robust to humidity and operational in air. The affinity of the iron-metalloporphyrin-functionalized nanotube towards CO can be modulated through the applied gate voltage. UV-Vis spectroscopy and differential pulse voltammetry indicate that increased sensitivity of the sensor towards CO arises from an in situ reduction of FeIII to FeII. These findings demonstrate the potential of a voltage-activated recognition in SWCNT-based sensors.
8:00 PM - NM02.08.06
Ultrafiltration Membranes Having Hydrophilic and Antibacterial Properties Fabricated from the Aminated Polyethersulfone and the Surface Treated Carbon Nano-Onions
Hyejin Park 1 , Somin Lee 1 , Jeoung Ung Nam 1 , Chang Keun Kim 1
1 , Chung-Ang University, Seoul Korea (the Republic of)
Show AbstractAn ultrafiltration membrane with high water flux and antibacterial properties was prepared from aminated poly(ethersulfone) (PES-NH2) and carbon nano-onions (NO) containing various functional groups. Nitration of PES and the reduction of nitro groups in the PES were performed to prepare PES-NH2. NO prepared from the nanodiamonds (ND) by the thermal annealing was functionalized with chemicals including amine, carboxylic acid, and thionyl chloride groups. The PES and PES-NH2 membranes did not exhibit antibacterial activity, whereas the PES membranes containing functionalized NO exhibited antibacterial activity, regardless of the functional groups on the NO. The solute rejection of the PES-NH2/NO membrane was nearly identical to that of the PES membrane. The water flux of the PES-NH2/NO membrane was much higher than that of the PES membrane. Membranes exhibiting antibacterial effectiveness, improved water flux, and antifouling characteristic without changes in solute rejection could be produced by hybridizing PES-NH2 and the functionalized NOs.
8:00 PM - NM02.08.07
Complementary Hybridization of Molybdenum Disulfide and Carbon Nanotubes for High-Performance Flexible Gas Sensors
Sung Ho Kim 1 2 , Sung Myung 1 , Wooseok Song 1 , Sun Sook Lee 1 , Jongsun Lim 1 , Ki-Seok An 1
1 , Korea Research Institute of Chemical Technology (KRICT), Daejeon Korea (the Republic of), 2 Advanced Materials Engineering, Sungkyunkwan University Advanced Institute of NanoTechnology, Suwon Korea (the Republic of)
Show AbstractLow dimensional materials such as single-walled carbon nanotube (swCNT) and molybdenum disulphide (MoS2) recently received a great deal of attention due to their remarkable mechanical, electrical, chemical and optical properties. There are many interests in hybrid films research for properties improvements and applications based on low dimensional materials. In this presentation, we fabricated a novel MoS2 and swCNTs hybrid films which applied to chemical gas sensors with excellent flexibility and highly-sensitive. In this hybrid system, the swCNTs were employed for improving their flexibility and surface area. The porphyrin-type organic promoter layer was used to obtain uniform MoS2 layers. The hybrid films were synthesized by thermal chemical vapor deposition (TCVD) and transferred to flexible polyethylene terephthalate (PET) films for fabricating flexible gas sensors. As a result, the hybrid film possessed high flexibility and optical transmittance (92.83% at 550 nm) and the hybrid film-based gas sensors revealed improved sensitivity for NO2 or NH3 gas, which was higher than that of solely MoS2. Our results suggest that a hybrid film could be used as next-generation flexible chemical sensors based on 2D materials.
8:00 PM - NM02.08.08
Preparation of Nitrogen-Doped Nano-Onions as Efficient Metal-fRee Catalysts for Oxygen Reduction Reaction
Somin Lee 1 , Hyejin Park 1 , Jeoung Ung Nam 1 , Chang Keun Kim 1
1 , Chung-Ang University, Seoul Korea (the Republic of)
Show AbstractNitrogen-doped nano-onions (NNO) were fabricated as non-precious catalysts for oxygen reduction reaction (ORR). The nano-onions (NO), spherical graphitic particles, were prepared by annealing of nanodiamond (ND). Oxidized NO (ONO) was prepared from NO via Hummers’ method and the oxygen content of the ONO was varied by controlling the reaction time of the Hummers’ method. The ONOs were mixed with urea, followed by pyrolysis to obtain the NNOs. The formation of NO was confirmed by Raman spectroscopy, X-ray diffraction analysis (XRD) and high resolution transmission electron microscopy (HR-TEM). X-ray photoelectron spectroscopy (XPS) analyses were conducted to confirm the formation of the NNO and characterize their active sites for the ORR. Rotating disk electrode (RDE) measurements were carried out to investigate the ORR activities of the NNOs. The NNOs exhibited higher onset and half-wave potentials than those of the NO, and the ORR activities of the NNOs were improved as the amount of the nitrogen-containing groups in the NNO increased. Moreover, the NNO showed high long-term durability and resistance toward methanol crossover during the ORR compared with the platinum-based catalysts.
8:00 PM - NM02.08.09
MoS2 Directly Grown on Graphene/Stainless Steel (304) Substrate Using Chemical Vapour Deposition for Water Splitting Application
Kovendhan Manavalan 1 , Eunji Han 1 , Ki-Joon Jeon 1
1 Department of Environmental Engineering, Inha University, Incheon Korea (the Republic of)
Show AbstractMolybdenum disulfide (MoS2), a hexagonally packed layered structure has attracted a lot of attention because of its unique spin orbit coupling, next generation switching, and opto-electronic devices. Moreover, it is earth abundant, stable, highly active, and widely reported as a promising HER electrocatalyst. Graphene, a two-dimensional carbon allotrope, is potentially attractive for electrochemical energy storage device and production. Among the various coating technologies, coatings with acid-resistant corrosiveness, while maintaining the characteristics of stainless steel is very important for researches. However, hardly there are few reports are available on the growth of graphene directly on stainless steel substrates. In this work, we have grown graphene directly onto the stainless steel (SS304) substrate via atmospheric pressure chemical vapor deposition (APCVD) and MoS2 was deposited over this graphene layer by a low pressure chemical vapor deposition. The presence of few layer graphene directly grown on stainless steel substrate was confirmed using Raman Spectroscopy. From Raman mapping it was confirmed that the defect ratio Id/Ig is very less. SEM image reveals the porous nature while XPS confirms the sample is free from impurity. From Raman spectra after 100 CV cycles in 1 M KOH, 0.5 H2SO4, 3.5% NaCl the three most intense features at 1351, 1576 and 2697 cm−1 confirms that the directly grown samples have a good corrosion resistance and stability. In addition to that from raman we observe the characteristic MoS2 peaks E12g (374 cm-1) and A1g (402 cm-1) assigned to the stretching vibration of MoS2. XPS confirms that the charge state of Mo is in 4+. The current density is 15 times higher for MoS2 when compared to stainless steel. Also for MoS2 the EIS decreases 1.5 times when compared to uncoated one. This confirms that the directly grown graphene is highly stable after 100 cycles and good HER activity was achieved. These results will be presented and discussed.
8:00 PM - NM02.08.10
Transition Metal Coordinated Nitrogen and Boron Co-Doped Highly Porous 3D Graphene Network as an Efficient and Durable Oxygen Reduction Reaction (ORR) Catalyst for Fuel Cell
Arpita Ghosh 1 , Ramaprabhu Sundara 1
1 , Indian Institute of Technology Madras (IIT Madras), Chennai India
Show AbstractFuel cells are one of the promising energy conversion devices providing high efficiency and low emission. The performance of this device limits by the sluggish oxygen reduction reaction (ORR) kinetics, which plays the crucial role to confine device performance in terms of power density as well as longevity. To overcome the sluggishness of the ORR, supported or unsupported noble metals have been playing the crucial role as cathode catalyst so far. But reducing the platinum usage and increasing its durability are the key hindrance towards the commercialization of fuel cells. Herein we report a novel material, synthesized in single step consists of nitrogen (N) and boron (B) co-doped highly porous graphene structure (BNG), that can be used as a catalyst as well as catalyst support material. The synthesis procedure has been optimized in order to increase the yield of B–C and N–C bonds over B–N species during in-situ boron and nitrogen co-doping which is crucial to determine the synergistic effect of both B and N dopants on ORR.
This material has been used as a metal free efficient ORR catalyst along with the incorporation of abundant transition metal (Fe) in the acidic medium for proton exchange membrane fuel cell (PEMFC). High concentration of dopant atoms makes it an ideal replacement of metal catalysts. Besides the porous network significantly increases the number of triple phase boundary (TPB) leads to superior fuel and catalyst utilization. Owing to its high surface area (~1000 m2 g-1) and enhanced pore size the faster diffusion of fuel leads to a reduction in mass transfer losses as well as enhanced power density. The catalytic activity of both the catalysts BGN and Fe/BGN has been investigated and compared with commercial Pt/C along with singly doped (nitrogen and boron) porous graphene in acid medium. Unlike the boron counterpart, it has been studied widely that introducing nitrogen atom in the sp2 carbon framework tunes the band gap as well as the electrical properties of graphene. The presence of graphitic and pyridinic nitrogen species coordinated with transition metal predominantly enhances the ORR activity. Similarly, being an electron deficient element, boron has the ability to induce electron density variation on the sp2 carbon lattice and accordingly favor ORR. The main contrast between the two dopants is, oxygen adsorption takes place on the carbon bonded to nitrogen whereas, in the case of boron, oxygen adsorbs directly on the boron sites. Effects of mass transfer, mass activity and the number of electron transfer on the kinetics of ORR were investigated with rotating ring disc electrode (RRDE) method. The hydrodynamic voltammograms were investigated to determine the kinetic parameters using the Koutecky–Levich equation. Polarization study has been carried out with the single cell measurement in order to estimate the durability, ohmic loss and efficiency of the fuel cell and discussed in conjunction with the half-cell results.
8:00 PM - NM02.08.11
Vertically Oriented MoS2 Nanoflakes and 3D Carbon Nanotube Hybrid Structure for Li-Ion Batteries
Eunho Cha 1 , Wonbong Choi 1
1 , University of North Texas, Denton, Texas, United States
Show AbstractRecently, non-graphene 2D material such as MoS2 has gained spotlight for their novel structure with potentials for high-energy storage devices. Thus, the development of advanced electrode materials has led to a performance enhancement of traditional battery system such as lithium ion batteries (LIBs). Here, we present novel binder-free MoS2 coated three-dimensional carbon nanotubes (3D CNTs) as an anode in LIBs synthesized by two-step CVD and magnetron sputtering processes. Scanning transmission electron microscopy analysis shows that vertically oriented MoS2 nanoflakes are strongly bonded to CNTs, which provide a high surface area and active electrochemical sites, and enhanced ion conductivity at the interface. The electrochemical performance shows a very high areal capacity of ~1.65 mAh cm−2 with an areal density of ~0.35 mg cm−2 at 0.5 C rate and coulombic efficiency of ~99% up to 50 cycles. The unique architecture of 3D CNTs–MoS2 is indicative to be a promising anode for next generation Li-ion batteries with high capacity and long cycle life.
8:00 PM - NM02.08.12
Functionalized Graphene/Semiconducting Carbon Nanotube Heterostructured Thin Film Transistors as Chemical Sensors
Zhiwei Peng 1 , Allen Ng 1 , Hyejin Kwon 1 , Peng Wang 1 , Chien-fu Chen 2 , Cheng Lee 1 , YuHuang Wang 1 3
1 , University of Maryland, College Park, Maryland, United States, 2 , National Taiwan University, Taipei Taiwan, 3 , Maryland Nanocenter, University of Maryland, College Park, Maryland, United States
Show AbstractSingle-walled carbon nanotubes (SWCNTs) have been proposed as promising materials for future electronic applications due to their outstanding properties, however covalent functionalization often destroys the intrinsic properties of SWCNTs, limiting their full realization in high-performance devices. Here, we demonstrate the fabrication of functionalized graphene/semiconducting SWCNT (T@fG) heterostructured thin film transistors and showcase their application as a chemical sensor. In this structural configuration, graphene acts as an atom-thick, impermeable layer to protect the underlying semiconducting SWCNT network even during a covalent chemical reaction. Meanwhile, such top-layer graphene is also covalently functionalized via facile diazonium chemistry to afford a high density of surface functional groups. The synthetic strategy presented in this work leads to the synergistic integration of conformal, high surface area functionalization on graphene surface with preserved SWCNT properties. As a result, the highly functionalized carbon-based T@fG hybrid structure exhibits excellent transistor properties with a carrier mobility and ON/OFF ratio as high as 64 cm2/Vs and 5400, respectively. To further demonstrate their use in potential applications, T@fG thin films are fabricated as aqueous ammonium sensors exhibiting a detection limit of 0.25 µM in a millimolar ionic strength solution, which is comparable with state-of-the-art aqueous ammonium nanosensors. The structural synthetic paradigm of T@fG may also lead the way toward the fabrication of multidimensional structures based on carbon nanomaterials for wider applications such as smart coatings, metal-free catalysis, and bioimaging.
8:00 PM - NM02.08.13
Excitation Wavelength Independent Multicolor Emission of Carbon Nanoparticles
Hua Wang 1 , Shengnian Wang 1 , William Yu 1
1 , Louisiana Tech University, Ruston, Louisiana, United States
Show AbstractCarbon nanoparticles often emit excitation wavelength dependent colors. It is highly desirable to have carbon nanoparticles with various bright color emissions that are excitation wavelength independent as the traditional metal chalcogenide quantum dots do. We have found a type of carbon nanoparticles which emit different color lights and the emissions are strictly excitation wavelength independent when they are dispersed in different solvents. Such unique and broad spectra solvatochromism can also be achieved when the same carbon nanoparticles are mixed with polymers as solid state phosphors and the solid state emissions are still excitation wavelength independent. These solid state carbon nanoparticles are able to be used as LED phosphors for various visible colors.
8:00 PM - NM02.08.14
Bio-Inspired Polymer Coating of Fluorescent Nanodiamond for Biomedical Applications
Haksung Jung 1 , Kyung Jin Cho 2 , Yeonee Seol 1 , Yasuharu Takagi 3 , Paul Roche 2 , Keir Neuman 1
1 , Laboratory of Single Molecule Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States, 2 , Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States, 3 , Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States
Show AbstractFluorescent nanodiamonds (FNDs) represent a new class of nanoparticles in the carbon family exhibiting superb physical and chemical properties. However, the surface of FNDs must be modified to prevent precipitation in physiological solutions and to facilitate functionalization with biomolecules for biological applications. Here, we introduce polydopamine (PDA) encapsulation of FNDs, which is inspired by the adhesion mechanism of marine mussels. The PDA shells can be further functionalized via Michael addition or Schiff base reactions with molecules presenting thiol or nitrogen derivatives. We demonstrate modification of PDA shells by thiol terminated polyethylene glycol (PEG) molecules that enhance colloidal stability in biological solutions and biocompatibility of PDA coated FND (FND@PDA). The PEGylated FND@PDA nanoparticles were utilized as fluorescent probes for cell imaging with immature bone marrow derived dendritic cells. The FND@PDA nanoparticles were taken up by the cells, while exhibiting reduced nonspecific membrane adhesion. The robust polydopamine encapsulation strategy that we present provides an avenue for the development of FND as multifunctional labels, drug delivery vehicles, and targeting agents for biomedical applications.
8:00 PM - NM02.08.15
Graphitization of Graphene Sheets Intercalated by Carbon Spheres for High-Performance Supercapacitor Electrodes
Zhipeng Wang 1 , Hironori Ogata 2 , Gong Wei 1 , Yanqing Wang 1 , Adavan Kiliyankil Vipin 1 , Gan Jet Hong Melvin 3 , Josue Ortiz-Medina 4 , Rodolfo Cruz-Silva 4 , Shingo Morimoto 4 , Yoshio Hashimoto 4 , Bunshi Fugetsu 1 , Ichiro Sakata 1 , Mauricio Terrones 4 5 , Morinobu Endo 4
1 , The University of Tokyo, Tokyo Japan, 2 , Hosei University, Tokyo Japan, 3 , Universiti Malaysia Sabah, Kota Kinabalu Malaysia, 4 , Shinshu University, Nagano Japan, 5 , The Pennsylvania State University, Pennsylvania, Pennsylvania, United States
Show AbstractDue to their excellent physicochemical properties, nanocarbons including fullerene, carbon nanotubes, graphene, and their derivatives have stimulated many researchers to explore their applications in flexible, portable, and wearable electronic devices, and high-performance energy conversion and storage systems. Among them, graphene, a two-dimensional atomic layer of hexagonal carbon atoms, is a dazzling star in the exploration journey of novel and promising applications. Until now, graphene has been synthesized by three main routes: chemical vapor deposition of carbonaceous gases, annealing of silicon carbide, and chemical exfoliation of graphite. Compared to the other two counterparts, the chemical exfoliation technique has some advantages such as easy mass production and low cost for graphene synthesis with a reduction process of graphite/graphene oxide to graphene. However, this technique could achieve only partial reduction of graphite/graphene oxide and encounter the problems of an agglomeration of graphene sheets during the drying of the solution, further affect their performances in the practical applications. Thus, it is highly desirable to develop a new synthetic approach to solve the issues and enhance the performances. For example, intercalation of other materials between two graphene sheets to form the composites is popular in the application of supercapacitors.
In this work, we employed a hydrothermal technique to fabricate a composite consisting of graphene sheets and carbon spheres, and graphitized our samples at high temperatures. Graphitization here could further remove the oxygen species of graphene sheets and carbon spheres, increase the conductivity of the composites, and adjust the microstructures of carbon spheres. The detailed results and discussion will be presented in the coming conference.
8:00 PM - NM02.08.16
Laser-Induced Graphene—Bio-Mass Derived Polymer Precursors and New Electrochemical Device Architectures
Dilara Yilman 1 , Irene Lau 1 , Nathan Chan 1 , Michael Pope 1
1 , University of Waterloo, Waterloo, Ontario, Canada
Show AbstractLaser patterning of commercially available polymer substrates (ex. Kapton tape) to produce laser-induced graphene has become a simple and versatile platform for the rapid prototyping of flexible energy storage devices. In this talk, we will discuss the development of polymer composites based on poly(furfuryl alcohol) (PFA) which is an inexpensive, waste biomass-derived polymer known to be a good carbon former. We demonstrate that composites of PFA and graphene oxide (GO) are capable of being converted into electrodes which are higher in surface area and density compared to electrodes obtained from Kapton or graphene oxide films alone. Using these materials we are able to create flexible, interdigitated supercapacitors with area capacitance as high as 100 mF/cm2. These promising results suggest that PFA-based composites could be both a more sustainable and less expensive substrate for more effective laser-scribing than specialty polyimides. In addition to the use of new materials, we will describe our more recent efforts to create flexible, high energy density, lithium-sulfur batteries using interdigitated arrays created by the laser-scribing method. We demonstrate a method to selectively nucleate/grow sulfur on laser-scribed cathodes as well as the ability to electroplate lithium metal directly onto laser-induced graphene. While a promising device for applications, the system is also useful for in situ investigations of battery operation.
8:00 PM - NM02.08.17
Designing Wetting Anisotropy on Layered Materials near the Molecular Scale Using Noncovalent Lying-Down Phases of Polymerizable Amphiphiles
Shelley Claridge 1
1 , Purdue University, West Lafayette, Indiana, United States
Show Abstract
Many strategies for noncovalent functionalization of layered materials such as graphene are based on lying down lamellar phases of amphiphiles. These highly ordered yet conformationally flexible ligand layers present alternating stripes of strongly hydrophilic and hydrophobic surface chemistries near the molecular scale (stripe periodicities ~5 nm). This unusual, chemically orthogonal interface architecture suggests the opportunity to direct wetting at unusually short length scales relevant to patterning in emerging hybrid material applications. However, significant aspects of directing wetting using a highly anisotropic, noncovalent monolayer chemistry require elucidation to enable control. For instance, ionizable functional groups such as carboxylic acids commonly used to control interfacial wettability begin to undergo significant changes in their wetting behavior when the surrounding environment is nonpolar -- at the length scales relevant in these interfaces, such effects become somewhat analogous to dimensional confinement effects observed in inorganic materials. As a result, selecting strongly wetting, topographically protruding functional headgroups becomes significant. We demonstrate control over both isotropic and anisotropic interfacial wetting from macroscopic to near-molecular scales using noncovalent monolayers of polymerizable amphiphiles -- this strategy brings significant new functionality to carbon nanomaterial interfaces.
8:00 PM - NM02.08.18
Tribological Investigation of Lubricants Containing Crumpled Graphene
Gordon Krauss 1 , Albert Dato 1 , Matthew Siniawski 2 , Jacob Garcia 1 , Ragini Kothari 1 , Sitoe Thiam 1
1 , Harvey Mudd College, Claremont, California, United States, 2 Mechanical Engineering, Loyola Marymount University, Los Angeles, California, United States
Show AbstractAnisotropic carbon nanomaterials have been shown to be promising lubricant additives that are capable of reducing friction and protecting surfaces from wear in tribological applications [1, 2]. Low concentrations of suspended graphene additives (.01 and .1 % by mass) are investigated as friction and wear modifiers in this study. This work investigates and compares gas-phase-synthesized graphene [3-5] to commercially available graphene nanoplatelets suspended in rapeseed oil during pin-on-disk testing. Previous studies have found a benefit to processing of flat graphene such that it is morphologically changed into a “crumpled” shape. Gas-phase-synthesized graphene is crumpled as a result of the synthesis process. As a result, gas-phase-synthesized graphene consists of folded and randomly oriented graphene structures. The wear and sliding friction of a 52100 steel ball counter-surface is measured during testing in neat rapeseed oil, in low concentrations (.01% wt.) and higher concentrations (.1% wt.). While significant difference is noted with respect to wear at even the low concentrations, friction differences are not apparent over the conditions tested.
[1] Berman, D., Erdemir, A. & Sumant, A.V. Graphene: a new emerging lubricant. Materials Today 17 (2014) 31-42;
[2] Dou, X., Koltonow, A.R., He, X., Jang, H.D., Wang, Q., Chung, Y. & Huang, J. Self-dispersed crumpled graphene balls in oil for friction and wear reduction. Proc. Natl. Acad. Sci. 113 (2016) 1528-1533;
[3] Dato, A., Radmilovic, V., Lee, Z., Phillips, J. & Frenklach, M. Substrate-free gas-phase synthesis of graphene sheets. Nano Lett. 8 (2008) 2012-2016;
[4] Dato, A. et al. Clean and highly ordered graphene synthesized in the gas phase. Chem. Commun. (2009) 6095-6097;
[5] Dato, A. & Frenklach, M. Substrate-free microwave synthesis of graphene: experimental conditions and hydrocarbon precursors. New J. Phys. 12 (2010) 125013;
8:00 PM - NM02.08.19
Anisotropic Fracture Toughness in Graphene Using Molecular Dynamics
Venkateswaran Santhanam 1
1 , University of Delaware, Newark, Delaware, United States
Show AbstractThe present study investigates the mechanical properties (stiffness, toughness and strength) of a monolayer graphene sheet deforming under uniaxial tension. We use a combination of atomistic simulations and mathematical calculations to extract the anisotropic behavior of the fracture toughness in graphene. To investigate the fracture toughness, ten chiral angles are considered ranging from 0° (Zigzag) to 30° (Armchair). A graphene sheet with an edge crack of finite length is considered for the simulations wherein multiple strain rates are applied. It was found that the maximum stress (strength) increases with the increase in chiral angle, but not at a linear rate. In fact, a quadratic trend is observed with both strength and toughness of the material. The quadratic trend is due to the change in crystallography in front of the crack tip with respect to anisotropy. This change has a direct influence on the local energetics during crack propagation and therefore on the strength. It is also found that the fracture toughness in graphene is only dependent on the strength of the material, and not the other mechanical properties. This is because the Young's Modulus in graphene is isotropic irrespective of the chirality. A 19.7% increase in the strength of the material during crack propagation was found for an applied strain rate. As the fracture toughness is related to the square of the strength value of the material, there is a 43.3% jump in fracture toughness. Similar results are found for the other strain rates applied as well, proving that the fracture toughness is indeed anisotropic
8:00 PM - NM02.08.20
Schwarzites for Natural Gas Storage—A Grand-Canonical Monte Carlo Study
Daiane Damasceno Borges 1 , Douglas Galvao 1
1 , University of Campinas, Sao Paulo Brazil
Show AbstractSchwarzites are 3D porous carbon-based structures idealized by Mackay and Terrones [1]. They proposed that inclusion of carbon rings with more than six atoms in a graphite hexagonal mesh could produce stable periodic graphitic arrangement with curvature analogous to zeolites. These structures exhibit negatively curvature topologies with tunable porous size and shape and interesting adsorption properties, which make them natural candidates for applications such as CO2 capture, H2 storage and filtration [2,3]. Following this motivation, we have carried out Grand-Canonical Monte Carlo simulations to study the adsorption properties for some Schwarzites structures, namely gyroid G688 and G8bal and primitive cells P688 and P8bal [4]. In this presentation, we will show our computation predictions on natural gas adsorptive capacity and selectivity process occurring inside these Schwarzites. A detailed analysis is provided on the preferential arrangement of the confined adsorbates, as well as the energetics of the host/guest interactions. Our results [5] show that P8bal is the most promising material with very high CO2, CH4 and CO adsorption capacity of 10.5, 9.2 and 6.3 mmol/g, respectively, with the advantage of having low pressure saturation (~1bar). The P688 is interesting for H2 storage due to its significantly higher H2 adsorption enthalpy value (~20kJ/mol) when compared to others porous materials in the literature. Moreover, our results show that these structures are highly hydrophobic, which could be exploited for removing natural gas from humidified environments.
