Symposium Organizers
Juan Beltran-Huarac, Harvard T. H. Chan School of Public School
Wojciech Jadwisienczak, Ohio University
Alessandro Ponti, National Research Council
Bo Zou, Jilin University
Symposium Support
Ohio University—Nanoscale and Quantum Phenomena Institute (NQPI)
NM03.01: Synthesis and Fabrication I
Session Chairs
Juan Beltran-Huarac
Gilbert Nessim
Dongseok Suh
Monday PM, November 27, 2017
Hynes, Level 3, Room 310
8:15 AM - *NM03.01.01
Patterned Growth of 3D Forests of Carbon Nanotubes Using Reservoirs and Overlayers
Gilbert Nessim 1
1 , Bar Ilan University, Ramat Gan Israel
Show AbstractDespite the massive progress achieved in the growth of carbon nanotube (CNT) forests on substrate, apart from lithographic patterning of the catalyst, little has been done to selectively (locally) control CNT height. Varying process parameters, gases, catalysts, or underlayer materials uniformly affects CNT height over the whole substrate surface. We will show here how we can locally control CNT height, from locally killing CNT growth to locally growing CNTs up to 6X the nominal CNT height from iron catalyst on alumina underlayer. By patterning reservoirs or by using overlayers we can grow a forest of CNTs with areas of different heights, from no CNTs to 6X the nominal CNT height, using a single growth process!
Reservoirs, meaning thin films positioned below the alumina underlayer, can significantly affect the catalyst morphology and composition through diffusion to the catalytic surface during the thermal process. We showed how an iron thin film reservoir placed below the alumina underlayer could almost double CNT height.1 When we used a copper/silver thin film reservoir, we observed poisoning of the iron catalyst placed above it, thus leaving no CNTs on the areas positioned above this Cu/Ag film.2 Finally, using a thin film reservoir of molybdenum, we could modulate an increase of CNT height up to a factor of 4X, depending on the thickness of the Mo reservoir.3
Overlayers, meaning patterned foils positioned as stencil or bridge above the catalytic surface, can also significantly affect the catalyst morphology and composition during the thermal process. This technique does not require lithography. We demonstrated how a copper overlayer placed above the catalyst surface during pre-annealing or during CNT growth deactivates the catalyst via interdiffusion and consequent poisoning of the iron catalyst.4 We recently showed how a nickel overlayer placed above the catalyst surface during CNT growth also effectively deactivated the catalyst, although the mechanism here was via local modification of the precursor gases and not interdiffusion.5
By combining patterns of reservoirs and overlayers, we can then produce a sample that would grow a forest of CNTs with areas of different heights, with a wide gamut of heights, from no CNTs up to 4X the nominal CNT height. This modulation of the CNT height is a significant improvement compared to the "CNTs (one height) / no CNTs" patterning that has been achieved to date using lithography of the catalyst, and moves us closer to building 3D architectures of CNTs.
1. Shawat, E. et al., Nanoscale 2014, 6, 1545-1551.
2. Shawat Avraham, E. et al., Under submission 2017.
3. Shawat Avraham, E. et al., In preparation
4. Yemini, R. et al., J Phys Chem C 2016, 120 (22), 12242−12248.
5. Yemini, R. et al., J Phys Chem C 2017, 121 (21), 11765–11772
8:45 AM - *NM03.01.02
From 2D Nanocrystalline Films to 1D Nanomaterials—An Overview
Chunxu Pan 1 , Gongsheng Song 1 , Chentian Shi 1 , Qiang Fu 1
1 , Wuhan University, Wuhan China
Show AbstractIn the past few years, our group worked on the area of transformation from the two-dimensional (2-D) nanocrystalline films to one-dimensional (1-D) nanomaterials by using thermal oxidation. In this paper, we overview the research works on controllable growth process, transformation phenomenon and growth mechanisms. In general, the preparation includes the following process, that is, firstly, preparing a pure metal nanocrystalline film by using pulse electro-deposition, then, using this film as catalyst for growing variant 1-D nanomaterials such as carbon nanotubes (CNTs), carbon nanofibers (CNFs) and 1-D metal oxide nanoneedles involving ZnO, CuO and Fe3O4, etc. This process exhibits the following features: 1) The growth mechanism of the 1-D nanomaterials is based on the “base growth” model and no residual catalyst exists at the tip of the products. 2) The diameter of the 1-D nanomaterials can be controlled by controlling grain sizes of the 2-D films through adjusting the pulse electro-deposition parameters. 3) It is more easily to grow the 1-D nanomaterials with a large area, uniform, vertical and good shape on the substrats.
1) Growth of 1-D carbon nanomaterials from the 2-D nanocrystalline films. It was found that the diameter of the 1-D carbon nanomaterials can be controlled by controlling the grain size of the films via carefully adjusting the deposition parameters. In addition, experimental results revealed that: (1) for the Ni film, the CNTs could be obtained within an ethanol flame; 2) for the Fe film, a kind of sold-cored CNFs could grew upon the film with the flames. The growth mechanism was based on the theory, i.e., Fe has a strong affinity for carbon and Ni has a weak affinity for carbon. That is to say, the pyrolyzed carbon atoms can be easily deposited on the surface and diffuse through the interior of the iron particles, and forms the solid-cored CNFs. However, when the pyrolyzed carbon atoms deposit upon the Ni-containing particles, carbon atoms generally move faster along the external surface than the interior, and the hollow-cored CNTs are formed.
2) Growth 1-D metal oxide nanoneedles from the 2-D nanocrystalline films. We found that when a metal (Fe, Zn or Cu) nanocrystalline film was deposited firstly on the substrate, the dense, flourishing and well–aligned Fe3O4, ZnO and CuO nanoneedles could be grown from the substrate during thermal oxidation. The reason is that compared with the regular process, the nanocrystalline films provide higher activity and surface energy and promotes the growth rate of the 1-D metal oxide nanoneedles. Different the V-L-S model, we proposed a "solid state base-up diffusion growth mechanism". That is, the growing process of the 1-D metal oxide nanoneedles is controlled by the diffusion of metal ions from the substrate, which is caused by the local electrical field set up by the ionization phenomenon of the metal and O atoms at the solid/gas interface.
9:15 AM - NM03.01.03
Development of Reference Engineered Nanomaterials for Toxicology Research
Juan Beltran-Huarac 1 , Zhenyuan Zhang 1 , Georgios Pyrgiotakis 1 , Glen DeLoid 1 , Nachiket Vaze 1 , Philip Demokritou 1
1 Center for Nanotechnology and Nanotoxicology, HSPH-NIEHS Nanosafety Center, Department of Environmental Health, Harvard T. H. Chan School of Public School, Harvard University, Boston, Massachusetts, United States
Show AbstractThere is a growing need to develop and characterize reference engineered nanomaterials (ENMs) of high purity and tunable intrinsic properties suitable for toxicology research. Here a high throughput and precision flame spray pyrolysis (FSP) approach coupled with state-of-the-art characterization techniques is utilized to generate such reference ENMs. The lab-based and industrially relevant FSP system produces the ENMs with controlled properties that includes the primary particle size, aggregate diameter, shape, crystallinity, stoichiometry and surface chemistry. A nanopanel of nine reference ENMs (silica, silver, silver supported on silica, alumina, ceria and iron oxide) was synthesized and characterized using combined electron microscopy, advanced spectroscopic techniques and physical analyses (e.g., BET, XRD, TEM, pycnometry, XPS, ICP-MS and FTIR). ENMs show a high degree of chemical purity and stoichiometry, and low content of carbon residuals, and are sterile and free of bacteria and endotoxins. Further, their colloidal properties and their implication in in-vitro dosimetry have been also investigated in both environmental and test biological media. The suitability of reference ENMs and protocols developed in this study brings forth new arenas to generate reliable and reproducible toxicological data in an effort to reduce conflicting and contradicting inter-laboratory data on relative toxic effects of ENMs.
9:30 AM - NM03.01.04
Rapid Open-Air Deposition of Uniform, Nanoscale, Functional Coatings on Nanorod Arrays via Atmospheric Pressure Spatial Deposition
Kevin Musselman 1 , David Muñoz-Rojas 2 , Robert Hoye 3 4 , Haiyan Sun 5 , Suman-Lata Sahonta 3 , Edmund Croft 3 , Marcus Boehm 4 , Cate Ducati 3 , Judith MacManus-Driscoll 3
1 Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario, Canada, 2 Laboratoire des Matériaux et du Génie Physique, Université Grenoble-Alpes, Grenoble France, 3 Materials Science and Metallurgy, University of Cambridge, Cambridge United Kingdom, 4 Physics, University of Cambridge, Cambridge United Kingdom, 5 , Istituto Italiano Di Tecnologia, Genova Italy
Show AbstractHigh-aspect-ratio nanostructures are critical for many emerging technologies. To improve their functionality, hierarchical coatings are commonly applied to their surfaces using wet-chemistry and vacuum-based batch processes, which have limited throughput. We demonstrate that an atmospheric pressure spatial deposition system can be used to rapidly deposit uniform, nanoscale coatings on nanorod arrays in open air. A variety of metal oxide coatings (Al2O3, Cu2O, ZnO, and related alloys) are deposited on ZnO nanorod arrays and characterized. Originally conceived for flat substrates, it was not known whether atmospheric pressure spatial deposition (based on alternating flows of precursor gases) would facilitate conformal coating of high-aspect-ratio nanostructures, particularly when high deposition rates, which include some chemical vapour deposition, are employed. Good electrical contact is observed between the coating and nanorod and functionality is demonstrated in colloidal quantum dot and hybrid solar cells. To our knowledge, this is the first demonstration of a rapid, open-air technique for the scalable deposition of coatings uniformly conformal to high-aspect-ratio nanostructures [1]. This marks an important conceptual shift in the degree of surface engineering and the complexity of nanoscale devices that can be conceived for inexpensive mass-production. Unlike batch processes, this technique can ultimately be combined with established high-throughput (roll-to-roll compatible) methods like gravure and inkjet printing.
[1] K. Musselman et al. Nanoscale Horiz., 2017, 2, 110-117.
9:45 AM - NM03.01.05
Controlled Molecular Beam Epitaxial Growth of 2D to 1D MoSe2
Sock Mui Poh 1 2 , Sherman Tan 1 2 , Xiaoxu Zhao 1 2 3 , Zhongxin Chen 1 2 , Ibrahim Abdelwahab 1 2 , Deyi Fu 1 , Hai Xu 1 , Yang Bao 1 , Wu Zhou 4 3 , Kian Ping Loh 1 5
1 Chemistry, National University of Singapore, Singapore Singapore, 2 , NUS Graduate School for Integrative Sciences and Engineering, Singapore Singapore, 3 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 4 School of Physical Sciences, CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing China, 5 SinBeRISE CREATE, National Research Foundation, Singapore Singapore
Show AbstractTransition metal dichalcogenide (TMDC) is a class of layered 2D materials. The confinement of electrons in the 2D limit leads to interesting layer-dependent properties, with great prospect for next-generation electronics.[1] These effects become more pronounced with the dimensional crossover to 1D, where additional confinement modulation leads to novel properties like 1D confined plasmons,[2] spin-polarized edge states[3] and Tomonaga-Luttinger liquid behavior.[4] It is therefore of great importance to develop a growth method for dimensional controlled growth of 2D to 1D nanostructures. Herein, we report the growth of 2D to 1D MoSe2 using molecular beam epitaxy (MBE). By controlling the growth temperature or Mo:Se ratio, high quality MoSe2 2D films to 1D nanoribbons are synthesized.[5] The growth is versatile, can be done on both insulating and conducting substrates, hexagonal boron nitride (hBN) and highly oriented pyrolytic graphite (HOPG), respectively. In addition, by using a two-stage growth process, we are able to synthesize 1D-2D-MoSe2 hybrid heterostructures. Our study opens up the exploration in cross-dimensional studies as well as for next-generation novel device structures.
[1] Q. H. Wang, et al. Nat Nanotech 2012, 7, 699, [2] a) K. Andersen, et al., Phys Rev B 2014, 90, 161410; b) Z. Fei, et al., Nano Lett 2015, 15, 8271. [3] a) Y. Li, et al. JACS 2008, 130, 16739; b) M. Gibertini, N. Marzari, Nano Lett 2015, 15, 6229. [4] H. Ishii, et al., Nature 2003, 426, 540.
[5] Sock Mui Poh, et al. Advanced Materials 2017, 29, 1605641. DOI: 10.1002/adma.201605641.
10:30 AM - *NM03.01.06
Macroscopic Superconducting NbN Yarn Templated by Carbon Nanotubes
Dongseok Suh 1 2
1 Department of Energy Science, Sungkyunkwan University, Suwon-Si Korea (the Republic of), 2 , Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon-Si Korea (the Republic of)
Show AbstractNanofiber superconducting NbN yarn was formed using the free-standing carbon nanotube sheets as a template for the deposition of superconducting NbN thin-film. The superconducting properties of NbN nanofiber yarn was comparable to that of NbN thin-film on the normal solid substrate. The reduction of normal state resistance for the application as a superconducting cable was successfully achieved by the addition of gold-layer inside the nanoporous structure of the carbon-nanotube-templated NbN yarn. This technique can open the possibility of the development of superconducting cable having much higher flexibility compared with other normal superconducting cable. [1]
[1] J.-G. Kim et al., Adv. Funct. Mater. (DOI: 10.1002/adfm.201701108) (2017)
11:00 AM - NM03.01.07
Low Temperature Synthesis of Germanium Nanorods and Nanowires
Sven Barth 1 , Patrik Pertl 1 , Michael Seifner 1 , Alois Lugstein 2
1 Institute of Materials Chemistry, Vienna University of Technology, Vienna Austria, 2 Institute of Solid State Electronics, Vienna University of Technology, Vienna Austria
Show AbstractGermanium nanowires and nanorods have a broad spectrum of potential applications including electronic devices, lithium ion batteries, sensors etc. However, the synthesis of these anisotropic nanostructures usually requires temperatures >300 °C hampering the growth on temperature-sensitive materials such as polymers.
We present in this contribution the growth of highly crystalline Ge nanowires and nanorods at temperatures as low as 170 °C. These structures grow either via the solution-liquid-solid (SLS) or the vapor-liquid-solid (VLS) mechanism depending on the growth conditions. In addition, we can show that the slow growth of these structures at low temperatures is due to the precursor decomposition characteristics as a limiting factor. Moreover, the decomposition of the Ge precursor is catalyzed by the presence of Ga seeds. Ge nanowires have been characterized by different analytical methods including TEM, EDX as well as XRD and the incorporation of unusually high Ga contents of up to 3% in the Ge structures has been observed. Unusually high metal incorporation in group IV nanowires has been observed for other semiconductor/metal combinations [1] and helped targeting metastable compositions [2]. Therefore, electrical characterization of individual Ge nanowires has been performed in order to quantify the impact of the Ga incorporation on their conductivity.[3] According to the phase diagram, Ga has excellent potential for the Ge nanowire formation at even lower temperatures using suitable Ge precursors, which will be targeted in future studies.
____
[1] O. Moutanabbir, D. Insheim, et.al. Nature 2013, 496, 78.
[2] M. S. Seifner, F. Biegger, A. Lugstein, J. Bernardi, S. Barth Chem. Mater. 2015, 27, 6125.
[3] P. Pertl, M. S. Seifner, A. Lugstein, S. Barth submitted.
11:15 AM - NM03.01.08
The Role of Wetting and Contact Angle in the Growth of III-As Nanowires
Lea Ghisalberti 1 , Jelena Vukajlovic-Plestina 1 , Heidi Potts 1 , Wonjong Kim 1 , Lucas Güniat 1 , Martin Friedl 1 , Gözde Tutuncuoglu 1 , W Craig Carter 1 2 , Anna Fontcuberta i Morral 1
1 , EPFL, Lausanne Switzerland, 2 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractA critical target for the progress of functional one-dimensional nanostructures is the understanding and mastering of their growth mechanism. In the particular case of Vapor-Liquid-Solid, pre-growth treatments and conditions play a role in determining the nanowires’ crystal structure1, 2 and the growth morphology3, 4. In this work, we analyze the wetting phenomena of droplets in the self-assisted growth of InAs and GaAs nanowires. Indium droplets have been obtained on InAs nanowires by an annealing procedure right after growth. Depending on their size, the droplets can attach to nanowire side and modify the growth direction5. The droplet location also depends on the annealing time. Our results show that the droplet morphological stability, with respect to whether the droplet remains pinned to the top of the NW, depends on droplet volume and wetting angle. We identify the range of critical volumes at which a droplet at the top of the wire becomes unstable with respect to a droplet attached to the NW side. Our experimental results are supported by our numerical calculations.
We also consider the initial stages of GaAs NWs on a lithographically patterned (111) Silicon substrate. The wetting morphology of Gallium droplets in the etched holes on the SiO2 mask changes both with the volume of the droplet and with the geometrical constraint of the holes. We investigated the shape evolution by computing the minimal energy with Surface Evolver6. It was thus possible to compute the total surface energy as a function of the volume for different contact angles regimes and geometrical configurations.
This identifies the relation between the volume of the droplets, their contact angle and their impact on the growth direction and phase in the self-catalyzed growth of III-As nanowires.
[1] Dick, K. A. et al. Nat Mater 3, 380–384 (2004).
[2] Glas, F et al. Phys. Rev. Lett. 99, 146101 (2007).
[3] Wang, J. et al. Nano Lett. 13, 3802–3806 (2013).
[4] Matteini, F. et al. Crystal Growth & Design 16, 5781–5786 (2016).
[5] Potts, H. et al. Nanotechnology 28, 054001 (2017).
[6] Brakke, K. A. “The Surface Evolver”, Experimental Mathematics 1, 141-165 (1992).
11:30 AM - NM03.01.09
Playing with Impurities in Oxide Nanowires to Get Complex Nanostructures
Manuel Alonso-Orts 1 , Ana Sanchez 2 , Iñaki Lopez 1 , Emilio Nogales 1 , Javier Piqueras 1 , Bianchi Mendez 1
1 , Univ of Complutense, Madrid Spain, 2 , University of Warwick, Coventry United Kingdom
Show AbstractSemiconducting oxides are an attractive family of functional materials with wide range of morphologies within the quasi-one dimension (nanowires, nanobelts, or nanorods). Besides, these oxides offer a lot of versatility in the applications: optical and mechanical resonators, lasing, sensors, photo-catalysis, solar cells, and biomedical and healthcare usages, to name a few. We have successfully grown a large variety of low dimensional semiconducting oxide structures, such as nanowires, nanotubes or nanorods of several oxides (ZnO, SnO2, GeO2, Sb2O3, In2O3, and Ga2O3) by thermal evaporation of the suitable chemical precursors on a catalyst-free basis via a vapor solid mechanism [1]. Once the control of the formation of single nanowires has been achieved, the next step to go further is to study the growth of more complex nanostructures in which oxide nanowires became the main building blocks. In this work, we report on the synthesis and characterization of oxide nano-heterostructures that exhibits a central core oxide nanowire (Ga2O3 or Zn2GeO4) as main axis and SnO2 crystallites or plates attached to the core or SnO2 nanowires crossing the axis. The achievement of each specific morphology depends on the nature of impurities and the growth parameters (mainly duration the treatment). Since the growth process takes place at rather high temperatures (1500 °C) for several hours, the impurities tend to out-diffuse towards the central nanowire surface and eventually act as nucleation sites for the development of further nanostructures [2,3]. In particular, the incorporation of certain amount of tin oxide into the substrate pellet leads to the formation of Ga2O3 nanowires decorated with SnO2 particles and Cr doping favours the appearance of crossing Ga2O3/SnO2 nanowires.
[1] www.finegroup.es
[2] M. Alonso-Orts, A. M. Sánchez, S. Hindmarsh, I. López, E. Nogales, J. Piqueras and B. Méndez, Nano Letters, 17, (2017) 515.
[3] G. Martínez-Criado, J. Segura-Ruiz, M.-H. Chu, R. Tucoulou, I. López, E. Nogales, B. Méndez, and J. Piqueras, Nano Letters, 14, (2014) 5479.
11:45 AM - NM03.01.10
Si-Ge Nanowire Heterostructures Prepared on TiN/Metal Layers
Jinkyoung Yoo 1 , Nan Li 1 , Todd Williamson 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractSemiconductor nanowires provide a unique opportunity for preparing high-quality materials on various substrates without severe limitation of materials compatibility. Crystalline semiconductor nanowires and their heterostructures on polycrystalline metal layers or foils have been considered as building blocks for economical production of devices and applications, such as photovoltaic cells and light-emitting devices, and catalysts. However, direct growth of semiconductor nanowires on metal layer with thermal processings brings an issue of interdiffusion in between metal and semiconductor wires, resulting in unintentional metal impurity incorporation, which is detrimental to minority carrier transport characteristics. To prevent the contamination, electrically conducting diffusion barrier such as TiN can be introduced in between semiconductor nanowires and metal layers.
We studied growth of Au-catalyzed Si-Ge nanowire heterostructures on metal foils with TiN. The interfacial regions of Si-Ge/TiN and TiN/metal layers were characterized by secondary ion mass spectrometry and transmission electron microscopy. The minority carrier diffusion lengths of Si-Ge nanowires and their heterostructures grown on metal layer with and without TiN were measured by electron beam induced current microscopy. We will discuss the effect of TiN on the physical properties of Si-Ge nanowire heterostructures grown on metal layer. Additionally, we will present device characteristics of photovoltaic cells and transistors based on Si-Ge nanowire heterostructures prepared on TiN/metal layer.
NM03.02: Synthesis and Fabrication II
Session Chairs
Wojciech Jadwisienczak
Chunxu Pan
Monday PM, November 27, 2017
Hynes, Level 3, Room 310
1:30 PM - *NM03.02.01
3-Aminopropyltrimethoxysilane Mediated Controlled Synthesis of Functional Noble Metal Nanoparticles and Its Multi-Metallic Analogues in the Presence of Small Organic Reducing Agents for Selective Applications
Prem Pandey 1 2
1 , IIT BHU, Varanasi India, 2 , BRD Medical College, Gorakhpur India
Show AbstractSynthesis of functional noble metal nanoparticles (AuNPs, AgNPs, PdNPs) and its multi-metallic analogues have received greater attentions for selective applications. The selective applications of the these nanoparticles essentially requires the processability of as synthesized nanoparticles in the medium of desired polarity index that manifest the potential exploration of nanomaterial based design in targeted area. The use of conventional reducing and stabilizing agents during routine synthesis of such nanoparticles are not suitable with the system of practical significance and require additional reagents that limit the optimum activity of nanomaterials in targeted design. According there is a challenging issue in the synthesis of noble metal nanoparticles that allow the controlled synthesis of such nanoparticles involving same starting material with option to control the processability of as generated nanomaterial in the system of desired polarity index. The present talk is focussed on such challenging issues. We have found that 3-aminopropyltrimethoxysilane (3-APTMS) capped noble metal cations can be precisely converted into respective monometallic, bimetallic and trimetallic analogues and can be made processable in water at one end having controlled option to reversed the processability of the same in the toluene as a function small organic reducing agents. The organic reducing agents only convert 3-APTMS-capped noble cations ito respective nanoparticles and control the processability of the as generated nanoparticles in the systems of desired polarity index. The similar process also allo the synthesis of function bimetallic and tri-metallic nanoparticles. The role of cyclohexanone, tetrahydrofuran hydroperoxide, formaldehyde, acetaldehyde, acetone, t-butyl methyl ketone in the presence of 3-APTMS will be discussed.
2:00 PM - NM03.02.02
Nucleation, Growth and Thermal Stability of Ge1-xSnx Nanowires and Nanorods
Michael Seifner 1 , Albert Romano-Rodriguez 2 , Sven Barth 1
1 Institute of Materials Chemistry, Vienna University of Technology, Vienna Austria, 2 MIND-IN2UB-Departament d’Electrònica, Universitat de Barcelona, Barcelona Spain
Show AbstractDirect band gap materials that are compatible with the silicon based semiconductor technology are desirable components for light emission in the mid-IR range. One promising candidate to achieve this goal is a germanium-tin alloy. However, the theoretically required Sn content of ~ 11 % to convert Ge to a direct band gap material [1] exceeds the solid solubility of < 1 % according to the binary phase diagram of Ge and Sn [2]. Therefore thermodynamically controlled processes are not feasible for the growth of this metastable material composition.
We are interested in the growth of Ge1-xSnx nanowires with Sn contents above the predicted transition point of x = 0.11. The nanowires are synthesised in a low temperature solution based process using metalorganic precursors in combination with microwave assisted heating enabling growth by kinetically driven processes [3, 4]. The successful synthesis enabled the incorporation of up to 30 % of Sn into the Ge lattice by this procedure, paving the way to potential band gap engineering of bottom-up grown Ge1-xSnx nanowires.
Independent and complementary methods including X-ray diffraction, Raman spectroscopy, and EDX elemental mapping are used to determine the Sn content, while TEM confirms the high crystallinity of the obtained products. The results presented in our contribution show new features of a low temperature nucleation regime and the impact on the obtained Sn concentration within the nanowires as well as their thermal stability [5]. These results will help to understand the nucleation and growth process in absence of a template and undesired growth promoters.
____
[1] K. Lu Low, Y. Yang, G. Han, W. Fan, Y.-C. Yeo, Journal of Applied Physics 2012, 112, 103715.
[2] R. W. Olesinski, G. J. Abbaschian, Journal of Phase Equilibria 1984, 5, 265-271.
[3] M. S. Seifner, F. Biegger, A. Lugstein, J. Bernardi, S. Barth Chem. Mat. 2015, 27, 6125-6130.
[4] S. Barth, M. S. Seifner, J. Bernardi, Chem. Commun. 2015, 51, 12282-12285.
[5] M. S. Seifner, A. Romano-Rodriguez, S. Barth submitted.
2:15 PM - NM03.02.03
Radial InAs/GaSb Heterostructure Nanowires on Si Substrates Grown by Metal-Organic Chemical Vapor Deposition
Xianghai Ji 1 , Xiaoguang Yang 1 , Tao Yang 1
1 , Institute of Semiconductors CAS, Beijing China
Show AbstractIII-V semiconductor nanowires have shown great potential in the fabrication of future nanodevices because of their unique geometrical, electronic and optical properties. Among the III-V semiconductor materials, InAs is a narrow band gap semiconductor with high electron mobility because of its small electron effective mass, whereas GaSb is a nearly-narrow band gap semiconductor with high hole mobility. In addition, because of the low lattice mismatch of 0.6% and the unique type-II-broken band alignment between InAs and GaSb, the growth of InAs/GaSb heterostructure nanowires is very attractive.
Here, we report on the growth of radial InAs/GaSb heterostructure nanowires on Si (111) substrates using metal-organic chemical vapor deposition (MOCVD) without any assistance of foreign catalysts. We realize the high quality InAs/GaSb core-shell nanowire arrays at 440 °C. Transmission electron microscopy (TEM) analysis reveals that the overgrowth of the GaSb shell is highly uniform and coherent with the InAs core without any misfit dislocations. To control the structural properties and reduce the planar defect density in the self-catalyzed InAs core nanowires, a trace amount of Sb was introduced during their growth. As the Sb content increases from 0 to 9.4%, the crystal structure of the nanowires changes from a mixed wurtzite (WZ)/zinc-blende (ZB) structure to a perfect ZB phase. From electrical measurements, ambipolar transport behavior is observed for the device of the nanowire with GaSb shell thickness of ~6 nm, indicating that both the n-type InAs core and p-type GaSb shell can work as active carrier transport channels. The obtained radial InAs/GaSb heterostructure nanowires may have strong potential for use in the fabrication of novel nanowire-based devices and in the study of fundamental quantum physics.