[1] A. L. Mackay and H. Terrones, Nature, v352, 762 (1991).
[2] R. Babarao et al., Langmuir v23, 659 (2007).
[3] P. Kowalczyk et al., Phys. Chem. Chem. Phys. v9, 1786 (2007).
[4] F. Valencia et al., New J. Phys. v5, 126.1 (2003).
[5] D. D. Borges and D. S. Galvao - submitted.
8:00 PM - NM02.08.21
Characterization of Wafer Scale Monolayer Graphene Using Azimuthal RHEED
Yu Xiang 1 , Xin Sun 1 , Fawen Guo 1 , Zonghuan Lu 1 , Dibyajyoti Mohanty 2 , Weiyu Xie 1 , Morris Washington 1 , Ishwara Bhat 2 , Shengbai Zhang 1 , Toh-Ming Lu 1 , Gwo-Ching Wang 1
1 Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 Department of Electrical, Computer and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractGraphene and transition metal dichalcogenide (TMDC) monolayer materials have attracted world-wide interest among researchers and have stimulated intense study of their unique fundamental properties and potential applications. One of the central issues is their structural determination. The challenge is that the signal from the minimal amount of monolayer material is easily overwhelmed by that from the substrate which the monolayer is grown on. Conventionally, one can transfer the monolayer material from a substrate to a transmission electron microscope (TEM) grid and examine its structural property or use low energy-electron diffraction (LEED) to examine its structure on a conductive substrate in situ. In this report, we present a new application of an old surface sensitive technique, reflection high-energy electron diffraction (RHEED), to azimuthally map out the reciprocal space structure of polycrystalline and single crystal monolayer graphene on amorphous SiO2 substrates where LEED is not applicable [1]. We show the number of orientation domains and quality of both the pre-transferred graphene on Cu(111) and post-transferred graphene on an amorphous SiO2 substrate. We demonstrate that structural information can be obtained from wafer scale monolayer materials even when they are transferred on amorphous substrates. The graphene layer can serve as a template to grow semiconductor materials and be characterized by azimuthal RHEED. Examples are epitaxial SnS [1], CdS [2], and CdTe [3] through van der Waals epitaxy despite the large lattice mismatch. This azimuthal RHEED technique can also be used to characterize other layered materials such as TMDCs on any amorphous substrates.
This work is supported by the NSF DMR-1305293, the NY State Foundation of Science, Technology and Innovation (NYSTAR) through Focus Center-New York C130117, and Rensselaer.
[1] Reflection high-energy electron diffraction measurements of reciprocal space structure of 2D materials, Y. Xiang, F.-W. Guo, T.-M. Lu and G.-C. Wang, Nanotechnology 27, 485703 (2016).
[2] van der Waals epitaxy of CdS thin films on single crystal graphene, X. Sun, Z. Lu, W. Xi, Y. Wang, J. Shi, S. Zhang, M.A. Washington, T.-M. Lu, Appl. Phys. Lett. 110, 153104 (2017).
[3] van der Waals epitaxy of CdTe thin film on graphene, D. Mohanty, W. Xie, Y.-P. Wang, Z. Lu, J. Shi, S.-B. Zhang, G.-C. Wang, T.-M. Lu, and I.B. Bhat, Appl. Phys. Lett. 109, 143109 (2016).
8:00 PM - NM02.08.22
Many-Body Effects on Anisotropic Mechanical Behavior in Graphene
Tousif Ahmed 1 , Md Hossain 1
1 Mechanical Engineering, University of Delaware, Newark, Delaware, United States
Show AbstractDuring uniaxial loading, graphene undergoes both bond-stretching and bond-bending deformation that involves two-body interactions and three-body interactions, respectively. However, how these many-body interactions affect the mechanical properties of graphene along its different crystallographic directions is not well understood. In this study, we delved deeper into this important subject to find an answer to that question from atomistic perspective. We carried out Molecular Dynamics (MD) simulation using a newly developed Stillinger-Weber interatomic potential (which accounts for both two-body stretching and three-body bending deformation effects) and investigate the role of anisotropy on toughness and strength in graphene for a set of chiral angles.
At 0o chiral angle, uniaxial deformation stretches all bonds. Bonds which are parallel to the loading direction stretch much more (13.3% higher at 20% macroscopic strain) compared to the rest of the bonds, and they reach the maximum force thus subject to rupturing earlier. With increasing chiral angle, one bond per atom, perpendicular to the loading direction, is subjected to contraction due to the Poisson's effect, and the other two bonds undergo stretching deformation. As a result, at higher chiral angle, bond stretching enhances toughness by deforming more bonds and bond bending enhances toughness by undergoing higher bending deformations. Graphene lattice therefore stores and releases the highest energy when loaded at 30o chiral angle (or along the arm-chair direction) due to the participation of more number of bonds in the deformation process (10% higher strength and 56% higher toughness than zig-zag).
Additionally, a critical chiral angle (θt = 12o) has been identified. The positive and negative bending modes of angular deformation switch their pattern at the critical angle. For chiral angles less than this critical angle, bonds per atom experience twice as much positive bending than negative bending. On the contrary, chiral angle greater than the critical angle exactly opposite outcome is observed.
We find that the variation of two-body and three-body energy per atom is non-linearly related to the chirality of the lattice. This investigation reveals that the details of many-body interaction plays a mojor role in defining the anisotropic behavior of graphene.
8:00 PM - NM02.08.23
Graphene Growth on Uniaxial Tensile Strained Platinum Substrates
Grzegorz Hader 1 2 , Daniel Kaplan 2 , Greg Stone 2 , Venkataraman Swaminathan 2 , Eui-Hyeok Yang 1
1 , Stevens Institute of Technology, Hoboken, New Jersey, United States, 2 , US Army RDECOM ARDEC, Picatinny Arsenal , New Jersey, United States
Show AbstractThe synthesis of graphene on both platinum and copper substrates is well established and is showing great promise towards large-area industrial scale production. However, growth of graphene on platinum substrates shows promise over copper in that it can be reused for repeated growth, be grown at atmospheric pressure, allow for easier transfer to arbitrary substrates, and exhibits higher quality defect free nanosheets. In addition, the control of strain in nanosheets is of great significance and has shown to open a band-gap in graphene [1], increase sensitivity in resonators [2], and increase photocurrent generation [3]. Despite vast research in the synthesis of 2D materials, there has been little to no discussion on the controlled strain of 2D materials during the growth process. One reason, is due to the extreme temperatures needed for the decomposition of the nucleation gas, which makes incorporating instruments within the thermal chamber at high temperatures prohibitive.
To conduct uniaxial tensile strain of platinum foils during the growth of graphene, our research team has developed a Tensile Test Actuator (TTA), fabricated from 309 stainless steel. The TTA allows the platinum foil to be doubly clamped, suspended, strained, and placed within the thermal chamber during the synthesis of graphene by atmospheric pressure chemical vapor deposition. Growth is conducted within a furnace with three zone temperature control and utilizes mass flow controllers to control the nucleation gas methane (CH4) and precursor gas hydrogen (H2). Polycrystalline platinum foil from Sigma Aldrich with 99.9 wt% metal basis at 0.025mm thickness is used as the metal catalyst. The TTA is placed inside the furnace, along with a control sample, to allow for comparison between strained and unstrained conditions.
To investigate growth of graphene on uniaxial tensile strained platinum foils, characterization of the nanosheet structure is conducted utilizing Scanning Electron Microscopy (SEM) and Raman spectroscopy. SEM of the platinum foil under thermal tensile strain shows evidence of thermal fatigue, consisting of striations along preferential grain directions. Comparison of strain between the control foil and strained foil are conducted by Raman Spectroscopy by observing splitting of the G band and a downshift in the 2D band, for increasing strain. Further growth experiments are showing unique morphologies and crystal structure on strained and unstrained substrates.
1. He, X.G., L.; Tang, N.; Duan, J.; Xu, F.; Wang, X.; Yang, X.; Ge, W.; Shen, B., Shear strain induced modulation to the transport properties of graphene. Appl. Phys. Lett., 2014. 105.
2. Lee, S., et al., Electrically integrated SU-8 clamped graphene drum resonators for strain engineering. Applied Physics Letters, 2013. 102(15): p. 153101.
3. Feng, J., et al., Strain-engineered artificial atom as a broad-spectrum solar energy funnel. Nature Photonics, 2012. 6(12): p. 866-872.
8:00 PM - NM02.08.25
Production of Graphene Based Upconversion Material Assist Solar Cells
Ahmet Duru 1 , Halil Yavuz 1 , Idris Candan 2
1 , Yuzuncu Yil University, Ankara Turkey, 2 , Middle East Technical University, Van Turkey
Show AbstractUpconversion materials has been attracting considerable attention to advanced applications in several optoelectronic apllications such as solar cells, sensing detectors and bio sensing. Upconversion materials, usually consisting of crystals doped with lanthanide ions, can convert low-energy incident radiation into higher energy emitted radiation. Nanocrystalline dye sensitized solar cells (DSSC) technology efforts to improve the better alternative choice on solar cell technology. This study aims at finding low cost and highly efficient DSSC design and production methods via examination of effects of both photoanode structure and photon-electron generation mechanism on photoanode layers. This will contribute to the commercialization of DSSC technology. Graphene based material has a good properties than other inorganic based materials due to having easy obtained and less toxicity. Upconversion material (UPC) assist photoanode structure is examined in this study. Structural, topographical and chemical analyses were performed using XRD, SEM and EDS . 8.32% conversion efficiency has been found by using this UPC material in the production of fully sol-gel based DSSCs. For the first time in the literature, Graphane Based UPC were synthesized by sol-gel method and this synthesis was used on DSSCs in order to increase the interaction between the transparent conductive layer and photoanode layer. These particles showed better performance rate than the traditionally produced photoanode layer.
8:00 PM - NM02.08.26
Flexible Cellulose-Nanocarbon Paper Substrate Decorated with PZT—Sensor and Eletrochemical Properties
Neftali Carreno 1 , Ricardo Silva 1 , Bruno Noremberg 1 , Jose Alano 1 , Antoninho Valentini 2 , Fabiana Motta 3 , Tomasz Tanski 4
1 , Univ Federal-Pelotas, Pelotas - RS Brazil, 2 , Federal University of Ceara, Fortaleza, CE, Brazil, 3 , Federal University of Rio Grande do Norte, Natal, RN, Brazil, 4 , Silesian University of Technology, Gliwice Poland
Show AbstractThe present work aimed to growth a thin layer of lead zirconate titanate (PZT) particles on a flexible cellulose-nanocarbon substrate by microwaves-assisted hydrothermal synthesis (MHS). The substrates based on chemical functionalized of micro-nano cellulose structure attached to carbon nanotubes or graphene oxide, respectively. The first step is an extraction of the cellulose from the banana stem under autoclaving process followed by delignification and chemical whitening. To obtain the substrate the cellulose is hydrolyzed in the presence of chemical groups on carbon nanotubes or graphene surface. The hydrolysis is conducted for 4 hours in an ultrasonic bath and then the material is filtered and washed until it reaches neutral pH. To obtain the paper, this material is dispersed in water and this dispersion is used in a casting drying. The second step was realized by MHS, where occurred the growth of the PZT particles on the cellulose-nanocarbon paper. For this, the reactions were conducted with the substrate present inside the reactor along with the PZT precursors and placed into microwaves. Thus, we reported a simple, efficient and low-cost process to chemical transform the residue of fruit as source of cellulose to produce a promissory capacitive, conductive and flexible nanocarbon composite material. With these material was prepared a paper film used to design an electrode. The transformation was monitored by transmission image, X-ray diffraction, spectroscopy techniques and analysis of average particle size. The gas sensor property was evaluated by measuring the electric current front exposure the electrode to methanol as function of concentrations and temperatures. The composite developed presented electrochemical properties which were measured by impedance spectroscopy, charge/discharge, cyclic voltammetry, and it suggests numerous applications.
References:
[1] Kim JH, Yun S, Ko HU, Kim J (2013) A flexible paper transistor made with aligned single-walled carbon nanotube bonded cellulose composite. Curr Appl Phys 13:897–901. doi: 10.1016/j.cap.2013.01.036
[2] Yun S, Kim J (2011) Mechanical, electrical, piezoelectric and electro-active behavior of aligned multi-walled carbon nanotube/cellulose composites. Carbon N Y 49:518–527. doi: 10.1016/j.carbon.2010.09.051.
[3] Noremberg, B.S, Silva, R.M, Paniz, O.P., Alano, J.H., Gonçalves, MR.F, Wolke, SI, Labidi, J., Valentini, A, Carreño, N.L.V., From banana stem to conductive paper: A capacitive electrode and gas sensor, Sensors and Actuators B: Chemical, 240, 2017, 459–467.
8:00 PM - NM02.08.27
Preparation and Charterization of High Performance Activated Carbon Fibers by Vaccum Ultaraviolet Surface Treatment
Hiroyuki Kuwae 1 , Kazuaki Mizokami 2 , Seren Maeda 1 , Shuichi Shoji 1 , Jun Mizuno 3
1 , Waseda University, Shinjuku-ku, Tokyo, Japan, 2 , Nippon API Co., LTD, Yokohama city Japan, 3 , Institute for Nanoscience and Nanotechnology, Waseda University, Shinjuku-ku Japan
Show AbstractWe developed high perfomenace activated carbon fibers (ACFs) by vacuum ultraviolet (VUV) sruface treatments. Surface of pitch-based ACF was modified by VUV light (172 nm) exposure in the presence of oxygen gas. VUV surface treatment improved surface morphology of the ACF. X-ray photoelectron spectroscopy (XPS) results obtained increment of oxygen-containing polar functional groups. Atmospheric pressure ionization-mass spectrometry (API-MS) analysis showed that VUV treated ACF obtained oxygen adsorptivity. In addition, gas desorption reactions of VUV treated ACF became faster than that of untraeted one. These results indicates that VUV traeament for ACF is a promising method for improving ACF characteristics.
Activated carbon materials have been widly used in many appilications such as purification, gas absorbant, electronic materials, and gas storages. Compared with other activated carbon materials, ACFs have unique characteristics: well-defined porous structures, flexibility [1]. Previously, we proposed a novel surface modification technique for woody carbon materials by using VUV (172 nm) irradiation in the presence of oxygen [2]. Surface area of the treated material was increased by approximately 50%. VUV treatment effect is explained by following two mechanism: chemical bonds of the materials are cleaved directly by high energy of VUV light (696 kJ/mol); the materials are oxidized by singlet oxygen and ozone which generate from oxygen by VUV irradiation. In this study, we developed high perfomenace ACF by VUV treatment. Both the surface changes and gas adsorption/desorption characteristics of ACF caused by VUV treatment were investigated.
Pitch-based commercial ACFs were treated by VUV light of Xe excimer lamp for 10 or 60 min. The oxygen pressure in the VUV systems was 2.4 Pa. Gas adsorption characteritics were evaluated at room tempreture, and then samples were heating up to 100 °C to evaluate gas desorption characteristics using API-MS. The API-MS analysis was operated in ppb level using water, hydrogen and oxygen gas.
Surface changes of the ACFs were evaluated by SEM and XPS. From the SEM image, wavy sturutures were observed on the ACF surface without the treatment. After the treatment, the ACF surface became rough with the VUV irradiation. C1s spectra of XPS showed that intensity of C-C bonds were reduced with the treatement, and those of oxygen-containing polar functional groups were increased by 11%. Further, API-MS analysis showed that the VUV treated ACF adsorbed water, hydrogen and oxygen, while the untreated ACF adsorbed only water and hydrogen. In addition, gas desorption of VUV treated ACF became faster with increasing the treatement time. These API-MS results are considered to be caused by effects on surface morphorogy and chemical changes by VUV treatment. The proposed surface treatment is a promising method for fucntionalizing ACFs.
[1] M. Suzuki, Carbon 32 (1994) 577.
[2] T. Funabashi, et al., APL Mater. 1 (2013) 032104.
8:00 PM - NM02.08.28
Modeling of Porous Carbon Supported Titanium and Its Application for CO2 Uptake
Difan Zhang 1 2 , Michael Dutzer 3 , Tao Liang 2 , Alexandre Fonseca 4 , Krista Walton 3 , David Sholl 3 , Suresh Bhatia 5 , Susan Sinnott 2
1 Department of Materials Science and Engineering, University of Florida, Gainesville, Florida, United States, 2 Department of Materials Science and Engineering, The Pennsylvania State University, State College, Pennsylvania, United States, 3 School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 4 Applied Physics Department, State University of Campinas, Campinas, SP, Brazil, 5 School of Chemical Engineering, University of Queensland, Brisbane, Queensland, Australia
Show Abstract
Metals supported by various carbon materials have been widely studied for gas adsorption. In recent years, an incomplete etching of carbide precursors in experiments was found to produce porous carbide derived-carbons (CDC) with residual metals. Here, we developed a new approach for modeling titanium carbide derived-carbon (TiC-CDC) systems with residual titanium and investigated their CO2 uptake. In our approach, a porous carbide derived-carbon structure from previous work was modified by removing carbon, adding carbon and titanium atoms. These new atomic scale carbide-derived carbon structures were investigated using classical molecular dynamics simulations, and their pure CO2 gas adsorption isotherms were evaluated using grand canonical Monte Carlo simulations. The TiC-CDC system with residual titanium was modeled as weighted combinations of pure carbon CDC structures, CDC structures with titanium and a TiC crystalline structure. Our modeling is able to produce both structural properties and adsorption isotherms in accordance with experimental data. The fraction of different models in the systems successfully reveals the structural differences in various experimental TiC-CDC samples. The fully etched CDCs show effective capture of CO2 gas. The modeling also suggests that in partially etched TiC-CDC systems, the CDCs could act as a porous support for titanium, and the titanium accessible to CO2 gas at structural interfaces may provide significant interaction sites for CO2 and leads to more efficient overall gas adsorption. This work also show the applicability of the proposed approach to the study of structural modeling and gas uptake in other residual metal-based porous structures.
8:00 PM - NM02.08.29
Covalent Surface Modification of sp2 Hybridized Carbon Nanomaterials Using an Inverse Electron Demand Diels-Alder Reaction
Jun Zhu 1 , R. Lennox 1
1 Department of Chemistry, McGill University, Montreal, Quebec, Canada
Show AbstractCarbon nanomaterials, such as carbon nanotubes, graphite, and graphene have a number of fascinating electric, thermal, and mechanical properties. However, their applications often requires physical adsorption or covalent attachment of chemical entities. Covalent chemical modification method is particularly challenging due to the limited reactivity of the extended conjugated pi-system. We have thus applied the inverse electron demand Dies-Alder reaction (IEDDA) to the modification of single-wall carbon nanotubes (SWCNT) and highly ordered pyrolytic graphite (HOPG). Tetrazine-derivatived small organic molecules or ligand-capped metal nanoparticle/nanorods are shown to react with these sp2 hybridized carbon nanomaterials under ambient conditions. Site-specific modification can also be achieved via a microcontact printing method using tetrazine deterivatives as the “ink”.
8:00 PM - NM02.08.30
Mechanism Studies and Characterization of Carbon incorporation into Al Alloys by Electrocharging Assisted Process
Xiaoxiao Ge 1 , Lourdes Salamanca-Riba 1 , Christopher Klingshirn 1 , Manfred Wuttig 1 , Karen Gaskell 1 , Balu Balachandran 3 , Peter Zavalij 1 , Liangbing Hu 1 , Daniel Cole 2
1 , University of Maryland, College Park, Maryland, United States, 3 Energy Systems Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 , U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland, United States
Show AbstractThe incorporation of carbon nanostructures into aluminum alloys, such as Al6061 and Al7075, has the potential to further improve the mechanical, electrical and anti-corrosion properties of these alloys. Previously, we reported on a novel electrocharging process to incorporate up to 10.0 wt% carbon into the crystal structure of Al 6061 alloys to form a new material “Al Covetic”. In this method, a DC current (~ 150A) is applied to molten Al metal containing activated carbon particles in an enclosed inert environment. The carbon has been successfully incorporated in the Al matrix and proved to transform into graphitic structures containing a high percentage of sp2 bonding.
In this study, we focus on the mechanism of Covetics conversion. Our hypothesis is that the current induces a plasma of carbon ions (similar to the method of creating carbon nanotubes in water1). The high current density first facilitates ionization of the carbon atoms and migration of charged carbon atoms similar to “electromigration in a plasma”. Then, the current further induces polymerization and formation of graphitic chains and ribbons along preferential directions of the Al lattice, and propagates the graphitic structures inside the Al matrix. The dependence of the carbon ionization and crystallization on current density will be presented. This knowledge is essential to improve the present electrocharging technology and to develop a better method to fabricate homogenous alloys with improved properties. Samples have been made by the modified eletrocharging method to understand the mechanism for carbon incorporation. X-ray Photoelectron Spectroscopy (XPS), Raman mapping measurements and Electron Energy Loss Spectroscopy (EELS) have confirmed that more carbon is incorporated more uniformly and forming ordered graphitic structures using the modified method.
Alternative carbon sources, such as graphene sponge or carbon nanofibers, which are already crystalline, are used to obtain a network of carbon nanostructures that extends throughout the metal.
Conductive AFM (c-AFM) indicates higher local electrical conductivity of the Covetics compared to the parent alloys. Next, nanomechanical testing will be performed by depth sensing indentation and AFM elastic modulus mapping to relate the local mechanical behavior to the local structure. The electrical resistivity and thermal diffusivity will also be measured for the bulk Covetics material and compared with pure Al6061.
Reference:
1.Formation of carbon nanotubes in water by the electric-arc technique, H.W. Zhu, X.S. Li, B. Jiang, C.L. Xu, Y.F. Zhu, D.H. Wu, X.H. Chen Chem. Phys. Lett. 366, 664-9 (2002)
8:00 PM - NM02.08.31
Carbon Oxide Nanoparticle Synthesis via Plasma Source—A Catalyst For Vanadium Redox Flow Battery Application
Eugenio Rovera 1 2 , Francesco Fumagalli 1 , Matteo Zago 2 , Andrea Casalegno 2 , Fabio Di Fonzo 1
1 , CNST@Polimi, Milano Italy, 2 Energy, Politecnico di Milano, Milano Italy
Show AbstractVanadium redox flow battery (VRFB) is an emerging storage system that has been addressed as a credible technology to be coupled with smart grids, due to their unique features such as indipendence of power density (stack size) and energy capacity (tank size), reversible crossover that guarantees long lifetime, wide range of operating condition (allowing peak power delivery), and low maintenance.
Among all the drawbacks hindering the spreading of VRFBs the main one is related to sluggish electrodes kinetic.
The present work will demonstrate how carbon nano-particles (C-NP) treatment on commercial electrode are an effective method to increase kinetics through the increase of specific area and through the high electrochemical activity due to the density of defects on the surface of the nano-particle.
C-NP are synthetized starting from acetylene precursor with a novel low-pressure RF capacitive plasma-based technique [1], able to provide very accurate control on NP degree of graphitization and on defects density, that have been demonstrated to be very important on VRFB kinetics [2].
C-NP will be then oxidized in order to make them more active towards vanadium cathodic reaction and to make them more hydrophilic and suitable for wet processing.
Plasma synthetized C-NP will be characterized in 3 electrode half cell with cyclic voltammetry measurement (CV) and electrochemical impedance spectroscopy (EIS) to evaluate their activity that will then be correlated with structural and chemical properties via Raman Spectroscopy (number of defects), FT-IR (surface functionalities), and BET measurement (surface area).
Afterwards the NP will be attached to commercial VRFB electrode with impregnation technique [3] and half cell [4] electrochemical measurements are performed to point out how the treatment affect mass transport, depending on loading and NP-deposition structure.
[1] - G. Nava, F. Fumagalli, S. Gambino, I. Farella, G. Dell’Erba, D. Beretta, G. Divitini, C. Ducati, M. Caironi, A. Cola and F. Di Fonzo, Towards an electronic grade nanoparticle-assembled silicon thin film by ballistic deposition at room temperature: the deposition method, and structural and electronic properties, J. Mater. Chem. C, 2017,
5, 3725
[2] G. Wei, W. Su, Z. Wei, X. Fan , J. Liu, C. Yan, Electrocatalytic effect of the edge planes sites at graphite electrode on the vanadium redox couples, Electrochimica Acta 204 (2016) 263–269
[3] L. Wei, T.S. Zhao, G. Zhao, L. An, L. Zeng, A high-performance carbon nanoparticle-decorated graphite felt electrode for vanadium redox flow batteries, Applied Energy 176 (2016) 74–79
[4] V. Yufit, B. Hale, M. Matian, P. Mazur, N. P. Brandon, Development of a regenerative hydrogen-vanadium fuel cell for energy storage applications, Journal of The Electrochemical Society 160 (2013) A856-A861.
8:00 PM - NM02.08.32
Mechanical Characterization of Drawn Electrospun Polyacrylonitrile (PAN) Carbon Nanofiber Precursors
David Brennan 1 , Vince Beachley 1 , Khosro Shirvani 1
1 , Rowan University , Glassboro, New Jersey, United States
Show AbstractIntroduction: Carbon nanofibers have exciting potential in biomedical applications for their mechanical strength, conductivity, and chemical stability. These properties make them ideal for mimicing native tissue in load-bearing scaffolds, relaying signals in neural interfaces, and resisting degradation in long term implants. However, common methods of carbon fiber production, such as chemical vapor deposition or pyrolyzing spun fibers, are difficult, costly, and can be limited to the microscale. Electrospinning offers a simple method of producing carbon nanofiber precursors from polyacrylonitrile (PAN) with favorable properties for tissue scaffolds, such as high surface area to volume ratio and mimicry of native extracellular matrix. However, electropun fibers lack mechanical strength comparable to load-bearing native tissue because most methods produce fibers without well-ordered polymer chains. A method of concurrently electrospinning and drawing is used to produce nanofibers with aligned and extended polymer chains, increased mechanical strength, and improved conductivity.
Methods: An electrospinning device was previously designed in our lab which employs a set of adjustable tracks and allows nanofibers to be simultaneously spun and drawn to induce macromolecular alignment. We hypothesize that carbon fibers made from drawn precursor PAN fibers will have enhanced mechanical and conductive properties. A polycarbonate enclosure houses this system which allows the relative humidity to be controlled and prevents interference from outside conductive points. Electrospinning was completed using 13wt% PAN dissolved in Dimethylformamide. Fibers are collected under four increasing draw ratios and mechanical strength is tested using a tensile testing device.
Results: The system was capable of producing nanofibers stretched from 4 up to 16cm during collection. Analysis of Fourier Transform Infared Spectroscopy(FTIR) is used to relate enhanced orientation with increased draw ratio. Polarized FTIR spectra shows shifts in peak intensity between the directions parallel and perpendicular to fiber orientation, indicating that the process of drawing causes a change in macromolecular ordering. Preliminary data shows a systematic increase of fiber tensile strength with increased draw ratio, indicating that the simultaneous collection and drawing of electrospun nanofibers improves fiber mechanical properties.
Conclusion: A method of simultaneously collecting and drawing electrospun nanofibers was successfully implemented in the lab. Testing reveals that electrospun nanofibers collected under increased draw ratio exhibit improved mechanical strength. This is attributed to a higher degree of polymer chain alignment and extension achieved by drawing the fibers during collection. Current data suggests that further testing will reveal carbon fibers made from precursors with improved macromolecular alignment will have enhanced mechanical strength and conductivity.
8:00 PM - NM02.08.33
Carbon Nano-Onions Synthesized by Laser Pyrolysis as Catalyst Support in Proton Exchange Membrane Fuel Cells
Sei Jin Park 2 , Je Hyeon Yeon 2 1 , Indae Choi 2 1 , Mansoo Choi 2 1
2 , Global Frontier Center for Multiscale Energy Systems, Seoul Korea (the Republic of), 1 , Seoul National University, Seoul Korea (the Republic of)
Show AbstractProton exchange membrane fuel cells (PEMFC) typically utilize nanostructured carbon (such as carbon black, carbon nanotubes, graphene and porous carbon) as the support material for catalysts. The durability and electrical conductivity of the material are important contributors to the fuel cell performance, as well as the structural design to maximize the triple phase boundary between the fuel, the catalyst and the electrolyte membrane. In view of engineering the structure and composition of the carbon catalyst support, a versatile manufacturing method with flexibility in size, shape, structure, and properties (such as electrical conductivity) of the carbon material would open up a chance to investigate an expansive composition matrix for potential improvements of the cell performance. In addition, for potential commercialization, processes that are clean and high-throughput are desired.
Laser pyrolysis of hydrocarbons has been established as a widely adopted gas phase production of carbon nanoparticles. In particular, multilayered particles with concentric graphitic shells, commonly called carbon nano-onions, are of interest as the size, shape and the number of graphitic shells are easily tuned by adjusting the experimental parameters. In this work, we present a CO2 laser induced pyrolysis of gaseous hydrocarbons (such as acetylene and ethylene) that generates various types of carbon nanoparticles, and demonstrate that these carbon nano-onions have superior durability and electrical conductivity to commonly used commercial carbon materials such as Vulcan XC-72. Platinum-decorated carbon nano-onions have been used to fabricate PEMFCs and they are shown to have comparable performance to conventional cells, and the accelerated stress test (AST) reveals that the durability of the cells have improved.
8:00 PM - NM02.08.34
Nitrogen Doped Carbon Nano-Onions for Efficient and Durable Electrochemical Reduction of CO2 to CO
Yan Zhang 1 , Ruixin Zhou 1 , Marcelo Guzman 1 , Doo Young Kim 1
1 Chemistry, University of Kentucky, Lexington, Kentucky, United States
Show AbstractElectrochemical reduction of CO2 in aqueous electrolyte is a promising route to suppress high CO2 level in environment, as well as to produce energy-rich chemicals. However, the electrochemical reduction of CO2 has been greatly challenged for decades, due to the lack of cost-effective and durable electrocatalysts. An ideal catalyst should satisfy the following requirements: (i) to overcome the sluggish electron-transfer kinetics of CO2 reduction process, (ii) to enable high faradaic selectivity toward a target product among the many possible products including CO, CH4, HCOOH, C2H5OH, etc, (iii) to possess electrochemical stability during the operation of catalysts, and (iv) to effectively inhibit the competing hydrogen evolution reaction. In this presentation, we will discuss the high catalytic performance of nitrogen doped carbon nano-onions (N-CNOs) for CO2-to-CO reduction. N-CNOs were prepared by thermal treatment of chemically oxidized CNOs after they were mixed with urea. The content of nitrogen in N-CNOs was about 3 % (atomic percentage). N-CNOs exhibited a significantly reduced overpotential for the reduction of CO2 to CO with a high faradic efficiency (onset potential of -0.48 V with 100% faradaic efficiently, clearly showing that the incorporation of nitrogen atoms provides active sites. In contrast, no significant catalytic activity was found in undoped CNOs. An accelerated degradation test was conducted to evaluate the long-term stability of N-CNOs. A negligible current decay was found during chronoamperometric current-time (i-t) test for 1 hour, suggesting the superior stability of N-CNO electrode. This presentation will address the impact of nitrogen dopants on catalytic sites for CO2 reduction and hydrogen evolution reaction. The prolonged stability and the tolerance against long-term deactivation of N-CNOs will be also presented.
8:00 PM - NM02.08.35
Broadband Terahertz Modulation in Electrostatically-Doped Artificial Trilayer Graphene
Ioannis Chatzakis 1 , Zhen Li 1 , Alexander Benderskiib 2 , Stephen Cronin 1 2
1 Electrical Engineering, University of Southern California, Los Angeles, California, United States, 2 Chemistry, University of Southern California, Los Angeles, California, United States
Show AbstractWe report a terahertz optical modulator consisting of randomly stacked trilayer graphene (TLG) deposited on an oxidized silicon substrate by means of THz-Time Domain Spectroscopy (THz-TDS). Here, the gate tuning of the Fermi level of the TLG provides the fundamental basis for the modulation of THz trans- mission. We measured a 15% change in the THz transmission of this device over a broad frequency range (0.6–1.6 THz). We also observed a strong absorption >80% in the time-domain signals and a frequency independence of the conductivity. Furthermore, unlike previous studies, we find that the underlying silicon substrate, which serves as a gate electrode for the graphene, also exhibits substantial modulation of the transmitted THz radiation under applied voltage biases.
8:00 PM - NM02.08.36
Polymer-Assisted Growth of Transition Metal Phosphide/Dichalcogenide Nanocrystals on Graphene Surface toward Hydrogen Evolution Catalysis
Minghao Zhuang 1 , Zhengtang Luo 1
1 , Hong Kong University of Science and Technology, Hong Kong Hong Kong
Show AbstractWith the combination of excellent electrical conductivity, high mechanical strength and surface area, graphene has been utilized as unique template for growth of nanomaterials, and further broadly applied in various research areas. Here, we developed a universal strategy to use polymer-assisted method to uniformly distribute transition metal based nanocrystals on heteroatom-doped graphene surface, eventually to use for energy based applications. Generally, we explored the potential applications by introducing graphene oxide and pristine graphene foam as templates, polyacrylamide (PAM) and gelatin with acryl groups (GelMA) as polymer scaffolds, to fabricate novel micro/nanostructure graphene-based composites. As one example, so as to fundamentally understand the edge/corner effect of TMDCs on hydrogen evolution catalysis, we carefully designed and engineered the perforated MoSe2 single-crystals of ~150 nm in lateral dimension on N-doped graphene toward hydrogen evolution. We observed a remarkably enhanced electrocatalytic activity resulting from significantly increased abundance of edge/corner atoms in hydrogen evolution measurements. Specifically, with this perforated MoSe2/NG-modified cathode, current density of -1 and -10 mA cm-2 were realized with the overpotentials of only 30 and 106 mV, along with a small Tafel slope of 57 mV dec-1 and large exchange current density of 127.4 mA cm-2 in 0.5 M H2SO4. Such efficient strategy makes the performance of TMDCs-based catalysts one-step closer to the commercial Pt/C, also opens a door for unparalleled design and fabrication of TMDCs-based nanocomposites.
8:00 PM - NM02.08.37
Tailoring the Top-Surface CVD Growth of Single-Crystal Graphene/h-BN by “Gettering” the Source Diffusion at Backside of the Copper Foil
Irfan Abidi 1 , Zhengtang Luo 1
1 , Hong Kong University of Science and Technology, Hong Kong Hong Kong
Show AbstractWe demonstrated a unique approach for the nucleation control of multilayer graphene (MLG) and single-crystal graphene domains at top surface of the Cu foil during the chemical vapor deposition (CVD) growth using a carbon “getter” support substrate for the Cu foil. In previous reports, the role of carbon diffusion from backside of the Cu foil is seldom explored for the unsolicited higher nucleation on the top surface. However, we demonstrate the backside carbon diffusion is the major source for the nucleation of MLG domains underneath the top layer of graphene. Nevertheless, we devised a strategy to mitigate this backside carbon diffusion by employing a nickel support for Cu foil, which getter all the carbon accumulated at the backside. This backside source gettering (BSG) approach not only restricted the nucleation of MLG domains but also lowers down the nucleation density of single-crystal graphene domains by two orders of magnitude. Consequently, BSG method enables us to grow strictly monolayer single-crystal graphene domains of ~ 6 mm lateral size on an untreated Cu foil, which shows significantly improved field-effect mobility of ~ 6800 cm2V-1s-1 and 97.7% transmittance. Later, we extend the BSG technique to the CVD growth of hexagonal boron nitride (h-BN), which shows very promising results as well. Therefore, we believe our approach provides an unusual methodology for controlled CVD growth of 2D materials and their heterostructures.
8:00 PM - NM02.08.38
Isolation, Purification and Characterization of Novel Nanocarbons Formed from the Detonation of High Explosives
Millicent Firestone 1 , Brian Mogavero 1 , John Despard 1 , Bryan Ringstrand 1 , David Podlesak 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractDetonation synthesis offers one avenue for the discovery and large scale production of new carbon frameworks. Critical to this endeavor is advancing our understanding on how detonation conditions predictably generate nanocarbons. For example, we recently discovered that subtle changes in water content in the atmosphere during the detonation of a high explosive, Composition B, yielded dramatic differences (yet highly reproducible) in the carbon frameworks formed.1 The novel nanocarbons were characterized through multi-length scale characterization of the unpurified recovered soot. Small-angle x-ray scattering (SAXS) and transmission electron microscopy (TEM) showed that nanocarbons formed during detonations of Composition B under ambient atmospheric conditions were predominately 46 nm diameter quasi-spherical hollow particles coated in sheets of 5.7 nm thick carbon. Diffraction, photoemission and Raman spectroscopy indicated the particles were composed of sp2 hybridized carbon. Conversely, nanocarbons recovered from Composition B detonations carried out under inert atmospheres (Argon or vacuum) produced particles morphologically similar to the naturally occurring allotrope, shungite. Specifically the nanocarbons were high aspect ratio, anisotropic particles (70 nm x 4 nm). These novel nanocarbons architectures are not readily synthesized employing traditional laboratory approaches. Full structure and functional characterization of these products necessitated isolation from the recovered detonation soot and purification. In this presentation, various solvent extraction procedures coupled with density gradient separations (e.g., sucrose gradients) will be detailed and characterization of the isolated products described.
Huber, R. C.; Ringstrand, B. S.; Dattelbaum, D. M.; Gustavsen, R. L.; Seifert, S.; Firestone, Nanocarbons formed under extreme conditions: The role of atmosphere during detonations of Composition B-3. Carbon submitted.
8:00 PM - NM02.08.39
Mechanical Properties of Ultralow Density Graphene Oxide/Polydimethylsiloxane Foams
Peter Owuor 2 , Cristiano Woellner 1 , Tong Li 3 , Soumya Vinod 2 , Sehmus Ozden 2 , Suppanat Kosolwattana 2 , Sanjit Bhowmick 4 , Luong Duy 2 , Rodrigo Salvatierra 2 , Bingqing Wei 4 , S. A. Syed Asif 4 , James Tour 2 , Robert Vajtai 2 , Jun Lou 2 , Douglas Galvao 1 , Chandra Tiwary 2 , Pulickel Ajayan 2
2 MSNE, Rice University, Houston, Texas, United States, 1 , University of Campinas, Campinas Brazil, 3 Mechanical Engineering, University of Delaware, Newark, Delaware, United States, 4 , Bruker Nano GmbH, Minneapolis, Minnesota, United States
Show AbstractLow-density, highly porous graphene/graphene oxide (GO) based-foams have shown high performance in energy absorption under high compressive deformations [1,2]. In general, foams are very effective as energy dissipative materials and have been widely used in many areas such as automotive, aerospace and biomedical industries. In the case of graphene-based foams, the good mechanical properties are mainly attributed to the intrinsic graphene and/or GO electronic and mechanical properties. Despite the attractive physical properties of graphene/GO based-foams, their structural and thermal stabilities are still a problem for some applications. For instance, they are easily degraded when placed in flowing solutions, either by the collapsing of their layers or just by structural disintegration into small pieces. In order to address some of these issues, in this work we propose a scalable synthesis of low-density 3D macroscopic GO structure interconnected with polydimethylsiloxane (PDMS) polymeric chains (pGO) [3]. A controlled amount of PDMS is infused into the freeze-dried foam resulting into a very rigid structure with improved mechanical properties, such as tensile plasticity and toughness. The PDMS wets the graphene oxide sheets and acts like a glue bonding PDMS and GO sheets. The ability of using the formed pGO as effective oil–water separator and highly stable thermal insulating material were further demonstrated. The structural rigidity of the sample was also tested using laser impact and contrasted against standard GO foams. Fully atomistic molecular dynamics (MD) simulations were also carried out in order to obtain further insights on mechanisms behind the enhanced mechanical pGO response. Based on MD results, we build up a structural model that can explain the experimentally observed mechanical behavior.
[1] S. Vinod et al., Nature Commun. V5, 4551 (2014).
[2] S. Vinod et al., Nano Lett., v6, 1127 (2016).
[3] P. S. Owuor, et al., Adv. Mater. Interfaces 2017, 4, 1700030 (2017) .
8:00 PM - NM02.08.41
Bottom-Up Fabrication of Graphene Nanoribbons—From Molecules to Devices
Gabriela Borin Barin 1 , Andrew Fairbrother 1 , Juan Pablo Llinas 2 , Matthieu Paillet 3 , Xinliang Feng 4 , Klaus Müllen 5 , Pascal Ruffieux 1 , Jeffrey Bokor 2 , Roman Fasel 1 6
1 Nanotech@Surfaces Laboratory, Empa-Swiss Federal Laboratories for Materials Science and Technology, Dübendorf Switzerland, 2 Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, California, United States, 3 Laboratoire Charles Coulomb (L2C), Université de Montpellier, Montpellier France, 4 Center for Advancing Electronics Dresden, TU Dresden, Dresden Germany, 5 , Max Planck Institute for Polymer Research, Mainz Germany, 6 Department of Chemistry and Biochemistry, University of Bern, Bern Switzerland
Show AbstractAtomically precise graphene nanoribbons (GNRs) exhibit a sizeable bandgap, which is inversely proportional to their width, and are thus excellent candidates for room temperature switching applications. However, in spite of their exceptional properties, significant challenges remain for GNR fabrication, processing and characterization. While the bottom-up synthesis of GNRs delivers the required atomic precision and selectivity with respect to width and edge structure1, it is commonly performed under ultra-high vacuum conditions, which is one of the bottlenecks in the further technological advancement of this material. Additionally, little is known about the stability of ultra-narrow GNRs under ambient conditions or during device processing. This contribution addresses some of the critical challenges in the further development of GNR technologies, in particular regarding GNR fabrication scalability, transfer and ex-situ characterization, and demonstrates that gate optimization allows for the fabrication of GNR-FET devices with high on/off ratios.We focus on 7- and on 9-atom wide armchair GNRs (7-AGNR; 9-AGNR) grown under high to ultrahigh vacuum conditions on 200 nm Au(111)/mica substrates and vicinal Au(11 12 12) crystals. High-resolution STM images show 9-AGNRs with an average length of 50 nm. The GNRs are transferred from the Au growth surface to SiO2/Si chips using two different transfer approaches. For the case of GNRs grown on the vicinal crystal an electrochemical delamination method is applied, which allows for a clean transfer of GNRs and preserves their structural quality and uniaxial alignment. Detailed characterization of GNRs transferred by this method, including polarized multi-wavelength Raman spectroscopy, STM and XPS, will be discussed. In the second approach, GNRs grown on Au/mica are transferred using a membrane-free method2. Raman spectra indicate no degradation of GNR quality upon transfer and reveal a homogeneous GNR distribution on the target surface. Furthermore, Raman characterization over a 1 year period shows that GNRs are remarkably stable under ambient conditions. Interestingly, multi-wavelength Raman studies (785 - 457 nm) on 7- and 9-AGNRs reveal the absence of dispersive behavior for the G, D and RBLM modes. The overall morphology of transferred GNR films, as characterized by AFM, is exceptionally smooth with very few tears and wrinkles. UV/VIS/NIR spectroscopy of GNRs transferred to transparent substrates reveals the lowest energy absorption around 0.9eV, which we assign to the first optical transition of the 9-AGNRs, and several other characteristic absorption features at higher energies. Finally, we report on the fabrication of short channel (~ 20 nm) GNR-FET devices using 9-AGNRs as channel material3. We demonstrate FETs with high on-currents of 1 μA at –1 V drain bias and high on/off ratios of ~105.
1. J. Cai et al, Nature 466.2010
2. A. Fairbrother et al, Nanoscale 8.2017
3. J.P. Llinas et al, Nature Comm 8,2017
Symposium Organizers
William Yu, Louisiana State University Shreveport
Vicki Colvin, Brown University
Yu Zhang, Jilin University
Symposium Support
MilliporeSigma (Sigma-Aldrich Materials Science)
NM02.09: Session VII
Session Chairs
Khaled Mahmoud
Michael Snure
Thursday AM, November 30, 2017
Hynes, Level 3, Room 302
8:15 AM - *NM02.09.01
Spectroscopy and Substitutional Functionalization of Single Walled Carbon Nanotubes
Paola Ayala 1
1 , University of Vienna, Klosterneuburg Austria
Show Abstract
The advances in sorting and purification of single-walled carbon nanotubes (SWCNTs) of the last years opened several possibilities for their applicability. On a different playground, SWCNTs with on-wall functionalization are nowadays produced with different methods. However, sorting and purification of functionalized materials has been scarcely explored. Therefore understanding how the energies of charge carriers and lattice vibrations are modified, among other effects due to the presence of heteroatoms and defects is still elusive despite many years of worldwide efforts. I will show our recent progress on establishing the prerequisites for studying the rich low-dimensional physics of substitutionally doped SWCNTs as an example. It will be discussed how metallicity-sorting combined with high energy spectroscopy techniques can nicely disentangle the characteristic density of states of B-doped SWCNTs with ultra-low doping unambiguously. We will discuss the changes in the site selective electronic structure within these substitutionally doped SWCNTs.
8:45 AM - NM02.09.02
Toxicity, Bactericidal and Environmental Applications of Two-Dimensional MXenes—Opportunities and Challenges
Khaled Mahmoud 1 , Kashif Rasool 1 , Ravi Pandey 1 , Gheyath Nasrallah 2
1 , Hamad Bin Khalifa University, Doha Qatar, 2 , Qatar University, Doha Qatar
Show AbstractRecently, we have presented Ti3C2Tx (MXene) as novel two-dimensional material for water treatment and environmental remediation applications. MXenes are a new family of atomically thin, two-dimensional (2D) transition metal carbides and carbonitrides that can challenge graphene and other well-studied 2D materials due to a unique combination of properties and a large diversity of compositions. MXenes show metallic conductivity combined with a negative surface charge and hydrophilicity which adds a possibility to control ion flux and biofouling by applying a small potential to the membrane. Ti3C2Tx shows a much higher antibacterial efficiency toward both Gram-negative and Gram-positive bacteria. Consequently MXene membranes showed high resistant to bio-fouling and offer bactericidal properties to the new UF/NF membranes. We used density functional theory (DFT) calculations to understand the mechanisms of charge-selective ionic transport through MXene membranes. MXene have been successfully used for the efficient adsorption and removal of heavy metals such as Cr, Hg, and Cu. To date, biological activity of Ti3C2Tx MXene has been largely unexplored. Even this newly discovered material has a wide range of potential applications, there are no studies investigated their in vitro/vivo cytotoxicity to bacterial or mammalian cells. It is very important to study cellular uptake and cytotoxicity of MXene to understand the health and environmental impact of MXenes. Concerns regarding toxicity are the major obstacles on the nanomaterials to further research and development on their applications in energy, environment and biomedical. We have recently investigated and compared the effect of the MXene nanosheets on the response of aquatic organisms using the zebrafish model and human cells. This tail will address the biocompatibility and cytotoxicity assessment of MXene and their impact on environmental and water treatment applications. This talk will discuss the new advancement of MXene in water treatment applications and will address the biocompatibility and cytotoxicity assessment of MXene and their impact on environmental and water treatment applications.