2:30 PM - NM03.02.04
Flow-Directed Synthesis of 1D ZnO Nano/Mesostructures with Controlled Morphology and Composition
Abhiteja Konda 1 , Stephen Morin 1 2
1 Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, United States, 2 Nebraska Center for Materials and Nanoscience, University of Nebraska–Lincoln, Lincoln, Nebraska, United States
Show AbstractThe use of fluid flow in the synthesis of morphologically controlled inorganic nanomaterials is a relatively underexplored area. Strategies that take advantage of flow properties (e.g., flow velocity, direction, etc.) in addition to conventional growth parameters (e.g., time, temperature, chemistry, and concentration), promise to provide additional levels of control in the bottom-up synthesis of functional nanomaterials. We used high-velocity fluid flow in micron-scale channels to control the solution-phase synthesis of spatially and compositionally variant arrays of branched zinc oxide (ZnO) nanorods. Specifically, we manipulated the flow velocity and direction and the chemistry of precursor solutions enabling control of the dislocation driven growth rates of branches within arrays of ZnO nanorods. Using this approach, we produced arrays of branched ZnO mesostructures with morphology dependent on the spatial location of the nanorods relative to the flow front of the precursor solutions. This approach complements and augments current synthetic strategies for the controlled synthesis of nano-/meso-scale inorganic materials, and is generally applicable to a range of materials with a diverse set of functional properties (e.g., optical, magnetic, electronic) and applications (e.g., in optoelectronics through the fabrication of nanorod arrays with spatially heterogenous scattering/absorbing properties, or in electroanalysis through rational design of nanostructured microelectrodes).
2:45 PM - NM03.02.05
Hydrothermal Synthesis and Modification of Undoped Silver and Zinc Oxide Nanostructures
Faith Bamiduro 1 , Nicola William 2 , Nicole Hondow 1 , Steve Milne 1 , Laurence Nelson 2 , Rik Brydson 1
1 School of Chemical and Process Engineering, University of Leeds, Leeds United Kingdom, 2 School of Chemistry, University of Leeds, Leeds United Kingdom
Show AbstractThe use of nanoparticle containing products has become prevalent in our everyday lives, from cosmetics to medical technology, but uncertainty surrounds any possible health and environmental implications [1,2]. This presentation relates to synthesising nanoparticles and assessing their biological impact as a component of an EU project, High level Integrated Sensor for Nanotoxicity Screening (HISENTS) [3]. The particles under consideration were selected based on their traceability, biological activity, and degree of use in the market. The synthesis of zinc oxide and silver nanoparticles with tuneable size and morphology using hydrothermal methods and their physical characterisation by electron microscopy and dynamic light scattering techniques will be discussed. Zinc oxide in nanoparticle form is employed in semiconductor applications, dietary supplements, targeted drug delivery and energy harvesting [1]. Nano silver finds use in medicinal applications, water purification and electronics [2]. The particle size and morphology of these two nanomaterials will be correlated to possible biological impact, screened via phospholipids based residual cyclic voltammetry. Spherical, multifaceted and rod-like particles are found to have differing responses; different nanoparticle sizes also generate distinctive phospholipid membrane contact patterns thus influencing the degree of interactions that occur. The nature of the medium employed during synthesis and generation of test samples is found to play a significant role in determining the severity of nanoparticle-membrane activity; the consequences on the reproducibility of results will be illustrated.
References
1. Ü. Özgür, Ya. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, V. Avrutin, S.-J. Cho, and H. Morkoç, J. Applied Physics, 2005, 98, 041301
2. X.K. Meng, S.C. Tang and S. Vongehr, J. Mater. Sci. Technol., 2010, 26(6), 487-522.
3. http://hisents.eu/
NM03.03: Theory and Modeling
Session Chairs
Monday PM, November 27, 2017
Hynes, Level 3, Room 310
3:30 PM - *NM03.03.01
Engineering One-Dimensional Wires of Free Carriers through Polar Discontinuities
Marco Gibertini 1 2 , Nicola Marzari 1 2
1 , École Polytechnique Fédérale de Lausanne, Lausanne Switzerland, 2 , National Centre for Computational Design and Discovery of Novel Materials (MARVEL), Lausanne Switzerland
Show AbstractUnprecedented and fascinating phenomena have been observed at oxide interfaces between centrosymmetric cubic materials, where polar discontinuities can give rise to polarization charges and electric fields that drive a metal-insulator transition and the appearance of a two-dimensional electron gas. Lower dimensional analogues are possible and here we suggest different realistic pathways to engineer one-dimensional electron and hole wires in 2D materials and devices, and support these suggestions with extensive first-principles calculations. Several approaches are discussed, based on: (i) nanoribbons, where a polar discontinuity against the vacuum emerges; (ii) functionalizations, where covalent ligands are used to introduce polar discontinuities by selective or total functionalization of the parent systems; and (iii) structural interfaces, including inversion domain boundaries, phase-engineered interfaces and strain profiles. All the cases considered have the potential to deliver innovative applications in ultra-thin and flexible solar-energy devices and in micro- and nano-electronics.
4:00 PM - NM03.03.02
Structure Prediction of One-Dimensional Nanostructures
Scott Woodley 1 , Isa Lough 1 , Alexey Sokol 1 , Tomas Lazauskas 1
1 , University College London, London United Kingdom
Show AbstractGlobal optimisation schemes have proven very good at predicting atomic structures for both nanoclusters and crystalline bulk materials [1] and are now being applied to surfaces and interfaces [2]. One-dimensional nanostructures, on the other hand, are typically constructed by either cutting from three-dimensional structures (bulk phases) to create nano-rods or wrapping of two-dimensional structures to create nano-tubes.
We have extensive experience of developing and applying global optimisation schemes based on Evolutionary, or Genetic Algorithms and Monte Carlo Basin Hopping to the prediction of low energy structures of binary ionic compounds: from microporous materials [3] to nanoclusters [4]. The algorithms are implemented with our in-house software, KLMC, whereas the predicted binary atomic structures are uploaded into the publically accessible WASP web-database [5] and then used as input for investigations of their physical and electronic properties [6]. Recently we have extended the KLMC code to enable us to predict the atomic structure of one-dimensional nanostructures. In this presentation the algorithms and results of KLMC applied to one-dimensional nanostructures of pure and doped ZnO and their electronic properties will be described.
[1] Crystal structure prediction from first principles, Woodley, S.M. & Catlow, R. Nat. Mater. 7 937–946 (2008)
[2] Interlayer cation exchange stabilizes polar perovskite surfaces, Deacon-Smith, D.E.E. et al., Adv. Mater. 26 7252–7256 (2014)
[3] Double bubble secondary building units used as a structural motif for enhanced electron-hole separation in solids, Farrow, M.R. et al., Mater. Sci. in Semicond. Proc. 42 147–149 (2016)
[4] An efficient genetic algorithm for structure prediction at the nanoscale, Lazauskas T., et al., Nanoscale, 9, 3850–3864 (2017)
[5] https://hive.chem.ucl.ac.uk/
[6] Structural and optical properties of Mg and Cd doped ZnO nanoclusters, Woodley, S.B., et al.,
J. Phys. Chem. C 117 27127–27145 (2013)
4:15 PM - NM03.03.03
Engineering the Shape and Size Distributions of Ordered GaAs Nanowires on Silicon
Jelena Vukajlovic-Plestina 1 , Wonjong Kim 1 , Vladimir Dubrovskii 2 , Gözde Tutuncuoglu 1 , Heidi Potts 1 , Martin Friedl 1 , Anna Fontcuberta i Morral 1
1 , Ecole Polytechnique Federale de Lausanne, Lausanne Switzerland, 2 , Ioffe Institute, St. Petersburg Russian Federation
Show AbstractReproducible integration of III-V semiconductors on silicon can open new paths for next generation energy harvesting devices but also in optoelectronics. GaAs nanowires can provide the platform for lasing on CMOS platform and for solar cells surpassing the so-called Schockley Queisser limit. For this, gold-free and defect-free synthesis is a requirement. In addition, the nanowire shape and position of the substrate should be engineered at will. Here, we provide understanding on the mechanisms and design elements affecting size uniformity and shape in ordered GaAs arrays obtained on silicon [1,2]. We analyze the size distributions and show that the length and diameter distributions in the initial stage of growth are not much influenced by the Poissonian fluctuation-induced broadening, but rather are determined by the long incubation stage. We outline how the size uniformity can be dramatically improved by increasing supersaturation. Finally, we show how the shape can be engineered towards pencil-like and needle-like shapes by post-growth annealing and strong modification of the growth conditions. Nanowire diameters down to 10 nm and lengths of few micron have been demonstrated. The consequences for the photonic and mechanical behavior will be discussed [3,4].
References:
[1] E. Russo-Averchi et al Nano Lett. 15, 2969 (2015)
[2] J. Vukajlovic-Plestina et al, Nano Lett (in review)
[3] P. Krogstrup et al, Nature Photonics 7, (2013) 306
[4] N. Rossi, et al. Nature Nanotechnology 12, 150 (2017)
4:30 PM - NM03.03.04
Effect of Nanowire Curviness on the Resistivity Scaling in One-Dimensional Metal Nanowire Networks for Transparent Conductors
Junying Li 1 , Chen Ying 1 , Jeremy Hicks 1 , Ant Ural 1
1 Department of Electrical and Computer Engineering, University of Florida, Gainesville, Florida, United States
Show AbstractTransparent, conductive electrodes have many applications in electronic and photonic devices such as flat panel displays, touch screens, solar cells, LEDs, and photodetectors. Metal nanowire networks are promising candidates for emerging applications as a replacement for indium tin oxide (ITO), which has problems such as high cost, scarcity, and brittleness. The conduction in metal nanowire networks is governed by percolation theory. Below critical dimensions, the network stops behaving like bulk and exhibits power-law resistivity scaling as nanowire and device parameters are reduced.
In most computational work, nanowires in these networks have been modeled as straight “sticks”. However, in real experiments, individual nanowires are not perfectly straight, but exhibit some degree of curviness. In this work, we perform systematic Monte Carlo simulations to study the effect of nanowire curviness on the scaling of percolation resistivity in nanowire networks. We generate the curved nanowires using 3rd-order Bézier curves. These curves are endowed with a curviness angle property that specifies how far away the two intermediate control points of the Bézier curve may lie, in the tangential sense, from a straight path connecting the two ends of the curve. The curviness angle is varied to obtain networks of differing values of curl ratio, which is defined as the ratio between the curved length of a nanowire and the straight distance between its two ends.
We find that, for random networks, the resistivity of the network increases with increasing nanowire curviness and the resistivity exhibits an inverse power law dependence on the curl ratio. We also find that the value of the inverse power law critical exponent extracted is not universal, but depends on other nanowire and device parameters. As a result, we also study the effect of nanowire density, nanowire length, device length, device width, and nanowire alignment angle on the scaling of network resistivity with nanowire curl ratio.
Curviness results in two competing effects on the percolation resistivity. First, curviness decreases the effective length of the nanowire between its two ends, which increases the resistivity. Second, it increases the effective width of the nanowire, which decreases the resistivity. For random networks, the first effect dominates over a wide range of nanowire and device parameters. For networks with aligned nanowires, on the other hand, increasing the curviness decreases the resistivity, indicating that the second effect starts to dominate. By simulating networks with varying values of alignment angles, we study the crossover from the first to the second regime.
These results show how the degree of curviness of individual nanowires contributes to the macroscopic resistivity of the network. They also show that computational studies are an essential tool for providing insight into the percolation transport in transparent, conductive nanowire networks.
4:45 PM - NM03.03.05
Kinetically Limited Composition of VLS Grown Ternary III-V Nanowires
Jonas Johansson 1 , Masoomeh Ghasemi 1 2
1 , Lund University, Lund Sweden, 2 , KTH Royal Institute of Technology, Stockholm Sweden
Show AbstractBandgap engineering is an important enabling technology for electronics and optoelectronics applications of III-V semiconductor nanowires. The most straightforward approach to bandgap engineering in nanowires is composition control in ternary nanowires, both for radial and longitudinal growth. There are a few experimental investigations with the aim to control the composition in ternary nanowires and one of the most investigated systems is InGaAs. Other experimentally investigated ternary nanowire systems are InGaSb, AlGaAs, InAsSb, and GaAsSb. Altough Dubrovskii [1] has proposed an analytical model, relating the composition of the solid nanowire to the composition of the vapor phase, there is limited understanding of how the composition of the seed particle influences the nanowire.
The aim of the current investigation is to explain how the nanowire composition during longitudinal, particle seeded growth depends on the composition of the seed alloy particle. We have previously discussed the composition of ternary III-V nanowires in the nucleation limited regime, approximating the composition of the solid material with the composition of the critical nucleus [2]. Here we follow up on our previous work and propose a model for the kinetically limited composition of metal particle seeded ternary III-V nanowires. The model is based on diffusion limited growth of supercritical nuclei within two-component nucleation theory. We derive the model for the general case and then we discuss it in terms of InGaAs nanowire growth. In this case, the diffusion of As is rate limiting and the composition of the nanowire is independent on diffusion and depends only on chemical potential differences.
Applying the model to gold-seeded and self-seeded growth of InGaAs we are able to explain the experimentally obtained features related to nanowire compositions, including the attainability of compositions within the miscibility gap. Based on our calculations and comparisons with experiments, we recommend that self-seeded growth with composition control should be carried out at low temperature, even if this seems technically challenging [3]. On the other hand, for gold seeded growth with composition control over the full range, we recommend growth at high temperature. In addition, by directly comparing with experiments we conclude that approximately 2% arsenic in the alloy particle during self-seeded growth of InGaAs is a realistic assumption.
[1] V.G. Dubrovskii, Cryst. Growth Des. 15, 5738 (2015).
[2] J. Johansson, M. Ghasemi, Cryst. Growth Des. 17, 1630 (2017).
[3] M. Heiss, B. Ketterer, E. Uccelli, J.R. Morante, J. Arbiol, A.F.I. Morral, Nanotechnology 22, 195601 (2011).
NM03.04: Poster Session I: Synthesis
Session Chairs
Tuesday AM, November 28, 2017
Hynes, Level 1, Hall B
8:00 PM - NM03.04.02
Self-Sensitization and Photo-Polymerization of Diacetylene Molecules Self-Assembled on a Hexagonal-Boron Nitride Nanosheet
Elisseos Verveniotis 1 , Yuji Okawa 1 , Kenji Watanabe 1 , Takashi Taniguchi 1 , Christian Joachim 1 2 , M. Aono 1
1 , NIMS, Tsukuba Japan, 2 , Centre National de la Recherche Scientifique (CNRS), Toulouse France
Show AbstractSingle, 1D, conductive polymers are expected to be integral parts in molecular electronic devices. They can play the role of on-surface fabricated molecular wires / interconnects1, which will aid the miniaturization of future electronics. We have already demonstrated that the end of a poly-diacetylene (PDA) chain can hybridize with different functional molecules2 forming an intramolecular junction3 (a prototype of a molecular-resonant-tunneling diode).
Recent work4,5 showed that hexagonal Boron Nitride (h-BN) is the ideal substrate for PDA-based devices as it is both atomically flat and insulating. In this work we proceed to evaluate the diacetylene polymerization rate under UV-light irradiation. The demonstrated rate for the h-BN/diacetylene system is shown to be at least 170 times faster than on its well-studied graphite/diacetylene counterpart. In addition, the demonstrated polymerization pattern on h-BN indicates selfsensitization, which increases the polymerization probability of pristine monomers adjacent to already polymerized ones. Both effects are attributed to the large electronic bandgap of h-BN (~ 6 eV). These results should be considered in future work towards PDA-based molecular electronic circuits as they demonstrate that an insulator with a bandgap significantly larger than the excitation energy of diacetylene (~3 eV) is necessary for efficient layer polymerization.
References:
[1] Y. Okawa et al. J. Am. Chem. Soc. 2011, 133, 8227.
[2] M. Nakaya et al. ACS Nano 2014, 8, 12259.
[3] Y. Okawa et al. Nanoscale 2012, 4, 3013.
[4] M. Makarova, et al. Nanotechnology 2016, 27, 395303
[5] E. Verveniotis, et al. Phys. Chem. Chem. Phys. 2016, 18, 31600
8:00 PM - NM03.04.04
Influence of Growth Limiting Factors on the Morphology and Sn Incorporation of GeSn Alloy Nanowires
Jessica Doherty 1 , Subhajit Biswas 1 , Dzianis Saladukh 3 , Quentin Ramasse 4 , Clive Downing 5 , Justin D. Holmes 1 2
1 Materials Chemistry and Analysis Group, University College Cork, Cork Ireland, 3 Department of Photonics, Tyndall National Institue, Cork Ireland, 4 SuperSTEM Laboratory, SciTech Daresbury Campus, Daresbury WA4 4AD United Kingdom, 5 Advanced Microscopy Laboratory, Trinity College Dublin, Dublin Ireland, 2 AMBER@CRANN, Trinity College Dublin, Dublin Ireland
Show AbstractThe development of direct bandgap, group IV one-dimensional nanoscale systems is critical for the advancement of silicon compatible device modules. Ge1-xSnx alloys are a promising solution to the lack of a direct band gap in group IV semiconductors such as Si and Ge. In this work we manipulate the growth parameters – temperature, precursor and catalyst – to influence the kinetics of the Ge1-xSnx growth system for the incorporation of above equilibrium Sn content in a vapour-liquid-solid growth paradigm. Ge1-xSnx nanowires with Sn content between 9-10.5 at. % Sn have been fabricated via a liquid-injection chemical vapour deposition process at 440 °C with AuAg alloy nanoparticle catalysts, and allyltributylstannane and tetraethyltin as the Sn precursors. Influence of the growth kinetics in Sn incorporation in Ge1-xSnx nanowires was clearly apparent as the fastest growing nanowires, with Ag rich AuAg catalysts, have the highest amount of Sn. Ge1-xSnx nanowires with large Sn assimilation of > 9 at. % are defect free and highly crystalline with uniform morphology. Sn was uniformly distributed throughout the Ge nanowire lattice, as determined by high resolution elemental analysis, with no metallic Sn segregation or precipitation at the surface or within the bulk of the nanowires. Direct bandgap has been identified for the Ge1-xSnx nanowires with > 9 at. % Sn through low temperature photoluminescence spectroscopy.
Employing tetraethyltin as the Sn precursor also produced “branched” nanostructures; a large, Ge1-xSnx "trunk” with smaller Ge1-xSnx nanowires branched off from this larger wire; for certain a Ge:Sn molar ratio in the injecting solution. The majority of these branches are well aligned; their angle of incidence relative to the trunk-wire is consistent along the trunk. High resolution microscopy studies show a continuity of the crystal lattice at the interface of branch and trunk without the formation of any stacking fault. While the trunks do not appear to be Sn rich (~ 2-4 at. %), the branched nanowires have a higher Sn incorporation (~ 6-8 at. %). Branched nanowire heterojunctions represent a unique architecture, where the high surface area of branches and efficient one-dimensional transport through the trunks can substantially benefit their application in Li-ion batteries. Electrochemical analysis on the branched GeSn nanowires demonstrated their suitability for use as anodes in a Li-ion battery.
8:00 PM - NM03.04.05
Thermodynamically Predicted Synthesis to Control Stoichiometry and Structure of Ni Phosphide/C Nanofibers for Hydrogen Evolution Reaction
Ji Yong Kim 1 , Dae-Hyun Nam 1 , In-Kyoung Ahn 1 , Ho-Young Kang 1 , Young-chang Joo 1
1 , Seoul National University, Seoul, SE, Korea (the Republic of)
Show AbstractNi phosphide has attracted much attention for its high hydrogen evolution reaction(HER) catalytic performance among other metal compounds. It exists in a lot of phases such as Ni2P, Ni5P2, Ni12P5, NiP2, etc. and there have been many studies that stoichiometry of Ni phosphide has crucial impact on HER performance. Therefore, controlling the stoichiometry is essential to optimize the catalytic activity. There were many attempts to synthesize Ni phosphide by differentiating the initial amount of Ni and P to control the stoichiometry. However, these exhibited the problems such as limited control range of Ni : P ratio within compound, the existence of mixed phase, and low homogeneity. It was due to the lack of understanding about the thermodynamics in the Ni phosphide formation. Here, we demonstrated a novel fabrication methodology to control the stoichiometry and structure of Ni phosphide precisely by considering the chemical potential of the compound, which provides a guidance to determine the stable phase formation. Thermodynamic calculation was applied as a tool to predict the phase under various synthetic conditions. It is meaningful that the composition of materials and processing parameters from calculation induce the targeted selective reaction in multi-atomic component system.
In this work, we fabricated Ni phosphide/C hybrid nanofibers for superior HER catalyst materials. Electrospinning proceeded with a solution of Ni acetate tetra-hydrate(C4H6NiO4) as metal precursor, phosphoric acid(H3PO4) as P precursor and polymer matrix. Our system is composed of Ni-P-C-O elements. For the effective structure and phase control of Ni phosphide/C nanofibers, the conditions for Ni phosphidation and C oxidation without Ni oxidation were considered in calculation and experiment. The materials composition (amount of relative ratio between precursor and polymer matrix) and processing parameters (temperature, pressure) during calcination after electrospinning were determined by the thermodynamic calculation. For utilizing the different chemical potential in oxidation according to the cations, we controlled an oxygen partial pressure (pO2). Also, calcination of nanofibers was progressed at 600, 800, and 1000°C, 5h. HER catalytic performance was evaluated by linear sweep voltammetry (LSV) with 2mV/s. Increasing the pO2, C was combusted during calcination. As a result, C nanofibers with high porosity and Ni phosphide with various size and distribution were formatted. Also, stoichiometry of Ni phosphide was modulated successfully with the wide range of Ni:P relative ratio. Structure and stoichiometry of Ni phosphide were optimized for excellent electrochemical performance, and we obtained superior performance of E vs. RHE less than -0.2V at -10mA/cm2.
8:00 PM - NM03.04.06
Production and Mechanical Characterization of Electrospun Ceramic Nanofiber for Future High Power Targets
Sujit Bidhar 1 , Vallerie Goss 2 , Robert Zwaska 1
1 Target Systems, Fermilab, Batavia, Illinois, United States, 2 Physics and Chemistry, Chicago State University, Chicago, Illinois, United States
Show AbstractThe possibility of fabricating non-woven metallic/ceramic nanofibers by electrospinning process is explored in an effort to develop and design next-generation high-power target materials for particle physics research . A low-cost electrospinning unit is set up for in-house production of nanofibers. Yttrium stabilized Zirconia nanofibers are successfully fabricated by electrospinning a mixture of Zirconium carbonate with high molecular weight polymer solution polyvinylpyrrolidone (PVP). Continuous long nanofibers of few hundreds of nano-meters in diameter are produced when high electrical potential is maintained between a syringe containing solution and a metallic plate. The as-spun nanofibers are subsequently heat treated up to 1200 oC to eliminate polymer and allow grain growth of Zirconia by recrystallization process. SEM, EDS, XRD are employed to study the morphology, composition, phase and grain structure of produced nanofiber. Atomic force microscopy (AFM) is used to evaluate the mechanical properties of single nanofiber. These information will be used in simulation frame work in order to improve and optimize different physical characteristics. Advantages and challenges of such nanofibers as potential future targets over bulk material targets are discussed.
8:00 PM - NM03.04.08
Electrochemical Deposition of Conformal and Functional Layers on High Aspect Ratio 1D Substrates
Tuncay Ozel 1 , Benjamin Zhang 1 , Ruixuan Gao 1 , Robert Day 1 , Charles M. Lieber 1 2 , Daniel Nocera 1
1 Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, United States, 2 , Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show AbstractDevelopment of novel synthetic tools for the precise modification of nanostructures has accelerated materials design advances to furnish complex architectures. In particular, top-down and bottom-up grown structures based on one-dimensional (1D) silicon (Si) micro/nanowires are exemplary nanodevices that have facilitated diverse applications in chemistry, physics, and medicine. Yet further elaboration of these structures with distinct metallic and polymeric materials, which could open up new opportunities, has been challenging. In this work, we present a general method based on electroplating for the deposition of conformal layers of a variety of materials onto high aspect ratio Si micro- and nanowire arrays. The deposition of a large library of coaxial layers comprising metals, metal oxides, and organic/inorganic semiconductors demonstrate the materials generality of this synthesis technique. Depositions are performed on wire arrays with varying diameter (70 nm to 4 µ), pitch (5 µ to 15 µ), aspect ratio (4:1 to 75:1), shape (cylindrical, conical, hourglass), resistivity (0.001–0.01 ohm/cm2 to 1–10 ohm/cm2), and substrate orientation. Anisotropic physical etching of wires with one or more coaxial shells using a directional reactive ion etching technique yields 1D structures with exposed tips that can be further site-specifically modified by a secondary electrochemical deposition step. High aspect ratio structures embedded in a photoresist matrix have also been coated to demonstrate both the compatibility of the technique with semiconductor fabrication and the possibility of tip-selective deposition on the structures. The electrochemical deposition methodology described herein features a high-throughput synthesis platform for the preparation of multifunctional nanoscale devices based on a 1D Si substrate.
8:00 PM - NM03.04.09
Synthesis of Pd and Pt Microtubes with Square Cross-Section Using Square Planar Ion Salt Templates
John Burpo 1 , Enoch Nagelli 1 , Stephen Winter 1 , Alvin Burns 1
1 , United States Military Academy, West Point, New York, United States
Show AbstractOne-dimensional noble metal structures assembled into 3-dimensional architectures with high surface area and tunable porosity offer a wide range of catalytic, sensing, and energy applications. Few techniques present a direct synthesis route to achieving metal tube structures that are easily assembled into a 3-dimensional array. Here we present the synthesis of palladium and platinum microtubes with a square cross-section using direct solution based reduction of precursor square planar salt templates. The addition of oppositely charged square planar noble metal ions results in the spontaneous precipitation of salt needles, which are subsequently reduced in solution. Resulting tubes possess a high aspect ratio with square cross-sectional geometry on the order of hundreds of nanometers, and lengths of tens of microns. Tubes may be mechanically pressed into free standing films, or freeze dried to form aerogels. Material characterization was performed using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffractometry, X-ray photoelectron spectroscopy (XPS), BET, impedance spectroscopy, and cyclic voltammetry. The resulting tube structures showed a dependence on the concentrations of both precursor salt and reducing agent solutions. Electrocatalytic activity of metal tubes is demonstrated in aqueous H2SO4 with distinct hydrogen adsorption and desorption, as well as surface oxide formation and reduction. These self-supporting metal tube films and aerogels synthesized via a single reduction step are envisioned to offer a flexible synthesis scheme to tune porosity, surface area, and mechanical robustness for noble metal catalytic, sensing, and energy applications.
8:00 PM - NM03.04.10
Self-Catalyzed Vapor-Liquid-Solid Growth of Single-Crystalline Lead Halide Nanowires and Conversion to Perovskite
Jonathan Meyers 1 , Seokhyoung Kim 1 , David Hill 1 , Emma Cating 1 , Lenzi Williams 1 , John Papanikolas 1 , James Cahoon 1
1 , University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
Show AbstractThe bottom-up approach to creating nanowires enables the synthetic precision required for many fundamental studies and technological applications. Specifically, the development of the vapor-liquid-solid (VLS) nanowire growth mechanism has been crucial in obtaining fine control over composition, crystal structure, growth direction, and morphology in group IV, III-V, and II-VI materials. Extending this technique to a new material system, we present the first demonstration of the self-catalyzed VLS growth of lead halide nanowires via a supersaturation of halide inside a liquid lead catalyst. The lead iodide nanowires presented here are single crystalline and are composed of a stoichiometric PbI2 shaft and a Pb spherical cap. The nanowires have a rectangular cross section and were determined by selected area electron diffraction to grow in the 〈-1 2 -1 0〉 direction. We utilize these nanowires as precursors for the synthesis of organolead halide perovskite nanowires via a facile low-temperature vapor-phase intercalation of an organic precursor. The resulting perovskite nanowires are crystalline and reproduce known perovskite optical properties including photoluminescence near 770 nm and an extinction spectrum similar to that predicted by finite element modeling. This synthetic route extends the benefits of the VLS mechanism to perovskite systems and is expected to enable the growth of high-quality and customizable perovskite nanowires that can be employed in nanophotonic applications.