9:00 AM - NM02.09.03
A Facile Approach to Mapping Graphene Grain Boundaries and Multilayer Regions on Copper
Katherine Young 1 , Corey Joiner 1 , Dale Hitchcock 2 , Steve Serkiz 2 , Walter Henderson 1 , Eric Vogel 1
1 , Georgia Institute of Technology, Atlanta, Georgia, United States, 2 , Savannah River National Laboratory, Aiken, South Carolina, United States
Show AbstractGraphene is a 2D material with sp2 covalently bonded C in a honeycomb lattice. It has shown noteworthy properties including near optical transparency, high electrical mobility, and low permeability; however, line and point defects significantly alter these properties.1,2 Therefore, the development of methods to measure the extent and character of graphene defects have received increased attention. Characterizing graphene grain boundaries and point defects can be challenging and time consuming with electron microscopy methods, such as TEM and STM, which provide atomic-scale details but little information on grain-size distribution or overall quality of the graphene. A faster and simpler method is the use of atomic layer deposition (ALD) to preferentially deposit on graphene grain boundaries and defect sites to create a visual roadmap of the graphene grains.1 However, previous work has required transfer of the graphene to another substrate, which can add contamination and damage the graphene film. In this work, a technique to directly map graphene grain boundaries and defects as well as the underlying Cu orientation is demonstrated without the need for a transfer step.
Mechanistically, ALD grows conformal thin films onto a substrate by alternating pulses of vapor-phase precursors that chemisorb onto the substrate’s surface. Because graphene has an inert basal plane, deposition is significantly limited.1 Grain boundaries and point defects, however, have a higher surface energy than the grain interiors; therefore, the precursors selectively chemisorb to these areas.1 SEM images of CVD-grown graphene were collected before and after < 1 nm HfO2 was deposited by ALD. The deposited HfO2 added contrast to the graphene grain boundaries, which were previously difficult to resolve. Electron backscatter diffraction (EBSD) was used to independently distinguish copper grains from graphene grains because the energy of the beam is high enough to penetrate the graphene and only detects the Cu crystallographic orientations. The results show that multiple graphene domains can span a single copper grain and that graphene domains can overlap copper grains. Multilayer graphene clusters and stacked hexagonal grains were also characterized using this technique. From these results using ALD/SEM/EBSD it was concluded: (1) graphene grain boundaries can be easily mapped without the need to transfer the graphene; (2) the distributions of graphene grain-size and multilayer regions can be quantified; and (3) the crystallographic orientations of the Cu growth substrate can be mapped.
9:15 AM - NM02.09.04
Ultrastretchable Graphene-Based Molecular Barriers for Chemical Protection, Detection and Actuation
Po-Yen Chen 1 2 , Ian Wong 2 , Robert Hurt 2
1 Chemical and Biomolecular Engineering, National University of Singapore, Singapore, Singapore, Singapore, 2 School of Engineering, Brown University, Providence, Rhode Island, United States
Show AbstractEffective molecular barriers are required against unfavorable chemical and biological substances in many aspects of everyday life. Yet, it is difficult to combine barrier performance (requiring dense, ordered, space-filling materials) with mechanical stretchability (achieved by dynamic atomic-scale reordering). Also, current technologies only provide passive protection, and smart materials could benefit from add-on technologies that sense, identify, and/or adapt to chemical exposure. The presentation explores the use of two-dimensional (2D) nanomaterials as components in smart, stretchable barrier technologies. We investigated textured multilayer graphene oxide (GO) and reduced GO (rGO) films on elastomer substrates as multifunctional molecular barriers with high stretchability, effective chemical protection, real-time sensing of threat identity, as well as significant actuation against chemical exposure. We first deposited a large-area GO film onto a pre-stretched latex substrate, followed by a biaxial contraction for the creation of bilayer GO-latex materials, which can be exerted as ultrastretchable chemical barriers. The GO-based barriers can be expanded reversibly to 1600% of its compressed area and are still resistant to the wide spectrum of target permeants, such as organic solvents and warfare agent surrogates. Additionally, we developed another fabrication route for rGO-elastomer (i.e., PDMS) materials that can sense and react to chemical exposure. The conformal rGO coating serves as a transducer to convert the swelling behaviors of PDMS substrate into electrical signals and enables the real-time identification of chemical exposure in the environment. The rGO-PDMS film also exhibited shape-morphing behaviors upon swelling and relaxation, and we propose a fundamentally new theory for this shape-morphing actuation based on transient concentration gradients in the elastomer backing. The rGO-PDMS actuator serves as a new basis of soft materials and is capable of imparting spontaneous “runaway” motion under chemical exposure. The stimuli-responsive actuation is programmable and can provide electrical connection to transmit the signals to another electronic device that improve the awareness of environmental monitoring. This type of 2D nanomaterial and elastomer bilayer material is of great interest for further exploitation for the applications including wearable chemiresistors, stretchable electronics, and soft robotics.
9:30 AM - NM02.09.05
Introduction of New Boron Chemistries into Graphene Aerogels—Synthesis and Properties
Sally DeMaio-Turner 1 , Brian Shevitski 2 , Wenjun Yan 1 , Kevin Nuckolls 1 , Maydelle Lorenzo 1 , Hu Long 1 , Thang Pham 1 , Carlo Carraro 1 , Roya Maboudian 1 , Art Nelson 3 , Marcus Worsley 3 , Alex Zettl 1
1 , University of California, Berkeley, Berkeley, California, United States, 2 The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractGraphene materials have received extensive interest and excitement in the materials science and condensed matter fields due to their high electrical conductivities and carrier mobilities, incredible Young’s modulus, and remarkably high thermal conductivities. The synthesis of a three dimensional, cross-linked, monolithic graphene aerogel allows for the incorporation of large quantities of graphene into a single high surface area, porous material with extremely low density. Graphene aerogels are promising materials for battery electrodes, gas sensing, supercapacitors, and waste water treatment. In order to optimize the material for these applications, doping is an attractive strategy. Boron doping of graphene has been theorized to improve the performance for gas detection and energy storage, but reports of boron doping of graphene aerogels in the literature are scarce.
In this talk, I will present two solution-processable methods to introduce boron into the graphene aerogel lattice, each with a distinct boron chemistry. One method yields substitutional boron doping and the second yields B-N clusters within the graphene. The two unique boron chemistries are characterized with X-ray Photoelectron Spectroscopy and X-Ray Absorbance Spectroscopy among other techniques to confirm the bonding and location of boron. As expected, the presence of substitutional boron or B-N moieties has an effect on the properties of the material. I will present the performance of the materials for low power NO2 detection and hydrogen storage. Substitutional boron doping greatly enhances the sensitivity and selectivity of the material and can detect NO2 concentrations as low as 50 ppb, while incorporation of B-N clusters in the aerogel compromises the sensing performance. However, BN is known to have a higher binding affinity for hydrogen than graphene. We study the hydrogen storage capacity of graphene aerogels with B-N clusters and find these materials to be superior hydrogen storage candidates to graphene aerogels.
10:15 AM - *NM02.09.06
Carbon Nanomaterial-Enhanced Scaffolds for Tissue Engineering
Shirley Tang 1
1 , University of Waterloo, Waterloo, Ontario, Canada
Show AbstractA series of studies in the past five years have shown that the incorporation of carbon nanomaterials (CNMs) in tissue scaffolds effectively tunes the physical and chemical properties of the scaffolds, therefore leads to engineered tissue with improved organization and physiological functions. In this talk, I’ll review our recent work on cardiac tissue engineering, where carbon nanotube, graphene oxide, reduced graphene oxide are incorporated into hydrogel scaffolds. With cardiomyocytes seeded onto CNM-incorporated hydrogel, centimeter scale stand-alone cardiac tissue constructs can be produced with incredible mechanical integrity and electrophysiological behaviors. Research efforts have also been dedicated to ever increasing the complexity of the engineered structures, with the aims to better mimic the natural myocardium and to achieve more precisely controlled bioactuators. Multi-layer cardiac tissue and that with embedded anisotropic electrodes have been demonstrated. Seeking the path towards reproducible fabrication of anisotropic tissue constructs, CNM-hydrogel hybrid ink formulations for 3D bioprinting have been developed. Results showing the effective tuning of ink rheological property and printability, as well as, printed high-fidelity cell-laden patterns will be presented. Our research demonstrates that utilization of CNMs, combined with biopolymers, provides new possibilities in tissue engineering and regenerative medicine.
10:45 AM - NM02.09.07
A Theoretical Investigation of the Structural and Electronic Properties of Graphene Oxide
Filippo Savazzi 1 , Francesca Risplendi 1 , Giuseppe Mallia 2 , Nicholas Harrison 2 , Giacarlo Cicero 1
1 , Politecnico di Torino , Torino Italy, 2 Thomas Young Centre, Imperial College London, London United Kingdom
Show AbstractIn recent years Graphene Oxide (GO) received great interest, as a cheap precursor to obtain graphene as well as a functional material with tunable electronic and optical properties. Accurate ab initio studies presented in this work allowed deepening the still limited knowledge of the material, beside opening the way to the prediction and interpretation of some fundamental experimental results (namely XPS spectra).
We studied the effects of the oxidation of graphene on its structure and electronic properties. Specifically, we aimed at generating realistic model samples of GO and at identifying experimentally useful fingerprints that allow determining the amount and type of oxygen containing functional groups. We prepared GO structures characterised by O/C ratios corresponding to 10, 15, 20% and with different relative content of hydroxyl, epoxide and ether groups. To obtain realistic structures we employed a combined Molecular Dynamics (MD) – Density Functional Theory (DFT) methodology. With a REAX classical force field we first simulated a thermal process to oxidize large graphene supercells, then we run DFT geometry optimisation of these structures using a B3LYP hybrid exchange-correlation functional for a more accurate description of the samples.
Our results show that epoxide groups induce large strain in the basal plane of graphene that is relieved with corrugation of the structures. This corrugation is associated with a substantial opening of the band gap in those samples containing a mostly epoxides. On the other side hydroxyl groups induce local strains only on the carbon to which they are bonded and yield less deformed, more planar, structures. An analysis of the energies of the carbon 1s core levels highlighted that specific energy shifts can be assigned unambiguously to different oxygen-containing moieties. The latter results open to the possibility of using our findings to complement and support experimental X-ray photon spectroscopy measurements.
11:00 AM - NM02.09.08
Growth of hBN Graphene Two-Dimensional Heterostructures
Gene Siegel 1 , Michael Snure 1
1 , AFRL, Wright Patterson AFB, Ohio, United States
Show AbstractThe ability to build heterostructures in an atomic layer-by-layer fashion selecting layers based on property with little regard for structure is one of the great promises of two dimensional (2D) materials. Unlike three dimensional materials, 2D materials have strong chemical bonding in-plane and weak van der Waals like bonding out-of-plane between layers. This bonding anisotropy provides the unique feature of 2D materials to be mechanically exfoliated or grown one atomic layer thick, and it has been used to construct heterostructures consisting of multiple mono-layers from different materials. Such structures have been used to enhance material performance, produce new devices, and engineer material properties. The most widely successful approach has been to build these heterostructures by exfoliation of individual layers from a high quality bulk source followed by transfer and assemble. Unfortunately, this process is not scalable and produces low quality interfaces. The best alternative, which is clean and scalable, is to grow these heterostructures in a layer-by-layer fashion using conventional semiconductor processes (CVD or MBE). However, this approach is still in its infancy, and a great many questions remain about the mechanisms of 2D or van der Waals epitaxial growth. In this paper we present results on growth of graphene hBN heterostructures grown layer-by-layer in the same reactor. Since graphene and hBN are structurally similar but functionally quite different (graphene is a zero band conductor and hBN a wide band insulator), they make for a good case study for van der Waals growth. Using Cu(111) films we grow epitaxial hBN and study the effect of key graphene growth conditions to determine their impact on nucleation, thickness, and morphology. In order to elucidate these effects, films were carefully characterized using techniques including AFM, XPS, TEM, and Raman. Pressure, H2 concentration, and substrate are critical to low defect graphene films. Due to the ability to grow epitaxial hBN films with thickness from mono-to-few-layer, we have explored the effects of catalytic or wetting transparence from the substrate through hBN films. Two layers of hBN were identified to be the limit of this transparence beyond, which growth is impacted significantly reducing growth rate and nucleation. The work presented improves our understanding of mechanisms involved in growth of 2D materials and will help to generate methods to achieve layer-by-layer growth of 2D heterostructures
11:15 AM - NM02.09.09
Characterization of Multilayered Conductive Films Produced by Multiple Transfer Printing Graphene onto Ultra-Thin PVC Foil
Ugur Inkaya 1 , Kubra Celik 2 , Ahmet Oral 1
1 , Middle East Technical University, Ankara Turkey, 2 , Firat University, Elazig Turkey
Show AbstractHaving high charge carrier mobility and superior elastic properties, graphene is a very suitable material for flexible electronics. However, it is usually desired to remove and prevent unintentional doping due to wet processes used for transfer printing of graphene. Although it does not produce a graphene film as smooth as an exfoliated graphene sheet transferred onto SiO2/Si wafer, dry transfer of graphene could be favored for applications that do not require very high charge carrier mobility. In addition, controlling the number of layers in synthesizing multilayer graphene will be an ability of great importance for applications involving resistances lower and charge carrier densities higher than that of single layer graphene. We developed a method for making multilayered graphene-based conductive films on 75μm-thick PVC film. The graphene is synthesized via atmospheric pressure chemical vapor deposition (APCVD) on 20μm-thick copper foils. After forming the Cu/graphene/PVC stack via lamination by hot rollers, selective etching with aqueous FeCl3 solution is provided by hydrophobic permanent marker ink deposited onto the parts of the copper layer to become contact pads. The multilayered conductive films can be obtained by iterative application of this scheme in which the selective etching is applied after the last lamination. The conductive film based on single layer graphene manifested sheet resistances of the order of 1 kΩ and Hall coefficients of up to 1200 Ω/T, and withstood current density greater than 1.9 x 109 A/m2. The resistance and Hall coefficient values were found to decrease with increase in the number of layers. Our method could be used as a platform for proof-of-concept works aiming to demonstrate graphene’s potential for flexible electronics. The structural, thermal, and electronic characterization of the multilayered graphene-based conductive films on the PVC film is to be presented.
11:30 AM - NM02.09.10
Exploring Fast Water Transport in 2D Graphene Nanochannels
Quan Xie 1 , Mohammad Alibakhshi 1 , Shuping Jiao 2 , Zhiping Xu 2 , Marek Hempel 3 , Jing Kong 3 , Hyung Gyu Park 4 , Chuanhua Duan 1
1 Department of Mechanical Engineering, Boston University, Boston, Massachusetts, United States, 2 Department of Engineering Mechanics , Tsinghua University, Beijing, Select State/Province, China, 3 Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 4 Department of Mechanical and Process Engineering, ETH Zürich, Zürich Switzerland
Show AbstractFast water transport across laminated graphene oxide (GO) membranes consisting of massive interconnected 2-D graphene nanochannels, has been discovered over the last decade. This new membrane structure has great potential for a variety of applications including water desalination, nanofiltration, energy harvesting and lab-on-a-chip. Further development of GO membranes relies on accurate measurement and fundamental understanding of the water flow enhancement and surface slippage down to the level of single graphene nanochannels. Here we report a hybrid nanochannel scheme to experimentally study water transport inside single graphene nanochannels via capillary filling. Without estimation of the capillary pressure, the hydraulic flow resistance and surface slippage of graphene nanochannel are accurately measured. Our results show that the apparent slip length of graphene surface in our nanochannel poses an average value of 16 nm, although varies in a wide range from 0 to 200 nm regardless of the channel height. The small-yet-widely-varying values of the graphene slip length are attributed to the surface charge of graphene and the interaction between graphene and underneath silica substrate, which are in good agreement with the prediction of our molecular dynamics (MD) simulation.
NM02.10: Session VIII
Session Chairs
Jianyong Ouyang
Kenji Ueda
Thursday PM, November 30, 2017
Hynes, Level 3, Room 302
1:30 PM - NM02.10.01
Degradable Conjugated Polymer Wrapper with Exceptional Selectivity for Large Diameter Semiconducting Carbon Nanotubes
Padma Gopalan 1 , Catherine Kanimozhi 1 , Matthew Shea 1 , Gerald Brady 1 , Michael Arnold 1
1 , Univ of Wisconsin, Madison, Wisconsin, United States
Show AbstractSeparation of electronically pure, narrow dispersed, pristine semiconducting single walled carbon nanotubes (S-CNT) from a heterogeneous as-synthesized mixture is essential for various semiconducting technologies and biomedical applications. While conjugated polymers are essential for this sorting step, it is highly desirable to remove any organic residues from the resulting devices. We report here the design and synthesis of a degradable conjugated polymer that is structurally analogous to the commonly used commercially available poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(6,6’-(2,2’-bipyridine))]. This polymer was synthesized via a high yielding chemistry with good control over the degree of polymerization. Even with a degree of polymerization of just ~10 showed excellent (> 99% electronic purity) selectivity towards large diameter (1.2-1.7 nm) arc-discharge S-CNTs with an yield of 0.443, similar to PFO-BPy but with the added advantage of complete depolymerization under mild conditions into recyclable monomers. We further show by UV-Vis, X-ray photoelectron spectroscopy (XPS) and SEM that the degradable polymer wrapped S-CNTs can be aligned into a monolayer array on gate dielectrics using a floating evaporative self-assembly process and the polymer can be completely removed from these aligned arrays using mild acid treatment. The resulting short channel FETs (Channel length = 100-700 nm) showed p-type mobilities upto ~128 cm2V-1s-1, current on/off ratio of ~105 with > 99.9% semiconducting electronic purity. More importantly removal of the polymer from the CNT arrays enabled FETs with improved sub threshold behavior in the metrics of on/off current ratio and subthreshold swing. Beyond FETs this discovery opens up the possibility of creating polymer free high purity S-CNT devices for solar cells, sensors and other applications.
1:45 PM - NM02.10.02
Non-Oxidized Graphene for Bioapplications—Preparation, Cytotoxicity and Integration in 3D-Scaffolds
Ester Vazquez 1
1 , UCLM, Ciudad Real Spain
Show AbstractGraphene has emerged as a new material, with outstanding mechanical and electronic properties that will permit a broad range of applications, from microelectronics to composite or even medicine. Although there has been a huge effort directed in the area of nanomedicine, biomedical applications of graphene derivatives have, so far, mainly focused on graphene oxide and reduce graphene oxide. The main reason for this fact is the difficulty to obtain pristine graphene flakes, directly in water or in culture media, due to the intrinsic hydrophobicity of this material.
Our group have recently described an interesting approach for the preparation of stable dispersions of graphene in water, without detergents or any other additives, driven by an easy and eco-friendly ball milling approach. These aqueous suspensions can be rapidly frozen and, subsequently, lyophilized giving rise to a very soft and low-density black powder. Powders of graphene can be safely stored or shipped and they can be readily dispersed in culture media within the presence or absence of serum and antibiotics.
During this talk, we will discuss (i) optimized ways to generate graphene dispersions in culture media; (ii) studies of interaction of so-prepared solutions with cells. (ii) the use of graphene in polymeric 3D structures for drug delivery purposes and for 3D cell culture media.
2:00 PM - NM02.10.03
Integration of 2D Materials into Layer-by-Layer 3D Vertical Structures for High Surface Density Applications
Jiaying Wang 1 , Oscar Vazquez-Mena 1
1 Department of Nanoengineering, University of California, San Diego, La Jolla, California, United States
Show AbstractThree-dimensional graphene architectures are widely utilized in energy environments, sensing and biology areas because of the high specific surface areas, strong mechanical strength and high electron-mobility. Most of these architectures are synthesized by assembling graphite oxides flakes (GOs) or reduced graphite oxide sheets (rGOs) by chemical or thermal reactions1. However, most of current methods give random arrangements of the 2D materials that prevent designing specific layout and geometries. Herein, we present a well-ordered layer-by-layer 3D architectures based on 2D materials with high control on the spacing, sequence and device dimensions. Furthermore, functional nanostructures such plasmonic and dielectric nanoparticles can be incorporated with specific geometries to deliver specific functionalities in a 3D layout.
Our devices are based on SU-8 supporting structures that hold suspended graphene layers with a well-controlled separation from 1 to 10 microns. In addition to 2D atomic materials, we can also incorporate silicon nitride thin films 50-200 nm thick. An important capability of our approach is the integration of micro and nanostructures on the suspended 2D layers that allow different functionalities on each suspended layer. We demonstrate the integration of silver microstructures on different graphene layers just separated by 5 microns. Furthermore, we demonstrate the integration of an array of metallic nanostructures fabricated by e-beam lithography. This allows a precise control on the positioning of nanostructures on the suspended graphene.
Our architecture with suspended 2D layers allows for the integration of different devices distributed vertically at each graphene/thin film layer, as well as a platform with high surface density for filtering and sensing applications. Each suspended graphene/thin film layer can host different materials for different and specific functionalities such as optoelectronics2, sensing3 or filtering4,5. Similarly to novel vertical flash memories, our architecture opens a new path for the vertical integration of micro and nanoscale devices.
References
1. Y. Xu, K. Sheng, C. Li and G. Shi: Self-assembled graphene hydrogel via a one-step hydrothermal process. ACS nano 4, 4324 (2010).
2. L. Ju, B. Geng, J. Horng, C. Girit, M. Martin, Z. Hao, H.A. Bechtel, X. Liang, A. Zettl and Y.R. Shen: Graphene plasmonics for tunable terahertz metamaterials. Nature nanotechnology 6, 630 (2011).
3. O. Vazquez-Mena, T. Sannomiya, L.G. Villanueva, J. Voros and J. Brugger: Metallic nanodot arrays by stencil lithography for plasmonic biosensing applications. ACS nano 5, 844 (2010).
4. B. Mi: Graphene oxide membranes for ionic and molecular sieving. Science 343, 740 (2014).
5. J. Shen, G. Liu, K. Huang, Z. Chu, W. Jin and N. Xu: Subnanometer two-dimensional graphene oxide channels for ultrafast gas sieving. ACS nano 10, 3398 (2016).
2:15 PM - NM02.10.04
Fabrication of Carbon Nanowalls/Diamond Heterojunctions and Their Electronic Properties
Kenji Ueda 1 , H. Itou 1 , H. Asano 1
1 , Nagoya University, Nagoya Japan
Show AbstractGraphene and diamond are typical allotropes of carbon that are necessary for the modern information society due to their superior physical properties. Recently, interfaces between carbon sp2 and sp3 structures attracted much attention because they are considered to be basis of various physical phenomena and electronic applications. Many theorists suggest hybrid structures of graphene including vertically aligned graphene, and diamond (C-sp2-sp3 hybrids) exhibit interesting electronic characters such as high-efficiency photoelectric conversion, etc. We also newly found that diamond-graphene heterojunctions showed photomemristive behaviors [1]. Graphene and diamond are important not only individually in electronic devices but also as building blocks for innovative electronic devices through the use of carbon sp2-sp3 interfaces. In this study, we have tried fabricating heterostructures of vertically aligned graphene (carbon nanowalls (CNW)) and diamond, and examined their electronic properties to find novel electronic functions of carbon sp2-sp3 interfaces.
CNW/diamond semiconductors heterostructures were fabricated on diamond (100) substrates by microwave plasma CVD. By tuning growth conditions, CNW can be formed in-situ on diamond semiconductors in the same reactor. Junctions with CNW/diamond heterostructures (area: 20-160 μmΦ) were fabricated and their current-voltage (I-V) characteristics were examined under photo and heat irradiation.
Many linear wall like structures with length and width of ~1 μm and ~10 nm were observed by SEM measurements of CNW on diamond. In the Raman spectrum of CNW on diamond, three major peaks were observed: G peak (~1580 cm-1) and 2D peak (~2700 cm-1), which are typical of graphene layers, and a D peak at 1350 cm-1. Intensity ratio of D to G peak, which is related to the in-plane sp2 crystalline size, was ~2, indicating smaller grain size of the graphene layers on diamond. The G peak was accompanied by a shoulder peak at ~1620 cm-1, which is characteristic of carbon nanowalls. These results indicate CNW were successfully grown on diamond semiconductors.