8:00 PM - NM03.04.11
AAO Template-Assisted Growth of PEDOT:PSS Nanowires
Hyejeong Lee 1 , Taejin Yoo 1 , Wan Sik Kim 1 , Hyeon Jun Lee 1 , Byoung Hun Lee 1 , Ji Young Jo 1
1 , GIST, Gwang-ju Korea (the Republic of)
Show AbstractFlexible electrode materials such as Ag nanowires, graphene, and conducting polymers possess the potential to replace brittle ITO. In particular, conducting polymers have additional advantages such as low cost, solution process, and ambient temperature processability. Compared with thin films, low dimensional structures such as 1-dimensional nanowires (NWs) of conducting polymers exhibit superior electrical properties due to confined movement of charge carriers. The 1-dimensional conducting polymer structures can be fabricated by interfacial polymerization methods, seeded polymerization methods, and through electrospinning techniques;[1] however, resulting nanowires with a diameter of a few hundred nanometers[2] exhibit similar electrical characteristics to those of a bulk film. In order to achieve higher electrical conductivity, it is critical to reduce the diameter of the NWs to limit the carrier path. Among the various conducting polymers, poly (3,4-ethylendioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been widely studied owing to its highest electrical conductivity (2170 S cm-1).[3] In this study, we successfully fabricated PEDOT:PSS nanowires with an average diameter down to 50 nm via AAO template without any synthesis process. We believe that the template assisted synthesis is a facile method for fabricating PEDOT:PSS nanowires.
At first, the AAO template was placed on a glass substrate and the PEDOT:PSS solution was dropped on to the AAO template. The PEDOT:PSS solution was dropped for 45 min at 3 min intervals. Then the template/glass was baked at 120oC followed by H2SO4 treatment for 10 min to improve the electrical conductivity of PEDOT:PSS. After the H2SO4 treatment, samples were rinsed and then baked at 120oC for 10 min. The template was then transferred to a thermal release tape. The AAO barrier layer was removed by immersing the template in HF followed by rinsing. The PEDOT:PSS nanowires were then transferred from thermal release tape to the desired substrate. The I-V characteristic, Raman spectra, and conductive-AFM results of the synthesized PEDOT:PSS nanowires will be presented.
[1] Moon Gyu Han and Stephen H. Foulger, Chem. Commun. 3092 (2005).
[2] Dian Chen et al., ACS Nano 6, 1479 (2012).
[3] Zeng Fan et al., Adv. Energy Mater. 7, 1602116 (2017).
8:00 PM - NM03.04.12
Microreactors for the Morphological “Shaping” of Zinc Oxide Nanocrystals
Michael Stoller 1 , Abhiteja Konda 1 , Stephen Morin 1 2
1 Chemistry, University of Nebraska–Lincoln, Lincoln, Nebraska, United States, 2 Nebraska Center for Materials and Nanoscience, University of Nebraska–Lincoln, Lincoln, Nebraska, United States
Show AbstractIn crystal growth, the propensity for ripening to proceed down energetically favorable pathways gives rise to particular morphologies (the crystal habit). Bottom-up strategies for the synthesis of nanomaterials, for example the use of structure-directing agents or templates, work to circumvent or exaggerate crystal habit and thus achieve desired morphologies, by design. We are investigating techniques that use fluid flow as a method of augmenting current synthetic strategies to achieve target structures—an approach that remains widely unexplored. Specifically, we used zinc oxide nanorods (ZnO NRs) as a model system to demonstrate selective, axial etching/dissolution in shear-flow, a process we refer to as morphological “shaping.” We employed high velocity laminar flow within micron-sized channels to rationally control the orientation, via fluid-mechanical shear, of ZnO NRs suspended in aqueous solutions, leading to partially hollowed NRs with predictable geometries. We observed: (i) that hollowing first occurred at the tips of the NRs and that the depth increased as flow time increased, and (ii) that hollowing occurred symmetrically at both ends of the NRs, a phenomenon we attribute to periodic “flipping” (Jeffery orbits) of the NRs within the microchannels (as predicted for transport in shear-flow). We believe these investigations provide insight into the fundamental processes associated with nanostructure evolution in dynamic flow environments. This knowledge can be used to design new synthetic strategies that augment current bottom-up approaches, and to understand the potential stability limitations of nanostructures in applications involving high-velocity flow environments (e.g., those present in biological vascular systems).
8:00 PM - NM03.04.13
Filamentary Growth of Metal Nanowhiskers
Gunther Richter 1
1 , Max Planck Institute Intelligent Systems, Stuttgart Germany
Show Abstract
One-dimensional structures have the prospect to change the physical properties of materials used in contemporary devices. Physical properties change with dimension and size enabling a tailoring of performance in nanometer sized devices. Ceramics, semiconductor and carbon materials are easily synthesized as one-dimensional structures with typical diameters of several nanometers and length-diameter ratios of 1000:1.
We present a recently developed process to grow perfect defect and flaw free metal nanowhisker (NW) with diameters of several ten nanometers, attached on substrates and based on physical vapor deposition. Traditional theories, e.g. Frank, Sears, attribute the growth of whiskers with the presence of a screw dislocation. However, our extensive microstructure studies by transmission electron microscopy (TEM) in metal NWs did not reveal any indication that screw dislocations are present nor needed for whisker growth. Growth studies revealed that the nanowhiskers grow via adatom incorporation into the nanostructure/substrate interface. Therefor the interface diffusivity, adatom impingement rate from the substrate surface diffusion has to be carefully balanced by substrate temperature, deposition rate and especially substrate surface structure and composition. Guidelines for choosing substrates for nanowhikser growth will be presented.
Basic physical properties (mechanical strength, conductivity and magnetic domain structure) were investigated and will be reported in the presentation. E,g, in situ bending experiments utilizing a micromanipulator inside a SEM allows mechanical probing of small volumes. This reduces the stochastic effect of slight deviations, especially on the surface facets, on the measured mechanical properties. Nanowhiskers which are attached on a standard TEM Cu grid were deflected in a cyclic manner with increasing load. After each deflection the load was reduced to check for plastic deformation. From the last bending experiment with elastic deformation the bending stress was calculated as a lower limit for the yield strength from the curvature of the deformed nanowhisker. The resulting bending stress reached values between 4 to 6 GPa. Almost no dependence on the nanowhisker diameter is observed. Knowing the crystallographic orientation of the whisker axis, a dislocation model is proposed for the deformation mechanism.
8:00 PM - NM03.04.14
Ideal Carbon Nanotube Conductors—Beyond Carbon Nanotube Fibres
Agnieszka Lekawa-Raus 1 , Daniel Janczak 1 , Tomasz Gizewski 2
1 , Warsaw University of Technology, Warsaw Poland, 2 , Lublin University of Technology, Lublin Poland
Show AbstractIt is already over 10 years since the production of the first carbon nanotube fibres [1]. Finding these forms analogous to traditional electrical wires and basing on the fact that at individual carbon nanotubes have better electrical properties than any metal, the researchers intuitively proposed that these assemblies could become the next generation of electrical wires. Yet, up to now none of the fibres has reached the ultimate conductivity. A recent paper of Xu et al. [2] has shown that indeed there should be a possibility of producing a fibre with negligible energy losses within its structure. It should be made of very long, crystalline and well packed armchair single-walled nanotubes of only one chirality. Going from there we have recently calculated a theoretical conductivity of such fibres connected to practical 3D electrodes and showed that in case of DC signals transport there are only 12 such ideal structures available, with many more to be considered in case of AC applications [3]. All these ideal structures should have orders of magnitude better absolute and specific conductivity than commonly used copper, which indicates that it is definitely worth optimizing the existing CNT fibres towards better electrical performance.
However, why should we think about electrical conductors as only round shaped bare, self-standing wires. For example, round cross-section of the wires does not ensure the best packing of electrical machines windings or there are important applications where it is better not to use self-standing wires like non-woven meshes in lightning strike protection systems or pathways in electronic circuits. The currently developed methods of CNT fibres production are not allowing sufficient flexibility to produce all the above-mentioned conductors, while the techniques developed for production of e.g. electrodes often do not take into account the experience of CNT fibre community and do not invest much in the proper alignment of the CNTs.
Having in mind all the above we have decided to explore the opportunities offered by printing techniques. Our first results obtained with the use of easily up-scalable screen printing technique show that it is capable of fast continuous production of micro-thin and wide CNT wires with highly precise dimensions. The wires are in the form of flexible conductive tapes printed on various polymer foils which may be further used as insulation of the wires. The first studies on the paste compositions, screens choice, annealing parameters and densification methods has led to specific conductivity of 0.01 S m2/g with room for further improvement.
[1] Lekawa-Raus et al. Adv. Funct. Mater. 24, 3661, (2014).
[2] Xu et al. J. Appl. Phys. 114 ,063714 (2013).
[3] Lekawa-Raus et al. Scripta Materialia 131, 112, (2017).
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Stable, Hexagonal Non-Close-Packed Gold Nanowires
Seonhee Lee 1 , Changdeuck Bae 1 , Hyunjung Shin 1 , Hochul Nam 1
1 , Sungkyunkwan University, Suwon-si Korea (the Republic of)
Show AbstractGold has been known as the most noblest metal with only face-centered cubic (fcc) structure in ambient conditions. Few exceptions in nanostructures having hexagonal close-packed (hcp) structure have been reported. However, they were stable under limited dimensions of 6 nm in thickness even with capping agents. Here we show stable hexagonal non-close-packed (ncp) gold nanowires (NWs) having about 50 nm in diameter and aspect ratios well over 500. We have grown Au NWs in the confined system of nanotubular TiO2 arrays via photoelectrochemical reduction of HAuCl4 precursors. Some of the resulting gold wires has been proved to be the ncp-2H structure by electron diffraction study. TEM tilting experiments and XRD were used carefully to characterize the crystal structure of the resulting gold. In some of them, we observed the 6-fold rotational symmetry, which is distinctively different from the fcc structure. This new polymorph was identified as hexagonal ncp-structure with lattice parameter of a = 2.884 Å and c = 7.150 Å showing a quite large interplanar spacing (c/a ~2.48). That is, gold atoms are close-packed along the ab plane, but each is not closely stacked along the c axis like in graphite. The structure is expected to be unstable, but the present ncp gold was stable under ambient and intense electron beam irradiation, and showed the thermal stability up to 400 °C. Moreover, the resulting physical properties as a result of the corresponding electronic structures change were investigated by comparing the optical properties of fcc and ncp-2H gold NWs.
8:00 PM - NM03.04.16
Self-Assembly and Magnetic Property of MnTe/Cr2Te3 Composite Nanorods
Fang Wang 1 , Jie Zhou 1 , Xiaohong Xu 1
1 Research Institute of Materials Science, Shanxi Normal University, Linfen China
Show AbstractHard magnetic materials with large coercivity have broad applications ranging from high-density data storage media to permanent magnets. Recently, 3d transition-metal chalcogenides have attracted widespread attention as the rare-earth-free permanent magnets due to their versatile magnetic properties from paramagnetism to ferrimagnetism and ferromagnetism [1]. To date, much effort have been made to prepare transition metal chalcogenide nanocrystallites through elemental reaction in vacuum at high temperatures or mechanical alloying [2,3]. These processes are usually complicated and time-consuming and their products are bulk materials with large grain sizes. However, the morphology and magnetic properties cannot be well modified. It is well known that MnTe is antiferromagnetic phase with a hexagonal NiAs-type structure, which is hard to obtain high coercivity. Li et al. synthesized the ferromagnetic Mn1-xCrxTe bulk with a coercivity of 300-985 Oe at 5 K[4]. In this work, we synthesized the self-assembly MnTe/Cr2Te3 composite nanorods with the coercivity larger than 6.0 kOe by one-pot chemical method. Both the morphology and magnetic properties can be controlled by Cr doping in MnTe nanowires.
The uniform and dispersed MnTe nanowires with length larger than 10 μm can be obtained. It is also found that pure MnTe is antiferromagnetic behavior. When Cr precursor is doping into Mn and Te precursors by one-pot reaction, MnTe/Cr2Te3 composite nanorods with knots at the end of the rods can be observed. TEM and EDX mapping results indicate that Cr2Te3 can epitaxy grow on the MnTe nanorods. Surprising, the ferromagnetic behavior can be induced in the composite nanorods and a significant enhancement in Ms and Hc is achieved. The maximum Hc is about 6.5 kOe for the sample with Cr precursor is only 14% compared with Mn precursor. The ferromagnetic behavior of composite nanorods is due to the exchange coupling between antiferromagnetic MnTe and ferromagnetic Cr2Te3. The formation of composite nanorods is attributed to the low solid solution of Cr in MnTe nanowires. Therefore, this self-assembly method will be a new avenue to explore new multifunctional magnetic materials.
References:
[1] Zhang, H.W.; Long, G.; Li, D.; et al. Chem. Mater. 2011, 23, 3769.
[2] Feng, Q.J.; Shen, D.Z.; Zhang, J.Y.; et al. Appl. Phys. Lett. 2006, 88, 012505.
[3] Mizuguchi, Y.; Tomioka, F.; Tsuda, S.; et al. Appl. Phys. Lett. 2008, 93, 152505.
[4] Li, Y. B.; Zhang, Y. Q.; Sun, N. K.; et al. Phys. Rev. B 2005, 72, 193308.
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Production and Characterization of Boron Nitride Nanotubes from Reaction of Ammonia with Mixture of Boron and Iron Powders
Naime Sezgi 1 , Selin Noyan 1
1 , Middle East Technical University, Ankara Turkey
Show AbstractNanoparticles have high thermal, electrical and mechanical properties and these properties cause them to be used for different applications in electronics, pharmaceuticals, medicine etc. Boron nitride nanotubes are one of the important types of nanoparticles which are produced by rolling and folding into cylindrical forms of boron nitride sheets. Boron nitride nanotubes have nice field emission property, high thermal conductivity and high Young’s Modulus. They have a constant band-gap (~5 eV), so the conductive properties of boron nitride nanotubes are more or less independent of chirality, diameter and even the number of walls in the tube.
In this study, boron nitride nanotubes were synthesized from the reaction of ammonia gas with mixture of boron and iron powders in an alumina tube which was connected to a mass spectrometer for on-line chemical analysis of the reactor outlet stream. Purification of the as-synthesized BNNTs was performed by applying successive acid treatments. There is no published work in which experimental evidence was reported for the formation of species by the on-line measurement of the reactor exit composition. The mass spectrometer analysis of the reactor effluent stream proved formation of nitrogen and hydrogen in addition to ammonia gas during the reaction of ammonia gas with the powder mixture. The analysis result showed that the only reaction taking place in the gas phase was decomposition reaction of ammonia gas. Boron nitride nanotubes were produced by the reaction of nitrogen formed from the decomposition reaction with FeB formed from the reaction of boron with iron. XRD results showed that hexagonal and rhombohedral boron nitrides and the iron boride were the solid phases formed in the synthesized materials. Boron nitride production was first observed at a temperature of 900 °C. An increase in the deposition rate of boron nitride was observed with an increase in the temperature. However, the deposition rate decreased after 1300 °C. This might be due to the sintering of the materials at higher temperatures. The purified BNNTs exhibited Type II isotherm and the multi-point BET surface area of the material synthesized at a temperature of 1300 °C was 147.6 m2/g and its average pore diameter was 38.02 A. Nanotubes were not in uniform size. SEM images showed that the outer diameter of the nanotube was in the range of 30-150 nm depending on the reaction temperature. Cylindrical boron nitride nanotubes were observed in the studied temperature range.
8:00 PM - NM03.04.18
Enhancing Fracture Toughness and Stress Energy Release Rate of Vinyl Ester Matrix Using Dual Reinforcement of CNT and GNP
Christopher Gapstur 1 , Hassan Mahfuz 1 , Javad Hashemi 1 , Andrew Terentis 1
1 , Florida Atlantic University, Boca Raton, Florida, United States
Show AbstractWhen considering materials for engineering and advanced applications, one of the most important characteristics of the material is the fracture toughness. In this paper we report a method of increasing fracture toughness KIc and strain energy release rate GIc of vinyl ester matrix by adopting a dual reinforcement strategy. Reinforcements were carbon nanotubes (CNT) and graphene nanoplatelets (GNP). Both categories of inorganic nanoparticles were functionalized with COOH. The idea was to enhance crack bridging and interface sliding through CNT due to their high aspect ratio, and in addition, promote crack-tip blunting and cross-linking density through GNP due to their platelet structures. Nanoparticles were dispersed into vinyl ester matrix using a sonic cavitation method. After mixing the hardener through a mechanical mixer, the admixture was desiccated, cast into silicon molds, cured at room temperature for 24 hours and further cured two hours at 99°C. Each specimen was machined to produce a sharp notch and a natural crack was induced within the sharp notch by means of sawing with a fresh razor blade. Then each specimen was tested in flexure mode using a Zwick-Roell materials testing machine. Both KIc and GIc were measured using ASTM D5045-14 for plain-strain fracture toughness and strain energy release rate of plastic materials. An exhaustive experimental study was conducted to come up with an optimum loading of both nanoparticles (0.25 wt% CNT and 0.5 wt% GNP) based on the highest combination of KIc and GIc values. It was observed that stress intensity factor KIc of neat vinyl ester increased by 43% from 1.14 to 1.62 MPa*(m½). On the other hand the improvement in GIc was even more impressive with an increase of 62%, i.e., from 370 to 601 J/(m2). Differential scanning calorimetry (DSC) studies revealed a discernible shift in glass transition temperature (Tg) from 123 to 127°C. Similar was the case with thermogravimetric analysis (TGA). We observed a slight increase in thermal decomposition temperature from 411 to 414°C as was evident in the derivative TGA (DTG) curves. Failure surfaces were examined under filed emission scanning electron microscope (FESEM) to determine the source of improvement as to nanoparticle dispersion, crack containment, particle-polymer interface, etc. Fourier transform infrared spectroscopy (FTIR) studies were also conducted to identify chemical bonds responsible for such enhancement. Details of nanocomposite synthesis, fracture tests, SEM and FTIR analysis will be described in the paper.
8:00 PM - NM03.04.19
Inducing Porosity and Growing Carbon Nanofibers in Ferroin Perchlorate—An Example of Morphological Transitions in Coordination Complexes
Efrat Shawat Avraham 1 , Ohad Fleker 1 , Laurent Benisvy 1 , Landon Oakes 2 , Cary Pint 2 , Gilbert Nessim 1
1 , Bar Ilan University, Ramat Gan Israel, 2 Mechanical Engineering, Vanderbilt University, Nashville, Tennessee, United States
Show AbstractOrganometallic complexes are important catalysts, and are interesting for other applications as well. Inducing porosity in solid organometallic crystals is critical for applications where a high surface area is required. However, unlike for metal organic frameworks (MOFs), fabrication of porous organometallic crystals remains a significant challenge. Here we demonstrate a simple method to modulate porosity using ferroin perchlorate, a model system that combines a common ionic complex with a very reactive counter-ion. Using thermal chemical vapor deposition (CVD), we show that by annealing ferroin perchlorate crystals at 350 °C under a flow of ethylene, hydrogen, argon, and oxygen, we induced pores in the crystal. We demonstrate that small amounts of oxygen that may combine with hydrogen to form water are essential to pore formation. We also demonstrate that pore size and density can be easily controlled by varying the ethylene flow. Upon raising the annealing temperature to 500 °C, we observed a second transition in which carbon nanofibers (CNFs) grew from the porous crystal. This approach represents a simple and effective method for the synthesis of porous materials with good control over pore size and density. It also enables the synthesis of complex networks of nanostructures (in our case CNFs) by simply varying process parameters such as temperature and gas flows. This represents an important advance for the fabrication of porous organometallic complex crystals that may open new doors to the application of these compounds in catalysis.
8:00 PM - NM03.04.20
Synthesis and Assembly of Ni and NiFe Micro/Nano Wires
Yan Liu 2 1 , Jing Li 1 , Shan Yan 1 , Zakiya Skeete 1 , Chuan-Jian Zhong 1
2 School of Metallurgy, Northeastern University, Shenyang China, 1 , State University of New York at Binghamton, Binghamton, New York, United States
Show AbstractThe ability to assemble magnetic micro/nanomaterials with controllable sizes and shapes is increasingly important because applications such as sensors, catalysis, medical diagnostics, and information storage depend strongly on the precise control of the nanoscale architecture or the device miniaturization. This report describes the synthesis of Ni and NiFe micro/nanowires using the hydrothermal method by controlling the concentration of the interparticle ligands. The growth mechanism of Ni and NiFe alloy one-dimensional materials is shown to be associated with the concentration of the inter-connecting ligands. The magnetic properties of the Ni and NiFe micro/nano wires were determined, revealing strong correlation with the size and shape of the micro/nano wires. Potential applications of the Ni and NiFe micro/nanowires in biosensors will also be discussed.
8:00 PM - NM03.04.21
Complementary Metal Oxide Semiconductor Compatible, High-Mobility,（111）-Oriented GaSb Nanowires Enabled by Vapor−Solid−Solid Chemical Vapor Deposition
Ziyao Zhou 1 , Zaixing Yang 1 , Sen Po Yip 1 , Dapan Li 1 , Lifan Shen 1 , Johnny Ho 1
1 , City University of Hong Kong, Hong Kong China
Show AbstractUsing CMOS-compatible Pd catalysts, we demonstrated the formation of high-mobility （111）-oriented GaSb nanowires (NWs) via vapor−solid−solid (VSS) growth by surfactant-assisted chemical vapor deposition through a complementary experimental and theoretical approach. In contrast to NWs formed by the conventional vapor−liquid−solid (VLS) mechanism, cylindrical-shaped Pd5Ga4 catalytic seeds were present in our Pd-catalyzed VSS-NWs. As solid catalysts, stoichiometric Pd5Ga4 was found to have the lowest crystal surface energy and thus giving rise to a minimal surface diffusion as well as an optimal in-plane interface orientation at the seed/NW interface for efficient epitaxial NW nucleation. These VSS characteristics led to the growth of slender NWs with diameters down to 26.9 ± 3.5 nm. Over 95% high crystalline quality NWs were grown in （111） orientation for a wide diameter range of between 10 and 70 nm. Back-gated field-effect transistors (FETs) fabricated using the Pd-catalyzed GaSb NWs exhibit a superior peak hole mobility of ∼330 cm2 V−1 s −1, close to the mobility limit for an NW channel diameter of ∼30 nm with a free carrier concentration of ∼1018 cm−3. This suggests that the NWs have excellent homogeneity in phase purity, growth orientation, surface morphology and electrical characteristics. Contact printing process was also used to fabricate large-scale assembly of Pd-catalyzed GaSb NW parallel arrays, confirming the potential constructions and applications of these high-performance electronic devices.
8:00 PM - NM03.04.22
Spectral Tuning of the Photoconductivity of Semiconductor Nanowires with Carbon Nanodots
Kseniia Zimmermann 1 , Davide Cammi 1 , Frank Dissinger 2 , Carsten Ronning 3 , Siegfried Waldvogel 2 , Tobias Voss 1
1 Institute of Semiconductor Technology, University of Technology Braunschweig, Braunschweig Germany, 2 Institute of Organic Chemistry, Johannes-Guttenberg University Mainz, Mainz Germany, 3 Institute of Solid States Physics, Friedrich-Schiller University Jena, Jena Germany
Show AbstractSemiconductor nanowires have allowed for the design and fabrication of novel nanoscale optoelectronic and sensing devices. Their unique electronic properties in combination with their excellent crystalline quality and their large surface-to-volume ratio have resulted in the demonstration of high-performance devices.
Fabrication of heterogeneous nanosystems via the integration of colloidal nanoparticles at the nanowire surface opens up further opportunities for tailoring and optimizing the optoelectronic properties of the nanodevices.1-3 Thus, surface functionalization of nanowires with colloidal carbon nanoparticles (carbon dots, C-dots) has recently emerged as a promising approach for realizing devices for “green” nanophotonics.4,5
In this work, we demonstrate spectral tuning of the photoresponse of semiconductor nanowires via surface functionalization with carbon dots. At first, carbon dots were synthesized by means of hydrothermal pyrolysis of citric acid and a selected stabilization agent. Subsequently, they were attached to the surface of ZnO nanowires, which were synthesized by a wet-chemical method. After functionalization, the photoconductivity of the nanowires was investigated with photon energies below and at the band edge of ZnO. We observed an increase of the photoconductivity by a factor between 2 and 1000 in the spectral range between 360 and 600 nm, depending on the applied stabilizing molecules of C-dots, their solvent and, in the case of an aqueous solution, the pH conditions. After application of modified synthesis protocols for the C-dots,6 we were able to shift their low-energy absorption band towards 430 nm by introducing aromatic amine-containing molecules. This shift is directly reflected by the corresponding photoconductivity measurements and thereby clearly demonstrates that electron transfer processes occur from the carbon dots to the nanowires after photoexcitation.
References
1 K. Liu et. al., J. Phys. Chem. C 114 (2010), 19835–19839.
2 K. S. Leschkies et al., Nano Lett. 7 (2007), 1793–1798.
3 T. Voss, and S. R. Waldvogel, Mater. Sci. Semicond. Process (2016), in press [DOI:10.1016/j.mssp.2016.11.027].
4 X. Wang et al., Phys. Lett. A 380 (2016), 262–266.
5 C. Xie et al., ACS Nano 8 (2014), 4015–4022.
6 W. Kwon et.al., Sci. Rep. 5 (2015), 12604.
8:00 PM - NM03.04.23
Development of a Portable Electrospinning System for a Durable UV Protection Coating
Hyunwoo Lee 1 , Sung Uk Hong 1 , Chan Park 1 , Hyunsuk Jung 1 , Seong Jin Cho 1
1 , Chungnam National University, Daejeon Korea (the Republic of)
Show AbstractUltraviolet (UV) can cause sunburn, wrinkles, immune degradation, premature aging, and cancer, so there is a permanent need to protect against UV radiation. However, current sunscreens have the disadvantages of promoting skin disorders due to chemical composition, waterproofing and short duration. Therefore, the manufacture of durable and hypoallergenic sunscreens has been a very challenging problem in the cosmetic industry. Here, we introduce a novel portable electrospinning system that can coat UV-blocking nanofibers directly onto the skin. Electrospun nanofibrous matrix is suitable structure for UV protection due to its high specific surface area, high moisture permeability, and adhesive property. However, conventional electrospinning systems are not portable, as they include a high voltage power supply (HVPS) that is large in size, heavy in weight, expensive and has a wired power supply. To overcome these limitations, we have developed a one-handed electrospinning system that replaces HVPS with batteries and high-voltage amplifiers, and has confirmed that nanofibers with similar structures to that of conventional electrospinning devices can be fabricated. Electrospun nanofibers were fabricated by polymeric materials such as PVP and PU, and nanoparticles such as ZnO or TiO2 to enhance the UV blocking effect. In addition, we confirmed that UV protection effect, durability and reduced irritation from the physical interception by analyzing ultraviolet transmittance, moisture permeability, water resistance, and removal test. Finally, we have successfully developed a portable electrospinning system for the UV blocking. Unlike conventional sunscreen agents, nanofiber-based sunscreen is expected to be very useful for organ transplant patients or skin disease patients who are vulnerable to UV rays.