In temperature dependence of I-V of the CNW/diamond junctions, ohmic behaviors (no rectification) was observed from R. T. to 200°C. However, the current density in a negative bias region was drastically decreased at 250°C, and the I-V curves changed from ohmic to rectification like behaviors. The current difference between negative and positive bias region became more than 103. Also, the large conductivity change (~102) was caused by white light irradiation below 200°C. These results suggest conductivity of CNW/diamond junctions can be controlled by photo-irradiation as well as heat. The mechanism for the conductivity change was under investigation. These results indicate the CNW-diamond, carbon sp2-sp3 heterointerfaces can be used as novel photo-controllable devices.
Ref. [1] K. Ueda et al., Appl. Phys. Lett. 108 (2016) 222102.
2:30 PM - NM02.10.05
Application of Graphene and Carbon Nanotubes as Electronic Textile and Wearable Sensors
Jianyong Ouyang 1
1 , National University of Singapore, Singapore Singapore
Show AbstractWearable electronic devices are becoming increasingly popular. They can bring a tremendous impact to human life. Wearable sensors, a class of wearable electronic devices, have attracted considerable attention because of their importance in healthcare. Here, we will report graphene-or carbon nanotubes (CNTs)-based wearable sensors, which can be directly integrated into clothes or textile products, are fabricated by simple and cost effective methods. The wearable sensors exhibit a high gauge factor at small strain, and the signal has good reproducibility in response to stretching, bending and pressure. They can respond to a series of human motions with the differentiation of various degrees of motions, and it can monitor small scale motions such as pulse and respiration.
2:45 PM - NM02.10.06
Facile Synthesis and Structural Evaluation of Nitrogen-Doped Porous Carbon and Its Application for Hydrogen Absorption
Tapas Das 1 , Seemita Banerjee 1 , P Sharma 2 , V. Sudarsan 1 , P. U. Sastry 3
1 Chemistry Division, Bhabha Atomic Research Centre, Mumbai India, 2 Department of Energy Science and Engineering, Indian Institute of Technology, Bombay, Mumbai India, 3 Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai India
Show AbstractNow a days, carbon based materials are getting extensive attention for energy related applications [1]. These materials include one dimensional (1D) carbon nanotubes, nanofibers, two-dimensional (2D) graphene, three-dimensional (3D) porous carbon, amorphous carbon etc. Nitrogen containing porous carbons find extensive application as electrode in electrochemical energy storage, storage of CO2, SO2, H2S, H2 etc.[2] due to their large surface area, good electrical conductivity and also eco friendly nature. There are various reports for preparation of N-doped porous carbon and among them the frequently used methods are carbonization of N-containing precursors such as acetonitrile, melamine, polyaniline, polypyrrole etc., co-carbonisation of nitrogen containing organic compounds with N-free materials and heat treatment of carbon with nitrogen containing gases like ammonia, certain amines, pyridines etc. The latter methods generally give low nitrogen incorporation in the carbon frame work. Properties of N-doped carbon materials, like surface area, pore size and pore volumes can be improved or modified by physical and chemical activation methods.
N-doped carbons have been prepared by a very simple method by charring commonly available precursor material namely EDTA with conc.H2SO4 followed by annealing at different temperatures. EDTA acts both as carbon and nitrogen source in this method. The as prepared samples were annealed at different temperatures to see the effect of annealing on nitrogen content and pore size. Further the samples were activated chemically with conc. H3PO4 at different temperatures to change pore size and dimensions. It has been found that with increase in the annealing temperature the graphitic character increases along with decrease in the nitrogen content as found by XPS, NMR and CHN analysis. The samples are found to have both micro and meso-pores as revealed by SAXS and TEM studies. H3PO4 activation leads to formation of larger smooth pores (~11 nm) with worm like pore structure and material shows higher N content (~20%) compared to the non-activated one. During activation, C atoms from the network structure gets oxidised preferentially giving rise to larger pores, which are confirmed by TEM and SAXS analysis. A possible mechanism has been suggested for the activation process based on NMR and XPS results. The pore size has been correlated with hydrogen storage capacity and it has been found that large number of pores with lower pore diameter is preferable for increasing hydrogen storage capacity of mesoporous carbon based materials. The work opens up a new exciting route to synthesize N doped carbon with high nitrogen content and its application in catalysis and energy storage.
References:
1. D. Pech, M. Brunet, H. G. Durou, P. H. Huang, V. Mochalin, Y. Gogotsi, P. L. Taberna and P. Simon, Nat. Nanotechnol. 5 (2010) 651-654.
2. H. Wang, Y. Wang, Y. Li, Y. Wan, Q. Duan, Carbon 82 (2015) 116-123.
3:30 PM - *NM02.10.07
Chemistry of Direct, Wafer-Scale and High-Quality Graphene Synthesis on Silicon-Based Dielectrics via Chemical Vapor Deposition
Phong Nguyen 1 , Sanjay Behura 1 , Michael Seacrist 2 , Vikas Berry 1
1 , University of Illinois at Chicago, Chicago, Illinois, United States, 2 , SunEdison Semiconductor, Saint Peters, Missouri, United States
Show AbstractGraphene intrinsically hosts charge carriers with ultra-high mobility and possesses high quantum capacitance, which are attractive for nanoelectronic applications requiring graphene deposition on substrates. However, most of the current techniques for graphene production rely on growth on metal catalyst surfaces and then contamination-prone transfer to desired dielectric substrates. Direct graphene production on dielectric surfaces is crucial to avoid polymer-adsorption related challenges from the transfer process. Here, we present the chemical-diffusion mechanism of a process for transfer-free growth of graphene on silicon-based dielectric-substrates via chemical vapor deposition. The process relies on the diffusion of catalytically produced carbon radicals through copper (Cu) grain-boundaries and their crystallization at the interface of Cu and silicon-based dielectrics. The graphene produced exhibits low-defect multilayer domains (La~140 nm) with turbostratic orientations. Further, graphene growth between Cu and substrate was 2-fold faster on SiO2/Si<111> substrate than on SiO2/Si<100>. The process parameters such as: growth temperature and the gas compositions (H2/CH4 flow rate ratio) play critical roles in the formation of high quality graphene films. The low-temperature back-gating transport measurements of the interfacial graphene show the density-independent mobility of 277 cm2V-1s-1 and 233 cm2V-1s-1 for holes and electrons, respectively. Consequently, the analysis of electronic transport at various temperature reveals a dominant Coulombic scattering, a thermal activation energy (2.0±0.2 meV), and two-dimensional hopping conduction in the thin graphene field-effect transistor. A band overlapping energy of 2.3±0.4 meV is also estimated by utilizing the simple two-band model.
4:00 PM - NM02.10.08
Structure and Dynamics of Water Confined in Nanoporous Carbon
Yuzi He 1 , Rajiv Kalia 1 2 3 , Aiichiro Nakano 1 2 3 , Priya Vashishta 1 2 3
1 Collaboratory of Advanced Computing and Simulations, Department of Physics and Astronomy, University of Southern California, Los Angeles, California, United States, 2 Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California, United States, 3 Department of Computer Science, University of Southern California, Los Angeles, California, United States
Show AbstractWe study the structure and dynamics of water confined in nanocarbon ribbons and graphitic nanostructures using molecular dynamics (MD) simulations. The nanocarbon ribbons and graphitic nanostructures are generated in a reactive MD simulation of oxidation of a silicon carbide nanoparticle. We find Si oxidizes rapidly and nanocarbon ribbons and graphitic nanostructures are a byproduct of Si oxidation. We embed water molecules in graphitic nanopores and study structural and dynamical properties of nanoconfined water as a function of temperature. MD simulation results indicate the presence of high-density water (HDW) and low-density water (LDW). Radial distribution functions of the HDW and LDW indicate that the second solvation shell of the HDW is broken. We calculated self-diffusion of confined water molecules as a function of temperature. The cage correlation function c(t) of confined water molecules at T = 200K exhibits stretched exponential decay, c(t) = exp((t/τ)β), with β≈0.60. The calculation of intermediate scattering function will also be reported.
This research was supported by the Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division, Theoretical Condensed Matter Physics,
Grant # DE-FG02-04ER46130.
4:15 PM - NM02.10.09
Dynamical Behaviors of Nanostructured Networks under High-Strain-Rate Mechanical Loads
Zhiping Xu 1 , Shijun Wang 1 , Enlai Gao 1
1 , Tsinghua University, Beijing China
Show AbstractNanostructured networks such as thin films of carbon nanotubes and graphene sheets hold great promise in structural applications according to the excellent mechanical properties and thermal stability of their nanoscale building blocks. However, mapping these merits to macroscopic materials are difficult because the lack of efficient techniques to grow large-scale samples, or control the microstructural orders in the macroscopic assemblies. To understand the microstructure-performance relationship of these complex materials, we carried out theoretical and experimental studies, with focus on their dynamical behaviors under high-strain-rate mechanical loads. Mesoscale simulations are performed with material microstructures characterized from fabricated samples, and the results are compared with other materials such as polymers and metals. We find that the deformation and fracture of interfaces between nanostructures play a key role in defining the dynamical responses of networked materials to external mechanical stimuli, which provide additional channels for efficient energy dissipation, and could preserve the structural integrity through a self-healing process.
4:30 PM - NM02.10.10
3D-Carbon Hybrid Nanostructure Formation Using Zeolite Template
Carolina Rojas 1 , Neida M Santacruz Sarmiento 2 , Frank Mendoza 2 , Gerardo Morell 1 , Brad Weiner 3
1 Department of Physics, University of Puerto Rico, San Juan, Puerto Rico, United States, 2 Department of Physical Sciences, University of Puerto Rico, San Juan, Puerto Rico, United States, 3 Department of Chemistry, University of Puerto Rico, San Juan, Puerto Rico, United States
Show AbstractThe emerging carbon-based materials possess properties that depend on the way how carbon is structured at the nanoscale. Synthesis of novel three dimensional (3D) nanostructures of carbon compound would be an important advance for fundamental research and various applications. In this work, we discuss the possibility of fabricating complex 3D nanostructures by growing carbon-compounds on pre-synthesized nanostructured zeolites templates by chemical vapor deposition (CVD) and then etching away the zeolites. We study two types of zeolites structures, NaX and NaY. We systematically study the roles of different parameters, such as the composition, morphology and crystallinity of the material on zeolites-template, as well as the CVD growth temperature and different carbon sources to synthesize the carbon-compound on zeolites. The same time we will shows that polycrystalline nanostructures start to growth at low temperature of 500 oC. However we observed that the crystallinity of the nanostructures was affected by the selection of reactive carbon source that is deposited on the zeolite from lower temperatures. Furthermore, the selection of a zeolite is also important, as type X are shown to be more resistant to thermal damage than their type Y. We could successfully remove the zeolite templates to form free-standing carbon-based hollow nanostructures. This 3D structure could be used in water or air filters in a potential biological application for removal of bacteria in conditioner airs or and plants of water treatments. The results presented in this analysis could to help the synthesis of other 3D-carbon nanostructures.
4:45 PM - NM02.10.11
Hyperspectral NanoRaman Imaging for Studying Carbon-Based Materials
Maruda Shanmugasundaram 1 , Andrey Krayev 2 , Marc Chaigneau 3 , Dmitry Evplov 2 , Vasily Gavrilyuk 2 , Sergey Saunin 2
1 , HORIBA Scientific, Edison, New Jersey, United States, 2 , AIST-NT, Novato, California, United States, 3 , HORIBA Jobin Yvon SAS, Palaiseau France
Show AbstractRaman spectroscopy is used to study the chemical composition of materials with a high degree of specificity, but it has poor sensitivity due to an inherent weakness of Raman scattering and its spatial resolution is diffraction-limited by far field optics to ~0.5λ. These drawbacks can be overcome by nanoRaman™ or tip-enhanced Raman spectroscopy (TERS). In TERS, a Scanning Probe Microscope (SPM) tip coated with gold or silver is brought into contact with the material of interest. This not only produces a near field Raman signal with orders of magnitude higher intensity due to an enhanced electromagnetic field, but also gives a spatial resolution proportional to the tip dimensions due to confinement of the electromagnetic field directly under the tip.
Carbon-based materials such as carbon nanotubes and graphene oxide have potentially a wide variety of applications in nanotechnology; they have also been some of the most widely studied materials using TERS. However, for a long time since TERS was first experimentally demonstrated, measurements were reported only from single points or from a series of points along a line. More recently, TERS mapping has been demonstrated, using which a near-field Raman image can be constructed from the hyperspectral dataset consisting of a two dimensional array of near-field Raman spectra. Such TERS measurements reveal chemical and morphological information in the nanoscale, and resolution better than 20 nm is commonly reported.
Here, TERS images of carbon nanotubes and graphene oxide are shown. They reveal inhomogeneity of chemical composition on the surface of carbon nanotubes that cannot be captured using SPM or micro Raman measurements alone. Interestingly, greater enhancement along the edge of graphene oxide flakes relative to adjacent portions was observed. Similar differences in TERS response is also obtained from folds and wrinkles in graphene oxide flakes as well as from areas that are patterned by pulsed force lithography compared to flat or unpatterned areas, and possible reasons are discussed. Finally, TERS images of multi-component samples are shown, which show the ability of TERS to detect individual components among them due to the inherent chemical specificity of Raman scattering, in addition to the improved sensitivity and spatial resolution of TERS.
NM02.11: Poster Session III
Session Chairs
Friday AM, December 01, 2017
Hynes, Level 1, Hall B
8:00 PM - NM02.11.01
Oxidation Dispersity Number for Graphene Oxide
Harish Kumar 2 , Chinthani D. Liyanage 1 , Douglas Adamson 2 1
2 Institute of Materials Science, University of Connecticut, Storrs, Connecticut, United States, 1 Department of Chemistry, University of Connecticut, Storrs, Connecticut, United States
Show AbstractGraphene oxide (GO) finds applications in variety of areas including, but not limited to, electronics, energy, biomedicine, and optics. Variations in oxidation of GO and its impact on various applications have not been much investigated even though these variations tend to effect the properties of GO. In order to universally understand this variation in oxidation, we have defined an oxidation dispersity number (OD) for GO samples. We divide a given GO sample in a number of differently oxidized parts. The characterization of these differently oxidized GO samples enable us quantifying the OD for a given batch and can be used to tune the density of oxygen functionalities in a GO sample. This emulsion based method is pH dependent and can also be used to isolate a reduced graphene oxide (rGO) like material with a reduced value of Raman defect density. This rGO like material has the capability of replacing the more expensive and topological defects inducing methods presently available. Further, we investigate the properties of different GO samples on the basis of their OD numbers. This number shows that the dispersity of oxidation in a given sample does have an impact on its properties and thereby performance of corresponding applications.
8:00 PM - NM02.11.02
Monolayer Graphene Etch Masks and Etch Stops for 2D Heterostructures
Jangyup Son 1 , Jun-Young Kwon 2 , SunPhil Kim 1 , Yinchuan Lv 3 , Jong-Young Lee 2 , Huije Ryu 2 , Pinshane Huang 3 , Gwan-Hyoung Lee 2 , Arend van der Zande 1
1 Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 Materials Science and Engineering, Yonsei University, Seoul Korea (the Republic of), 3 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractSelective etching is a crucial process in many microfabrication processes. Various techniques, such as chemical or plasma etching, have been used for nanopatterning thin films, suspending microstructures and accessing buried layers with atomic precision [1,2]. A significant challenge in the emerging class of nanoelectronic devices made from 2D material heterostructures is that there are no demonstrated processes for selective etching of materials which would enable access to a desired layer. In most processes, contacts are achieved either by offsetting the layers or through edge contacts where the entire structure is etched [3]. Highly selective etches that enable the creation of etch masks and etch stops for specific 2D materials are a necessary step to the integration of 2D materials as a viable technology by allowing the fabrication of complex nanoelectromechanical systems (NEMS) and nanoelectronic devices which are impossible with current techniques.
In this presentation, we show a novel selective etching technique of 2D heterostructures using XeF2 etching gas. We demonstrate that atomically-thin monolayer graphene is chemically functionalized, i.e. fluorographene, but not etched. In contrast, most inorganic 2D materials, such as hexagonal boron nitride (h-BN), transition metal dichalcogenides (TMDs), and black phosphorus (BP), are efficiently etched away by their exposure to XeF2 gas at room temperature. Based on this, we used a graphene layer as etch mask and etch stop for patterning other 2D layers in van der Waals (vdW) heterostructures. We also demonstrate the use of this selective etch process and graphene etch masks in two different applications: 2D NEMS and buried 2D electrodes. First, we fabricate a suspended graphene membrane by vapor phase etching of a BP thin film supporting graphene. We show that the graphene membrane behaves as a nanomechanical resonator with a frequency of 5.24 MHz and quality factor of ~255, comparable to graphene NEMS prepared on conventional substrates. Second, we fabricate an electrical device using graphene as an etch stop layer to make buried contacts in a 2D material heterostructure. Holes were etched through the top layer of h-BN in an encapsulated BN-G-BN heterostructure to locally expose the buried graphene layer and contacts were fabricated by evaporating metal electrodes on the exposed graphene regions. The resulting encapsulated graphene field effect transistor had a low contact resistance of about 300 ohm um (n = −1×1012 cm2) at room temperature, leading to high carrier mobility of 40,000 cm2V-1s-1, which is comparable to the electrical properties of state-of-the-art edge contacted graphene devices [3]. These methods will lead us a step closer to realization of new fully-2D-materials-based applications.
References
[1] J. Feng et al, Nanoscale 4, 4883 (2012).
[2] M. G. Stanford, B. B. Lewis, and K. Mahady, J. Vac. Sci. Technol. B 35, 030802 (2017).
[3] L. Wang et al, Science 342, 614 (2013).
8:00 PM - NM02.11.03
Carbon Materials from Rapidly Solidified Nickel-Carbon Alloys
Gina Greenidge 1 , Bernard Gaskey 1 , Bijan Varjavand 1 , Jonah Erlebacher 1
1 , Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractMelt spinning, a process whereby a liquid metal is ejected through a nozzle and rapidly solidified onto a rotating wheel, is perhaps most popular for its role in the production of metallic glasses and alloys. Here we discuss the use of melt spinning in the manufacture of a variety of nanostructured carbon materials such as carbon fiber precursor material and high surface area “activated” carbon. Melt spinning does not involve any polymer synthesis, and therefore might significantly reduce costs for manufacture of the nanostructured carbon materials. Via the use of this rapid solidification technique, where typical cooling rates can exceed 105 K/sec, we have been able to access non-equilibrium phases in the nickel-carbon alloy system, supersaturating nickel ribbon with up to 20 at% carbon. We will discuss the experimental conditions leading to such high supersaturations, as well as the precipitation kinetics and morphology of carbon recovered from the ribbons upon dissolution of the nickel.
8:00 PM - NM02.11.04
Application of rGO-Zn0.8Cd0.2S in Schottky Barrier Diode for Significant Improvement in Device Performance and Superior Charge Transport Properties
Mrinmay Das 1 , Joydeep Datta 1 , Arka Dey 1 , Partha Ray 1
1 Department of Physics, Jadavpur University, Kolkata, West Bengal, India
Show AbstractEver since graphene was first isolated in 2004, there has been a stunning growth in the application of graphene to electronic devices such as Schottky barrier diodes (SBDs). Meanwhile, reduced graphene oxide (rGO)-ZnxCd1−xS nanocomposites have shown good promise for various applications but so far there are no detailed investigations on SBDs based on this material. Schottky barrier diode, which is a key building block in modern electronics, is often formed at a metal-semiconductor (M-S) interface. In this context, here we present the synthesis of a rGO–Zn0.8Cd0.2S composite with different weight ratios of rGO (rGO = 0.25%, 0.5%, 1% and 2%) via a facile coprecipitation-hydrothermal reduction strategy and its performance in Al/rGO-Zn0.8Cd0.2S/ITO SBD. The device performance was compared with Al/Zn0.8Cd0.2S/ITO SBD. In this regard, current-voltage (I-V) measurements were performed in dark and under illumination, and important diode parameters were obtained for both conditions. All the rGO-Zn0.8Cd0.2S based devices showed much better rectification and photoresponse compared to the Zn0.8Cd0.2S based SBD, while the best performance was obtained for 2% rGO. Due to the incorporation of graphene, the photoresponse of the Al/rGO–Zn0.8Cd0.2S/ITO SBD was enormously enhanced by almost 448% compared to its counterpart. Furthermore, the detectivity also increased by 2 order of a magnitude. Moreover, a considerably lower barrier height of 0.16 eV was achieved for Al/rGO- Zn0.8Cd0.2S/ITO SBD, compared to 0.28 eV for the Zn0.8Cd0.2S based device. To illustrate the improved performance of rGO-Zn0.8Cd0.2S, the charge transport properties of the materials were explored by space charge limited current (SCLC) theory, which demonstrated superior charge transfer kinetics after incorporation of rGO. Notably, there was an exceptional 300% increase in effective carrier mobility for rGO-Zn0.8Cd0.2S. Not only that, the carrier concentration and diffusion length of the carriers were also higher in the rGO-Zn0.8Cd0.2S composite. The charge transport analysis from SCLC was further verified by photoluminescence and electrochemical impedance spectroscopy (EIS) measurements. In the composite, the excited electrons are transferred from the CB of Zn0.8Cd0.2S to the rGO sheets, which serve as an extended electron collector and transporter, thus retarding charge recombination and significantly enhancing the mean free path of electrons, in turn leading to a higher current. These results demonstrate the beneficial impact of graphene on a Zn0.8Cd0.2S based SBD. Indeed, the Al/rGO–Zn0.8Cd0.2S/ITO SBD exhibited a vastly improved performance, with a considerably lower barrier height, highly enhanced photoresponse and superior charge transport. Overall, the picture emerging from present study shed light on the carrier transport of rGO-Zn0.8Cd0.2S and demonstrates that rGO-Zn0.8Cd0.2S have great potential in future designing of multifunctional optoelectronic devices.
8:00 PM - NM02.11.05
Direct Growth of Spatially Layer-Tuned Graphene Using Self-Assembled Monolayer
Gwangseok Yang 1 , Hyunik Park 1 , Hong-Yeol Kim 1 , Jihyun Kim 1
1 , Korea University, Seoul Korea (the Republic of)
Show AbstractGraphene has attracted great attention due to its unique optical and electrical characteristics. Graphene grown by chemical vapor deposition (CVD) method has been generally used to obtain large-area graphene with high quality. However, CVD grown graphene usually requires a transfer process which can induce defects, pollution, as well as consume additional time. Furthermore, tears and wrinkles can easily occur if graphene is transferred onto a non-planar substrate. Therefore, direct growth of graphene onto the target substrate is one of the upcoming issues in graphene synthesis.
In this work, we demonstrate a direct growth method of multilayer graphene on various substrates, including SiO2/Si, Quartz, GaN, and patterned sapphire substrates using self-assembled monolayer (SAM). SAM was used as a carbon source for graphene growth because it can be uniformly coated even on non-planar substrate. The metal catalyst was deposited on SAM, followed by thermal annealing to convert SAM to graphene. Comparative investigations on the kind of catalytic metals such as Cu, and Ni were conducted to ascertain the effects of the metal catalyst. Also, a bilayer catalyst metal, Ni patterns on Cu films, was used to grow spatially layer-tuned graphene. Electronic and optical properties of graphene were successfully modulated by introducing spatially layer-tuned graphene because its optical and electrical properties could be controlled by its thickness. The details of our experiment and results will be discussed.