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Synthesis and Characterization of Boron Nitride Nanotubes on Ceramic Nanofibrous Materials
Aysemin Top 1 , Deniz Koken 2 , Emin Kondakci 1 , Nuri Solak 1 , Fevzi Cebeci 2 , Elif Ozden Yenigun 1 , Hulya Cebeci 1
1 , Istanbul Technical University, Istanbul Turkey, 2 , Sabanci University, Istanbul Turkey
Show AbstractFor demanding technological applications in aerospace, construction, automotive, and military industries, high mechanical strength materials with good electrical and thermal properties are desired. Nanocomposites have potentials to meet these structural requirements. Boron nitride (BN) nanostructures are good candidates as reinforcement materials for nanocomposites due to their excellent properties such as high thermal conductivity, semiconductivity, high oxidation resistance at high temperatures. Although superior properties of these nanocomposites, there are two main challenges that prevent widespread applicability of BNs; namely poor dispersibility due to hydrophobic nature of the boron nitrides, and loss of properties due to poor interactions between boron nitride nanostructures and the matrix.
To enhance the interface interactions between nanofibers and the matrix, a hierarchical structure of nanotubes on nanofiber was prepared by synthesis of boron nitride nanotubes (BNNTs) on ceramic nanofibers such as boron nitride nanofibers (BNNFs). Continuous morphology of the ceramic nanofibers provides full coverage of nanotube and with very high specific surface area. Therefore, improvements in the interface interactions as well as better dispersibility of reinforcement inside the matrix could be obtained and this is expected to contribute mechanical properties of the composite.
In this scope, firstly BNNFs as ceramic nanofibers were synthesized by electrospinning and nitridation process, respectively. In the second step, a catalyzing process was applied to the nanofibers and BNNTs were synthesized on the surface of BNNFs. Fourier Transform Infrared Spectroscopy and Raman spectroscopy was used to detect BN formation. Thermogravimetric Analysis was used to investigation of thermal oxidation behavior of BN nanomaterials in air atmosphere. Presence and morphological properties of nanotubes on nanofibers were characterized by scanning electron microscopy.
8:00 PM - NM03.04.25
Selective Electrothermal Growth of ZnO Nanowire on ZnO Nanoparticle Functionalized Ag Nanowire Network
Habeom Lee 1 , Jinhyeong Kwon 1 , Hyunmin Cho 1 , Sukjoon Hong 2 , Seung Hwan Ko 1
1 , Seoul National University, Seoul Korea (the Republic of), 2 , Hanyang University, Ansan-si Korea (the Republic of)
Show AbstractThe development of hydrothermal growth enabled facile growth of ZnO NW over large area at mild environments, yet its usage in actual electronic devices has been restricted due to poor spatial selectivity in the growth and a difficulty in the integration to other components. We introduce selective electrothermal growth of ZnO NW based on the electrical current induced resistive heating in liquid environment for easy fabrication of metal-semiconductor hierarchical NW structure. Through vacuum filtration transfer and laser ablation process, patterned conductive network composed of ZnO NP functionalized Ag NW is prepared on a glass substrate. Upon the application of proper bias voltage, confined temperature field is generated in the vicinity of the conductive network to trigger the growth of ZnO NW from the Ag NW backbone. As the temperature rise is related to the electrical current flow, ZnO NW is mostly obtained at the area subject to the maximum current density. Furthermore, it is revealed that the growth characteristics of ZnO NW can be altered solely by changing the temperature with electrical current condition.
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Fabrication of Ordered Array of ZnO Nnanorods Using Anodic Porous Alumina
Toshiaki Kondo 1 , Taiga Sakamoto 1 , Takashi Yanagishita 1 , Masuda Hideki 1
1 , Tokyo Metropolitan University, Hachioji Japan
Show AbstractZnO nanorod that is one of typical semiconductor nanomaterials has been proposed to be applied to various functional optical devices such as photovoltaic cells due to its wide applicability of anisotropic electric conductivity originating from its anisotropic structure. Performance of the functional devices depends on the geometrical structures and the crystallinity of ZnO nanorods. Until now, several fabrication processes of ZnO nanorod arrays based on sol-gel method, electroplating method and Vapor-Liquid-Solid (VLS) method have been proposed. Among them, fabrication process based on hydrothermal synthesis method has attracted attention because the ZnO nanorods with high crystallinity can be easily obtained. However, arrangement of the obtained nanorods is usually random. Recently, formation process of an ordered array of geometrically controlled ZnO nanorods has been proposed [1,2]. In advance of hydrothermal synthesis, a mask with an aperture array was prepared on surface of a substrate. During hydrothermal synthesis, each aperture acted as a starting site for formation of the ZnO nanorods. By top-down processes using electron beam lithography and focused ion beam etching, the mask with an aperture array can be obtained. But these processes are thought to be time consuming. In contrast, by applying bottom-up process based on self-organizing materials, efficient fabrication of the mask can be expected. Anodic porous alumina that is obtained by anodizing Al in acidic electrolyte is one of the typical self-organizing materials. Anodic porous alumina has an ordered array of straight nanoholes. Diameter and interval of the nanoholes can be easily controlled by changing applying voltage of anodization. Due to its unique geometrical structures, anodic porous alumina is widely used as a starting material to fabricate various nanodevices. Until now, our group has investigated fabrication of nanostructure arrays using anodic porous alumina and its application to functional optical devices. In this presentation, fabrication of an ordered array of ZnO nanorods by hydrothermal synthesis method based on the anodic porous alumina will be presented. Starting sits for the formation of ZnO nanorod during hydrothermal synthesis were fabricated on surface of a substrate by dry etching using an anodic porous alumina mask. The diameter of ZnO nanorods could be controlled by adjusting the diameter of nanoholes of the anodic porous alumina. The present fabrication process is expected to be applied to fabricate not only the ZnO nanorod array but also various functional optical devices requiring highly ordered pattern of semiconductor nanostructures.
[1] B. Liu, H. C. Zeng, J. Am. Chem. Soc., 125, 4430 (2003).
[2] T. Shinagawa, S. Watase, M. Izaki, Cryst. Growth Des., 11, 5533 (2011).
8:00 PM - NM03.04.27
Improving Production Yield for Laser Vaporization Synthesis of Single-Wall Carbon Nanotubes
Stephen Polly 1 , Michael Hladky 1 , Andrew Bucossi 1 , Chris Schauerman 1 , Matthew Ganter 1 , Brian Landi 1 , Ryne Raffaelle 1
1 , Rochester Inst of Technology, Rochester, New York, United States
Show AbstractSingle-wall carbon nanotubes (SWCNTs) have become an important material due to their low dimensionality, high strength and electrical conductivity, and ability to couple these properties to composites and other organic semiconductors. Laser vaporization synthesis is one mechanism of producing SWCNTs that have been used to make high conductivity metal-free wires, as well as improve the specific power density of lithium-ion batteries. The synthesis process makes use of a high power density pulsed laser focused on a target made of compressed graphite, with a small percentage by weight of metal catalyst, inside a furnace tube with a flow of inert gas. This process produces a black “soot” which then contains, among metallic and other nominally undesired carbonaceous impurities, some percentage of SWCNTs in a range of diameters and chiralities. This soot can be used as-produced for some purposes, such as conductive additives, or can be further purified to remove the non-SWCNT constituents, resulting in a high purity SWCNT material. While the laser vaporization process creates SWCNTs with favorable electronic properties, the process is slow compared to other synthesis methods, so increasing overall production is of great interest. Improving the yield of SWCNTs was investigated through controlled manipulation of the incident laser pulse energy density, the laser pulse rate, the type (size) of metallic catalyst, the type and flow rate of inert gas, the furnace temperature, and the pressure used to compress the graphite target. The production rate of soot and the resulting yield purity (percent by weight SWCNTs in the soot) was then determined using previously developed purity assessment methods based on optical absorbance. The metallic content of the raw soot was analyzed using thermogravimetric analysis. Additionally, the effect of these parameters on the diameter distribution of the produced SWCNTs will be presented through analysis of optical absorbance and Raman spectroscopy data.
8:00 PM - NM03.04.29
Fabrication of Ordered Porous Alumina Through-Hole Membranes by Two-Layer Anodization
Takashi Yanagishita 1 , Atsushi Kato 1 , Toshiaki Kondo 1 , Masuda Hideki 1
1 , Tokyo Metropolitan University, Tokyo Japan
Show AbstractOrdered anodic porous alumina through-hole membranes, which have a unique geometrical structures composed of hexagonally arranged array of straight holes with uniform diameters, have attracted significant interest owing to its various applications such as filtration membranes, sensors, and templates to fabricate various one-dimensional (1D) functional nanostructures. Recently, we reported a facile and high-throughput process for the preparation of porous alumina through-hole membranes by two-layer anodization using concentrated sulfuric acid [1-3]. In this process, a highly soluble alumina layer is formed underneath the anodic porous alumina, which is formed under standard anodizing conditions using diluted acidic electrolyte, by subsequent anodization in concentrated sulfuric acid. The porous alumina through-hole membrane can be separated from the Al substrate by selective etching of the highly soluble alumina layer in an appropriate etchant. In addition, ordered anodic porous alumina can be formed by subsequent anodization of the Al substrate. Here, we show the preparation of ordered tubular through-hole membranes by two-layer anodization. In this work, tubular alumina membranes were prepared by anodization of Al tubes. After the second anodization of Al tubes in sulfuric acid solution, tubular membranes were detached from substrate by etching treatment. The Al substrate was repeatedly used for the preparation of tubular membranes. Obtained tubular through-hole membranes are expected to be used in various application fields. [1] T. Yanagishita, and H. Masuda., Electrochim. Acta, 184, 80, L804 (2015), [2] T. Yanagishita, and H. Masuda, ECS Transaction, 75, 21 (2016), [3] T. Yanagishita, A. Kato, and H. Masuda, Jpn. J. Appl. Phys., 56, 035202 (2017).
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Improving Stability of Silver Nanowire Networks with ZnO Thin Coatings by Atmospheric Pressure Spatial Atomic Layer Deposition (AP-SALD) Technique
Afzal Khan 2 1 , Vient-Huong Nguyen 1 3 , David Muñoz-Rojas 1 , Sara Aghazaddehchors 1 , Carmen Jimenez 1 , Daniel Bullet 1
2 Department of Physics, University of Peshawar, Peshawar Pakistan, 1 , University Grenoble Alpes, Grenoble France, 3 , EA/LITEN/DTS, INES, Le Bourget-du-Lac France
Show AbstractMetallic nanowire networks, in particular those composed of silver nanowires (AgNW), have attracted much attention in the past few years due to their excellent electro-optical properties(∼90 % transmittance in the visible range and ∼10 Ω.sq-1 sheet resistance), low cost and mechanical flexibility. It has also been shown that AgNW networks have the capability to surpass the electro-optical properties of the indium tin oxide (ITO) by optimizing its deposition conditions and post-deposition treatments. Transparent electrodes based on AgNW networks have already been efficiently integrated into devices such as transparent heaters, solar cells, touch screens, electromagnetic shielding or antennas, OLEDS, electrically conductive fabrics and thermal therapy devices.
In spite of promising electro-optical properties of AgNW networks and few already successful uses, their integration in real devices is not yet widely performed due to their potential thermal and electrical instabilities, as well as low adhesion and ageing issues. For instance, while this is well known that a thermal annealing is beneficial for inducing local sintering at junctions between adjacent AgNWs, it is also well understood that reaching excessively high temperatures would lead to spheroidization of, which destroy the percolative nature of the network, eventually leading to an infinite electrical resistance. Previous works has shown thata thin oxide coating could increase resistance of AgNW networks to these instabilities, but exhaustive studies on the effect of the coating on other properties such as transparency or adhesion are missing.
In this work, we present an in-depth study of the properties of ZnO coated AgNW networks using different coating thicknesses. ZnO thin layers were deposited by AP-SALD technique on silver nanowires previously deposited on glass substrates by spin coating. The AP-SALD technique offers very conformal coating at much higher deposition rate when compared with conventional ALD and operating in the open air. Properties of the bare and ZnO coated networks were compared after the application of thermal and voltage ramps. We found a drastic enhancement of both thermal and electrical stabilities of AgNWs by coating them with a thin layer of ZnO. We found that the thermal stability of the AgNWs is greatly enhanced from 300 oC (for bare networks) to 500 oC (for ZnO coated networks). Similarly, the electrical stability is improved from 8 to 18 volts by the use of a thin ZnO coating. Adhesion of AgNWs to the glass substrate was greatly increased as revealed by the scotch tap test. Similarly, the adverse ageing effect on AgNW netwroks was reduced by ZnO coating. Optically transparency of the ZnO coated networks was found to be reduced by 8 % as compared to the bare AgNW networks. It was found that increasing the thickness of the ZnO coating enhances the network stabilities, while decreasing the optical transparency accordingly.
8:00 PM - NM03.04.31
Polarity-Dependent Formation Mechanisms and Physical Properties of Selective Area Grown ZnO Nanorods
Thomas Cossuet 1 , Estelle Appert 1 , Jean-Luc Thomassin 2 , Fabrice Donatini 3 , Alex Lord 4 , Julien Pernot 3 , Vincent Consonni 1
1 , Université Grenoble Alpes, CNRS, Grenoble INP, LMGP, Grenoble France, 2 , Université Grenoble Alpes, CEA, INAC-PHELIQS-LATEQS, Grenoble France, 3 , Université Grenoble Alpes, CNRS, Institut Néel, Grenoble France, 4 , Center for Nanohealth, College of Engineering, University of Swansea, Swansea United Kingdom
Show AbstractControlling the growth and properties of ZnO nanorods (NRs) is critical for their efficient integration into nanoscale engineering devices. Owing to the non-centrosymmetric nature of the wurtzite structure, ZnO exhibits a spontaneous polarization along the c-axis. The resulting polarity is known to affect the growth and properties of ZnO single crystals and epitaxial films [1], but the polarity-induced effects are mostly unknown in NRs. While ZnO NRs grown by vapor phase techniques are Zn-polar, ZnO NRs grown by chemical bath deposition (CBD) can be of either O- or Zn-polarity [2], which opens the way for more deeply investigating these effects.
In this context, we thoroughly address the issue of the polarity-dependent growth and properties of ZnO NRs by CBD following the selective area growth approach [3]. To leave polarity as the only varying parameter, well-ordered O- and Zn-polar ZnO NR arrays with high structural uniformity are grown under identical conditions and during the same run of experiment on O- and Zn-polar ZnO single crystals patterned by electron beam lithography with the same pattern (i.e. fifteen domains combining a wide range of hole diameters and periods). The comparison of their typical dimensions unambiguously reveals that Zn-polar ZnO NRs have significantly higher growth rates than O-polar ZnO NRs for all the fifteen domains [3]. The distinct growth rates are explained in the framework of the surface reaction- / diffusive transport-limited elongation regime analysis, which yields a much larger surface reaction rate constant for Zn-polar ZnO NRs. The origin of the difference is discussed in the light of surface dangling bond configurations and interactions in aqueous solution at the top polar c-faces of the ZnO NRs. Additional electrical characterizations of the NRs using four-point probe resistivity measurements [4] are performed on single O- and Zn-polar ZnO NRs to investigate their electrical and contact properties. These findings show the relevance of considering polarity as an important quantity to control the growth and physical properties of ZnO NRs.
[1] J. Zúñiga-Pérez, V. Consonni et al., Applied Physics Reviews 3, 41303 (2016).
[2] V. Consonni et al., ACS Nano 8, 4761-4770 (2014).
[3] T. Cossuet et al., Langmuir 33, in press (2017) [10.1021/acs.langmuir.7b00935].
[4] A.M. Lord et al., Nano Letters 15, 4248-4253 (2015).
8:00 PM - NM03.04.32
Tunable Morphology and pH–Dependent Doping of ZnO Nanowires by Chemical Bath Deposition Using Aluminium Nitrate
Claire Verrier 1 2 , Estelle Appert 1 , Odette Chaix-Pluchery 1 , Laetitia Rapenne 1 , Quentin Rafhay 2 , Anne Kaminski-Cachopo 2 , Vincent Consonni 1
1 , Université Grenoble-Alpes, CNRS, Grenoble INP, LMGP, Grenoble France, 2 , Université Grenoble Alpes, CNRS, Grenoble INP, IMEP-LAHC, Grenoble France
Show AbstractOver the last decade, ZnO nanowires (NWs) have been used for a wide variety of sensing, electronic, and optoelectronic devices, including gas sensors, piezoelectric nanogenerators, UV photodetectors, and solar cells. For all these applications, their electrical properties, such as their conductivity and mobility, should be controlled as much as possible. ZnO is intrinsically n-type owing to the high density of zinc interstitials and hydrogen and can intentionally be n-doped, for example, by aluminium. The doping of ZnO NWs has however been mainly performed by vapor phase deposition techniques and is still a major issue by solution deposition techniques. In the present work, ZnO NWs are doped with aluminium by using the low-cost, low-temperature, and easily implemented chemical bath deposition (CBD) technique. Aluminum nitrate is added to the standard precursors (i.e. zinc nitrate and HMTA [1]) in deionized water and the [Al(NO3)3] / [Zn(NO3)2] ratio is varied from 0 to 10 %. It is shown by scanning and transmission electron microscopy (TEM) that this addition completely modifies the structural morphology of ZnO NWs [2]. The formation mechanisms are thoroughly investigated and supported by thermodynamic simulations yielding theoretical solubility plots and speciation diagrams. Their dependence on the pH of the solution through the addition of ammonia is further studied thoroughly [3]. The incorporation of aluminium is eventually investigated by energy dispersive x-ray spectroscopy using scanning TEM. Furthermore, temperature-dependent Raman spectroscopy measurements show the occurrence of additional modes, revealing the thermally activated aluminium-doping of ZnO NWs from an annealing temperature of 200°C [2].
[1] R. Parize et al., The Journal of Physical Chemistry C 120, 5242 (2016).
[2] C. Verrier et al., The Journal of Physical Chemistry C 121, 3573 (2017).
[3] C. Verrier et al., “pH-dependent structural and aluminium doping properties of ZnO nanowires by chemical bath deposition using ammonia”, submitted (2017).
8:00 PM - NM03.04.33
M13 Virus Aerogels as Scaffold for Functional Inorganic Materials
Sung Mi Jung 2 1 , Jifa Qi 3 , Dahyun Oh 3 , Angela Belcher 3 , Jing Kong 2
2 Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 1 Future Environmental Research Center, Korea Institute of Toxicology, Jinju Korea (the Republic of), 3 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThe filamentous M13 viruses are widely used as a bio-template to assemble many different functional structures. In this work, based on its shape anisotropy, reasonable aspect ratio (length to diameter of ≈130), and low density, freestanding, bulk 3D aerogels are assembled from M13 for the first time. These ultralight porous structures demonstrate excellent mechanical properties with elastic behavior up to 90% compression. Furthermore, as the genome of M13 virus can be rationally engineered so that proteins on its
capsid or ends can specifically bind to various inorganic materials, aerogels made from inorganic-complexed M13 structures with versatile functionalities are also developed. As examples for mono- and multi-component structures, M13-Ru and M13-CoFe2O4 are explored in this work. This method enables the production of a wide variety of freestanding inorganic material aerogels with
extensive opportunities for bio-scaffolds, energy storage, thermoelectrics, catalysis, hydrogen storage applications, etc., in the future.
8:00 PM - NM03.04.34
One-Step Synthesis of Large Diameter Complex Multipodal Nanotubes—Insights on Their Formation Mechanism and Light Scattering
Mostafa Omar 2 1 , Samar Fawzy 1 , Adel El-Shabasy 2 , Nageh Allam 1
2 Design and Production Department, Faculty of Engineering, Ain Shams University, Cairo Egypt, 1 , American University in Cairo, New Cairo Egypt
Show AbstractTuning surface morphology of different nanostructures is considered as a critical factor determining their behavior in different applications. Herein, large-diameter multipodal Ti-Nb-Zr-O nanotubes having 2 or more pods with a common top pore were successfully synthesized using 1-step potentiostatic anodization of Ti-Nb-Zr alloy in a formamide-based electrolyte containing NH4F. Tubes with diameters up to 507 nm and lengths up to 36 micrometer was grown. Large-diameter (comparable to visible light wavelength) multipodal nanotubes would act as a promising candidate in light harvesting applications enhancing materials’ performance and functionality, owing to their superior light scattering ability based on Mie’s scattering theory. The influence of time on the formed morphology was investigated. Multipodal nanostructure formation is owed to bending and fusion of discrete nanotubes. Multipodal nanotubes formation mechanism is discussed in detail and confirmed using SEM. Additionally, the preconditions required for their formation were analyzed using a theoretical model considering nanotubes as a bottom-fixed cantilever. The model findings suggest that bending only occurs when the net forces acting on the nanotubes overcomes the nanotubes stiffness as it passes a critical length.
8:00 PM - NM03.04.35
Indium Assisted Indium Gallium Arsenide Nanowires Growth on Silicon Substrate by Metal Organic Chemical Vapor Deposition
Sisir Chowdhury 1 , Pallab Banerji 1
1 , Indian Institute of Technology Kharagpur, Paschim Medinipur India
Show AbstractInGaAs is an important III-V ternary semiconductor which has wide application in electronics and optoelectronics application. Band gap of InGaAs lies in infrared region and can be tuned by varying the composition. So, it shows good response over a broad spectral range in Infrared region and is a potential candidate for the use of infrared detector. InGaAs has a large lattice mismatch with Silicon as well as there is a difference in thermal expansion coefficients. So, Epitaxial growth of InGaAs on silicon substrate is a challenge. Here, we demonstrate the growth of InGaAs nanowire on Silicon substrate by metal-organic chemical vapor deposition. In this work, trimethylindium (TMIn) is sent to reactor at 400 0C and decompostion of TMIn leads to the formation of indium droplets on Silicon substrate. Grown nanowires are characterized by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Composition of the grown also studied by Energy Dispersive X-Ray (EDS) Analysis. These experimental results confirm the growth of InGaAs nanowire on Silicon substrate without using any foreign catalysts.
From the microscopic investigation it is found that indium assisted VLS growth of InGaAs nanowires successfully carried out at 600 0C. The average diameter of the nanowires lies in the range 50-60nm. However, the nanowires are not aligned, it is also noticed that there is no reasonable tapering throughout the length of the nanowire. So, optimization is required the growth parameters to get properly aligned InGaAs nanowires.
8:00 PM - NM03.04.36
ZnO Nanorod Synthesis and Their Applications in Chemical Sensors
Ying Tu 1 , Joe Briscoe 1 , Steffi Krause 1
1 , Queen Mary University of London, London United Kingdom
Show AbstractMetal oxide semiconductor (MOS) based chemical or biological sensors have recently received a lot of attention, with the aim either to detect volatile organic compounds for the protection of environmental safety as well as human health. Zinc oxide is one of the most promising materials for electronic and optoelectronic devices because of its direct wide band gap (~ 3.3 eV) and large exciton binding energy (60 meV). Nanostructured ZnO with specific size and dimensions has been demonstrated to have excellent sensing properties originating from its large aspect ratio, high surface area and large amount of surface active sites as well as the recently-recognized effect of certain crystal facets. However, the majority of these types of sensor operate at elevated temperature in the range of 150 – 450°C with high power consumption, which greatly limits their application in harsh working conditions and for portable devices. Furthermore, the selectivity of the ZnO sensor can be a problem.
In order to reduce the working temperature, large aspect ratio ZnO nanorods were synthesized using an aqueous solution method at low temperature by optimising synthesis time, solution pH and concentration. Devices incorporating a ZnO/Au Schottky junction showed sensor responses of 24.0%, 3.29%, 2.90%, 3.57% and 2.76% of the current output to 40 ppm NH3, acetone,ethanol, CO and CO2, respectively at room temperature. This indicates high sensitivity as well as great selectivity to ammonia gas down to 10 ppm when working at room temperature with a power consumption of less than 0.2 mW. Long-term sensor tests demonstrated good electronic stability of the ZnO nanorods, which is an important factor for commercialisation.
In conclusion, ZnO nanorods with high-aspect ratio have been demonstrated to have a great potential to be utilized as sensing material in chemical sensor applications.
8:00 PM - NM03.04.37
Fabrication and Physicochemical Properties of Chiral Nano-Fibrillar Materials Including Rhenium Complexes with a Glutamide Molecular Assembling Tool
Yutaka Kuwahara 1 , Aiki Kamo 1 , Kyohei Yoshida 1 , Makoto Takafuji 1 2 , Hirotaka Ihara 1 2
1 , Kumamoto University, Kumamoto Japan, 2 , Kumamoto Institute for Photo-Electro Organics, Kumamoto Japan
Show AbstractAddition of functionalities by assembly of molecules in organic materials is an interesting technique toward the development of advanced materials for various applications. We have reported the development of functional molecules and materials including glutamide (G) derivatives, introduced from bis(alkylamide) glutamic acid, as self-assembling molecular tools. The strong self-assembling functionality of the G group mainly arises from three amide groups and can facilitate accumulation of functional moieties. The resultant assemblies formed one-dimensional chiral (1D) nanostructures such as nano-fibers, nanotubes, and nano-helical-ribbons and exhibited new and/or additional properties important for the fabrication of advanced materials. Recently, we have reported the synthesis and properties of some G derivatives linked by organic functional groups such as fullerene, anthracene, and pyrene groups.
In this study, we demonstrate the fabrication of 1D functional materials assembled by G derivatives modified with rhenium complexes as the functional moiety. Re complexes have been well known to exhibit fluorescence and catalytic ability.
The synthesized Re-complex-modified G (Re/G) derivatives formed organo-gels in polar (ethanol, N,N-dimethylformamide, and acetonitrile) and non-polar (diethyl ether and toluene) solvents at higher concentrations after heat treatment at 60 °C for 30 min and subsequent cooling at 10 °C for 10 min. Transmission electron microscopy images form the Re/G derivative solutions showed aggregates of Re/G derivatives as nano-sized fibrils in various solvents. The Cotton effect for Re moieties and amide bonds of G groups was observed in solutions of Re/G derivatives through circular dichroism (CD) spectroscopy. The optical properties obtained by UV-visible and CD spectroscopies indicated that the Re/G derivatives aggregated with a fibrillar structure with chirality in various solutions. In this paper, the effect of the assembling on the physicochemical properties will be discussed for the 1D materials including Re complexes with and without G groups.
8:00 PM - NM03.04.38
Synthesis of Boron Nitride Nanotubes on Silicon Carbide Fibers and Investigation of the Mechanical Properties
Deniz Koken 1 , Aysemin Top 2 , Hulya Cebeci 2 , Beyza Bozali 3 , Elif Ozden Yenigun 3 , Fevzi Cebeci 1
1 Materials Science and Nanoengineering, Sabanci University, Istanbul Turkey, 2 Astronautical Engineering, Istanbul Technical University, Istanbul Turkey, 3 Textile Engineering, Istanbul Technical University, Istanbul Turkey
Show AbstractSilicon carbide (SiC) fibers attracted high amount of interest in ceramic matrix composite (CMC) research due to their high mechanical strength in elevated temperatures and high thermal stability with good corrosion resistance. SiC fiber reinforced silicon carbide matrix composites (SiCf/SiCm) have been investigated as structural materials in elevated temperatures in aerospace applications especially in gas tribune engines. For these composites one of the most important parameters are interphase interactions between the reinforcement fibers and the matrix material. Good interphase interactions result in better interlaminar shear strength, delamination resistance, fatigue and corrosion resistance in addition to increased load transfer between fiber and matrix. Carbon based coatings, especially carbon nanotubes (CNT), were proposed to improve the interphase interactions between the fiber and matrix however, insufficient thermal stability of the carbon materials hinders the thermal properties of the SiCf/SiCm composites. Boron nitride nanotubes (BNNT) exhibit similar extraordinary mechanical and electrical properties like CNTs in addition to higher thermal stability than CNTs. Incorporation of thermal resistant BNNTs onto SiC fibers could solve the interphase interaction problems between fiber and the matrix material since it increases the specific surface area of the fibers and ensure better interphase interactions between fiber and matrix that could result in higher mechanical strength. Furthermore, intrinsic high thermal stability and the high corrosion resistance of the BNNTs could also enhance the thermal and corrosion resistance properties of the SiC fibers as well as SiCf/SiCm composites.
In this work, BNNTs were successfully synthesized onto SiC fibers in fuzzy fiber architecture by decoration surface of the fibers with iron and magnesium followed by chemical vapor deposition method in combination with growth vapor trapping to create fuzzy fiber nanotube coating on all surfaces of SiC fibers. Elemental boron was used in combination with MgO and FeO catalysts as boron source and ammonia was used for the nitrogen source for the BNNT synthesis. Catalyzing SiC surfaces with iron and magnesium provided nucleation sites for the BNNTs and ensured efficient synthesis of BNNTS on the SiC fiber surface. The impact of BNNT synthesis on SiC fiber mechanical strength was also investigated. It is found that fuzzy fiber BNNT synthesis on the fibers improved the mechanical strength of the SiC fibers.
8:00 PM - NM03.04.39
Fabrication of Nano-Micro Composite Structure Using Nanowires and Surface Treatments on the Structure
Yeonho Jeong 1 , Seunghang Shin 1 , Hyunmin Choi 1 , Yoon Gyo Jung 1 , Young Tae Cho 1
1 , Changwon National University, Changwon Korea (the Republic of)
Show AbstractNanoscale structures such as nanoparticles, nanowires, nanopillars and nanotubes, have attracted attention due to their hidden characteristics in minute regions in various fields such as electricity, electronics, bio surfaces and optics. Anodic Aluminum oxide (AAO) is widely used in the fabrication of nano strctures, which has many nano-sized pores and well organized nano patterns. Nanowires with very high aspect ratio could be fabricated by using AAO filter as a template for replication.
In this study, we investigated to fabricate a nono-micro composite structure using nanowires with two PUA resins (viscosity 257.4 cPs and 7.2 cPs) replicated from AAO filter. First, Polymer resin was coated between PET film and AAO filter. Next, AAO filter was pressed by roller to fill the polymer resin into AAO filter and it cured by UV. Finally, it was etched by NaOH for 10 minutes for removing AAO filter. It is because AAO filter is too stiff to separate from PET film physically. In this time, nanowires are aggregated by surface tension, and this phenomenon makes new patterns with micro-size. we called this fabricated shapes to nano-micro composite pattern because it has nano sized wires and micro sized structures at the same time.
And then the effects of various surface treatments on the structure with the PUA resin of viscosity 257.4 cPs were investigated like surface behavior and surface wettability. UV-Ozone treatment, octadecyltrichlorosilan (OTS) coating and double treatment were proceeded on the structure. The structure behavior was changed after UV-Ozone treatment. And the wettability was altered by handing surface treatments. Consequently, we showed that nano micro hybrid structure could be formed in the middle of nanowire replication, then the shape and attributes of surface could be controlled by surface treatment.
8:00 PM - NM03.04.40
Nanoscale Spirals by Directed Self-Assembly
Hongkyoon Choi 1 2 , Jae-Byum Chang 2 3 , Adam Hannon 2 4 , Joel Yang 2 5 , Karl Berggren 2 , Alfredo Alexander-Katz 2 , C. A. Ross 2
1 , Kongju National University, Daejeon Korea (the Republic of), 2 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 , Sungkyunkwan University , Suwon Korea (the Republic of), 4 , National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 5 , Singapore University of Technology and Design, Singapore Singapore
Show AbstractThere has been extensive work on the templated self-assembly of diblock copolymer (BCP) thin films, forming both periodic and aperiodic arrays of microdomains which have applications in diverse fields including nanofabrication, filtration, or photonics. The microphase separation of BCPs can be templated using topographical or chemical patterns on a substrate which register the microdomains at specific locations, and which can generate a range of microdomain geometries including cylinders or vesicles, stacked tori or disks, helices. Chiral nanostructures are especially attractive due to their interesting optical properties such as circular dichroism or optical rotatory dispersion. However, there has been little work on the control of the chirality of helical structures or spirals using BCP self-assembly.
In this study, we demonstrate that confinement of a cylindrical-morphology BCP in a shallow circular pit can produce either concentric rings or a spiral. A spiral is promoted by the presence of a notch-shaped feature within the template which controls the spiral chirality. The length of the spiral increases with the diameter of the template. Design of the notch geometry enabled double spirals to be formed. A notch of width ≈ L0 promotes spirals even for commensurate pit sizes indicating the critical importance of the inner shape of the template. For smaller notches, spirals formed for incommensurate template diameters and rings for commensurate template diameters. Analogous to using a notch to initiate a spiral in a circular pit, our approach could be extended to guide the chirality of 3D helical spirals formed in cylindrical confinements with a helical ramp template.
2D and 3D chiral nanostructures have a range of potential applications in the sensing of molecular chirality or as chiral metameterials. Chiral nanostructures have so far only been fabricated by top-down lithography or self-assembly of nanoparticles interacted with chiral molecules, and this study provides an effective alternative route to fabricate chiral nanostructures via directed self-assembly.
8:00 PM - NM03.04.41
Branched Aramid Nanofibers
Jian Zhu 1 , Nicholas Kotov 2
1 School of Materials Science and Engineering, Nankai University, Tianjin China, 2 Department of Chemical Engineering, University of Michigan–Ann Arbor, Ann Arbor, Michigan, United States
Show AbstractInterconnectivity of molecular or nanoscale components in three-dimensional networks (3DNs) is essential for stress transfer in hydrogels, aerogels, and composites as well as for other materials and properties. Entanglement of nanoscale components in the network, such as ceramic nanowires, carbon nanotubes, and polymer/cellulose nanofibrils, relies on weak short-range intermolecular interactions. The intrinsic stiffness and rod-like geometry of nanoscale components reduces the cohesive energy of the physical crosslinks weakening the 3DN materials. Nature realizes networked gels differently using self-assembling components with extensive branching. Here, we describe branched aramid nanofibers (BANFs) that readily produce 3DNs with high efficiency stress transfer. Individual BANFs have a diameter of 4-5 nm, are flexible, and bear 3-9 branches, the number of which can be controlled by the strength of the base in the hydrolysis of parent KevlarTM nanofibers. The extensive connectivity of the BANFs allows them to form hydro- and aerogel monoliths with an order of magnitude less solid content than rod-like nanocomponents. Branching of the nanofibers also leads to improved gel mechanics, exemplified by higher critical shear strength, which allows the preparation of continuous microscale luminescent fibers. BANF gels can be infiltrated with polymers to obtain a large family of 3DN nanocomposites with high toughness and strength.
Symposium Organizers
Juan Beltran-Huarac, Harvard T. H. Chan School of Public School
Wojciech Jadwisienczak, Ohio University
Alessandro Ponti, National Research Council
Bo Zou, Jilin University
Symposium Support
Ohio University—Nanoscale and Quantum Phenomena Institute (NQPI)
NM03.05: Energy Storage and Photocatalysis
Session Chairs
Juan Beltran-Huarac
Il-Doo Kim
Tuesday AM, November 28, 2017
Hynes, Level 3, Room 310
8:30 AM - *NM03.05.01
Highly Aligned Oxide Nanotube Arrays—1D Geometry and Applications
Patrik Schmuki 1 , Ning Liu 1 , Marco Altomare 1
1 , University of Erlangen-Nuremberg, Erlangen Germany
Show AbstractTiO2 nanomaterials have over the last 30 years attracted tremendous scientific and technological interest. Main research direction using TiO2 in functional applications are s the use in photocatalysis e.g. for the direct splitting of water into H2 and O2 to generate the potential fuel of the future, hydrogen; the use in Grätzel type solar cells and in biomedical applications. Over the past decades various 1D and highly defined TiO2 morphologies were explored for the replacement of nanoparticle networks and were found in many cases far superior to nanoparticles or their assemblies. Nanotubes or wires can be grown by hydrothermal or template methods, or even more elegantly, by self-organizing anodic oxidation. The latter is not limited to TiO2 but a full range of other functional oxide structures on various metals and alloys can be formed. These advanced and doped morphologies can be grown on conductive substrates as ordered layers and therefore can be directly used as functional electrodes (e.g. photo-anodes). The presentation will focus on these highly ordered nanotube arrays of TiO2 and discuss most recent progress in synthesis, modification and applications.
9:00 AM - *NM03.05.02
Construction of TiO2 Nanobelt Heterostructures—A Powerful Tool for Building High-Performance Photocatalysts
Hong Liu 1 2 , Zhaohui Yan 1 , Wenfeng Wang 1
1 Institute for Advanced Interdisciplinary Research (IAIR), University of Jinan, Jinan, Shandong, China, 2 State Key Laboratory of Crystal Materials, Shandong University, Jinan, Shandong, China
Show AbstractSemiconductor photocatalysis is a promising approach to combat both environmental pollution and the global energy shortage. Advanced TiO2-based photocatalysts with novel photoelectronic properties are benchmark materials that have been pursued for their high solar energy conversion efficiency. Among the different morphological TiO2 nanostructures, TiO2 nanobelts (NBs) attract more attention due to their unique physical properties and ideal 1D ribbon-like morphology that is favorable for constructing heterostructures by assembling second-phase nanoparticles on the surface of the NBs. A large number of studies have proven that well-designed TiO2 NB heterostructures can not only broaden the photocatalytically active light band of TiO2 but also enhance the light absorption performance and the photo-induced carrier separation ability. The TiO2 NB heterostructure has become a versatile and powerful tool for building high-performance TiO2-based photocatalysts, which has stimulated intense research activities focused on the growth, properties, and applications of the 1D TiO2 NB and its heterostructures.
In this talk, we will summary all the above aspects, including the underlying principles and key functional features of TiO2 NBs and TiO2 NB heterostructures in a comprehensive way and also discuss the prospects of this type of novel hybrid photocatalyst. Several new NIR and full solar spectrum light photocatalysts will be introduced. In addition, the devices for full solar light photocatalysis base on TiO2 nanobelt heterostructures will be reviewed.
References
1. Xiaofei Zhang, Yana Wang, Baishan Liu, Yuanhua Sang, Hong Liu*, Heterostructures construction on TiO2 nanobelts: a powerful tool for building high-performance photocatalysts, Applied Catalysis B-environmental, 2017, 202, 620-641
2. Jian Tian, Yuanhua Sang , Guangwei Yu , Huaidong Jiang , Xiaoning Mu , and Hong Liu*, A Bi2WO6 Based Hybrid Photocatalyst with Broad Spectrum Photocatalytic Properties under UV, Visible, and Near Infrared Irradiation， Advance Materials, 2013, 25, 5075–5080
3. Yuanhua Sang, Zhenhuan Zhao, Mingwen Zhao, Pin Hao, Yanhua Leng, Hong Liu*, From UV to Near-Infrared, WS2 Nanosheet: A Novel Photocatalyst for Full Solar Light Spectrum Photodegradation. Advance Materials, 2015, 27, 363–369.
4. Jian Tian, Zhenhuan Zhao, Anil Kumar, Robert I. Boughton and Hong Liu*, Recent progress in design, synthesis, and applications of one-dimensional TiO2nanostructured surface heterostructures: a review, Chem. Soc. Rev., 2014,43, 6920-6937
5. Zhenhuan Zhao, Jian Tian, Yuanhua Sang, Andreu Cabot and Hong Liu*. Structure, Synthesis, and Applications of TiO2 Nanobelts, Advanced Materials, 2015, 27 (16), 2557-2582
6. Haidong Li, Yuanhua Sang, Sujie Chang, Xin Huang, Yan Zhang, Rusen Yang, Huaidong Jiang, Hong Liu* and Zhong Lin Wang. Enhanced Ferroelectric Nanocrystal Based Hybrid Photocatalysis by Ultrasonic-Wave-Generated Piezophototronic Effect, Nano Letters, 2015, 15 (4), 2372–2379
9:30 AM - NM03.05.03
Tunnel Manganese Oxide Nanowires for High-Performance Electrochemical Energy Storage and Water Desalination
Bryan Byles 1 , Ekaterina Pomerantseva 1
1 , Drexel University, Philadelphia, Pennsylvania, United States
Show AbstractNanowire morphology combined with one-dimensional (1D) diffusion pathways is advantageous for the enhanced electrochemical performance of materials in a wide range of applications. In this work, we report the superior performance of tunnel manganese oxide (TuMO) nanowires with 1D crystallographic channels in hybrid capacitive deionization (HCDI) of water and energy storage systems such as Li-ion (LIB) and Na-ion batteries (SIB). TuMOs are a family of low cost, sustainable, and highly electrochemically active materials. Using hydrothermal treatment, these materials are synthesized with nanowire morphologies (diameters 10-100 nm, lengths up to several microns). The crystal structures of TuMOs are built from MnO6 octahedra arranged around stabilizing cations to form tunnels of various size/shape. Tuning synthesis parameters allows for atomic-scale control of the size of structural tunnels used for ion diffusion. Thus, TuMOs provide a unique platform to investigate the relationship between the size/ionic content of 1D diffusion channels and the size of diffusing ions in electrochemical processes.
We study the performance of four TuMOs with distinctly different tunnel structures in both aqueous and non-aqueous electrochemical systems. In non-aqueous intercalation-based batteries, the four TuMOs demonstrated initial capacities as high as 186 mAh g-1 (in LIBs) and 128 mAh g-1 (in SIBs). We find that Na-stabilized tunnel structures exhibit superior capacity retention and rate performance in SIBs compared to structures stabilized by other cations, highlighting the importance of ionic content in 1D tunnels. We found that in both LIBs and SIBs, TuMOs with larger structural tunnels show higher capacities, confirming that greater crystallographic volume available for ions insertion results in larger stored charge. When applied for the first time as electrode materials for removal of ions from aqueous solution in an HCDI system, TuMOs exhibited high performance with ion removal capacities as large as 27.8, 44.4, and 43.1 mg g-1 in NaCl, KCl, and MgCl2 solutions, respectively, and high ion removal rates. Notably, in HCDI application TuMOs demonstrated superior stability compared to non-aqueous systems, retaining their ion removal capacity and crystal structure with repeated ion removal/release. Further, it was found that TuMOs with larger structural tunnels showed superior removal of cations with larger hydrated radii, indicating that in order to achieve maximum desalination efficiency, the size of the structural tunnels must be matched to the size of the ions being removed from solution. In summary, we show that by understanding the relationship between ion size and host crystal structure, the performance of materials with 1D diffusion pathways in applications based on ions insertion/deinsertion can be maximized. Utilizing inexpensive and sustainable materials, this work addresses the critical and interconnected issues of water and energy facing our society.
9:45 AM - NM03.05.04
One-Dimensional Vanadium Oxide Nanowires—Experimental Synthesis and Investigations of the Electrochemical Behaviors for Energy Storage
Tianyu Liu 1 , Yu Song 1 2 , Xiaoxia Liu 2 , Yat Li 1
1 , University of California, Santa Cruz, Santa Cruz, California, United States, 2 Department of Chemistry, Northeastern University, Shenyang China
Show AbstractVanadium oxide is one of the earth-abundant functional materials for applications associated with energy storage. The multivalence of vanadium, such as V5+, V4+ and V3+ can be readily inter-converted via a number of redox reactions. Such redox reactions render vanadium oxide large capacity for electrical energy storage.
In this presentation, a facile electrochemical strategy on the synthesis of the 1D vanadium nanowires with mixed valence state of vanadium (that is, V5+ and V4+) will be presented. In addition, investigations of their extraordinary electrochemical behavior in the context of supercapacitors will be thoroughly discussed. Specifically, previous studies demonstrate that vanadium oxide suffers from severe capacity decay during long-term charge-discharge cycles in aqueous electrolytes, which has hindered their practicability of electrochemical energy storage. On the contrary, the aforementioned 1D vanadium oxide nanowires deposited on an exfoliated and functionalized carbon cloth substrate exhibit record-high stability in the aqueous electrolyte with no capacity loss in 100000 charge-discharge cycles without any protective coating. Various physical and electrochemical studies suggest that the outstanding stability can be ascribed to two major factors: on one hand, tuning the V4+/V5+ ratio via electron injection can efficiently suppress the dissolution of vanadium oxide in aqueous electrolytes; On the other hand, the oxygen-functionalized carbon shell of the exfoliated carbon cloth can bind strongly with vanadium oxide nanowires through formation of C-O-V bonds, which retains the electrode integrity and suppresses the structural pulverization of the oxide during the long-time charge-discharge cycling test. At last, the mechanism of the capacity increment observed in the initial 2000 charge-discharge cycles will be elucidated.
10:30 AM - NM03.05.05
Carbon Nanofiber Aerogel from Bacterial Cellulose for Kilohertz AC-Supercapacitors
Nazifah Islam 1 , Md Nadim Ferdous Hoque 1 , Yujiao Zuo 2 , Shu Wang 2 , Zhaoyang Fan 1
1 Department of Electrical and Computer Engineering and Nano Tech Center, Texas Tech University, Lubbock, Texas, United States, 2 Department of Nutritional Sciences, Texas Tech University, Lubbock, Texas, United States
Show AbstractCompact-size kilohertz (kHz) AC-supercapacitors, in contrast to the conventional supercapacitors that only work under DC current, are being pursued for ripple current filtering and pulsed energy storage. However, their development is limited by a small areal capacitance density due to very thin electrode used for meeting frequency requirement. In our work, crosslinked carbon nanofiber aerogel (CCNFA) was investigated as freestanding electrode for kHz AC-supercapacitors with areal capacitance density increased by one order of magnitude. The CCNFA was obtained in a rapid plasma carbonization process of bacterial cellulose. The fabrication route adopted here is simple and straightforward, and the produced CCNFA electrode was found to be very suitable for high-frequency AC-supercapacitors. In particular, kHz supercapacitors with 120 Hz areal capacitance density as large as 4.5 mF cm-2 in an aqueous electrolyte was confirmed. The operating voltage range of CCNFA based AC-supercapacitors was further expanded to 3 V by utilizing an organic electrolyte. The morphology and material properties of bacterial cellulose aerogel and CCNFA will be reported. The applications of prototyping kHz AC-supercapacitors for ripple current filtering in AC/DC conversion and rapid pulse energy storage for vibrational energy harvesting will also be demonstrated.
NM03.06: Electronics and Photonics I
Session Chairs
Wojciech Jadwisienczak
Jongwook Kim
Tuesday PM, November 28, 2017
Hynes, Level 3, Room 310
10:45 AM - *NM03.06.01
Nanowires as Means to Realize High-Performance III-V and III-Nitride Materials
Lars Samuelson 1 2 3
1 , Lund University, Lund Sweden, 2 , Glo AB, Lund Sweden, 3 , Sol Voltaics AB, Lund Sweden
Show AbstractCompound semiconductors like III-Vs and III-Nitride materials form the basis for a wide range of applications in fields like electronics, photo-voltaics and light-emitting diodes. Replacing thin film or bulk material with nanowire (NW) structures has created much interest. In many cases, such NWs form the active structures in the devices while in other cases NWs merely function as enablers for the realization of high-quality materials.
In this talk I will first give an introduction to the development of the field, starting with the early studies of VLS (vapor-liquid-solid) and VSS (vapor-solid-solid) growth and investigations of mechanism by which NWs nucleate and grow. A key aspect at this time was the very novel opportunity to create hetero-structures between materials with very different lattice constants, including the opportunity to nucleate different NW materials on a silicon platform.
Among systems I will present are all-around wrap-gate transistors as well as tunnel field-effect transistors, where NW transistor devices based on abrupt axial hetero-structures incorporating arsenide-, phosphide- and antimonide-segments are key. As we approach single digit nm nodes for integrated circuit technology, such NW-based transistors are expected to have important roles to play, being scalable and in terms of their power consumption.
Applications towards photo-voltaics applications typically involve replacing planar solar-cell structures by arrays of vertically standing NWs, with each of these NWs constituting a p-i-n diode with modeling-based design of pitch and diameters. The very sensitive cost issue for terrestrial applications has been seen as preventing the use of III-V materials, in spite of their advantageous properties. However, with the recent development of the Aerotaxy growth method, very much less expensive fabrication of device quality NW p-i-n diodes was realized.
A very strong effort involves the use of NWs to initiate the selective area nucleation of GaN NWs, enabling the formation of ideal vertical GaN NWs, later to be used as templates for radial growth of the pn-junctions and the radial active quantum well layers. LEDs fabricated in this way show excellent performance as part of micro-LED technology realizing high-performance RGB-pixels for direct-view displays.
A recent focus of our research has involved the use of the ideal nucleation-seeds of GaN formed in the opening of the growth mask, enabling the formation of high-quality nano-pyramids of InGaN pyramids with high indium-compositions. We explore the possible use of such pyramids, via transformation of the pyramid shape into c-oriented dislocation-free and realaxed InGaN platelets, as templates to form green-, yellow- and red-emitting LEDs vertically on top of these platelets.
11:15 AM - NM03.06.02
High Intensity Light-Nanowire Interaction Phenomena—From Tunnel Excitation to Hard X-Ray Generation
Robert Roeder 3 , Richard Hollinger 1 2 , Zhanna Samsonova 1 2 , Christian Spielmann 1 2 , Carsten Ronning 3 , Daniil Kartashov 1
3 Institute of Solid State Physics, University of Jena, Jena Germany, 1 Institute of Optics and Quantum Electronics, Abbe Center of Photonics, University of Jena, Jena Germany, 2 , Helmholtz Institute Jena, Jena Germany
Show AbstractIndividual semiconductor nanowires (NW) and NW arrays are well-investigated material systems upon light irradiation with low to moderate intensities below GW/cm2. In this excitation regime, NWs exhibit extraordinary capabilities as photodetectors [Tchernycheva et al., Nano Lett. 14, 3515 (2014)], waveguides, continuous wave nanolasers [Röder et al., Nano Lett. 13, 3602 (2013)], ultrafast modulators [Röder et al., Nano Lett. 15, 4637 (2015)] and solar cells [Wallentin et al., Science 339, 1057 (2013)], which are caused by their near-perfect material quality and NW morphology. However, irradiating single NWs and NW arrays with very intense (1012 – 1019 W/cm2), ultrashort (below 100 fs) laser pulses with sub-band gap photon energies offers novel promising aspects of material and nanostructure research as well as a lot of applications, which have not been considered yet. Here, we will cover two non-conventional light-matter interaction effects: (i) The transition from conventional multiphoton (three-photon absorption) pumping in individual ZnO nanowire lasers and NW laser arrays to an efficient tunnel excitation process using MIR laser pulses [Keldysh, Soviet Physics JETP 20, 1307 (1965)]. Although the pump photon energy of ~ 0.31 eV exhibits only less than one tenth of the band gap energy of ~ 3.4 eV of the active medium, the tunnel excitation mechanism provides a sufficiently high electron-hole pair generation rate in order to establish laser oscillations even in individual nanowires at room temperature. (ii) If the peak intensity of the exciting laser pulses is increased to values up to ~ 1019 W/cm2, the efficient absorption in ZnO NW arrays supports the generation of a hot and dense plasma enabling the generation of highly charged states of Zn, up to He-like Zn. The plasma obtained from the NW arrays indeed generates X-ray fluxes that are several times stronger than in bulk samples. Furthermore, highly pumped NW arrays allow hard X-ray generation (gamma-ray energy regime) above of 100 keV with efficiencies more than one order of magnitude higher than in bulk samples. Thus, using nanowire targets opens up a new exciting field in high intensity light-matter interactions.
11:30 AM - NM03.06.03
Optical and Structural Properties of Zinc Germanate Nanowires
Pedro Hidalgo Alcalde 1 , Bianchi Mendez 1 , Javier Piqueras 1
1 , Univ of Complutense, Madrid Spain
Show AbstractSemiconducting oxide nanowires are essential functional nanomaterials with a view to building novel optoelectronic and energy devices. One of the most relevant family of materials in this field is the Transparent Conductive Oxide (TCO), which are required in the electrical contacts. Most of the TCO research involves oxide compounds, such as ZnO, SnO2 or ITO, but recently a novel TCO family derived from germanium oxide alloys has been proposed due to their excellent optical and electrical properties. Examples of these materials are SrGeO3, In2GeO7 or Zn2GeO4 [1].
In this work, we explore the synthesis of nanostructures of zinc germanate (Zn2GeO4) by a rather simple evaporation method. By using a mixture of ZnO, Ge and graphite, we have produced Zn2GeO4 nano- and microstructures after a thermal treatment at 800 °C for 8-10 hours under an argon flow [2]. The morphology, chemical structure and optical properties have been characterized by means of electron microscopy and optical confocal microscopy techniques. In addition, we have investigated the influence of Mg and Sn doping in the shape and optical properties of the nanostructures. The first consequence is an increase in the yield production of nanowires for both dopants, as well as a noticeable reduction in the nanowires diameter in the case of Sn doping. Besides, impurity segregation leads to the formation of more complex nanostructures, such as nanowires with a modulated diameter or heterostructures of SnO2/ZnGeO4.
[1] H. Mizoguchi, T. Kamiya, S. Matsuishi, and H. Hosono, Nature Comm. 2:470 (2011)
[2] P. Hidalgo, A. López, B. Méndez and J. Piqueras, Acta Materialia, 104, 84-90 (2016).
11:45 AM - NM03.06.04
Radial Modulation-Doped Nanowire Channel for Millivolt Switch
Katsuhiro Tomioka 1 , Kohei Chiba 1 , Akinobu Yoshida 1
1 Graduate School of Information Science and Technology and Research Center for Integrated Quantum Electronics (RCIQE), Hokkaido University, Hokkaido Japan
Show AbstractTunnel field-effect transistors (TFETs) involving non thermionic emission have been attracting much attention as building blocks for future low-power integrated circuits (ICs) and complementary metal-oxide-semiconductor (CMOS) technologies. There are, however, several challenges in modern TFETs achieving outermost performances such as steep subthreshold slope (SS) with higher transconductance. Here, we fabricated vertical TFET structure using InGaAs-related core-multishell nanowires with radial modulation-doping on Si and demonstrated steep SS and higher transconductance efficiency for low power analog ICs.
In experiment, the vertical InGaAs nanowire were grown at 670°C by using specific sequence for aligning vertical InGaAs nanowires on Si(111) [1]. As for radial modulation-doped layers, InP/InAlAs/δ-dope InAlAs/InGaAs multishell layer was formed by using lateral-over growth mode. The delta-doped layer was formed with mono-silane (SiH4) gas. After the growth of the nanowire-channel, vertical TFET structure was fabricated by etch-back procedures [1].
The grown InGaAs nanowires with the radial modulation-doped layers were characterized by HAADF-STEM and EDX elemental mappings. The EDX elemental mapping showed that the diameter of the core InGaAs nanowire was 17 nm and the radial-modulation doped layer were formed around the sidewalls of the nanowire-channel. In this device, surrounding-gate structure modulates both tunneling transport across the InGaAs nanowire-channel/Si junction and generation of electron-gas inside the InGaAs nanowire-channel. Therefore, high tunneling probability is expected because the sheet carrier in the core InGaAs nanowire-channel is increased under the gate bias. The device demonstrated steep SS (~ 36 mV/dec.) at room temperature. The DIBL was 16 mV/V. The drive current offered by the radial modulation doped layer was 1000-folded enhancement, to an estimated 3 mA/mm as compared to that of bare InGaAs/Si junction TFETs. Furthermore, the transconductance efficiency of the device, which is important parameter indicating a potential of electrical switch low power analog ICs [2], was above 1000 V-1 at supply voltage of 0.25 V. This is much higher efficiency than that of conventional FETs (theoretically ~ 38.5 V-1). This indicates that the demonstrated TFETs are promising candidate for a millivolt switch in future ICs.