8:00 PM - NM02.11.06
Modifications of Single-Layer Graphene Transferred onto SiO2/Si Induced by Water Vapor Annealing
Guilherme Rolim 4 , Nicolau Bom 4 , Joao Lopes 1 , Gabriel Soares 2 , Claudio Radtke 3
4 PGMICRO, UFRGS, Porto Alegre, RS, Brazil, 1 , Paul-Drude-Institut für Festkörpereletronik, Berlin Germany, 2 Instituto de Física, UFRGS, Porto Alegre, RS, Brazil, 3 Instituto de Química, UFRGS, Porto Alegre, RS, Brazil
Show AbstractGraphene is the two-dimensional building block for carbon allotropes, exhibiting fascinating physical properties such as very high carrier mobility and near-ballistic transport at room temperature. In order to graphene fulfill its potentialities, a detailed knowledge of processing and modification of this material is required. In particular, the adsorption of different species is of central importance. Understanding these processes is necessary in order to meet the physical requirements for industrial applications of graphene. In this context, we systematically investigated the incorporation of H and O in single-layer graphene (SLG) transferred onto SiO2/Si substrates, upon annealing in water vapor. For that, the concentration of these elements was obtained by using water enriched in 2H (deuterium, D) and 18O rare isotopes (natural abundances of 0.0115% and 0.205%, respectively). The use of isotopic tracing in conjunction with nuclear reaction analysis (NRA) enabled the quantification of species specifically incorporated in the annealing step. Complementary X-ray spectroscopies using synchrotron radiation and Raman spectroscopy were employed in order to investigate the related physico-chemical changes induced by the annealings. Transport properties were also accomplished. Thus, the correlation between structural changes with charge carrier characteristics could be obtained. Results evidenced that the incorporation behavior is strongly dependent on the annealing temperature for O and H. The reactivity of graphene toward water exposure presents a threshold of around 400 °C: (i) Below this threshold, the increase in p-doping is associated with the physical adsorption of H2O in the SLG/SiO2/Si structure and to the closer contact between SLG and the SiO2 surface as an effect of heating. (ii) For 400 °C and above, the concentration of defects sharply increases, which favors the chemical adsorption of O atoms in the graphene network, as evidenced by NRA. Thus, the structural disorder verified in the SLG could be associated with the adsorption of species from the gas phase (identified by isotopic labeling), a hypothesis previously suggested in the literature. This structural disorder is related to rippling of graphene and creation of oxygen related functionalities. Finally, the connection between physico-chemical modifications induced by annealings and the electrical properties of the SLG/SiO2/Si structures is made for each adsorption regime.
8:00 PM - NM02.11.07
Room Temperature Dielectric Characteristics of Chitosan-Graphene Films Embedded in Cellulose Fabric
Radha Perumal Ramasamy 1 , Swathi Somanathan 1 , Vinod Kumar Aswal 2 , Miriam Rafailovich 3
1 , Anna University, Chennai India, 2 Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai, Maharashtra, India, 3 Materials Science and Engineering, Stony Brook University, Stony Brook, New York, United States
Show AbstractDevelopment of solid polymer electrolytes is important for battery technology. Membranes should be environment friendly and also have high conductivity. We use chitosan, cellulose and graphene in this research. In this work, 1% (w/v) of chitosan powder and 1.5% (w/v) of acetic acid were dissolved in double distilled water. The solution was heated to 60°C under constant stirring until the chitosan powder was completely dissolved and a semitransparent thick chitosan solution was obtained. To this chitosan solution appropriate amounts of graphene (grade H5-XG Sciences) was added to have 5,10,20 and 30% graphene (weight with respect to chitosan). The solution was sonicated for dispersing graphene and then 100ml of it was poured on plastic dishes with and without cellulose fabric in it. The films were dried by slow evaporation technique. The sample thickness varied from 200 to 300µm .SEM images showed that chitosan film formed on cellulose and had grid like structures. Chitosan deposited more on the fibers of the cellulose. This is attributed to the rectangle shaped microspores of cellulose. From the cross section of the films, it was observed that graphene arranged in stacks along the plane of the cellulose fabric and the fabric became darker as graphene concentration increased.The dielectric properties such as dielectric constant, impedance, conductivity and dissipation factor were measured from 102 - 106 Hz. The conductivity of the sample increases as the frequency increases. The conductivity of the samples at room temperature increases with an increase in Graphene concentration. The conductivity varies from 10-8 to 10-5 S/Cm as the graphene concentration increases from 0 to 30%. Hence conductivity increases significantly as graphene concentration increases. From the dissipation factor for the films, the relaxation process could be observed in the frequency ranging from 102 to 105 Hz. It is observed that as frequency increases, the relaxation tend to shift towards higher frequency indicating that graphene affects the relaxation of the polymer. At high frequency ( 106Hz) dissipation factor for cellulose fabric, Chitosan in cellulose, chitosan with 5% graphene in cellulose, chitosan with 10% graphene in cellulose, chitosan with 20% graphene in cellulose, chitosan with 30% graphene in cellulose are 0.14,0.19,0.4,0.8 and1.38 respectively. This shows that dissipation factor increases as the graphene concentration increases. This implies that graphene favors heat dissipation in these films. The dielectric constant was observed to be maximum for chitosan with 10% graphene in cellulose indicating that the graphene may assemble as chains for higher concentrations of graphene (20 and 30%) thereby reducing the capacitance and favoring conductivity. Small angle neutron scattering analysis showed that fractals formed for graphene containing samples while lamellar shapes formed for chitosan film on cellulose.
8:00 PM - NM02.11.10
Deformation in Graphene through Hyperspectral Synchrotron Spectroscopy
Allen Winter 1 , Wudmir Rojas 1 , Steve Kim 2 , Daniel Fischer 3 , Conan Weiland 3 , Sarbajit Banerjee 4 , Rajesh Naik 2 , Apurva Mehta 5 , James Grote 2 , David Prendergast 6 , Eva Campo 1
1 , Bangor University, Bangor United Kingdom, 2 , Wright-Patterson Air Force Base, Dayton, Ohio, United States, 3 , National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 4 , Texas A&M University, College Station, Texas, United States, 5 , Stanford University, Stanford, California, United States, 6 , Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show Abstract
The promise from graphene to produce devices with high mobilities and detectors with fast response times is truncated in practice by strain and deformation originating during growth and subsequent processing. This work describes how graphene growth and processing (to encompass multiple layer transfer, and substrate termination) affect out of plane deformation, which has been identified earlier as critical to future device performance. The advent of hyperspectral large-area detectors in synchrotron spectroscopy allows not only the molecular sensitivity typically afforded by these techniques, but also the ability to map at wafer lenghtscales, bringing up a suitability to informing industrial processes. Full exploitation of these technologies to adequately describe growth and processing in graphene also involve the development of data analytic strategies.
Indeed, a study of methodologies typically used in data analysis discouraged dichroic ratio approaches in favor of orbital vector approximations and data mining algorithms. This work has identified orbital vector methods to be suitable for the analysis of this data. Orbital vector methods provide a physical insight into mobility-detrimental rippling by identifying ripple frequency as main actor, rather than intensity. In addition, these findings were confirmed by data mining algorithms, which are also in good agreement with electron scattering theories of corrugation in graphene. The approach presented here is an efficient vehicle towards the analysis of deformation in graphene at wafer scales.
8:00 PM - NM02.11.11
Dry Cleaning of Polymeric Residues from Graphene with High Density Hydrogen Plasma—The Issue of Plasma Purity
Hasan-al Mehedi 1 , Djawhar Ferrah 2 , Camille Petit-Etienne 1 , Hanako Okuno 3 , Vincent Bouchiat 4 , Olivier Renault 2 , Gilles Cunge 1
1 Laboratoire des Technologies de la Microelectronique, Centre National de la Recherche Scientifique (CNRS) and UJF, Grenoble France, 2 Leti-Minatec, CEA, Grenoble France, 3 INAC/SP2M/LEMMA, CEA, Grenoble France, 4 Institut Néel, Centre National de la Recherche Scientifique (CNRS) and UJF-INP, Grenoble France
Show AbstractGraphene is purely two-dimensional: it consists of two exposed sp2-hybridized carbon surfaces and has no bulk. Therefore, graphene surface contamination by adsorbed polymer residues have a critical influence on its electrical properties and can drastically hamper its widespread use in device fabrication. These contaminants also impact fundamental studies of the electronic and structural properties at the atomic scale. Therefore, graphene-based technology and research requires “soft” and selective surface cleaning process to limit or to suppress this surface contamination. However, polymeric contamination is resistant to cleaning due to p-stacking and is problematic because it originates from typical technological processes used to fabricate graphene devices. Since solvents are not efficient to clean these residues, other strategies based on reactive plasma have been proposed. Here, we investigated a high density H2 plasma cleaning process of transferred CVD graphene monolayer on SiO2/Si substrate in an industrial ICP plasma reactor designed to etch 300mm diameter wafers.1 Firstly, we show that there is a considerable issue associated with the use of H2 plasmas to treat graphene (and other 2D materials): H atoms and H3+ ions reduce the surface of all the materials exposed to the plasma, which include the reactor walls (typically made of Al2O3, Y2O3 or SiO2) and the substrate holder (i.e. the 300 mm diameter wafer on which the graphene sample is stuck). As a result, metallic and O atoms are released in the H2 plasma, resulting respectively in graphene metallic contamination and damages (Si stick on graphene while O atoms etch it spontaneously). We investigated various different coating of the reactor walls to prevent this phenomenon. We concluded that the only solution to get rid of parasitic O is to use a wafer holder made of Aluminum and to fully fluorinated the reactor walls and the wafer with a F-rich plasma prior the H2 process. Under such well controlled conditions, we show that H2 plasmas can provide an infinite etching selectivity between the sp2 and sp3 hybridized form of carbon, i.e. H2 plasma can clean polymer residues such as PMMA from graphene. The quality of the cleaning and the absence of graphene damages are characterized by various surface diagnostic techniques, including k-PEEM to measure its band structure and simple electrical measurements. We show that the cleaned graphene lattice remains undamaged by H2 high density ICP plasma, but it displays higher electrical resistivity than pristine graphene even after H desorption by thermal annealing in vacuum. While yet to be confirmed, the plasma might induce cutting along grain boundaries separating individual grains. Once controlled, this H2 plasam dry-cleaning has the advantage to be an industrially mature technology adapted to large area substrates as well as to other 2D materials and heterostructures.
[1] Journal of Applied Physics 118, 123302 (2015).
8:00 PM - NM02.11.12
Synthesis of Nitrogen-Doped Graphene on Metals from Azafullerene
Xiangmin Fei 1 2 , Joshua Neilson 1 , Yanbang Li 3 , Harutiun Chinkezian 1 , Vanessa Lopez 1 , Simon Garrett 4 , Liangbing Gan 3 , Hongjun Gao 2 , Li Gao 1
1 Department of Physics and Astronomy, California State University, Northridge, California, United States, 2 , Institute of Physics, Chinese Academy of Sciences, Beijing China, 3 Key Laboratory of Bioorganic Chemistry and Molecular Engineering of the Ministry of Education, College of Chemistry and Molecular Engineering, Peking University, Beijing China, 4 Department of Chemistry and Biochemistry, California State University, Northridge, California, United States
Show AbstractSubstitutional doping of graphene with heteroatoms is one of the most fascinating strategies for tailoring various properties of graphene and hence expanding the practical applications of this wonder material. The synthesis of nitrogen-doped graphene from nitrogen-containing sole precursors has recently demonstrated its feasibility with several different sole precursors. In this talk, I will present our recent studies on the synthesis of nitrogen-doped graphene on metals by using a nitrogen-containing sole precursor azafullerene. The synthesis process and doping properties are investigated by combining scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) measurements. Three different metal substrates have been used, including the Ru(0001), Cu(111), and Ir(111) surfaces. For the synthesis experiments performed on the Ru(0001) surface, we found that the concentration of nitrogen-related defects in the graphene layer can be tuned by adjusting the dosage of sole precursor azafullerene and the number of growth cycles. The spatial homogeneity of nitrogen-related defects is high and improves with increasing doping concentration. The predominant doping configuration is pyridinic nitrogen, while some nitrogen atoms are in an anionic state due to their bonding with the ruthenium surface. The pyridinic nitrogen doping configuration is correlated to single-atom vacancies in the graphene layer, as suggested by STM and XPS measurements. For the synthesis experiments performed on the Cu(111) surface, we observed that within graphene islands almost all nitrogen dopants are in the form of graphitic nitrogen and they tend to arrange into rings after multiple growth cycles. XPS measurements indicate that the predominant doping configuration on the sample surface is pyridinic nitrogen, which suggests that most nitrogen atoms on the sample surface are bonded to the edges of graphene islands in the form of pyridinic nitrogen. In addition, some results for the synthesis experiments performed on the Ir(111) surface will also be presented. Our studies indicate that azafullerene is an effective nitrogen-containing sole precursor for the controlled synthesis of nitrogen-doped graphene, and the growth substrates strongly influence the synthesis process and doping properties.
8:00 PM - NM02.11.13
Atomic Level Cleaning of Poly-Methyl-Methacrylate Residues from the Graphene Surface Using Radiolized Water at High Temperatures
Benji Maruyama 1 , Ahmad Islam 1 , Dmitri Zakharov 2 , Jennifer Carpena-Nunez 1 , Ming-Siao Hsiao 1 , Lawrence Drummy 1 , Eric Stach 2
1 , Air Force Research Laboratory, Wright Patterson AFB, Ohio, United States, 2 CNM, Brookhaven National Laboratory, Upton, New York, United States
Show AbstractGraphene is a two-dimensional (2-D) material of extreme interest with applications in electronics, optoelectronics and bio-/chemical sensors. It is conventionally grown on thin films of Cu and Ni using chemical vapor deposition (CVD). Large-scale applications of graphene, however, require transfer of graphene from Cu foils to the surfaces of arbitrary substrates like oxides, semiconductors, or even on other 2-D materials in order to make 2-D heterostructures. All the existing transfer methodologies, however, leave residues at different degrees on graphene surfaces and can only provide atomically clean graphene surfaces in areas as large as ~ 10-4 µm2 [1]. Poly-methyl-methacrylate (PMMA) film is routinely used as a support layer to transfer CVD-grown graphene on to different substrates [1,2], as it imposes the least physical damage to the graphene layer during transfer and yields larger substrate coverage with no mechanical forces being applied to complete the transfer. These features of PMMA also make it attractive as a support layer for transferring graphene from Cu foil to silicon nitride chips that can be used for liquid cell transmission electron microscopy (TEM) imaging and in-situ heating. (In addition to transfer, PMMA is also popular for lithographic patterning of graphene-based and other devices.) Here, we transfer CVD-grown graphene using Poly-methyl-methacrylate (PMMA) and present a method that can atomically clean the PMMA residues from a larger surface area of graphene using radiolized water obtained via electron-water interaction at high temperatures. The cleaning process was monitored in-situ using an environmental-mode transmission electron microscopy and electron energy loss spectroscopy. These showed the effectiveness of PMMA removal over areas as large as ~ 0.02 µm2 (which is ~100 times larger than previous reports [1]), whose size was only limited by the size of electron-beam and the presence of inorganic residues after the transfer process. By overcoming these limitations, we may achieve atomically clean graphene transfer to even larger areas – enabling more challenging device applications.
[1] G. Cunge, D. Ferrah, C. Petit-Etienne, A. Davydova, H. Okuno, D. Kalita, V. Bouchiat and O. Renault, Journal of Applied Physics 118 (12) (2015)
[2] X. S. Li, Y. W. Zhu, W. W. Cai, M. Borysiak, B. Y. Han, D. Chen, R. D. Piner, L. Colombo and R. S. Ruoff, Nano Letters 9 (12), 4359-4363 (2009).
8:00 PM - NM02.11.14
Electrical-Potential Dependent Enhancement of Electrical/Thermal Conductivity in Graphite/Water and Graphite/Ice Suspensions
Shien Ping Feng 1 3 , Peng Zhai 1 2 , Xun Wang 1
1 Mechanical Engineering, The University of Hong Kong, Hong Kong Hong Kong, 3 Zhejiang Institute of Research and Innovation (ZIRI), The University of Hong Kong, Hangzhou China, 2 School of Science, Northwestern Polytechnical University, Xi’an China
Show AbstractNanofluids, liquids containing suspensions of solid nanoparticles, have attracted wide attention due to the enhancement in heat transfer and their potential applications in energy technologies. Carbon-based materials with a high aspect ratio, such as carbon nanotubes (CNT), graphite, and graphene, are excellent additives to achieve high thermal and electrical conductivity. Our previous experimental investigations of stable graphite suspensions in ethylene glycol (EG) and poly α-olefin oil (PAO) suggest that the enhanced electrical and thermal conductivity are mainly due to nanoparticle clustering and the thermal percolation effect. It is known that chemically modified nanoparticles gain a surface charge when dispersed into the solution because surface functional groups tend to adsorb ions in the base solution or dissociate themselves spontaneously. However, conventional models of effective electrical conductivity in nanofluids do not account for the surface charge effect. The effect may be negligible in the majority of previous experiments because of the lack of external electrical potential. In this work, we found an interesting enhancement in electrical/thermal conductivity in phenyl-sulfonic functionalized graphene (SG)/water suspension, which can be greatly enhanced by applying an external electrical potential after a few tens of seconds, indicating the formation of a graphite network in the suspension. Here, we report the effective use of an electrical field to enhance and regulate the electrical conductivity in SG/water suspensions, where the formation of percolation networks is dependent on the volume fraction and the intensity of the electrical field. Chronoamperograms provide evidence that isolated SG clusters percolate to 3D networks under an external electrical potential. AC impedance explains the corresponding change in the potential-dependent interaction between SG-SG and cluster-cluster by manipulating the electrical field. When the SG/water suspension is frozen under the electrical field, the liquid-solid phase transition produces conductive SG/ice with a one-order magnitude improvement in electrical conductivity compared with pure ice. Our experiments lead to new insights into the state of dispersion and connectivity of SG in liquid suspension and liquid-solid phase transition when an electrical field is applied. The electric-field-tunable nanofluids may find applications in energy systems, such as thermal convection and thermal energy storage.
8:00 PM - NM02.11.15
Sterically Governed Molecular Conjugation across Nanoscale Pores in Graphene Membranes for Improved Selectivity
Doojoon Jang 1 , Sui Zhang 1 , Yunxia Hu 1 , Rohit Karnik 1
1 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractRecent reports of experimental measurements of water and mass transport across nanoporous graphene membranes have demonstrated the possibility of using graphene in membrane separation. Nevertheless, current methods to create sub-nanometer or nanometer-scale pores in graphene result in a finite pore size distribution. Diffusive leakage of solutes across larger non-selective pores in the distribution compromises the selectivity of the graphene membranes, resulting in inadequate retention performance compared to conventional nanofiltration or reverse osmosis membranes.
Herein, we present a method to introduce high molecular weight conjugates of primary amine and N-Hydroxysuccinimide (NHS) across leaky graphene pores to mitigate diffusive solute leakage. Multi-branched polyethylenimine and NHS-functionalized polyethylene glycol were selected for crosslinking across the membranes and were introduced on opposite sides of nanoporous graphene. These multi-branched molecules were selected such that they are larger than the non-selective pores, but their arms are expected to penetrate through the non-selective pores and crosslink with the molecules on the opposite side. The resulting conjugates with stable amide bond are expected to provide hindrance to solute passage across large defects. After the amine-NHS crosslinking, the diffusion of salts and organic molecules across leaky nanopores decreased by 40-70%. The solute transport decreased by 60-70% in forward osmosis, resulting in >90% rejection of multivalent salts. This work presents a new perspective of molecular conjugation across atomically thin nanoscale defects to enhance the membrane performance.
8:00 PM - NM02.11.16
In Situ Production of Graphene-Fibers Hybrid Non-Woven Structures
Mandana Akia 1 , Lee Cremar 1 , Mircea Chipara 1 , Edgar Munoz 1 , Hilario Cortez 1 , Hector de Santiago 1 , Fernando J. Rodriguez-Macias 2 , Yadira Vega-Cantú 2 , Hamidreza Arandiyan 3 , Hongyu Sun 4 , Timothy P. Lodge 5 , Yuanbing Mao 1 , Karen Lozano 1
1 , University of Texas Rio Grande Valley, Edinburg, Texas, United States, 2 , Tecnologico de Monterrey, Monterrey Mexico, 3 , University of New South Wales, Sydney, New South Wales, Australia, 4 , Technical University of Denmark, Lyngby Denmark, 5 , University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractThis presentation will focus on the development of a scalable method to obtain large graphene sheets seamlessly connected to carbon fibers. Film-fiber hybrid nonwoven polymeric mats are formed during fiber processing and converted to carbon structures after a simple thermal treatment. The developed graphene “veils” extend directly from one fiber into another forming a continuous surface. An aqueous solution of poly(vinyl alcohol) and sodium chloride is subjected to centrifugal spinning to produce fine nanofiber mats. The salt, at the optimum humidity level, stimulates a capillarity effect that promotes the formation of thin veils, which become graphene sheets upon dehydration by sulfuric acid vapor followed by carbonization (at relatively low temperatures, below 800 °C). These veils extend over several micrometers within the pores of the fiber network, and consist of crystalline graphene layers that crosslink the fibers to form a highly interconnected hybrid network. The surface area and pore diameter of the hybrid structures were measured to be 520 m2g–1 and 10 nm, respectively. The resulting structure shows high electrical conductivity, 550 S/m, and promising shielding of electromagnetic interference, making it an attractive system for a broad range of electronic applications. This method overcomes major hurdles for scaling up, unleashing the foreseen commercial growth of important laboratory discoveries.
8:00 PM - NM02.11.17
Atomistic Simulations of the Initial Disintegration Stages of Graphene Oxide in Basic Media
Marcos Moreira 2 , Jose de Sousa 3 4 , Vitor Coluci 1
2 Instituto de Ciências Exatas, Naturais e Educação, Universidade Federal do Triânngulo Mineiro, Uberaba, MG, Brazil, 3 Departamento de Física, Universidade Federal do Piauí, Teresina, PI, Brazil, 4 Instituto de Física ``Gleb Wataghin'', UNICAMP, Campinas, SP, Brazil, 1 School of Technology, UNICAMP, Limeira, SP, Brazil
Show AbstractDespite the great interest in graphene oxide (GO) and its properties, there is currently no consensus on its structure. Recently, the model where GO is comprised by high oxidized regions (82%), graphene-like, oxygen-free regions (16%), and holes (2%) [1] has been revisited [2]. Rourke et al. [2] has proposed a two-component model comprised of low oxidized graphene sheets and highly oxidized graphene fragments (oxidation debris - OD) physisorbed on them. According to this model, the OD are produced during the transformation of graphite in GO and dominate electroactivity, surface adsorption, and fluorescence on GO. Recently, Dimiev and Polson have contested the two-component model by proposing that OD are not part of GO but are produced by disintegration of GO through reactions involving hydroxide ions and diol chains in GO during NaOH reflux treatment [3]. In this work, we studied these reactions by first principles calculations and reactive molecular dynamics simulations. Total energy calculations have been performed using density functional theory within the generalized gradient approximation with the exchange-correlation functional proposed by Perdew, Burke, and Ernzerhof. The electron-ion interactions were described by norm-conserving fully separable Troullier-Martins pseudopotential and the Kohn-Sham wavefunctions were expanded using linear combination of numerical pseudoatomic orbitals for the valence electron wavefunctions. ReaxFF-based reactive molecular dynamics simulations were used to study hydroxide-diol reactions on water. In addition to the diol chain proposed in [3], we found at least two diol chains (i.e. inline zigzag and armchair) that present lower formation energies. Our calculations also revealed that stable diol chains can be formed by the adsorption of hidroxide ion on graphene-like regions. Chains with hydroxyl groups alternating in different sides of the sheet are more stable than the ones where these groups stay on the same side. Reactions of hydroxide with some of these formed chains removed the hydrogen atom from the alcohol group to form water. Additional hydrogen removal caused bond breaking on the inline zigzag and armchair chain configurations. No bond breaking was observed when hydroxyl groups are isolated and not arranged in chains.
References
[1] K. Erickson, et al. Advanced Materials 22, 4467-4472 (2010)
[2] J. P. Rourke, et al. Angewandte Chemie 123, 3231-3235 (2011)
[3] A. M. Dimiev and T. A. Polson, Carbon 93; 544-554 (2015)
8:00 PM - NM02.11.18
Effect of Graphene Quantum Capacitance in the Presence of Charged Impurities on the C-V Characteristics of Graphene Gate MOS Devices
Ruixue Lian 1 , Yanbin An 1 , Ant Ural 1
1 Department of Electrical and Computer Engineering, University of Florida, Gainesville, Florida, United States
Show AbstractThere has been significant research interest in graphene for electronics applications, due to its good electrical conductivity, high optical transparency, mechanical flexibility, and two-dimensional structure. However, the potential of graphene as a channel material replacing silicon is limited due to the absence of a bandgap. On the other hand, graphene is an excellent candidate as a transparent, conductive, and flexible electrode for electronic and optoelectronic devices. Unlike conventional metals, whose Fermi level is typically pinned at the surface, the Fermi level and hence workfunction of graphene can be tailored by electrostatic gating, chemical doping, or surface engineering. As a result, graphene is also a promising candidate as the gate electrode in metal-oxide-semiconductor (MOS) devices, particularly when transparency, mechanical flexibility, or workfunction tunability is a requirement.