References:
[1] K. Tomioka et al., Nature 488 (2012) 189.
[2] L. Barboni et al., J. Elec. Dev. Soc. 3 (2015) 208.
NM03.07: Electronics and Photonics II
Session Chairs
Alessandro Ponti
Lars Samuelson
Tuesday PM, November 28, 2017
Hynes, Level 3, Room 310
1:30 PM - NM03.07.01
Luminescent Rare-Earth Nanorods as a Three-Dimensional Orientation Marker
Jongwook Kim 1 , Jacques Peretti 1 , Lucio Martinelli 1 , Sebastien Michelin 1 , Michiel Hilbers 2 , Charles N. Baroud 1 , Albert M. Brouwer 2 , Thierry Gacoin 1
1 , Ecole Polytechnique, Palaiseau France, 2 , University of Amsterdam, Amsterdam Netherlands
Show AbstractLuminescent particles are widely used for labelling, and tracking of microscopic objects. Anisotropic emitters such as semiconductor nanowires or quantum rods exhibit polarised luminescence providing an additional sensitivity to the orientation. The polarisation is often dominated by the size and shape anisotropy of the emitter particle in which the electric field is confined. Rare-earth phosphors, however, exhibit a distinguished nature of polarised luminescence originating from the anisotropic symmetry of the emitter ion’s chemical environment. When rotating the host crystal, the emission spectrum of the rare-earth dopants manifests variation of its line shape (not simply the overall intensity) due to the distinct angular orientations of the transition dipoles. This phenomenon is independent of the particle size, morphology, and also of the excitation condition, which is a crucial advantage as a stable orientation marker. We synthesized europium-doped lanthanum phosphate (LaPO4:Eu) nanorods performing an efficient and dramatically polarised photoluminescence. The three main polarization components (σ, π, and α spectra) were measured from a single nanorod, nanorods-oriented film, and eventually from a liquid crystalline self-assembly of the nanorods. Using this set of spectra as a reference, we present how one can determine the unknown three-dimensional orientation (polar and azimuthal angles) of a nanorod[1]. This method, in principle, allows to precisely monitor the rotational motion of nanorod-tagged objects such as micro-biosystems (cells, genes, enzymes, etc.) of which the study of complex dynamic motion is of utmost importance. Furthermore, based on the fact that flowing nanorods tend to orient along the flow shear, we use the rod-orientation analysis to spectroscopically measure the local shear rate in a flowing liquid. The potential of this approach is demonstrated through a tomographic imaging of the shear rate distribution in a microfluidic channel[1].
[1] J Kim*, L Martinelli, J-P Boilot, E Fradet, S Michelin, C Baroud, M Hilbers, A M Brouwer, J Peretti, T. Gacoin* “Monitoring the orientation of rare-earth doped nanorods for flow shear tomography” Nature Nanotechnology (2017) DOI: 10.1038/nnano.2017.111
1:45 PM - NM03.07.02
Electronic and Morphological Superlattices in Silicon Nanowires through Non-Equilibrium Doping
David Hill 1 , Taylor Teitsworth 1 , Seokhyoung Kim 1 , Joseph Christesen 1 , James Cahoon 1
1 , University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
Show AbstractAlthough silicon (Si) nanowires (NWs) grown by a vapor-liquid-solid (VLS) mechanism have been demonstrated for a range of photonic, electronic, and solar-energy applications, continued progress with these NW-based technologies requires increasingly precise compositional and morphological control of the growth process. However, VLS growth typically encounters problems such as non-selective deposition on sidewalls, inadvertent kinking, unintentional or inhomogeneous doping, and catalyst-induced compositional gradients. Here, we overcome several of these difficulties and report the synthesis of uniform, linear, and degenerately-doped Si NW superlattices with abrupt transitions between p-type, intrinsic, and n-type segments. The synthesis of these structures is enabled by in situ chlorination of the NW surface with hydrochloric acid (HCl) at temperatures ranging from 500-700 °C, yielding uniform NWs with minimal non-selective growth. Surprisingly, we find the boron (B) doping level in p-type segments to be at least one order of magnitude above the solid solubility limit, an effect that we attribute to a high incorporation of B in the liquid catalyst and kinetic trapping of B during crystallization at the liquid-solid interface to yield a highly non-equilibrium concentration. For growth at 510 °C, four-point-probe measurements yield active doping levels of at least 4.5 x 1019 cm-3, which is comparable to the phosphorus (P) doping level of n-type segments. Because the B and P dopants are in sufficiently high concentrations for the Si to be degenerately doped, both segments inhibit the etching of Si in aqueous potassium hydroxide (KOH) solution. Moreover, we find that the dopant transitions are abrupt, facilitating nanoscale morphological control in both B- and P-doped segments through selective KOH etching of the NW with a spatial resolution of ~10 nm. . We synthesize morphologically controlled p-i-n structures and demonstrate the ability to tune the optoelectronic properties of these junctions through structure. These results enable the growth of complex, degenerately-doped p-n junction nanostructures that can be explored for a variety of advanced applications, such as Esaki diodes, multi-junction solar cells, and tunneling field-effect transistors.
2:00 PM - NM03.07.03
ElectronicsFunctionalized DNA Origami Nanostructures for Molecular Electronics
Turkan Bayrak 1 , Bezu Teschome 1 , Jinging Ye 2 , Seham Helmi 3 , Tommy Schoenherr 1 , Ralf Seidel 2 , Artur Erbe 1
1 , Helmholtz-Zentrum Dresden-Rossendorf, Dresden Germany, 2 , Universität Leipzig, Leipzig Germany, 3 , University of Oxford, Oxford United Kingdom
Show AbstractThe DNA origami method1 provides a programmable bottom up approach for creating nanostructures of any desired shape, which can be used as scaffolds for nanoelectronics2 and nanophotonics3 device fabrications. This technique enables the precise positioning of metallic and semiconducting5 nanoparticles along the DNA nanostructures. In this study, two nanostructures i.e. DNA origami nanotube and DNA origami molds are used for the fabrication of nanoelectronic devices. To this end, the DNA origami nanotubes are modified to assemble 14 gold nanoparticles (AuNPs) along them. Then electroless gold deposition is used to selectively grow the AuNPs and create eventually continues nanowires. Similarly, AuNPs are also grown within the DNA origami molds.6 In order to investigate the transport properties of the so-fabricated two nanostructures, a method is developed using electron beam lithography2 and the 1D DNA origami based metallic wires were electrically characterized from room temperature to 4K. Additionally, the assembly of heterogeneous nanostructures, i.e. AuNPs and semiconductor quantum dots (QDs), on a single DNA origami nanotube is demonstrated and further metallized, thus representing a first step toward the future fabrication of DNA origami-templated quantum dot transistors.
1Rothemund, Paul WK. "Folding DNA to create nanoscale shapes and patterns." Nature 440.7082 (2006): 297-302.
2Teschome, Bezu, et al. "Temperature-dependent charge transport through individually contacted DNA origami-based Au nanowires." Langmuir 32.40 (2016): 10159-10165.
3Samanta, Anirban, Saswata Banerjee, and Yan Liu. "DNA nanotechnology for nanophotonic applications." Nanoscale 7.6 (2015): 2210-2220.
4Teschome, Bezu, et al. "Alignment of Gold Nanoparticle-Decorated DNA Origami Nanotubes: Substrate Prepatterning versus Molecular Combing." Langmuir 31.46 (2015): 12823-12829.
5Helmi, Seham, et al. "Shape-controlled synthesis of gold nanostructures using DNA origami molds."Nano letters 14.11 (2014): 6693-6698
2:15 PM - NM03.07.04
Ballistic One-Dimensional Transport in InAs Nano-Structures
Siegfried Karg 1 , Johannes Gooth 1 , Heinz Schmid 1 , Vanessa Schaller 1 , Stephan Wirths 1 , Kirsten Moselund 1 , Heike Riel 1
1 , IBM Research, Ruschlikon Switzerland
Show AbstractBallistic one-dimensional (1D) electron transport has been shown in several nanowire materials fabricated by different techniques. However, envisioned electronic circuits based on quantized transport e.g. for quantum computing, require more complex quantum networks than just straight nanowires. The growth method Template-Assisted Selective Epitaxy (TASE) developed at IBM allows for the monolithic integration of semiconductor nano-structures with well-defined geometry and position on a Si platform [1]. TASE provides high-quality III–V nanostructures with low defect densities and surface roughness. We have fabricated InAs nanowires (NWs) and cross-junctions showing 1D ballistic transport with conductance quantization in units of 2e2/h controlled by the electric field of a global back gate. In single NWs control of up to four individual modes was achieved and the sub-band structure was investigated using bias spectroscopy [2]. Length-dependent studies revealed ballistic transport for up to 300 nm and quasi-ballistic transport with a mean free path of 470 nm at 30 K. Moreover, we demonstrate that the sensitive ballistic conduction and confinement conditions can be maintained across NW intersections [3]. Characteristic 1D conductance plateaus were resolved in field-effect measurements across up to four NW-junctions in series. The 1D ballistic transport and sub-band splitting was preserved for both crossing directions. We show that the 1D modes of a single injection terminal can be distributed into multiple NW branches. We believe that NW cross-junctions are well-suited as cross-directional communication links for the reliable transfer of quantum information as required for quantum computational systems.
[1] H. Schmid, M. Borg, K. Moselund, L. Gignac, C. M. Breslin, J. Bruley, D. Cutaia, H. Riel, Appl. Phys. Lett. 106, 233101 (2015).
[2] J. Gooth, V. Schaller, S. Wirths, H. Schmid, M. Borg, N. Bologna, S. Karg, and H. Riel Appl. Phys. Lett. 110, 083105 (2017).
[3] J. Gooth, M. Borg, H. Schmid, V. Schaller, S. Wirths, K. Moselund, M. Luisier, S. Karg, and H. Riel, Nano Lett. 17, 2596−2602 (2017).
2:30 PM - NM03.07.05
Charge Carrier Dynamics in GaAs/(In,Ga)As/(Al,Ga)As Core-Multishell Nanowire Heterostructures
Hanno Küpers 1 , Pierre Corfdir 1 , Ryan Lewis 1 , Timur Flissikowski 1 , Abbes Tahraoui 1 , Holger Grahn 1 , Oliver Brandt 1 , Lutz Geelhaar 1
1 , Paul-Drude-Institut für Festkörperelektronik, Berlin Germany
Show AbstractSemiconductor nanowires (NWs) exhibit a wide range of features beneficial for optoelectronic applications. The quasi one-dimensional structure enhances light coupling and the small NW diameter enables the elastic relaxation of strain in axial and radial directions, allowing for highly lattice mismatched heterostructures to be realized in nanowires. In particular, (In,Ga)As shell quantum wells in GaAs NWs are highly interesting for tunable light emission in the near-infrared spectral range, which is of importance for optical communication, as well as for biological applications. In particular, the core-shell geometry leads to a very large active region compared to the overall sample volume. However, the high surface-to-volume ratio of NWs results in pronounced nonradiative charge carrier recombination at the surface, and hence a good surface passivation strategy is necessary for achieving devices with high efficiencies.
We present results on the growth by molecular beam epitaxy and on the optical properties of GaAs/(In,Ga)As/(Al,Ga)As core-multishell structures. NW cores with a diameter of 50 nm were grown selectively on patterned Si substrates using the Ga-assisted growth mode. On the side-facets of the core, a 10 nm thick In0.15Ga0.85As shell was grown, acting as a quantum well. The quantum well was then covered with an outer barrier shell consisting of either pure GaAs or a multishell combination of GaAs and AlAs shells.
For temperatures above 80 K, the continuous-wave photoluminescence (PL) signal for the NWs with a pure GaAs outer shell shows a strong decrease in intensity, with an activation energy Ea of 80 meV. In contrast, for samples with outer shells containing AlAs, the PL intensity quenching is less pronounced. However, in time-resolved PL at 10 K, the PL decay for the samples with AlAs barriers is fast compared to that for the sample with only a GaAs outer shell. These findings indicate a combination of surface recombination and interface recombination as the main non-radiative mechanisms. At low temperatures, the recombination of charge carriers is dominated by nonradiative recombination at the outer interface between the quantum well and the barrier shell. The interface quality for AlAs-based shells is lower, leading to a faster PL decay at 10 K. In contrast, for temperatures larger than 80 K, the thermal escape of charge carriers from the quantum well is activated. Without AlAs in the outer shell, carriers can reach the NW surface and recombine nonradiatively, leading to the strong PL intensity quenching observed in continuous-wave PL. Our study thus exemplifies the importance of surface effects for NW heterostructures. By optimizing the structure of the outer barrier shell for surface passivation, we demonstrate an improvement in room temperature luminescence intensity by more than two orders of magnitude.
2:45 PM - NM03.07.06
Electrical Transport Properties of Single MnAs/InAs Hybrid Nanowires Grown by Selective-Area Metal-Organic Vapor Phase Epitaxy
Patrick Uredat 2 1 , Matthias Elm 1 2 3 , Ryutaro Kodaira 4 , Ryoma Horiguchi 4 , Peter Klar 2 1 , Shinjiro Hara 4
2 Institute of Experimental Physics I, Justus Liebig University, Giessen Germany, 1 Center for Materials Research, Justus Liebig University, Giessen Germany, 3 Institute of Physical Chemistry, Justus Liebig University, Giessen Germany, 4 Research Center for Integrated Quantum Electronics, Hokkaido University, Sapporo Japan
Show AbstractIII-V nanowires are both, an intriguing model system to study quantum interference effects in mesoscopic systems and building blocks for future nanoelectronic or optoelectronic devices, such as field-effect transistors, sensors or solar cells. To be suitable for magnetoelectronic or spintronic applications nanowires need to have adjustable magnetic properties. As the number of dilute magnetic III-V nanowires with Curie temperatures above 300K is limited, we present the fabrication of MnAs/InAs hybrid nanowires. First, InAs nanowires were grown on GaAs(111)B substrate using selective-area metal-organic vapor-phase epitaxy. In a second growth step MnAs clusters are introduced to the InAs nanowire. By varying the growth temperature and time one can tune the shape and the number of the MnAs nanoclusters. At low growth temperatures smaller MnAs clusters with diameters below 100nm are found on the surface of the InAs nanowire, whereas high temperatures lead to larger MnAs clusters which penetrate into the entire InAs nanowire. Structural analysis of the crystal structure reveals the high crystal quality of the MnAs nanoclusters. High resolution transmission electron microscopy and magnetic force microscopy confirm the formation of ferromagnetic nanoclusters in NiAs-type structure with a c-plane aligned parallel to the <111>B growth direction of the InAs nanowire. Magnetotransport measurements of the pure InAs nanowire reveal universal conductance fluctuations and weak Anderson localization at low temperatures. The phase coherence length was determined by analyzing the quantum interference effects and shows a temperature dependence, which is typical for one-dimensional structures. For magnetic fields larger than 3 T a strong positive magnetoresistance effect up to 150% dominates, whereas MnAs/InAs hybrid nanowires show only a linear decreasing, negative magnetoresistance up to 10% at 10 T.
NM03.08: Sensors
Session Chairs
Juan Beltran-Huarac
Patrik Schmuki
Tuesday PM, November 28, 2017
Hynes, Level 3, Room 310
3:30 PM - *NM03.08.01
Tailoring Nanoscale Fibers—From Fundamental to Practical Use
Il-Doo Kim 1
1 , Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
Show AbstractElectrospinning has been recognized as one of the most efficient techniques for producing non-woven fiber webs on the order of several hundreds of nanometers by electrically charging a suspended droplet of polymer solution with/without inorganic precursors or melt. Various types of materials with a high degree of porosity, a large surface area, superior mechanical properties and modified surface functionalities, can be electrospun into nanofiber structures. These materials include polymeric nanofibers as well as metallic and metal-oxide nanofibers which are prepared by a subsequent heat treatment in a reducing or oxidizing atmosphere of metal salt precursor/polymer composite fibers. In particular, the simplicity of the process combined with the possibility of large-scale production through the use of multiple-nozzles (> 10,000 pieces) makes this process very attractive and therefore opens up new commercial markets for diverse applications. In this presentation, I summarize recent progress and a collection of advances, particularly focused on the synthesis, characterization, and utilization of electrospun nanofibers. I will end my presentation by suggesting possible future research direction and potential suitability of 3D nanofibers for applications in colorimetric sensors, exhaled breath gas analyzing sensors for early stage disease diagnosis, and nanocatalysts for next generation energy storage devices.
4:00 PM - NM03.08.02
Solution Processable Carbon Nanotube Biosensing Devices: a Nanoscale Multi-Sensing Platform
Pierrick Clement 1 , Xinzhao Xu 1 , Mark Freeley 1 , Jorge Chavez 2 , Matteo Palma 1
1 , Queen Mary University of London, London United Kingdom, 2 , Human Effectiveness Directorate, Dayton, Ohio, United States
Show AbstractElectrical detection methodologies are among the most promising candidates for the fabrication of miniaturized, ultra-sensitive and portable biomarker detection protocols. Advances in nanofabrication techniques and novel nanoscale tools have opened up new avenues for developing electrical analytical methods that can be effectively merged with miniaturized hardware. Moreover, electrical (bio)sensing based on nanomaterials offers unique advantages, such as simplicity, low-cost processability, and label-free real-time electrical detection in a non-destructive manner.
In this context, there has been great interest in the use of one-dimensional nanostructured materials for the development of new nanoscale biosensors, and single walled carbon nanotubes (SWCNTs) emerged as strong candidates. It has indeed been demonstrated that target biomolecules in close proximity to SWCNTs, can alter the electronic properties of SWCNTs via various mechanisms.
Here we present a strategy for the fabrication of reconfigurable and solution processable nanoscale biosensors with multi-sensing capability, based on individual SWCNTs. DNA-wrapped (hence water-soluble) CNTs were immobilised from solution between two pre-patterned electrodes via dielectrophoresis (DEP). The CNTs were functionalized with specific nucleotide sequences to be employed as selective recognition elements for analytes of interest.
In particular, we will demonstrate the electrical detection of hybridization and de-hybridization events on few CNTs in device configurations. Control experiments have been performed with non-complementary DNA sequences and no significant current variation was observed. Additionally, as a proof-of-concept, we functionalized our CNTs with three different steroid selective aptamers, and employed our devices for the simultaneous detection of these hormones on the same biochip This allowed us to detect on our nanoscale devices and in real-time physiological relevant concentrations of specific hormones correlated to several stress conditions.
The herein presented strategy is of general applicability for the electrical sensing of multiple biomarkers in real time and with high sensitivity. Furthermore, the environmentally friendly and low-cost fabrication method (aqueous solution-processable via DEP) can be scaled up in array configurations for the development of nanoscale point of care and portable biosensing platforms.
4:15 PM - NM03.08.03
Site-Specific Growth and In Situ Integration of Nanowire Networks for Sensing Applications
Lukas Hrachowina 1 , Guillem Domènech-Gil 2 , Michael Seifner 1 , Jordi Sama 2 , Isabel Gracia 3 , Carles Cane 3 , Albert Romano-Rodriguez 2 , Sven Barth 1
1 Institute of Materials Chemistry, Vienna University of Technology, Vienna Austria, 2 MIND-IN2UB-Departament d’Electrònica, Universitat de Barcelona, Barcelona Spain, 3 , Centre Nacional de Microelectrònica, Bellaterra Spain
Show AbstractNanostructured, porous oxides are prominent sensing materials due to the reversible change in resistivity upon changes in the surrounding atmosphere. Nanowires have gained considerable attention in gas sensing devices due to their high surface to volume ratio and high crystallinity. However, the cost effective integration of nanowires in functional devices is usually challenging and costly.
We present a cost effective and simple growth strategy using CMOS-compatible micromembranes containing a buried heating element, which is used for thermally induced chemical vapour growth of SnO2, WO3 and Ge. In addition, the buried heater can be used as the heating source for the effective operation as sensor. The small membrane volume and area requires low power (few mW) for both the growth and the operation of the resulting devices. The actual devices contain a porous network of nanowires bridging interdigitated electrodes on top of the membrane for the electrical readout. Secondary deposition products are negligible, which can be demonstrated by cross-sectioning of the active part of the device. The devices have been successfully used in monitoring changes in CO [1], ammonia [2] and humidity [3] concentrations and show long-term stability. This contribution will address growth strategies and specific considerations for three different materials in regards to their applicability for sensor applications and the simple fabrication of an electronic nose configuration.[4]
References
[1] S. Barth, R. Jimenez-Diaz, J. Sama, J. D. Prades, I. Gracia, J. Santander, C. Cane, A. Romano-Rodriguez. Chem. Commun. 2012, 48, 4734.
[2] J. Sama, S. Barth, G. Domenech-Gil, J. D. Prades, N. Lopez, O. Casals, I. Gracia, C. Cane, A. Romano-Rodriguez, Sens. Actuators B, 2016, 232, 402.
[3] J. Sama, G. Domenech-Gil, M. Seifner, J. Santander, C. Calaza, I. Gracia, S. Barth, A.Romano-Rodriguez, Sens. Actuators B, 2017, 243, 669.
[4] L. Hrachowina, G. Domenech-Gil, M. Seifner, I. Gracia, C. Cane, A.Romano-Rodriguez, S. Barth, manuscript submitted.
4:30 PM - NM03.08.04
Vertical Nanodevice Array for Flexible High-Spatial-Resolution Sensors
Youngbin Tchoe 1 , Heehun Kim 1 , Minho Song 1 , Joon Young Park 1 , Hongseok Oh 1 , Jun Beom Park 1 , Keundong Lee 1 , Hosang Yoon 1 , Gyu-Chul Yi 1
1 , Seoul National University, Seoul Korea (the Republic of)
Show AbstractFlexible nanodevices with high-spatial-resolution, performance, and reliability are in high demand for wearable and implantable sensors. Although inorganic semiconductors based sensors have high accuracy, fast response time, and long-term stability, they have intrinsic limitation to be fabricated into flexible form. As an alternative solution, re-assembly techniques of inorganic semiconductor thin film pieces on flexible substrates were developed and many promising applications based on this approach were demonstrated. However, for the fabrication of high-spatial-resolution nanodevice arrays, because of the difficulties in handling nano- or micro-sized structures and a long time to assemble multiple elements, a fundamentally different approach should be employed. Here, we suggest a method of fabricating flexible high-spatial-resolution nanodevice array based on one-dimensional (1D) inorganic semiconductor nanomaterials arrays grown on two-dimensional (2D) layers nanomaterials. Individual addressing of 1D nanomaterial based nanodevices in a crossbar array is essential for the fabrication of high-spatial-resolution nanodevice array.
Here, we report on the fabrication and electrical and photoresponse characteristics of individually addressable ZnO nanotube Schottky diode array as an example of the flexible high-spatial-resolution nanodevice array. For the fabrication of the Schottky diode array, position- and dimension-controlled ZnO nanotube arrays were vertically grown on a chemical vapor deposited graphene layers prepared on SiO2/Si substrate with a submicrometer-hole-patterned SiO2 growth-mask layer using selective-area metal-organic vapor phase epitaxy. As an essential step for creating the flexible device, freestanding layers composed of ZnO nanotubes/graphene layers were prepared by coating a polyimide layer and mechanical lifting-off the entire layers from the substrate. Then, top gold (Au) electrode lines as a Schottky contact were formed on the ZnO nanotube arrays by standard electron beam lithography, metal deposition, and subsequent metal lift-off procedures. After flipping the freestanding layers, bottom chromium (Cr)/Au electrode lines as an ohmic contact were formed in the same manner. Then, we dry etched the graphene layers that were not covered with Cr/Au, forming graphene layers/Cr/Au bottom electrodes. The final device structure exhibited that Au and graphene layers/Cr/Au electrodes are contacting the top and bottom surface of a single nanotube and crossing each other. The electrical and optical characteristics of the nanodevice array fabricated on graphene layers were investigated by measuring their current–voltage curves, and time-resolved and spectral photoresponses at various bending conditions. We also confirmed that the device layer had an ultrathin and extremely flexible form and reliable operation.
4:45 PM - NM03.08.05
An Array of Metal Oxides Nanoscale Hetero p-n Junctions toward Designable and Highly-Selective Gas Sensors
Hyunah Kwon 1 , Jun-Sik Yoon 1 , Yuna Lee 1 , Dong Yeong Kim 1 , Chang-Ki Baek 1 , Jong Kyu Kim 1
1 , POSTECH, Pohang Korea (the Republic of)
Show AbstractMetal oxides gas sensors have been intensively studied due to their advantages of low cost, and simple fabrication and operation, thus widely used in many applications. On the other hand, they have a critical disadvantage of poor selectivity because most of adsorbed gas molecules may change the resistance of metal oxides sensing layers, making them difficult to distinguish gas species. In this regard, metal oxides heterostructures, in which two different metal oxides form a physical interface, have recently become attractive candidates as sensing layers due to their potential to enhance not only gas sensitivity by large heterojunction barrier modulation, but also gas selectivity by increased degree of freedom in materials selection. There have been numbers of attempts to fabricate metal oxides heterostructures as gas sensing layers, most of which have randomly distributed heterojunctions. Although gas sensitivity and selectivity were reported to be enhanced, there are remaining challenges such as poor stability and reproducibility in sensing performances and difficulty in quantitative investigation on gas sensing mechanism with such not-well-defined heterojunctions. In order to take full advantages metal oxides heterostructures offer and design highly sensitive and selective gas sensors, fabrication and characterization of well-defined and highly-gas-accessible hetero-interfaces between metal oxides are strongly required.
In this study, we demonstrated a nano-helical array of p-NiO/n-SnO2 hetero p-n junctions as gas sensing layers where the heterojunctions are well-defined and gases can easily access to both metal oxides surfaces and hetero-interfaces. The nanoscale array, fabricated by oblique angle deposition (OAD) between top and bottom electrodes, shows p-n junction current-voltage (I-V) characteristics. Interestingly, the p-NiO/n-SnO2 gas sensor shows a similar trend in current modulation under both reducing H2 and oxidizing NO2 gases, which is very unusual considering the changes of electrical properties occurring in the single p-NiO and the n-SnO2 gas sensors. Such unexpected sensing properties can be explained by the predominant modulation in barrier height at the hetero-interfaces over the change in the carrier concentration of each oxide layer, which is confirmed by the Shockley diode equation as well as the simulation results obtained by Sentaurus TCAD software. To the best of our knowledge, it is the first time to quantitatively investigate the heterojunction effects on gas sensing behaviors based on both experimental and simulation results. Our results, together with the ability to fabricate a variety combination of metal oxides heterostructures by using reproducible and controllable OAD, can give a promising strategy to design and realize a highly-selective gas sensor array or electronic-nose optimized towards target gases on demand, avoiding empirical and trial-and-error approaches.
NM03.09: Poster Session II: Electronics and Photonics and Sensing
Session Chairs
Wednesday AM, November 29, 2017
Hynes, Level 1, Hall B
8:00 PM - NM03.09.01
Copper Nanowire Based Transparent Electrodes with Improved Oxidation Stability
Sevim Polat Genlik 1 , Dogancan Tigan 1 , Sahin Coskun 1 , Husnu Unalan 1
1 , Middle East Technical University, Ankara Turkey
Show AbstractFigure of merit transparency and sheet resistance values of the metal nanowire networks are very close, if not better, than those of commercially available transparent and conducting thin films. In addition, nanowire networks carry the prominent advantage of solution processability and flexibility. Among scalably synthesized metal nanowires copper stands alone as the most promising one due to its low cost. However, copper nanowires (Cu NWs) are more prone to oxidation compared to their silver counterparts and this have limited their large-scale utilization. Bulk copper is also susceptible to oxidation and many methods have been proposed for protection to improve its service life in electronics. Inspired from bulk copper, in this work, we utilized benzotriazole (BTA) as an organic corrosion inhibitor to improve the stability of Cu NWs. High aspect ratio Cu NWs are synthesized by an environmentally benign hydrothermal method and highly transparent and conducting Cu NW network electrodes (20 ohm/sq sheet resistance at a transmittance of 85%) are fabricated through spray deposition. Following their fabrication, electrodes are dip coated with a solution of BTA for passivation. Long term stability of the passivated electrodes under different and severe humidity conditions and temperatures is systematically investigated and compared to that of bare control samples. It was found that BTA inhibits the formation of oxide layer on Cu NWs for at least 150 days of storage under ambient conditions and sheet resistance of passivated Cu NW networks remain almost unchanged (R/R0 < 1.07). This highly effective and simple strategy to improve the stability of Cu NWs will certainly open new avenues for their large scale utilization in various optoelectronic devices.
8:00 PM - NM03.09.02
Direct On-Chip Integration of Metal Oxide Nanowires for Gas Sensing Applications Using a Modified CVD Technique
Thomas Fischer 1 , Yakup Gonullu 1 , Sanjay Mathur 1
1 Institute of Inorganic Chemistry, University of Cologne, Cologne Germany
Show AbstractGas sensing devices need to fulfil the common "S"-criteria: Selectivity, Sensitivity, Speed and Stability. When targeting commercialization also Scalability as well as Systemability come into play, as the devices need to be manufactured in reasonable quantities and comply with modern microelectronic systems as well as established fabrication techniques. Although anisotropic metal oxide nanostructures have been studied as advanced gas sensing materials, due to their favorable surface to volume ratio for enhanced sensitivity, further commercialization is hampered mainly by slow and cost intensive scaled-up manufacturing. Chemical Vapor Deposition (CVD) has been the method of choice for the bottom-up fabrication of inorganic 1D nanostructures using the metal seeded VLS growth mechanism and can be scaled up to wafer scale. The localized growth using CVD methods however remains challenging and can be achieved by structured localized areas and heating, respectively.
This presentation will highlight a modified CVD technique, which allows the direct and site selective growth of 1D metal oxide nanowires on multifunctional gas sensing substrates utilizing the preexisting sensing electrodes and micro heaters. The direct integration of nanowire bundles as well as their surface functionalization enables the facile and reproducible integration of 1D nanostructures on gas sensing platforms. In addition, an in-situ growth monitoring of gas sensing layers can be realized by continuous I-V measurements, resulting in reproducible final sensor configurations. This general approach of direct 1D nanostructure integration is demonstrated using SnO2 nanowire based heterostructures and their performance as chemoresistive gas sensors. Variations in growth conditions, seed materials as well as tailored molecular single-source precursors and their effects on gas sensing ability of resulting nanowires, heterostructures and nanowire meshes will be discussed in detail.
8:00 PM - NM03.09.03
Omnidispersible Spiky Hedgehog Particles as a SERS Probe
Douglas Montjoy 1 , Joong Hwan Bahng 1 , Nicholas Kotov 1 2 3
1 Chemical Engineering, Univ of Michigan, Ann Arbor, Michigan, United States, 2 Materials Science and Engineering, University of Michigan–Ann Arbor, Ann Arbor, Michigan, United States, 3 Biomedical Engineering, University of Michigan–Ann Arbor, Ann Arbor, Michigan, United States
Show AbstractSurface-enhanced Raman spectroscopy (SERS) spectroscopy is a powerful, sensitive, and nondestructive technique for identification of molecular species. Plasmonic hotspots generated from aggregation of nanoparticles have been shown to increase SERS intensity but can be unreliable and difficult to control due to poor reproducibility and limited colloidal stability. Colloidal templates increase dispersion stability, allow for dense coatings of plasmonic particles, and provide multiple functionalities. Additionally, nanorod arrays are commonly used as a support since they allow close contact of nanoparticles, and have a high surface area and aspect ratio for SERS. Hedgehog Particles (HPs) recently developed in the Kotov lab, consist of polystyrene microparticles with nanoscale zinc oxide spikes that result in marked reduction of Van der Waals interactions and enable dispersion in both polar and nonpolar solvents. HPs offer the advantages of a nanorod array in a colloidal format and can be used as a dispersible SERS probe in complex fluid environments. Conformal coating of HPs with functional nanoparticles and polyelectrolytes was achieved by layer-by-layer films, as demonstrated by electron and confocal microscopy. Dispersion stability in nonpolar solvents is maintained with these surface modifications indicating promise in forming a new class of omnidispersible materials. Additionally, gold-modified HPs show increased SERS activity compared to gold-modified polystyrene beads in detection of methylene blue. These omnidispersible particles can be used for SERS Detection in biological fluids including blood, urine, and saliva.
8:00 PM - NM03.09.04
Fabrication of Interconnected Silicon Nanowire Networks and Their Photovoltaic Properties
Emmet Sheerin 1 , John Boland 1
1 Chemistry, CRANN Trinity College Dublin, Dublin Ireland
Show AbstractMaterials at the nanoscale have been shown to possess enhanced or even entirely new and exotic behaviours over their bulk counterparts and are therefore of significant interest for applications in next generation technologies. One dimensional materials such as nanowires and nanotubes have demonstrated impressive properties when incorporated into devices such as field effect transistors [1], gas sensors [2] and photodetectors [3]. Despite the promising results of these and many other studies, widespread commercial application of nanowire based devices is still yet to be realised. This is primarily due to the significant difficulties associated with the manipulation of individual nanostructures on a large and reproducible scale. Nanowire networks offer the possibility of bypassing these difficulties of precision placement while retaining the desirable behaviours inherent to 1D nanoscale materials. Additionally, the variations between individual nanowire properties are averaged out when assembled into networks allowing greater reproducibility across devices. However, the unfavourable geometry of junctions between wires invariably has a detrimental effect on device performance [4] and necessitates additional processing steps on the network, ultimately limiting their applications.
In this work we present a highly scalable technique for the fabrication of large area interconnected silicon nanowire networks using a sacrificial polymer nanowire template. Polymer nanowires with extremely high aspect ratios are formed through an electrospinning process and are deposited as a random overlapping network on a silicon on insulator (SOI) substrate. A plasma etching process is then carried out which precisely maps the nanowire network structure onto the underlying silicon layer forming a continuous network with seamless junctions between wires. By controlling the electrospinning parameters, nanowire networks with narrow width distributions can be obtained across a range of diameters, from greater than one micron down to tens of nanometres. The network wire density can be controlled by the length of time of the electrospinning process allowing for the fabrication of both sparse and highly dense networks. Following removal of the polymer template, the SOI nanowire networks are then contacted and devices have demonstrated high photocurrent gains with fast response times over a broad spectrum of wavelengths.
1. E. N. Dattoli, Q. Wan, W. Guo, Y. Chen, X. Pan and W. Lu, Nano letters, 2007, 7, 2463-2469.
2. Y. Cui, Q. Wei, H. Park and C. M. Lieber, Science, 2001, 293, 1289-1292.
3. K. Das, S. Mukherjee, S. Manna, S. Ray and A. Raychaudhuri, Nanoscale, 2014, 6, 11232-11239.
4. A. T. Bellew, H. G. Manning, C. Gomes da Rocha, M. S. Ferreira and J. J. Boland, ACS nano, 2015, 9, 11422-11429.
8:00 PM - NM03.09.05
Light Absorption in Axially Heterostructured Semiconductor NWs
Jose Luis Pura 1 , Priyanka Periwal 2 , Thierry Baron 2 , Juan Jimenez 1
1 , University of Valladolid, Valladolid Spain, 2 , University of Grenoble, Grenoble France
Show AbstractSemiconductor NWs present advantages with respect to thin films, as the possibility of combining highly mismatched materials, allowing the growth of structures that are not available as thin layers; in particular, a large range of mismatched heterostructures free of defects can be grown as compared to the limitations imposed to thin films by the lattice mismatch. Furthermore, NWs are shown to be very efficient optical collectors and emitters, which makes them suitable for the development of high performance photovoltaic cells, sensitive light detectors, electro-optic modulators and light sources, e.g. one single photon sources, and random lasers, among other applications. The optical response of these complex structures suggests the possibility of developing complex photonic devices. As a prerequisite for the extended use of these heterostructured NWs one needs to understand their optical properties. In particular, understanding the interaction of complex heterostructured semiconductor NWs with light is crucial for the achievement of advanced photonic devices. In bulk materials this interaction is mainly governed by the refractive index, however, when dealing with NWs one adds other factors such as the NW dimensions. Additionally, the complex electromagnetic field distribution inside the NWs adds a note of complexity to the understanding of the optical response of both axially and radially heterostructured NWs. The light /NW interaction is usually engineered only by means of the NW diameter, however, this has the limited possibilities associated with diameter dependent absorption/ scattering resonances. Recently, we have reported a local optical enhancement at the heterojunctions of axially heterostructured Si/SiGe NWs. We present herein a complete study of the optical response of axially heterostructured Si/SiGe. The influence of Ge composition, the NW diameter, and the heterojunction abruptness on the optical response of the NWs is considered.
8:00 PM - NM03.09.06
Fabrication of Aptamer-Modified Electropolymerized Polypyrrole Nanowires for Highly Sensitive FET HBsAg Biosensor
Kyung Hee Cho 1 , Jyongsik Jang 1
1 , Seoul National University, Seoul Korea (the Republic of)
Show AbstractHBV infection is a worldwide health issue which is a major cause of liver cirrhosis, hepatocellular carcinoma, and liver failure. For the diagnose of HBV infection, hepatitis B virus surface antigen (HBsAg) can be used as a serological marker, because it reflects progress of the disease whether it is acute or chronic, and predicts the curative effect on chronic HBV. There are two commercialized techniques to detect serum HBsAg, such as enzyme-linked immunosorbent assay (ELISA) and radioimmunoassay (RIA). However, these methods have disadvantages: they require complex procedures, special equipment, and are time-consuming. To overcome these issues, several researches have been demonstrated chemiluminescence, fluorescence, and surface plasmon resonance detection. Nevertheless, most of these still remain at low level of sensitivity similar to ELISA (0.5 ng/mL). Therefore, a new strategy for HBsAg detection must be developed.
Recently, there have been active studies to diagnose diseases easily and quickly by a noninvasive method using saliva. Conventional detection methods were inevitable for painful blood collection process. In contrast, saliva-based diagnostics have several advantages: easy to collect, cost-effective, simple and safe to handle. The frequency of HBsAg detection in saliva is consistent with blood, but the concentration is much lower. Hence, implementing high-performance sensor through enhancing the surface area and immobilized amount of bioreceptors are essential to achieve salivary HBsAg detection. Conducting polymer (CP) nanomaterials are great signal transducer for biosensors due to its inherent electrical and biocompatible properties. Also, CPs are easily fabricated into various structures such as nanoparticles, nanowires, nanotubes, and nanofibers by electrochemical and chemical polymerization methods. Facile creation of the nanostructure into three-dimensional (3D) form and readily modifiable chemical functionality of CPs enable highly dense and stable binding of probe molecules on the surface of the CP transducer.
In this study, we report a fabrication of HBsAg aptasensor based on vertically oriented carboxylated polypyrrole nanowires (CPNWs) via electropolymerization and acid treatment. HBsAg aptamers were subsequently attached to CPNWs and field effect transistor (FET) sensor was assembled with liquid-ion gate configuration. The 3D structure of transducer consisting of vertically aligned nanowires with high length-to-diameter (L/D) ratio and sufficient surface modification enhanced the loading amount of aptamers. As a result, the aptasensor showed good sensitivity toward HBsAg, exhibiting low detection limit of 1 fM and fast reaction time (< 5 s). Furthermore, this aptasensor could distinguish HBsAg from human saliva, showing a potential for the noninvasive diagnose of HBV infection.
8:00 PM - NM03.09.07
Copper Nanowire Network Transparent Thin-Film Heaters
Dogancan Tigan 1 , Sevim Polat Genlik 1 , Bilge Imer 1 , Husnu Unalan 1
1 , Middle East Technical University, Ankara Turkey
Show AbstractExtensive amount of research on the synthesis and utilization of silver nanowires has been conducted to date. Copper nanowires, on the other hand, are relatively unexplored, almost equally conducting and 100 times cheaper than silver. In this work, thin film heaters were fabricated using random copper nanowire networks. Copper nanowires were synthesized via a simple solution based method. Following purification and dispersion of nanowires, thin films were deposited by spray coating. Figure of merit sheet resistances below 100 Ω/sq and transmittances above 80% were obtained. In terms of their performance in thin film heaters, heater failure is almost inevitable for bare copper nanowires since they easily oxidize at elevated temperatures. To overcome this problem, aluminum oxide shell layers with different thicknesses were deposited onto copper nanowire thin films via atomic layer deposition. In terms of heating performance, with the applied potential, the temperature of bare copper nanowire thin films was found to increase up to 100 °C and then dropped progressively due to the oxidation of copper nanowires. On the other hand, aluminum oxide deposited copper nanowire thin films were successfully heated to temperatures above 200 °C without any failure. The detailed analysis of electrical, optical and thermal properties of copper nanowire random network thin films will be presented. The use of copper nanowires for transparent heaters opens up new avenues for the realization of cost effective heaters with different form factors.
8:00 PM - NM03.09.08
Ozone Gas Sensor Based on One-Dimensional V2O5/TiO2 Heterostructures
Waldir Avansi 1 , Tomas Florido 2 , Luis Fernando da Silva 1 , Khalifa Aguir 2 , Valmor Mastelaro 3
1 , Univ de Sao Carlos, Sao Carlos Brazil, 2 , Aix Marseille Université, Marseille France, 3 , Universidade de São Paulo, São Carlos Brazil
Show AbstractOver the last decades, there has been considerable interest in the synthesis of one dimensional (1D) metal-oxides nanostructures for gas sensor. Heterostructures, obtained by combination of different semiconductor nanomaterials with different band energies have been extensively studied in order to improve the gas sensor performance. In this sense, this study investigated the potential of a combination of TiO2 nanoparticles and V2O5 nanowires, which was obtained via a hydrothermal method, for effective ozone gas sensor. In a typical procedure to obtain V2O5/TiO2 heterostructures, an appropriated amount of solution containing V2O5 nanowires and titanium peroxo-complex was prepared. Then, this mixed solution was submitted to a hydrothermal treatment. The precipitates were separated by centrifugation, washed with pure alcohol for several times and then dried in an electric furnace. The method employed for the synthesis of vanadium pentoxide nanowires and TiO2 nanoparticles was described in greater detail by Avansi et al [1] and Mendonça et al [2], respectively. The as-obtained samples were studied by X-ray diffraction (XRD) which confirm the presence of V2O5 orthorhombic and TiO2 anatase crystalline phases. Transmission electron microscopy (TEM) showed that the morphology of the as-synthesized samples were composed by nanowires decorated with nanoparticles with sizes of 5-10nm. High resolution transmission electron microscopy (HRTEM) shows that the nanowires and nanoparticles are related to V2O5 orthorhombic and TiO2 anatase, confirming the formation of V2O5/TiO2. The gas sensor performance to detect O3 were performed comparing the sensibility of V2O5 nanowires and V2O5/TiO2 samples. The results showed a maximum sensor response at 300 oC, which is close to that of traditional metal oxide gas sensors such as ZnO, In2O3, WO3 and SnO [3]. It is noteworthy that both samples displayed good sensitivity even at lower O3 levels as well as total reversibility. However, the V2O5/TiO2 heterostructure didn’t show any evidence of saturation, unlikely of pristine V2O5 samples, which indicates the presence of additional adsorption sites. Compared with the V2O5 nanowires, the gas response of the V2O5/TiO2 heterostructure was dramatically enhanced where the studied samples presented a promising gas-sensing properties, evidenced by their sensor response and repeatability, as well as a good range of detection (0.09 - 1.25 ppm). This work also proposes an efficient way to obtain 1D V2O5/TiO2 heterostructures that exhibit interesting ozone sensing properties.
References
[1] W. Avansi, Jr., C. Ribeiro, E. R. Leite and V. R. Mastelaro (2009). Crystal Growth & Design 9, p. 3626-3636.
[2] V. R. de Mendonça and C. Ribeiro (2011). Applied Catalysis B: Environmental 105, p. 298-305
[3] X. Zhou, S. Lee, Z. Xu and J. Yoon (2015). Chemical Reviews 115, p. 7944-8000.
8:00 PM - NM03.09.09
Localized Optical Sensing Based on Single Silicon Nanowire Probes
Ardeshir Moeinian 1 , Steffen Strehle 1
1 , Ulm University, Ulm Germany
Show AbstractSingle silicon nanowires are frequently highlighted as electrical transducers for ion-sensitive field effect transistors but this requires elaborate microfabrication. Here, we utilized silicon nanowires as optical transducers for biochemical sensing using Surface Enhanced Raman Spectroscopy (SERS). Since the discovery of SERS in 1973, extensive research was done leading to the implementation of SERS in several analytical disciplines ranging from spectroelectrochemistry to single molecule detection. However, miniaturization of SERS devices, comprising nanowires for highly localized SERS, was hardly studied. Here, bottom-up synthesized silicon nanowires functionalized with gold nanoparticles were used as high aspect ratio and biocompatible SERS probes confining the sensing volume drastically. Silicon nanowires were grown by the gold catalyzed vapor-liquid-solid method using SiH4 as a precursor gas. After growth, silicon nanowires on their growth substrate are decorated with closely packed gold nanostructures, which is a vital part of Raman signal enhancement. Gold nanostructures were attached using several strategies comprising colloidal nanoparticles and gold evaporation that will be discussed also based on transmission electron microscopy studies. Using ultrasonication of the growth substrate in ethanol, the decorated silicon nanowires are separated from the growth substrate and deposited onto target substrates for further analysis or to build single-nanowire SERS probes. We show for instance the ability of single silicon nanowires to enable highly localized Raman scattering signal enhancement allowing to detect 2.8×10-8 mol/l of methylene blue (methylthioninium chloride) in ethanol. Here, an inter-particle spacing of only a few nanometers must be realized to create so-called "hot-spots” leading to strong surface plasmon radiation. Raman spectra were obtained using a Nd:YAG laser with 532 nm wavelength. An Andor CCD for Raman spectroscopy mounted in WITec monochromator was used to detect the emitted/reflected photons from the surface of the sample.
8:00 PM - NM03.09.10
In2O3 Ceramic Nanofibers as Gas Sensor Platform
Rafaela Andre 1 , Luiza Mercante 1 2 , Jessica Pereira 1 , Luiz Henrique Mattoso 1 2 , Daniel Correa 1
1 , Embrapa Instrumentation, Sao Carlos Brazil, 2 Materials Engineering, Federal University of Sao Carlos, Sao Carlos Brazil
Show AbstractHigh performance sensors employed for monitoring volatile compounds, ensuring safety and controlling emission of toxic gases are highly demanded for environmental, biomedical, and industrial application [1]. In addition, volatile monitoring can also help on evaluation of food quality for safety consumption. For instance, meat in decomposition process can release nitrogenated gases such as biogenic amines and ammonia, which monitoring and detection are of great interest for food safety. Ceramic nanofibers (CNF), also known as inorganic one-dimensional nanostructures, have been widely studied in the past few years due to their interesting properties for varied applications [2]. More recently, ceramic nanofibers have been explored [3] as gas sensors for monitoring volatile organic compounds (VOCs), namely H2S and NH3. Once both sensibility and selectivity are dependent on the charge transfer ability of the sensitive layer and on the analyte chemical functionality, the CNF composition can be optimized for specific analytes detection. Indium oxide is a inorganic semiconductor with outstanding (opto)electronic properties for gas detection at high temperatures [4]. Here we developed In2O3 CNF in optimized conditions by using the electrospinning method followed by a calcination step, aiming the ceramic crystallization and polymeric matrix removal. The polymer matrix employed was Polyvinylpyrrolidone in dimethylformamide solution (14% w/w) while the inorganic counterpart was InCl3. In2O3 CNF were obtained by calcination at 500 °C for 3 hours. The CNF had their structural and crystalline phase composition characterized by X-ray diffraction (XRD), while the morphology and the dimensions were characterized by scanning electron microscopy (SEM-EDS). For chemical composition, the X-ray photoelectron spectroscopy (XPS) was carried out. The CNFs were tested toward NH3 gas detection presenting high sensibility and good reproducibility at room temperature, proving its potential for biogenic amine detection in food quality monitoring. The authors thank to CAPES, FAPESP (2016/23793-4), CNPq (402287/2013-4) SISNANO/MCTI and Embrapa AgroNano.
[1] A. Kaushik, R. Kumar, S.K. Arya, M. Nair, B.D. Malhotra, S. Bhansali, Organic–Inorganic Hybrid Nanocomposite-Based Gas Sensors for Environmental Monitoring, Chem. Rev. 115 (2015) 4571–4606. doi:10.1021/cr400659h.
[2] L.A. Mercante, V.P. Scagion, F.L. Migliorini, L.H.C. Mattoso, D.S. Correa, Electrospinning-based (bio)sensors for food and agricultural applications: A review, TrAC Trends Anal. Chem. 91 (2017) 91–103. doi:10.1016/j.trac.2017.04.004.
[3] J. Huang, Q. Wan, Gas Sensors Based on Semiconducting Metal Oxide One-Dimensional Nanostructures, Sensors. 9 (2009) 9903–9924. doi:10.3390/s91209903.
[4] A. Vomiero, S. Bianchi, E. Comini, G. Faglia, M. Ferroni, N. Poli, et al., In2O3 nanowires for gas sensors: morphology and sensing characterisation, Thin Solid Films. 515 (2007) 8356–8359. doi:10.1016/j.tsf.2007.03.034.
8:00 PM - NM03.09.11
Single-Crystalline Tungsten Ditelluride (WTe2) Nanobelts Grown from Eutectic Alloy Reservoir
Seunguk Song 1 , Jinsung Kwak 1 , Jong Hwa Lee 1 , Jae-Ung Lee 2 , Se-Yang Kim 1 , Jung Hwa Kim 1 , Sungwoo Lee 3 , Yeoseon Sim 1 , Yongsu Jo 1 , Gun-Do Lee 3 , Hyeonsik Cheong 2 , Euijoon Yoon 3 , Zonghoon Lee 1 , Soon-Yong Kwon 1
1 School of Materials Science and Engineering and Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST), Ulsan Korea (the Republic of), 2 Department of Physics, Sogang University, Seoul Korea (the Republic of), 3 Department of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of)
Show AbstractAmong diverse transition metal dichalcogenide compounds, semimetallic tungsten ditelluride (WTe2) in the distorted 1T phase has received renewed attention from the experimental observations of non-saturating large magnetroresistance and high mobility and from the theoretical prediction of large-gap quantum spin Hall insulator [1-4]. Furthermore, WTe2 atomic layers and their alloys with MoTe2 (i.e., WxMo1-xTe2) are also predicted to be type-II Weyl semimetals and two-dimensional (2D) topological insulators, triggering a lot of enthusiasm for studying fundamental physical phases [3,4]. However, most of the observed novel physical phenomena have been demonstrated in mechanically exfoliated samples, which are irregular and not scalable. Chemical vapor deposition (CVD) has so far adapted for the synthesis of current 2D atomic layers; however, the production of high-quality WTe2 layers remains an unsolved challenge mainly due to the low environmental stability and activity of Te, and difficulties in Te incorportation during growth.
In this study, we have obtained single-crystalline 1D WTe2 nanobelts at low temperatures (T ~<500 °C) in large scale via the use of Te-rich eutectic metal alloys (e.g., CuxTey). The as-synthesized WTe2 samples exhibit a distinct 1D belt-like morphology with layered cross-section of <12.2 ± 6.6 nm in thickness. The introduction of Te-rich eutectic metal alloys as a Te reservoir eliminates the Te deficiency in the resulting products and the contamination by impurities encountered with CVD. As a result, the resulting 1D products are highly pure, stoichiometric, structurally uniform, and free of defects, resulting in high electrical performances. All tested WTe2 nanobelt devices showed low resistances (ρ < 1 mΩ cm), close to that of the mechanically exfoliated ones by the order of magnitude [2]. Furthermore, they showed a remarkably high breakdown current density (JB) of up to ~40 MA/cm2, promising their future device applications as a downscaled interconnect. We believe that this approach may be used as a general strategy for fabricating 1D layered nanostructures and truly exciting opportunity that can lead to dozens of new 1D nanomaterials of electronic quality, which may offer unique properties that are not available in other materials.
[1] Ali, M. N. et al. (2014). "Large, non-saturating magnetoresistance in WTe2." Nature 514: 205-208.
[2] Wang, L. et al. (2015). "Tuning magnetotransport in a compensated semimetal at the atomic scale." Nature Commun. 6: 8892.
[3] Soluyanov, A. A. et al. (2015). "Type-II Weyl semimetals." Nature 527: 495-498.
[4] Wang, Y. et al. (2016). "Gate-tunable negative longitudinal magnetoresistance in the predicted type-II Weyl semimetal WTe2." Nature Commun. 7: 13142.
8:00 PM - NM03.09.12
1D Copper Nanowires for Flexible Printable Electronics and High Ampacity Conductive Wires
Tan Zhang 1 , Atif Aziz 2 , Yen-Hao Lin 1 , Farhad Daneshvar 1 , Hung-Jue Sue 1 , Mark Welland 2
1 Materials Science and Engineering, Texas A&M University, College Station, Texas, United States, 2 Nanoscience Centre, University of Cambridge, Cambridge United Kingdom
Show AbstractHydrothermal growth of one dimensional copper nanowires (CuNWs) was carried out using bromide ions (Br-) as a co-capping agent. The yield of CuNWs increases significantly when the molar ratio of alkyl amines and Br- is kept at 3:1. The electrical properties of individual nanowire were characterized using a novel fabrication method which does not require any e-beam lithography process. The ampacity of the CuNWs is found to be 4 Χ 107 A/cm2, which is more than an order of magnitude larger than that of bulk Cu. These good quality and easy to synthesize CuNWs are an excellent candidate for applications that demand high ampacity and for fabrication of high performance flexible printable electronics.
8:00 PM - NM03.09.13
Preparation and Characterization of Thermal Conducting Films Containing Boron Nitride Nanotubes (BNNT)
Chankyu Kwak 1 , Young Ryul Kim 1 , Min Kyung Zo 1 , Soonduk Lee 1 , Jiwon Lee 1 , Jaewoo Kim 1
1 , Naieel Technology, Daejeon Korea (the Republic of)
Show AbstractAs electronic devices such as a smartphone and a laptop computer are faster and thinner, more heat is generated inside the devices causing serious malfunctioning. In this regard, polymer based electrical insulating and thermal conducting films, sheets, and adhesives required for assembling the chips and processors are very important for dissipating the heat inside the devices. Among many materials in this category, epoxy resin has been widely used due to its excellent mechanical and electrical insulation properties, chemical stability, and high temperature endurance, etc. Epoxy resin is in general mixed with ceramic fillers such as Al2O3, AlN, SiC, and/or h-BN solely or combined to increase its low thermal conductivity (~0.2 W/mK). To achieve enough thermal dissipation capability, it is necessary to add a large amount of filler particles into the matrix, while the material properties decrease as the filler content increases. In addition, it is more difficult to disperse ceramic fillers homogeneously into the polymer matrix as the filler concentration increases. To overcome the material degradation and the difficulties in preparation, we explored the epoxy nanocomposites mixed with a small amount of boron nitride nanotubes (BNNT) and a ceramic filler such as h-BN to enhance the thermal conductivity as well as material properties.