For gate electrode materials having a low density of states, such as graphene, the contribution of the quantum capacitance, which is in series with the oxide capacitance, can be observed when the equivalent oxide thickness (EOT) is small. In this work, we numerically calculate the capacitance-voltage (C-V) characteristics of graphene gate MOS devices taking into account the quantum capacitance based on the modified density of states (DOS) of graphene. This modified DOS results from the presence of charged impurities, which are known to cause electron-hole puddles and random local electrostatic potential fluctuations described statistically by a Gaussian distribution.
First, we study the quantum capacitance of graphene as a function of the graphene electrostatic potential at different temperatures and strengths of the potential energy fluctuations. We compare the exact computational results to various approximations made in the literature when fitting experimental data. Next, we numerically compute the gate voltage as a function of the graphene potential and the resulting C-V characteristics of the graphene gate MOS device at different temperatures, strengths of the potential energy fluctuations, and equivalent oxide thicknesses. We also consider the effect of the series and parallel parasitic impedance on the overall shape of the C-V curves. Furthermore, we numerically compute the C-V characteristics at different values of the equivalent oxide thickness, silicon doping density, and Dirac voltage of graphene. Finally, we fit our recent experimental C-V data with these theoretical calculations to extract the strength of the potential energy fluctuations and the parasitic impedances. These results provide important insights into the effect of the graphene quantum capacitance on the C-V characteristics of MOS devices and the potential of graphene as a gate electrode in future MOS technology.
8:00 PM - NM02.11.19
Graphene Templated, Atomically Thin Pt Films Derived from Metal Foams
Christopher Arnold 1 , Parker Buntin 1 , Thomas Samuels 2 , Jamie Warner 2 , Faisal Alamgir 1
1 , Georgia Institute of Technology, Atlanta, Georgia, United States, 2 , University of Oxford, Oxford United Kingdom
Show AbstractThis research explores the synthesis of graphene templated, atomically thin Pt films on three-dimensional Ni foams at room temperature via a surface-limited redox replacement (SLRR) electrochemical method. Pt was selected for this work based on its critical role in electronic and catalytic devices. Previous work has shown that utilizing graphene as an interface on two-dimensional substrates allows for room temperature, solution-based synthesis of stable Pt mono/multilayers. By preventing the agglomeration of Pt into nanoparticles, this technique approaches the theoretical maximum utilization for both Pt atoms and available substrate surface area. Additionally, the graphenated substrate induces a strain which varies as a function Pt thickness, allowing for tunable electronic and electrocatalytic properties. Successful application of this process on three-dimensional substrates—characterized by SEM/EDS, CV, LSV, XPS, and high resolution TEM analysis—displays the broad applicability of this technique in manufacturing of high utilization and low-loading precious metal based devices.
8:00 PM - NM02.11.20
Graphene Synthesis on SiC via Formation of Diffusion Couple
Ilker Kaygusuz 1 , Omer Caylan 1 , Dogukan Senyildiz 1 , Goknur Cambaz Buke 1
1 , TOBB University of Economics and Technology, Ankara Turkey
Show AbstractIn this study, graphene is formed on SiC single crystal wafers by resistive heating under vacuum. During resistive heating, SiC wafers and the metal plates are put in contact to from a diffusion couple. In order to investigate the effect of plate type, Mo, Ta, W and graphene foils are used. Studies showed that depending on the diffusion couple, it is possible to decrease the graphene formation temperature on SiC. The morphology of the synthesized graphene on SiC is characterized by using Raman spectroscopy, SEM, EDS, AFM and XPS.
8:00 PM - NM02.11.22
Water Flow through Nanopores in Large Area Double-Walled Carbon Nanotube Membranes
Yasuhiko Hayashi 1 3 , Hidetoshi Matsumoto 2 , Shuji Tsuruoka 4 , Koji Abe 5 , Kenjiro Hata 5 , Shaoling Zhang 2 , Yoshitaka Saito 2 , Motohiro Aiba 2 6 , Tomoharu Tokunaga 7 , Hirotaka Inoue 1 , Takuma Hayashi 1 , Toru Iijima 1 , Gehan Amaratunga 8 9
1 Department of Electrical and Electronic Engineering, Okayama University, Okayama Japan, 3 Institute of Innovative Research, Tokyo Institute of Technology, Tokyo Japan, 2 Department of Materials Science and Engineering, Tokyo Institute of Technology, Tokyo Japan, 4 Institute of Carbon Science and Technology, Shinshu University, Nagano Japan, 5 , YOUTEC Co., Ltd., Saitama Japan, 6 , Nagoya Municipal Industrial Research Institute, Nagoya Japan, 7 Department of Quantum Engineering, Nagoya University, Nagoya Japan, 8 Department of Engineering, University of Cambridge, Cambridge United Kingdom, 9 , Sri Lanka Institute of Nanotechnology, Homagama Sri Lanka
Show AbstractThe water flow suppression, or water-freezing occurs in the carbon nanotube (CNT) confined space significantly, depending on temperature. It suggests that the structural change of the confined water is governed thermodynamically. Latent heat of ice confined in the CNTs was found to be smaller than that of the bulk one. Additionally, it is confirmed that the obtained permeability correlates to the reported experimental results with regard to the relationship between CNT length and permeability, and the correlation does not agree with permeability predicted from the Hagen-Poiseuille law. These results give rise an insight into the inherent water transport characteristics in the CNT confined space.
High quality dense and vertically aligned double-walled CNTs (VA-DWCNTs) on Si was grown rapidly by a water vapor free thermal chemical vapor deposition (CVD) using Fe catalyst with hydrogen as the process gas and acetylene as a carbon source around 973 K. The array was coated with parylene-C, the coated surface was milled, and finally the VA-DWCNT membrane was peeled off from the substrate. A conventional characterization technique is applied to the membranes to find the transport properties of water through VA-DWCNT membrane. Before the present work, most VA-CNT composite membranes consist of VA-CNT with a diameter of 4-20 nm and a typical wall number of 5-10. On the other hand, in the present work, it is successfully controlled that the narrower diameter of VA-DWCNT array is grown with the desirable wall-number.
Based on the statistical analysis, the mean diameter and number of walls of VA-CNTs are 3.7- 4.5 nm and 2.1-2.2 layers, respectively. To date, most VA-CNT composite membranes consist of VA-CNT with a diameter of 4-20 nm and a typically wall number of 5-10. On the other hand, in the present work, it is successfully controlled that the narrower diameter of VA-CNT array is grown with the desirable wall-number.
The water flow suppression, or water-freezing occurs in the CNT confined space significantly, depending on temperature. It suggests that the structural change of the confined water is governed thermodynamically. Latent heat of ice confined in the CNTs was found to be smaller than that of the bulk one. Additionally, it is confirmed that the obtained permeability correlates to the reported experimental results with regard to the relationship between CNT length and permeability, and the correlation does not agree with permeability predicted from the Hagen-Poiseuille law. These results give rise an insight into the inherent water transport characteristics in the CNT confined space.
8:00 PM - NM02.11.23
High-Performance Flexible Carbon Nanotube Thin-Film Transistors and CMOS Circuits
Jianshi Tang 1 , Qing Cao 1 , George Tulevski 1 , Luca Nela 1 , Shu-Jen Han 1
1 , IBM T.J. Watson Research Center, Yorktown Heights, New York, United States
Show AbstractWith high mobility, low cost and good stability, carbon nanotube (CNT) based thin-film transistor (TFT) is an attractive candidate for flexible electronics and large-scale display. Here we report a high-yield, scalable process to fabricate high-performance CNT TFTs and complimentary circuits on flexible substrates. Both the purity of semiconducting tubes and CNT density have been dramatically improved over previous work. The fabricated flexible TFTs have shown state-of-the-art device performance with exceptional current density (~15 μA/ μm), large current ON/OFF ratio (~106), steep subthreshold slope (<200 mV/dec), and high field-effect mobility (~50 cm2/Vs). Impressively, these key metrics are significantly better than those reported in literature for flexible CNT TFTs, and are even at par with the best values from those made on rigid substrates. Repeated bending tests with bending radius down to 5 mm have proven excellent durability of the flexible TFTs. In addition, a stable n-type doping method has been developed and integrated to demonstrate high-quality CNT COMS inverters. Our scalable process provides a useful pathway to make low-cost, high-performance flexible electronics.
8:00 PM - NM02.11.24
Enhancement Mechanism of Catalyst Activity of Rh Particles Supported on Al2O3 Layers in SWCNT Growth
Takahiro Maruyama 1 , Hoshimitsu Kiribayashi 1 , Takayuki Fujii 1 , Takahiro Saida 1 , Shigeya Naritsuka 1
1 , Meijo University, Nagoya Japan
Show AbstractPreviously, we have demonstrated that Rh catalysts are effective to synthesize single-walled carbon nanotubes (SWCNTs) by chemical vapor deposition (CVD) at low temperature [1]. To grow SWCNTs by CVD, amorphous Al2O3 support layers have been widely used to enhance the SWCNT yield. In this study, we carried out SWCNT growth using Rh catalysts on Al2O3 support layers that were prepared by various methods and investigated the effects of the crystalline property of Al2O3 layers on the catalyst activity.
To grow SWCNTs, we used five kinds of Al2O3 layers to support Rh catalysts: native oxidation of Al layer deposited by electron beam (EB); thermal oxidation of Al layer deposited by EB; EB deposition of Al2O3 layer; native oxidation of Al layer deposited by rf-sputtering; thermal oxidation of Al layer deposited by rf-sputtering. After deposition of Rh catalysts on them, we carried out SWCNT growth by alcohol catalytic CVD. The SWCNTs were characterized by Raman measurements and scanning electron microscopy (SEM) observation. The Al2O3 support layers were analyzed by X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge structure (XANES), atomic force microscopy (AFM), transmission electron microscopy (TEM) and ellipsometry. Rh particle sizes were characterized by TEM.
Among the five Al2O3 layers, SWCNT yield became the largest on the Al2O3 layer prepared by native oxidation of Al layer deposited by rf-sputtering. XPS, XANES and ellipsometry results showed that oxidation degree of an Al2O3 layer was dependent on the fabrication method, which affected the inward diffusion of Rh catalysts. TEM results showed that crystallization of Al2O3 layers affected surface migration of Rh catalysts, and aggregation of Rh catalysts occurred on crystallized Al2O3 layer surfaces. Based on these results, we discussed the enhancement mechanism of the catalyst activity in SWCNT growth.
[1] T. Maruyama et al. Carbon 116 (2017) 128.
8:00 PM - NM02.11.25
Interdigitated Electrode with High Mass Density Carbon Nanotube Forests for Electrochemical Biosensors
Hisashi Sugime 1 , Takuya Ushiyama 2 , Yutaka Ohno 2 , Suguru Noda 3
1 Waseda Institute for Advanced Study, Waseda University, Tokyo Japan, 2 Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya Japan, 3 Department of Applied Chemistry, Waseda University, Tokyo Japan
Show AbstractElectrochemical label-free sensing using redox reactions is one of the powerful and feasible methods to detect biomolecules with high sensitivity. Among several geometries of electrodes, interdigitated electrode (IDE) has an advantage for high sensitivity because the current by redox reactions is amplified by shuttling of analytes if the distance of the electrodes is smaller than the diffusion length of analytes. As a candidate material for the electrodes in IDE, carbon materials are widely studied due to their fast electron transfer kinetics and wide potential windows.1 Among others, carbon nanotubes (CNTs) have several advantages such as high aspect ratio with large surface area and high electrical conductivity. Direct growth of CNTs on substrates by chemical vapor deposition is especially a suitable way to integrate the CNTs into the IDE. We have previously engineered the catalyst design and achieved low temperature growth (450 °C) of ultra-high mass density CNT forests (1.6 g cm-3) on conductive supports.2,3 They are suitable for the electrode material in IDE as the CNTs and supports have an ohmic contact which is different from the conventional CNT forests on insulators (e.g. SiO2 or Al2O3).
In this report, we applied the dense CNT forests on conductive supports to the IDE by combining the UV-lithography and the low temperature CVD process (<500 °C). By optimizing the geometry of the electrodes (width and gap) and the morphology of the CNT forests (height and density), the performance of the IDE was significantly improved. The cyclic voltammetry (CV) measurements of K4Fe(CN)6 showed that the current of IDE with CNTs reached to the diffusion-limited current much more easily compared to that of conventional metal IDE. By the shuttling of the analytes, the current of the redox reaction was amplified by a factor of ~18 and ~70 in the CV and the chronoamperometry measurements, respectively. As a model case of the biomolecules, dopamine (DA) which is one of the main neurotransmitters was measured under coexistence of ascorbic acid (100 µM). The selective detection of DA was achieved with the linear range of 100 nM – 100 µM and the limit of detection (LOD, S/N=3) of ~40 nM with the optimized electrode structure.
References:
[1] Niwa et al., Anal. Chem. 66, 285 (1994).
[2] Sugime et al., Appl. Phys. Lett. 103, 073116 (2013).
[3] Sugime et al., ACS Appl. Mater. Interfaces 6, 15440 (2014).
Corresponding author: Hisashi Sugime
E-mail: sugime@aoni.waseda.jp Tel&Fax: +81-3-5286-2769
Web: http://www.aoni.waseda.jp/sugime/
8:00 PM - NM02.11.26
Evaluating the Performance of Carbon Nanotubes from Different Commercial Sources in Rigid and Stretchable Transistors
Alex Chortos 1 , Igor Pochorovski 1 , Pei Lin 1 , Gregory Pitner 2 , H.-S. Philip Wong 2 , Zhenan Bao 1
1 Chemical Engineering, Stanford University, Stanford, California, United States, 2 Electrical Engineering, Stanford University, Stanford, California, United States
Show AbstractSingle-walled carbon nanotubes (SWNTs) have been used as high performance semiconductors in transistors, photodetectors, and thermoelectric devices, and each application has different optimal diameters. Isolating semiconducting SWNTs using conjugated semiconductor dispersions has potential advantages of low cost and high throughput if the conjugated sorting polymer can be reused. In this work, we describe the use of a supramolecular conjugated polymer to disperse commercially available SWNTs that were fabricated using different methods (CoMoCat, HiPCO, plasma discharge, arc discharge, and Tuball). The supramolecular sorting polymer exhibits the ability to selectively disperse semiconducting SWNTs with diameters from 0.7 to 0.9 nm for CoMoCat SWNTs to 1.4 to 2.2 nm for Tuball SWNTs. In contrast, different covalent copolymers are typically required to sort SWNTs with dramatically different diameters. The sorting yield was highest for SWNTs with a medium range of diameters from 1.0 to 1.5 nm. While the sorting purity for medium-diameter SWNTs was ~99%, the sorting purity for very large diameter (1.4 to 2.2 nm) Tuball SWNTs was measured by short channel measurements to be ~97.5%; sorting large diameter SWNTs is more challenging due to the smaller difference in electronic properties between the semiconducting and conducting nanotubes.
The sorted SWNT solutions were used to evaluate the impact of the source of SWNTs on the transistor performance in both rigid transistors with silicon dioxide dielectrics and intrinsically stretchable transistors with elastomeric dielectrics. In rigid devices, large diameter (1.2 to 1.7 nm) arc discharge SWNTs exhibited the highest mobility values of 61 cm2/Vs. The mobility values for transistors were compared with structural parameters of the sorted SWNT solutions, including the bandgap, average length, and Raman G/D ratio. The mobility increased exponentially with a decrease in the bandgap of the SWNTs except for Tuball SWNTs, which showed anomalously low mobility values. The parameter that exhibited the best correlation with the mobility was the G/D ratio from Raman measurements, indicating that defects or contaminants may explain the impaired performance of Tuball SWNTs. Intrinsically stretchable transistors were fabricated using a nonpolar elastomer as the substrate and dielectric, resulting in low areal capacitances of ~1 nF/cm2. As a result, the optimal SWNT diameter shifted to smaller diameters (1.0 to 1.5 nm) than for rigid devices.
8:00 PM - NM02.11.27
Graphene/Titania Nanotubes for Electrochemical Sensing of Hg, Cu, and Mn as Water Pollutants
Ibrahim Abdullah 1 , Mona Mohamed 1 , Nashaat Abd Eltawab 1 , Nageh Allam 1
1 , American University in Cairo, New Cairo Egypt
Show AbstractDue to its potent and harmful effect toward public health, heavy metal levels in the environment are extremely important to monitor. Many conventional analytical methods are used for this purpose. Although they introduce acceptable accuracy, they suffer from high interference, time consumption, and tedious preparation procedures. Carbon paste electrodes (CPEs) are one of the promising electrochemical alternatives that could be easily modified to provide highly sensitive and selective heavy metal detection. Herein, a novel carbon-based nanocomposite of Reduced Graphene Oxide/Tintania nanotubes (RGO/TNT) is proposed to have an excellent conductivity and adsorptivity to be used for the application of electrochemical sensing of Hg, Cu, and Mn as water pollutants. FESEM, HRTEM, FTIR, XRD, BET, CV, EIS, ASSWV techniques were employed to characterize the different morphological, structural, and electrochemical properties of the suggested modifier. Hg(II), Cu(II), Mn(II) ions were proven to be detected in a linear response from 2.4×10-10 to 8.5×10-5 mol L-1 each, with a high linearity and correlation (0.997). The detection and quantification limits for each observed metal were found to be down to 8.9×10-11 and 2.9×10-10 mol L-1, respectively. The selectivity of the proposed electrode modifier was tested in multi-spiked solution against different heavy metal ions. The proposed material’s performance has been also tested in real polluted water samples from various locations in Egypt showing promising results for the sensor to be used in the field of aquatic pollution monitoring.
8:00 PM - NM02.11.28
Mechanical Properties of Stacked Carbon Nanocones Investigated by Impact Molecular Dynamics Simulations
Samir Coutinho 2 , Alexandre Fonseca 1 , Vitor Coluci 1 , Douglas Galvao 1
2 , Instituto Federal do Maranhao, Sao Luis Brazil, 1 , State University of Campinas, Campinas Brazil
Show AbstractCarbon nanocones are hollow fullerene structures with a conical shape, as their name suggests [1]. They can form stacked structures, the so-called cup-staked nanotubes [2]. In this work we investigated the mechanical properties of tubular stacked nanocones by impact molecular dynamics using the reactive force field AIREBO (Adaptative Intermolecular Reative Empirical Bond-Oder) [3]. Potentials like AIREBO have the advantages of being capable of handling cases where chemical bonds are broken and/or formed.
We have considered three different types of cones (cone-60, cone-120, and cone-180, where these numbers refer to the cone aperture angle [2,4]), and tubular structures formed by different number of cones, as well as, tubes formed by different kind of cones. We investigated the mechanical response of these structures under ballistic impact. We considered different projectiles with different kinetic energies and different impact angles. Our results show that these tubular structures are very efficient in absorbing mechanical impacts, far superior to the observed responses of cylindrical and helical nanotubes [5]. How to improve their mechanical properties in association with amorphous carbon layers is also addressed.
[1] M. Ge and K. Sattler, Chem. Phys. Lett. v220, 192 (1994).
[2] T. Hayashi et al., Nanoscale v5, 10212 (2013).
[3] D. W. Brenner, Phys. Rev. B 42, 9458 (1990).
[4] A. Krishman et al., Nature 388, 451 (1997).
[5] V. R. Coluci, A. F. Fonseca, D. S. Galvao, and C. Daraio, Phys. Rev. Lett. v100, 086807 (2008).
8:00 PM - NM02.11.29
Polymer Matrix Composites Reinforced with Anisotropic Carbon Nanomaterials
Jacob Knego 1 , Albert Dato 1
1 , Harvey Mudd College, Claremont, California, United States
Show AbstractPolymer matrix composites are used in a wide range of engineering applications, such as adhesives, coatings, and structural components in aircraft and automobiles. The addition of carbon nanomaterials into polymers can result in composites with enhanced mechanical properties. Here we present our investigation into the mechanical properties of polymer composites filled with a range of anisotropic carbon nanomaterials, including graphite, graphene, and carbon nanotubes. A facile method of fabricating composites will be presented. Furthermore, the dispersion of nanomaterials in polymer resins by this fabrication method will be discussed. For each carbon nanomaterial, composites of increasing weight percentage were produced and subjected to tensile testing according to the ASTM D638 standard test method. The results of our research provide a direct comparison of the stiffness, strength, and toughness of polymer matrix composites reinforced with anisotropic carbon nanomaterials.
8:00 PM - NM02.11.30
Nanotube Alignment Mechanism in Floating Evaporative Self-Assembly
Katherine Jinkins 1 , Jason Chan 1 , Gerald Brady 1 , Kjerstin Gronski 2 , Padma Gopalan 1 , Harold Evensen 2 , Arganthaël Berson 1 , Michael Arnold 1
1 , University of Wisconsin-Madison, Madison, Wisconsin, United States, 2 , University of Wisconsin-Platteville, Platteville, Wisconsin, United States
Show AbstractThe challenge of assembling semiconducting single-wall carbon nanotubes (s-SWCNTs) into densely packed, aligned arrays has limited the scalability and practicality of high-performance nanotube-based electronics for decades. While individual s-SWCNTs exhibit exceptional electronic properties including high charge carrier mobility and current carrying capacity, highly-aligned arrays of multiple s-SWCNTs are needed to realize high-performance, next-generation field effect transistors (FETs) for semiconductor technologies.
Here, we show that Floating Evaporative Self-Assembly (FESA) enables large-area deposition of highly-aligned arrays of s-SWCNTs with near-optimal packing density for FETs, demonstrating immense potential to overcome this long-standing obstacle in nanotube assembly. For example, FETs fabricated from FESA-aligned s-SWCNTs have outperformed gallium arsenide (GaAs) and silicon (Si) FETs with respect to on-state current density and conductance [1]. In FESA, a substrate is lifted out of a water trough while s-SWCNTs in organic solvent (s-SWCNT ink) is sequentially dosed at the air/water/substrate contact line [2]. The ink droplets spread almost instantaneously on the water surface, with each droplet resulting in the deposition of a band of aligned s-SWCNTs across the substrate.
We gain insight into the FESA process by optically tracking the dynamics of the ink/water and ink/air interfaces during FESA and relating this behavior with the properties of the resulting s-SWCNT stripes [3]. We show that the FESA mechanism is primarily governed by two processes. First, the ink/water interface collects and confines s-SWCNTs. Second, s-SWCNTs deposit onto the substrate from the ink/water interface during the depinning of the ink/water/substrate and ink/air/substrate contact lines. The depinning of the contact lines and the outward spreading of the ink likely aid in the alignment of the already-confined s-SWCNTs as they deposit onto the substrate.
We further demonstrate that the interband spacing and bandwidth of the s-SWCNT stripes can be tailored by varying the substrate lift rate and s-SWCNT ink concentration, respectively [3]. Packing densities of 11 to 20 µm-1can be achieved. Finally, we demonstrate scaling of FESA to align s-SWCNTs on a 2.5×2.5 cm2 scale while preserving a high degree of nanoscale alignment [3]. The insight gained here may help realize the scalable fabrication of well-aligned s-SWCNT arrays to serve as large-area platforms for next-generation semiconductor electronics.
[1] Brady, G. J. et al. Quasi-Ballistic Carbon Nanotube Array Transistors with Current Density exceeding Si and GaAs. Sci. Adv. 2, (2016).
[2] Joo, Y., Brady, G. J., Arnold, M. S. & Gopalan, P. Dose-Controlled, Floating Evaporative Self-Assembly and Alignment of Semiconducting Carbon Nanotubes from Organic Solvents. Langmuir 30, 3460–3466 (2014).
[3] Jinkins, K. R. et al. Nanotube Alignment Mechanism in Floating Evaporative Self-Assembly. In Preparation (2017).
8:00 PM - NM02.11.31
First-Principles Study of the Structural and Electronic Characteristics of Graphene-Metal Epitaxial System
Jiil Choi 1 , Faisal Alamgir 1 , Seung Soon Jang 1
1 , Georgia Inst of Technology, Atlanta, Georgia, United States
Show AbstractPlatinum is a face centered cubic structured crystal that has been widely known as a superior catalyst for various chemical reactions, while low-dimensional structures, such as mono- or bi-layer platinum, have attracted less attention due to experimental difficulties in synthesizing such 2D structures. In this study, for the first time, we present a computational research on the unique architecture of epitaxial platinum (mono/multi) layers grown on graphene (Pt_ML/GR), in support of remarkable recent progress in the synthesis of these architectures in simple cubic-like (SC-L) and face-centered cubic-like (FCC-L) phases on the graphene. In these architectures, Pt exhibits registry with the C-C bridge sites along the armchair and zigzag directions. Here, the detailed band structure and the partial/total densities of state (DOS) of the Pt_ML/GR architectures, with Pt in an SC-L registry, is presented. Pt atoms on graphene prefer bonding with two carbons covalently, turning C-C sp2 bond to sp3 bond, while metallic bonding prevails on the Pt atoms. Investigation of the hybrid bonding configuration and electronic properties requires well-described ground-states of the metallic and covalent bonding configuration, simultaneously. Recently proposed strongly constrained and appropriately normed (SCAN) density function study (DFT) is employed to investigate the structural and electronic properties of the epitaxial SC-L Pt layered graphene. First, the epitaxial geometry of Pt layers as well as inter-layer distance between graphene and Pt layer are in good agreement with the experimental observations. Second, the covalent bond character is observed between Pt and C while Pt layer attains the metallic bond character. Furthermore, as an application for electrochemical system such as fuel cells, the efficacy and the stability of Pt ML/GR catalysts under the canonical oxygen reduction reaction are presented.
8:00 PM - NM02.11.32
Dielectric Investigation of Polymer/Anisotropic Carbon Nanotube Sheets For Employment in LC Cells
Hakam Agha 1 , MD Asiqur Rahman 1 , Ji Hyun Park 1 , Thuy Kieu Truong 2 , Dongseok Suh 2 , Ricardo Vergaz Benito 3 , Giusy Scalia 1
1 Physics and Material Science Unit, University of Luxembourg, Luxembourg Luxembourg, 2 Department of Energy Science, Sungkyunkwan University, Suwon Korea (the Republic of), 3 GDAF-UC3M. Dep. Tecnología Electrónica, Universidad Carlos III de Madrid, Madrid Spain
Show AbstractLiquid crystals (LCs) are the active medium used in most common display technology, where the LC is filled between two conducting transparent electrodes (e.g. Indium Tin Oxide). The surfaces of the electrodes are usually coated with an alignment layer, like polyimide (PI) to induce homogeneous alignment of the LC molecules on the glass plates. However, efforts are being made to replace these materials with cheaper and more abundant ones. Aligned Carbon nanotubes (CNTs) are attractive candidates for incorporation in liquid crystal displays (LCDs) to replace both, at the same time, the electrodes and alignment layer due to their optical transparency and electrical conductivity. Also, more interesting compared to ITO, they have mechanical stability, and low cost. Uniformly aligned CNT sheets can be obtained by pulling the tubes from vertically grown forests [1],[2]. When CNTs are unidirectionally oriented, they can act as alignment templates for the LC molecules, inducing unidirectional planar alignment[3],[4].
In this work, we use In-plane Switching (IPS), which is one of the two successfully used techniques for LC switching in displays. We focus on IPS mode aiming at implementing CNT sheets as aligning layer, and characterizing the electro-optic behaviour related to the reorientational threshold transition of liquid crystals on top of CNTs. But first, a thin, transparent, and insulating polymeric film should be coated on top of the in-plane patterned electrodes to prevent any undesired short circuits between the CNT sheet and the in-plane electrodes. We have employed different polymers with various thicknesses in this multilayer system, and here we report on the adhesion behaviour of CNT sheets on top of them. Special attention is dedicated to the dielectric properties of the system, obtained through electrochemical impedance spectroscopy, and its effect on LC switching as a direct result of changes in the electric field due to the different impedance behaviour. In summary, we propose a new architecture of anisotropic CNT sheet, polymer film, and LC with attractive functionalities that can be a successful candidate for future displays and flexible electronics.
References:
[1] M. Zhang, S. Fang, A. A. Zakhidov, S. B. Lee, A. E. Aliev, C. D. Williams, Ken R. Atkinson, Ray H. Baughman, Science, 2005, 309 (5738), 1215-1219.
[2] K. Truong, Y. Lee, D. Suh, Curr. Appl. Phys. 16 (9), pp 1250–1258(2016).
[3] J. M. Russell S. Oh, I. LaRue, O. Zhou, E. T. Samulski, Thin Solid Films, 2006, 509, 53-57.
[4] W. Fu, L. Liu, K. Jiang, Q. Li, S. Fan, Carbon , 2010 , 48, 1876-1879.
8:00 PM - NM02.11.33
Reduction of Iron Oxide Catalyst in the Presence of Water and Its Effect on CNT Nucleation and Growth
Pavel Nikolaev 1 , Kevin Decker 1 , Rahul Rao 1 , Ahmad Islam 1 , Gordon Sargent 1 , Jennifer Carpena 1 , Benji Maruyama 2
1 , AFRL/UES Inc, Dayton, Ohio, United States, 2 , Air Force Research Laboratory (AFRL), WPAFB, Ohio, United States
Show AbstractIron is catalytically active with respect to carbon nanotube nucleation and growth only in its fully reduced state. Ex-situ deposited iron catalyst, however, is always present as an oxide due to oxidation in room air. We study simultaneous iron oxide reduction, dewetting from alumina support, and CNT nucleation in a cold-wall CVD reactor in pure ethylene and ethylene / hydrogen mixtures. CNTs grow on catalyst – coated silicon micro-pillars, rapidly heated by a laser on a fraction of a second time scale. Introduction of water at increasing partial pressure shifts the thermodynamic equilibrium of the reduction process, and requires higher temperatures to nucleate CNTs, while hydrogen added to ethylene does not influence catalyst reduction. Reduction by hydrogen, while thermodynamically favored, is too slow to affect CNT nucleation on a subsecond time scale. Rapid reduction and dewetting of iron that drives CNT nucleation is due to reaction with acetylene, a product of ethylene decomposition.
8:00 PM - NM02.11.34
Single Walled Carbon Nanotube Functionalization with a Non-Conjugated Polymer
Giulio Mazzotta 1 , Markus Dollmann 1 , Severin Habisreutinger 1 , Moritz Riede 1 , Robin Nicholas 1
1 , University of Oxford, Oxford United Kingdom
Show AbstractCarbon nanotubes (CNTs) have attracted a lot of attention for their potential use in electronic and energy-related devices. One of the main issues hindering a widespread application is their poor solubility in organic and aqueous solvents, resulting in a difficult processing for large area applications. One of the main methodologies to overcome this problem has been surface functionalization, in particular non-covalent wrapping with conjugated polymers (i.e. P3HT, PFO). This has enabled production of very stable and homogeneous solutions allowing the use of carbon nanotubes in solar cells as charge transporting layers. However, the use of expensive semiconducting polymers might prevent the use of this methodology in lower cost devices such as solar cells, sensors, biomedical devices and conductive coatings.
In this work we show how a non-conjugated insulating polymer is able to functionalize single walled carbon nanotubes (SWCNTs) to obtain stable and homogeneous solutions. Photoluminescence excitation maps, Raman and optical absorbance measurements show the ability of the polymer to individually functionalize tubes.
We studied how the load concentration of polymer and CNTs influences the properties of the films made from these solutions. Functionalization of 0.25 mg/mL of CNTs happens from polymer concentrations as low as 0.01 mg/mL up to 5 mg/mL. Atomic force microscopy studies show very uniform networks of individual CNTs, with a thicker polymer coating when a high concentration of polymer is used. Electrical measurements show conductivities varying from 40 S/m up to 1000 S/m , with the most conductive film given by a 1.0 mg/mL polymer concentration, which resulted in a 30 nm thick film with a 30 kOhm/sq sheet resistance and a 84% transparency at 550 nm, comparable with CNTs wrapped with semiconducting polymers.
Finally, the functionalized carbon nanotubes have been tested in perovskite solar cells to show their potential application as charge extraction layer.
8:00 PM - NM02.11.35
On-Surface Synthesis and Nano-Scale Characterization of One-Dimensional sp-sp2 Hybrid Carbon Atomic Wires
Francesco Tumino 2 , Andi Rabia 2 , Valeria Russo 2 , Alberto Milani 2 , Andrea Li Bassi 2 , Qiang Sun 1 , Chunxue Yuan 1 , Wei Xu 1 , Carlo Casari 2
2 Department of Energy, Politecnico di Milano, Milan Italy, 1 College of Materials Science & Engineering, Tongji University, Shanghai China
Show AbstractOver the last 30 years, carbon nanostructures have been playing a leading role in nanoscience and nanotechnology, showing a wide variety of nano-scale morphologies and structures whose properties depend on several physical aspects, such as dimensionality, hybridization, chirality and topology. The rise of graphene and the study of its remarkable properties have fostered great research effort toward the synthesis and study of novel low-dimensional carbon-based systems, such as one-dimensional (1D) carbon-atom wires and hybrid sp-sp2 architectures, e.g. graphyne and graphidyne, which are expected to show tunable optical and electronic behaviours over a broad range of potential applications [1]. Although many recent theoretical investigations have addressed the properties of hybrid sp-carbon nanomaterials, the experimental research is still on its early stages.
In this work, we conducted an experimental investigation of sp-carbon-based chains deposited on a metal substrate, i.e. the Au(111) surface, with the aim to characterize their morphological, structural and electronic properties at the nanometer scale. To this purpose, we performed in situ Scanning Tunneling Microscopy (STM) and Spectroscopy (STS) measurements, which allow us to probe the sample surface and its electronic properties with a sub-nanometer spatial resolution. The synthesis procedure has been performed under ultra-high vacuum conditions, by molecular beam epitaxy (MBE) of a molecular precursor onto the freshly cleaned Au(111) surface. The deposited molecules (called bBEBP) have a linear structure containing two connected benzene groups and terminated at each end by Br atoms [2]. The Au substrate plays a fundamental role in the formation of longer 1D structures, as the result of a gold-mediated dehalogenative homocoupling. STM measurements allowed us to study such structures and their morphological arrangement for increasing temperature. In particular, 1D carbon-based chains are observed to form well-oriented domains at relatively low temperature (about 100 °C), while at higher temperatures a more disordered morphology is revealed. STS and ex situ Raman measurements provided valuable experimental information on the electronic and vibrational properties and their interpretation, with the support of density functional theory (DFT) calculations, will contribute to unveil the fundamental physics of this material, and thus to envision its potential applications.
Our work represents a first step toward a better understanding of surface-supported sp-carbon systems and a valuable experimental approach for future studies of novel 1D and 2D nanostructures in the family of carbon-based materials.
References:
[1] Casari, C. S., Tommasini, M., Tykwinski, R. R., and Milani, A. Nanoscale, 8(8), 4414-4435 (2016)
[2] Sun, Q., Cai, L., Ma, H., Yuan, C., and Xu, W. ACS nano, 10(7), 7023-7030 (2016)
8:00 PM - NM02.11.37
Hot-Electron Photodetection with Graphene/Strontium Titanate Schottky Junction
Haozhe Wang 1 , Yi Song 1 , Wei Sun Leong 1 , Cong Su 1 , Jing Kong 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractMultiple hot-carrier generation in graphene has recently attracted tremendous research attention as it holds great promise for high-efficiency opto-electronic applications. Previous research efforts have been relying on the photoexcitation of back-gated graphene field-effect transistors, in which precise alignment of photon source to the graphene-metal junction is required to generate zero-bias photocurrent. Here, we present the first demonstration of hot electron generation in graphene by creating a Schottky contact between graphene and a large bandgap semiconductor, Strontium Titanate (SrTiO3 or STO). Thus far, we have been able to extract 150 nA of photocurrent and achieve an open-circuit voltage (VOC) of nearly 400 mV under a 532 nm laser illumination. We note that the photocurrent output is limited by the 2.3% absorbance of monolayer graphene. In addition, the incident photon-to-current conversion efficiency (IPCE) of our device has also been characterized using LEDs with different wavelengths. Furthermore, we demonstrate that the Schottky barrier height of such graphene/STO junctions can be tuned up to one order of magnitude (from 0.13 eV to 1.46 eV) by chemically doped the graphene that effectively alters its work function. In summary, we have shown that graphene is able to generate electron-hole pairs under visible illumination by measuring the carriers extracted via a conventional Schottky barrier.
*Haozhe Wang and Yi Song contribute equally in this work.
8:00 PM - NM02.11.38
Growth of Spin-Capable MWCNT Forest Using Mist CVD Method for In Situ Fe Catalyst Nanoparticles Formation
Toshiya Kinoshita 1 , Motoyuki Karita 2 , Takayuki Nakano 2 , Yoku Inoue 2 , Hirokazu Nagaoka 3
1 Graduate school of Science and Technology, Shizuoka University, Hamamatsu Japan, 2 Department of Electronics and Materials Science, Shizuoka University, Hamamatsu Japan, 3 , JNC Petrochemical Corporation, Ichihara Japan
Show AbstractDry-spinning phenomena of long and dense carbon nanotube (CNT) forest have been used for fabrication of large-scale CNT assemblies including CNT yarns, CNT sheets, CNT/polymer composites. Recently, a floating catalyst chemical vapor deposition (CVD) method has been reported for the CNT forest growth on a substrate as a simplified CNT CVD method. It does not require pre-deposition of catalyst, however, a certain amount of metallic impurity is involved in CNTs, which makes CNT usage complicated. In this study, as a modified method, we adopted a mist CVD method to the thermal CVD growth of CNT forest, in which catalyst formation and CNT growth were successively conducted. First, catalyst particles were formed on an oxidized Si substrate by flowing mist of catalyst solution consisting of ferrocene and ethanol. Ferrocene was decomposed on the substrate and it forms Fe nanoparticles. Then, ambient gas was purged and CNTs were grown by flowing acetylene gas as carbon source. Grown multi-walled CNT forest height is 400 μm. The CNTs have an average diameter of 11.0 nm and a high areal density of 3.42×1010 cm-2. Purity of a CNT forest was analyzed by TGA measurement. Weight loss of the CNT sample was 99%, which shows high purity with low Fe inclusion. In addition, the CNT forests have good spin-capability. We fabricated CNT spun-yarn by twisting the web [1]. The yarn has high tensile properties including tensile strength of 1.4 GPa and Young’s modulus of 131 GPa. Since the present CVD method requires only simple gas-flow processes, it is compatible to large-scale production system, such as roll-to-roll CVD, for spin-capable CNT mass-production.
[1] A. Ghemes, et al., Carbon 50, 4579 (2012).
8:00 PM - NM02.11.39
Free-Standing Flexible Rollable and Foldable Carbon Nanostructure Mats for Electromagnetic Interference Shielding
Hammad Younes 1 , Amal Al Ghaferi 1 , Md. Mahfuzur Rahman 1
1 , Masdar Institute of Science and Technology, Abu Dhabi United Arab Emirates
Show AbstractThe current approaches of electromagnetic interference shielding (EMI SH) are to use metal-based materials or carbon-based nanomaterials (CNMs) composites such as polymer nanocomposites or foams. Metals have been widely used in EMI SH because of their high electrical conductivity values along with their super mechanical properties. However, this use is associated with many limitations such as heavy weight, high processing cost, and corrosion susceptibility. Therefore it is believed that CNMs could be a potential candidate for radiation shielding application. CNMs in its intrinsic form show very high electrical conductivity, however its magnetic properties are very low and at the same time their electrical conductivity degrades when they are agglomerated, which is due to the very strong Van der Waals attraction forces at the nano-scale among the tubes. As a results it is believed that proper use of CNMs still remains as a challenge. The electromagnetic interference shielding effectiveness of flexible low-cost lightweight carbon nanostructures (CNS) mats made of carbon nanostructure flacks with 300–350 μm in length and with various widths has been reported. Vacuum filtration technique has been used to fabricate the mats with density from 0.6 to 1.6 g/cm3. In order to increase the electrical conductivity which ultimately increases the EMI SH, the papers will be subjected to compression. Pressing the papers increases network density by decreasing the gap within and between CNTs that creates better contacts and reduces at the same time the electrical resistance by reducing air gaps and providing more conductive pathways for the charge carriers, which yields to an increase in conduction within the papers. The EMI SH was measured for the fabricated CNMs papers and found to be 75 dB.
8:00 PM - NM02.11.40
A New Paradigm of Atomically Thin Metal Films Epitaxially Grown on Graphene
Faisal Alamgir 1 , Ali Mahmoud 1 , Adam Vitale 1 , Parker Buntin 1 , Alex Robertson 2 , Jamie Warner 2
1 , Georgia Institute of Technology, Atlanta, Georgia, United States, 2 , Oxford University, Oxford United Kingdom
Show AbstractIn this presentation we will demonstrate large-area, fully-wetted, atomically thin metal films can be grown epitaxially on graphene (GR). We will focus particularly on Pt films that are one to several multilayers thick (Pt_ML) epitaxially grown on graphene (Pt_ML/GR). These Pt_ML/GR 2D systems have covalent bonds at the interface between Pt_ML and GR and this intimacy between the layers serves to make the GR a ‘chemically transparent’ barrier that allows catalytic chemistry to take place above it, while protecting the Pt below it from loss. As an example, we will specifically show that graphene does not restrict access of the reactants for the canonical oxygen reduction reaction (ORR) but does block Pt from dissolution or agglomeration. Using these architectures, we show that it is possible to simultaneously achieve enhanced catalytic activity and unprecedented stability, retaining full activity for ORR beyond 1000 cycles. Using x-ray photoemission/absorption spectroscopy (XPS/XAS), high resolution TEM, AFM, Raman, and electrochemical methods, we show that, due to intimate graphene-Pt epitaxial contact, Pt/GR hybrid architectures are able to induce a compressive strain on the atomically thin Pt films and increase their catalytic activity for ORR. Our demonstration of a room-temperature, fully-wetted synthesis approach, should allow for efficient transfer of charge, strain, and phonons and photons, between atomically thin Pt films and their support, impacting not just the performance of catalysts, but also those of electronic, thermoelectric and optical materials.
8:00 PM - NM02.11.41
All CVD Direct Growth of Large-Scale Graphene and Hexagonal Boron Nitride Heterostructures
Sanjay Behura 1 , Phong Nguyen 1 , Chen Wang 1 , Songwei Che 1 , Rousan Debbarma 1 , Michael Seacrist 2 , Vikas Berry 1
1 , University of Illinois at Chicago, Chicago, Illinois, United States, 2 , SunEdison Semiconductor, Saint Peters, Missouri, United States
Show AbstractTransfer-free and direct growth of large-scale graphene/hexagonal boron nitride (h-BN) heterostructures will be an important advancement in the development of high performance nano and optoelectronic devices. Atomically flat surface and lack of charged impurities enable h-BN an ideal substrate platform for complex 2D heterostructured circuits. However, current techniques mostly rely on the transfer (mechanical or chemical) of both h-BN and graphene to build the 2D heterostructures, which ultimately degrade their structure and properties, implying underperformance of the final devices. Here we report the direct growth of large-scale graphene/h-BN heterostructures via chemical vapor deposition (CVD). First, h-BN is directly synthesized on SiO2/Si substrates via chemical-interaction guided mechanism followed by the deposition of a thin metal film (Cu) on h-BN/SiO2/Si substrates. Then graphene is grown via a process, which relies on the diffusion of catalytically produced carbon radicals through Cu grain-boundaries and their crystallization at the interface of Cu and h-BN/SiO2/Si dielectrics. Finally, removing the top graphene and Cu, produces the graphene/h-BN heterostructures with a sharp defect-free interface. The directly-grown, van der Waals bound graphene/h-BN heterostructures are characterized by scanning Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Futuristically, this all-CVD direct growth strategy will be a transformative approach for scalable production of complex 2D van der Waals heterostructures.
8:00 PM - NM02.11.42
Improving Ge Nanomembranes via Surface Cleaning and Graphene Passivation
Xiaorui Cui 1 , Abhishek Bhat 1 , Yingxin Guan 1 , Richard Delgado 1 , Shu Yen Khor 1 , Robert Jacobberger 1 , Shelley Scott 1 , Michael Arnold 1 , Thomas Kuech 1 , Max Lagally 1
1 , University of Wisconsin-Madison, Madison, Wisconsin, United States
Show AbstractGermanium, although it is has an indirect bandgap, attracts wide attention for its potential to be used as a CMOS-compatible platform for optoelectronics applications, particularly as biaxial tensile strain of >1.7% can change Ge to direct-bandgap [1]. Up to 2% biaxial strain has been successfully demonstrated in Ge nanomembranes (NMs) [2]. Higher strains are desirable, because they would allow a better tunability of the band structure and a highly useful bandgap region, but sample failure occurs.
Formation of cracks initiating on the surface or edges of the Ge NM is believed to be the reason for the inability to reach higher strains. We attempt to address this problem by modifying the surface chemistry and/or covering the surface to prevent access of molecules that may aid crack formation. We follow various chemical cleaning procedures in order to obtain oxidized and unoxidized Ge surfaces. Aiming to keep the surface stable, we transfer graphene onto the Ge NM as a passivation layer in order to isolate it from the ambient [3]. Graphene can conform to the Ge NM while restricting molecular species from reaching the Ge surface.
We use GeNMs with thicknesses ~100nm or less, made via growth on III-V substrates or from bond-and-etch-back GOI. Graphene is grown either on Cu or on Ge, released, and transferred. We present initial work of transferring graphene to Ge NMs. The Ge surface condition is determined by XPS; transferred graphene and strained Ge are characterized by Raman spectroscopy. Ge passivation of NMs is consistent with behavior of bulk Ge [3].
Support: DOE, NSF-MRSEC
References:
[1] M. El Kurdi, G. Fishman, S. Sauvage, and P. Boucaud, “Band structure and optical gain of tensile-strained germanium based on a 30 band k?p formalism,” J. Appl. Phys., vol. 107, no. 1, p. 13710, Jan. 2010.
[2] J. R. Sanchez-Perez et al., “Direct-bandgap light-emitting germanium in tensilely strained nanomembranes,” Proc. Natl. Acad. Sci., vol. 108, no. 47, pp. 18893–18898, Nov. 2011.
[3] R. R. Delgado et al., “Passivation of Germanium by Graphene Passivation of Germanium by Graphene,” 2017.
8:00 PM - NM02.11.43
Uniform Plasmon Hybridization and Volumetric Field Enhancements in Graphene Nanocubes
Kriti Agarwal 1 , Daeha Joung 1 , Andrei Nemilentsau 1 , Chunhui Dai 1 , Chao Liu 1 , Qun Su 1 , Jing Li 1 , Tony Low 1 , Steven Koester 1 , Jeong-Hyun Cho 1
1 , University of Minnesota, Minneapolis, Minnesota, United States
Show Abstract
Two-dimensional (2D) graphene nanoribbons (GNR) when irradiated at their resonant excitation, undergo localized surface plasmon resonance (LSPR) characterized by near-field enhancement of the incident far-field electromagnetic wave. The rapid decay of the near-field enhancement away from the surface of graphene has limited the application of the graphene-based plasmonic sensors to a large extent. Developments in nanoscale self-assembly have allowed surface tension driven self-folding of diverse 2D patterns transforming them into 3D nanostructures with unique optoelectronic properties. Through the self-assembly of 2D patterned GNR, 3D micro/nanoscale polyhedral structures such as closed and open cubic structures can be obtained with free-standing 2D materials (graphene or graphene oxide) acting as faces of the cube. Additionally, the folded 3D structures can include 2D materials with surface modifications of desired patterns to tailor the optical response while simultaneously leveraging the properties of pristine graphene. Through the transformation of 2D GNR into 3D graphene nanostructures, uniform 3D coupling of the plasmons occurs from all directions resulting in distinct plasmon hybridization modes not achievable in 2D structures. The 3D plasmon hybridization induces a nontrivial spatial distribution of strong near-field enhancement of the incident electric field. The strong fields created within and outside the uniformly coupled 3D hollow cubes demonstrate a much slower decay away from the surface of the graphene, generating a strong field within the volume of the cube that is 2 orders of magnitude higher than the 2D ribbons. The highly confined volumetric field within the nanocubes provides an opportunity for the development of non-contact ultrasensitive 3D plasmonic sensors where the sensing area is not limited to the graphene surface (as with 2D graphene sensors) but rather extends to the entire volume of the cubes.