We evaluated the thermal conductivity, dielectric strength, and mechanical properties of the prepared h-BN/BNNT/epoxy films. The films were coated on the copper and aluminum sheets, respectively. The thermal conductivity of prepared films was compared with the neat metal sheets and h-BN/epoxy coated metal sheets, respectively. The thickness of the prepared films were 50, 75 and 100 µm, respectively. We observed the thermal conduction property of h-BN and BNNT combined epoxy nanocomposites can be enhanced as high as 3 times by adding as less as 0.5 wt% of BNNT. We assume that BNNT may offer the solution for the heat problems in various ITs, IoTs, wearable sensors/robots, energy harvesting systems, and electric vehicles, etc.
8:00 PM - NM03.09.14
Individual (In1-xGax)2O3 Nanowire-Based Gas Sensor
Guillem Domènech-Gil 1 2 , Elena Lopez-Aymerich 1 2 , Paolo Pellegrino 1 2 , Mauricio Moreno 1 2 , Sven Barth 3 , Albert Romano-Rodriguez 1 2
1 Institute of Nanoscience and Nanotechnology , Universitat de Barcelona, Barcelona Spain, 2 MIND-Department of Electronics, Universitat de Barcelona, Barcelona Spain, 3 Institut für Materialchemie, Vienna University of Technology, Vienna Austria
Show AbstractThe gas sensing properties of Ga2O3 and In2O3, either in thin films or nanowire (NW) morphology, have been widely studied, establishing the charge transfer mechanisms that lead to resistance changes correlated with the concentration of the gas species. The synthesis of a mixed (Ga, In)2O3 material has been attempted and reported, but, to the best of our knowledge, there has been no attempt to use this material as gas sensor. In our study, we present the synthesis of different (Ga, In)2O3 NWs and the study of the sensing properties of gas sensors based on individual nanowires of this material. Working with sensors based on individual NWs permits a much lower power consumption compared to their bulk counterpart, attainable by an adequate device layout, allows to match the limits required in mobile gas sensing applications and the detailed study of the sensing material.
(In1-xGax)2O3 metal oxide nanowires have been fabricated according to a vapor-liquid-solid (VLS) mechanism, via carbothermal reduction using a chemical vapor deposition (CVD) furnace. The NWs have been structurally and optically characterized using X-ray diffraction, scanning and transmission electron microscopy and related techniques as well as photoluminescence and Raman spectroscopy. Correlation between shape, crystallinity and optical properties of the formed nanostructures and their chemical composition will be shown and will be discussed and justified based on the known properties of the pure forming materials.
After the structural and optical properties of the (In1-xGax)2O3 NWs were analyzed, the gas sensing properties of these nanostructured materials have been tested. To achieve this goal, the NWs were removed from the substrates applying sonication, followed by the deposition on top of suspended microhotplates with prepatterned electrodes. Finally, individual nanowires were contacted by a Focused Electron-Beam Induced Deposition (FEBID) technique. The fabricated gas nanosensors have been tested towards relevant gases in air quality monitoring, like CO and NO2, water vapor as well as towards O2 and ethanol. The measurements have been carried out at different gas concentrations and operating temperatures. The results will be discussed and correlated with the morphological and chemical properties of the sensing material.
8:00 PM - NM03.09.15
Fabrication of Asymmetrically Functionalized Silica Nanotube for Smart Nanocarrier
Young Deok Seo 1 , Jyongsik Jang 1
1 , Seoul National University, Seoul Korea (the Republic of)
Show AbstractThe preparation of asymmetric building-blocks has expanded the ambitious applications of nano-objects because of their advantages over conventional isotropic particles. In the last three decades, anodic aluminum oxide (AAO) membranes have been used to prepare 1-D nanofibers or nanotubes. The preparation of bar-coded or bamboo-like nanofibers using stepwise filling of an AAO template has also been reported. In comparison, nanotubes containing different internal and external functional groups, which can be considered a different type of anisotropic nanotube, have attracted limited attention, despite involving a relatively simple process. Anisotropic nanotubes with different internal and external functional groups have many potential applications, such as for smart nanocarriers and Janus-type catalyst supporters. For example, nanotubular structures prepared with an outer hydrophilic wall and an inner hydrophobic wall, and using specific functional groups, acted as smart nanocarriers that can harvest specific molecules from water.
Silica nanotube containing spatially controlled functional group were prepared on a simple pathway and were used in a Heck coupling nanoreactor for the olefination of aryl iodides. The Heck reaction is a widely used organic reaction because of its simple methodology and stereoselectivity. Vinyltype olefin monomers, such as styrene and n-butyl acrylate, are useful, versatile precursors of industrial copolymers. However, these monomers usually self-polymerize when stored without inhibitors. Consequently, the Heck reaction of vinyl olefin monomers with aryl iodide might be a practical way to prevent self-polymerization. The Heck reaction with anisotropic nanocarriers has increased the dispersibility as a consequence of surface modification. Silica nanotubes with an anisotropic structure were fabricated using an AAO template via vapor phase synthesis (VPS) and the internal and external surfaces of the nanotubes were functionalized with hydrophilic and hydrophobic groups, respectively.
In this presentation, 200 nm-diameter silica nanotubes were fabricated by VPS using AAO as a hard template. The internal wall and the outer surface of the silica nanotubes were functionalized with different functionalities using selective polymer/ silane treatment. The F-PAA-silica nanotubes were further treated with Pd salt and hydrogen gas was injected to reduce the Pd salt inside the silica nanotubes. The silica nanotubes containing Pd nanoparticles were used as nanocarriers for the Heck reaction catalysis of olefination and a maximum efficiency of 99% and TON of 7.5 were calculated based on GC/MS and TGA. The fabrication of F-PAA-silica nanotubes and selective insertion of Pd nanoparticles may be expanded to the spatially controlled introduction of metal nanoparticles and their application as nanocatalysts. We propose that surface modified silica nanotubes can be used as homogeneous catalysts with enhanced dispersibility in diverse solvents.
Symposium Organizers
Juan Beltran-Huarac, Harvard T. H. Chan School of Public School
Wojciech Jadwisienczak, Ohio University
Alessandro Ponti, National Research Council
Bo Zou, Jilin University
Symposium Support
Ohio University—Nanoscale and Quantum Phenomena Institute (NQPI)
NM03.10: Devices and Applications
Session Chairs
Letian Dou
Hong Liu
Bo Zou
Wednesday AM, November 29, 2017
Hynes, Level 3, Room 310
8:00 AM - NM03.10.01
Nanowires of Metal Halide Perovskites for Optoelectronic Applications and Fundamental Photophysical Studies
Yongping Fu 1 , Haiming Zhu 2 , Jie Chen 1 , Xiaoyang Zhu 2 , Song Jin 1
1 , University of Wisconsin-Madison, Madison, Wisconsin, United States, 2 Department of Chemistry, Columbia University, New York, New York, United States
Show AbstractThe remarkable performance of lead halide perovskites in solar cells can be attributed to the long carrier lifetimes and low non-radiative recombination rates, the same physical properties that are ideal for semiconductor lasers and other optoelectronic applications. Here we first report new insights on the crystal growth of the perovskite materials and developed the solution growth of single crystal nanowires of methylammonium, formamidinium and all-inorganic cesium lead halides perovskites (APbX3) via a dissolution-recrystallization pathway. For perovskite compositions unstable at room temperature, an ionic exchange can enable the kinetic access to these phases or a new chemical strategy based on surface functionalization can stabilize the metastable perovskite phases. We show room temperature and wavelength tunable lasing from single-crystal APbX3 NWs with very low lasing thresholds, high quality factors, nearly unit lasing quantum yields, and broad tunability of emission color from 410 nm to 820 nm using different stoichiometry. Furthermore, we have also developed the vapor-phase epitaxially growth of high-quality crystalline inorganic perovskites with controllable morphologies and aligned growth directions in network structures, which are more convenient for photonic and optoelectronic device applications. These facile solution and vapor synthesis of single-crystal nanostructures of the diverse families of perovskite materials with different cations, anions, and dimensionality with different properties are convenient building blocks for proof-of-principle studies of device design and improvement and will enable many interesting optoelectronic applications with high performance.
8:15 AM - NM03.10.02
Brush-Like ZnO Nanorods for Enhanced Efficiency in Dye-Sensitised Solar Cells
Joe Briscoe 1 , Simona Pace 4 2 , Ilenia Tredici 2 , Alessandro Resmini 2 , Xuan Li 1 , Steve Dunn 1 3 , Umberto Anselmi-Tamburini 2
1 , Queen Mary University of London, London United Kingdom, 4 , Imperial College London, London United Kingdom, 2 , University of Pavia, Pavia Italy, 3 , Deregallera Ltd., Caerphilly United Kingdom
Show AbstractZinc oxide nanorods have been investigated as an alternative to mesoporous TiO2 for use in dye-sensitised solar cells (DSSCs) due to improved charge transport properties and a direct current pathway to the transparent electrode. However, due to the significantly lower surface area and subsequent reduction in dye loading, low current densities generally limit efficiency around or below 1 %.
Here we present a method for the growth of lamellae on the surface of ZnO nanorods to produce brush-like structures which allows higher dye adsorption, leading to increased efficiency. ZnO nanorods are grown by a low-temperature, solution-based method using additives to control growth giving aspect ratios up to 150. By coating ~ 15 μm long nanorods using an optimised precursor concentration for lamellae growth, a power conversion efficiency of over 2% is achieved for cells using N719 dye and iodide-based electrolyte, which is one of the highest efficiencies reported for ZnO nanorod-based DSSCs. A number of methods are used to maximise the device efficiency. For example, it is shown that by increasing the nanorod growth time, greater length and therefore surface area is achieved. In addition, the use of a hydrogel-derived seed layer is shown to lead to a higher density of thinner nanorods, further contributing to the high surface area and therefore efficiency. Correct choice of annealing conditions is also shown to be important to improve the crystallinity of the ZnO lamellae while retaining the high surface area of the structure.
Overall this study shows that a number of methods can be used to increase the surface area of ZnO nanorod arrays, including correct choice of seed layer, extended growth time, and the addition of appropriate surface structures. Combining these techniques through systematic optimisation has produced high-efficiency ZnO nanorod-based devices. Further efficiency improvements may be possible using these methods in order to fully capitalise on the benefits offered by the 1D nanorods, for example by further increasing the nanorod length or using dyes optimised for ZnO-based devices.
8:30 AM - NM03.10.03
High-Voltage Quintuple-Junction (and Higher) p-i-n Silicon Nanowires for Solar Energy and Optoelectronics
Taylor Teitsworth 1 , David Hill 1 , Seokhyoung Kim 1 , James Cahoon 1
1 Chemistry, University of North Carolina, Chapel Hill, North Carolina, United States
Show AbstractP-type/intrinsic/n-type (p-i-n) silicon nanowires are well-studied and promising materials for future solar energy optoelectronic devices. However, the photovoltage produced by a single junction is insufficient for some desired applications, such as solar fuels production. Multijunction devices can yield a higher photovoltage, but synthesis is difficult, especially at tunnel junctions where precise control of doping level and dopant transition width is required. Here, we present the vapor-liquid-solid (VLS) growth of repeating p-i-n junctions in a single nanowire with degenerately-doped segments, abrupt dopant transitions, and minimal radial overcoating. Electrical characterization of single-nanowire devices shows a nearly linear increase in voltage with each additional junction, allowing the first demonstration of quintuple junction, and higher, devices. Resistance of the tunnel junctions is low and negative differential resistance is observed at low temperatures. We expect that the output photovoltage is fully tunable and will continue to increase with increasing numbers of junctions in series, limited only by the physical length of the nanowire. The development of single nanowires encoded with arbitrary numbers of p-i-n junctions opens the door to new high-voltage devices for solar fuels and optoelectronics.
8:45 AM - NM03.10.04
Vertical Nanowire Based Single Electron Transistor Self-Assembled by Ion Beam Mixing and Phase Separation
Karl-Heinz Heinig 1 , J. von Borany 1 , Gregor Hlawacek 1 , R. Huebner 1 , Daniel Wolf 1 , Hans-Juergen Engelmann 1 , Lothar Bischoff 1 , X. Xu 1 , Thomas Pruefer 1 , W. Moeller 1 , Stefan Facsko 1
1 , Helmholtz-Zentrum Dresden-Rossendorf, Dresden Germany
Show AbstractElectronics has been dominated by silicon since half a century. Si will dominate electronics another decade, however its functionality might change from classical field-controlled currents through channels (the Field Effect Transistor FET) to quantum mechanical effects like field-controlled hopping of single electrons to a quantum dot (Single Electron Transistor SET). The SET is the champion of low-power consumption. This is attractive for the Internet of Things: more and more devices need batteries and plugs. Together with improved batteries, advanced computation must be delivered at extremely low-power consumption. At low temperatures, the functionality of SETs has been proven. Large-scale use of SETs requires room temperature operation, which can be achieved with tiny Si dots (<4 nm) in SiO2, exactly located between source and drain with distances of ~1…2 nm. Manufacturability of such nanostructures is the roadblock for large-scale use of SETs. Lithography cannot deliver such feature sizes. Therefore, there are currently intense studies to fulfill these requirements by self-organization processes.
The ion beam technique is a well-established technology in microelectronics used for doping and amorphization, and even for ion beam mixing [1]. The parameters of ion beam processing are very well controllable. We searched for a self-organization process in a vertical silicon nanowire with an embedded, very thin (~6nm) SiO2 layer. Ion beam mixing transforms this layer to metastable SiOx. If the nanowire is thin enough, a subsequent thermal treatment leads by phase separation to a single Si nanodot (~3nm) self-aligned to the lower and upper Si at distances of <2nm.
Here, we present 3D computer simulations on ion beam mixing (TRI3DYN code [2]) and Si nanodot formation (3D kinetic Monte Carlo code [3]). Such simulations predicted successfully the fabrication of non-volatile memories using ion beam mixing [4].
Experimentally, single Si nanodot formation has been proven by local mixing in a c-Si/SiO2/a-Si layer stack. The nanoscale mixing has been performed with a Helium Ion Microscope using an Argon beam of ~2nm diameter. After Rapid Thermal Annealing, the self-organized single Si nanodot has been imaged by cross-section energy-filtered transmission electron microscopy EFTEM.
In a vertical nanowire the very small volume of mixed SiO2 is not due to nanoscale ion beams but due to the small diameter of the wire. It will be shown, how a vertical nanowire gate-all-around SETs operating at room temperature can be CMOS-compatibly fabricated by this method.
This work has been funded by the European Union’s Horizon 2020 research and innovation program under grant agreement No 688072.
[1] K.H. Heinig, T. Müller, B. Schmidt, M. Strobel, W. Möller, Appl. Phys. A77 (2003) 17.
[2] W. Möller, NIM B322 (2014) 23.
[3] M. Strobel, K.-H. Heinig, W. Möller, Phys. Rev. B64 (2001) 245422.
[4] T. Mueller et al., Appl .Phys. Lett. 81 (2002) 3049; ibid 85 (2004) 2373.
9:00 AM - *NM03.10.05
Recent Development of 1D Inorganic Halide Perovskite Nanostructures
Peidong Yang 1 2 , Minliang Lai 1 , Letian Dou 1 2
1 Department of Chemistry, University of California, Berkeley, Berkeley, California, United States, 2 Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractSemiconductor nanowires (NWs) are considered as a good perform for studying their interesting physical properties and potential building blocks for various applications in electronics, optoelectronics, and energy harvesting. Recently, there is a renaissance of halide perovskites as a promising class of semiconductor materials for a variety of photovoltaics and optoelectronics. Particularly, the inorganic halide perovskites attracted more and more attention, owing to their enhanced stability toward moisture, oxygen, and heat, compared to the organic-inorganic hybrid perovskites (e.g. methylammonium lead iodide). This talk will focus on the new strategies to synthesize 1D inorganic halide perovskite NWs and utilizing them as a unique system to study anion exchange and phase transition dynamics.
We develop the advanced synthetic methodology of CsPbX3 nanowires with desired size, composition, and properties, including colloidal, solution-phase and vapor-phase approaches. Colloidal NWs exhibit well-controlled morphology and efficient photoluminescence, with tunable diameter range from 10 to 2 nm. Sub-micrometer single-crystal NWs from solution-phase growth were demonstrated as an efficient optical medium for high-performance and robust laser application. Vapor-phase NWs generally have improved crystalline quality and lower defect density. Due to the relatively weak bonding in halide perovskites, anion exchange was demonstrated in these 1D materials with high PLQY throughout the exchange reaction. Therefore, solid-solid anion exchange dynamics can be resolved in CsPbBr3-CsPbCl3 heterojunction nanowires through a non-destructive optical method. The rich phase transformation in inorganic perovskites enables kinetics study in 1D systems. Overall, inorganic halide NWs offer unique opportunities for exploring fundamental research and enable nanoscale optoelectronic devices.
10:15 AM - NM03.10.07
High Temperature Limit of Semiconductor Nanowire Lasers
Maximilian Zapf 1 , Carsten Ronning 1 , Robert Roeder 1
1 Institute of Solid State Physics, Friedrich Schiller University Jena, Jena Germany
Show AbstractSemiconductor nanowires (NWs) are promising nanoscale building blocks in visionary concepts of integrated photonic circuit devices. A broad variety of possible applications emerge for semiconductor NWs, as they inherently provide a combination of the semiconductor material properties and the beneficial NW morphology. Indeed, NW-based coherent light sources are key components for applications in photonic chips, nanospectroscopy, or nanosensing. In the past years research focused on fundamental mechanisms such as temporal dynamics[1] and emission characteristics[2]; now practical device applications such as on-chip nanolaser driven applications working in different temperature ranges up to values far beyond room temperature are becoming the focus of current research. The optical output intensity of individual semiconductor NW laser devices follows the characteristic pump power dependency of a multimode laser system upon moderate optical pumping[3]. Thus, different emission regimes are observed for increasing the pump power gradually, namely the regime of spontaneous emission, amplified spontaneous emission (ASE), and lasing. However, for extremely high pump powers an additional regime of vanishing laser oscillations is observed due to active material degradation. Yet, experiments and future applications require a degradation-free lasing operation in order to retain reliable and durable devices. Thus, we developed a method[4] for identifying the threshold value of any degradation process and its underlying physics. Therefore, the three threshold values for ASE, lasing, and degradation are thoroughly evaluated as a function of operating temperature. This enables the determination of an upper temperature limit for stable CdS NW lasing, at which the degradation threshold drops below the lasing threshold. Furthermore, the degradation mechanism of the CdS nanolasers will be proposed.
[1] Röder et al., Nano letters 15, 4637 (2015)
[2] Röder et al., Nano letters 16, 2878 (2016)
[3] Geburt et al., Nanotechnology 23, 365204 (2012)
[4] Zapf et al., Appl. Phys. Lett. 110, 173103 (2017)
10:30 AM - NM03.10.08
Toward Flexible Actuator Films by Super-Aligned VO2 Nanobelts
Pengcheng Chen 1 , Dejun Kong 1 , Run Shi 1 , Yanjing Wang 1 , Liang Zhang 1 , Chun Cheng 1
1 Materials Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, China
Show AbstractRecently, vanadium dioxide (VO2) has attracted intensive attention due to its specific metal-insulator transition (MIT) and the company suddenly changes on its valume and physical properties. As reported, microsized bimorph actuators based on pulsed laser deposition (PLD) grown VO2 films have been demonstrated a output work density of 0.63 J/cm3[1], which is far below the theoretically expectation of 7 J/cm3[2]. The divergence between experiments and theoretical prediction results from the disordered polycrystal structures of the VO2 films by PLD [3]. In additional, PLD methods are time and money consuming and only offer mimimeter sized sample and thus cannot afford the practice applications.
To break these limitations, we propose to fabricate flexible and high performace actuator films using aligned VO2 nanowire films, which can be fabricated by scale up method in large scale. Firstly, we prepared the high aspect ratio（several hundreds） vanadium oxide nanowire by hydrothermal method in a large yield. Then we assemble the nanowire horizontally by an enhanced water-oil-air interfacial self-assembly method. After that, we conducted an annealing process to reduce the vanadium oxide into monoclinic VO2. Through this strategy, we can achieve large area super-aligned VO2 nanowire thin film (several square centimeters) without any complicate operations and expensive facilities compare to Langmuir-Blodgett method (LB method). Finally, macro-sized bimorphs actuator films based on the super-aligned VO2 nanobelts film are fabricated and demonstrated excellent performance. Overall, we have fabricated a super-aligned VO2 nanowire thin film, and several high performance devices through this method, which could be generalized to other nanobelt or nanowire based device’s fabrication.
Reference:
[1] Liu, K., Cheng, C., Cheng, Z., Wang, K., Ramesh, R., & Wu, J. (2013). Giant-amplitude, high-work density microactuators with phase transition activated nanolayer bimorphs. Nano Letters, 12(12), 6302-6308.
[2] Wang, K., Cheng, C., Cardona, E., Guan, J., Liu, K., & Wu, J. (2013). Performance limits of microactuation with vanadium dioxide as a solid engine. Acs Nano, 7(3), 2266.
[3] Wang, T., Torres, D., Fernández, F. E., Green, A. J., Wang, C., & Sepúlveda, N. (2015). Increasing efficiency, speed, and responsivity of vanadium dioxide based photothermally driven actuators using single-wall carbon nanotube thin-films. Acs Nano, 9(4), 4371.
10:45 AM - NM03.10.09
Silicon Nanowire Electron Ratchets as High-Frequency Morphological Diodes
James Custer 1 , David Hill 1 , Joseph Christesen 1 , Helen Hansel 1 , Collin Mckinney 1 , James Cahoon 1
1 , University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
Show AbstractMorphological diodes operate by breaking the symmetry of a material on a length scale comparable to the electron mean free path. The asymmetry causes the scattering of charge carriers to depend on the direction of charge transport, allowing them to flow more easily in the forward direction than the reverse direction simply based on the shape of the nanostructure. Thus, this structure is able to ratchet electrons, an effect that is manifested by the generation of a DC voltage when the structure is subjected to an AC signal with a time-averaged voltage of zero. The theoretical RC time of morphological diodes is much lower than traditional diodes, which gives them potential applications in high-speed wireless data transfer and long-wavelength energy harvesting. In this work, morphological diodes have been created from precisely etched silicon nanowires. The wires are grown and encoded with dopants using the vapor-liquid-solid mechanism. Following the growth, a dopant-selective wet-chemical etch is used to create the desired “sawtooth” nanostructure. These sawtooth structures act as morphological diodes, which produce asymmetric, diode-like current-voltage (I-V) curves. The asymmetry of the curves can be similar to a traditional diode, and the device performance and I-V characteristics can be intelligently tuned using the wire’s geometry and surface. Rectification of an AC signal has been measured up to 1 GHz; however, the diodes have a theoretical frequency response into the terahertz regime. These ratcheting nanostructures could be used as a new platform to harvest energy from microwave and infrared radiation.
NM03.11: Health Effects of 1D Nanomaterials I
Session Chairs
Wednesday PM, November 29, 2017
Hynes, Level 3, Room 310
11:00 AM - *NM03.11.01
Flame Nanomaterial and Device Engineering for Biomedicine
Georgios Sotiriou 1
1 , Karolinska Inst, Solna Sweden
Show AbstractNanoscale materials show great potential in the biomedical field as they can serve as superior bioimaging contrast agents, diagnostic and therapeutic tools. A key element for the successful implementation of nanoscale materials in clinical applications is multi-functionality. However, the two main bottlenecks for the successful commercialization of such nanotechnologies, that are often neglected in studies, are scalability and reproducibility. Here, I will showcase a few recent examples of how flame nanoparticle synthesis, a highly scalable and reproducible nanomanufacture process, may be employed for the production of sophisticated nanoscale materials to tackle specific medical problems. A specific focus will be placed on the control of the shape and aspect ratio of flame-made nanostructures from spherical nanoaggregates to nanorods and how their surface properties may be tuned for increased biocompatibility and superior performance. Finally, the direct deposition of freshly-formed flame-made nanoparticles on selected substrates will be described towards the rapid fabrication of reliable devices such as magnetic actuators and biosensors.
Related references
[1] G. A. Sotiriou, WIREs Nanomed. Nanobiotechnol. 5, 19-30 (2013).
[2] G. A. Sotiriou, A. M. Hirt, P. Y. Lozach, A. Teleki, F. Krumeich, S. E. Pratsinis, Chem. Mater. 23, 1985-1992 (2011).
[3] G. A. Sotiriou, T. Sannomiya, A. Teleki, F. Krumeich, J. Vörös, S. E. Pratsinis, Adv. Funct. Mater. 20, 4250-4257 (2010).
[4] G. A. Sotiriou, F. Starsich, A. Dasargyri, M. C. Wurnig, F. Krumeich, A. Boss, J.-C. Leroux, S. E. Pratsinis, Adv. Funct. Mater. 24, 2818-2827 (2014).
[5] G. A. Sotiriou, C. Watson, K. M. Murdaugh, T. H. Darrah, G. Pyrgiotakis, A. Elder, J. D. Brain, P. Demokritou, Environ. Sci.: Nano 1, 144-153 (2014).
[6] A. Teleki, F. L. Haufe, A. M. Hirt, S. E. Pratsinis, G. A. Sotiriou, RSC Adv. 6, 21503-21510 (2016).
11:30 AM - *NM03.11.02
Oxidative Stress and Inflammation Induced by Nanomaterials—Discriminating between Defensive Reactions and Health Risk
Diana Boraschi 1
1 Institute of Protein Biochemistry, National Research Council (CNR), Napoli Italy
Show AbstractThe increasing exposure to engineered nanomaterials (ENM) generates concerns on their possible toxicity.
One of the potential cause of toxicity is the redox interaction of ENM with living entities, well studied for carbon nanotubes (CNT). At the single cell level ENM induce oxidative stress in a three-tiered hierarchical sequence, in which the decreased regulation of reactive oxygen species (ROS) directly correlates with cell damage/necrosis. This sequence however does not apply to toxicity for complex systems (tissues, organs, organisms). We propose here a three-pronged model to describe the inflammatory response of complex living systems to ENM, in which the response is either inconsequential (ignorance, tolerance, silent elimination), or it develops as a classical defensive inflammatory response (elimination of the danger and re-establishment of homeostasis), or it becomes a persistent inflammatory reaction. The latter may be the case of persistent materials (e.g., fiber-like particles), and is the only situation that can be eventually harmful to the organism.
Inflammation is a very important defensive mechanism that eliminates potentially dangerous agents (including ENM), although with some collateral damage, i.e. the death of some cells. At the single cell level inflammation can resolve without cell death or end with cell death, but at the organ level both events can be included in an inflammatory reaction that succeeds in eliminating the danger at the cost of some cell death and some tissue damage.
High aspect ratio ENM (rigid fiber-like or needle-like materials) are particularly challenging for leukocytes (immune defensive cells) and can lead to persistent leukocyte inflammatory activation, including ROS production. This can evolve into ROS-induced lipid peroxidation, destabilization of the cell membrane and genotoxic DNA damage. Cell death can also be mechanically induced by the rigid needle-like ENM that literally punch holes in the cell membranes and induce necrotic cell death, an event that perpetuates the inflammatory reaction leading to tissue damage or to fibrotic or granulomatous reactions. Leukocytes can successfully degrade some high aspect ratio EMN, as in the case of multi-walled CNT, which can be successfully degraded by several leukocytic enzymes.
Central to ENM-induced inflammation is the capacity of activating the NLRP3 inflammasome, a cytoplasmic complex responsible of the production of the inflammatory cytokine IL-1 beta. Crystals and high aspect ratio ENM can activate the NLRP3 inflammasome by mechanisms that include ROS generation and destabilization of phagolysosomal membranes. It must be however kept in mind that inflammasome activation is not per se a sign of toxicity or pathological inflammation, but only sign of an ongoing defensive reaction.
In order to discriminating between protective and pre-pathological inflammation induced by ENM, a deeper kinetic analysis is required.
Work supported by H2020 grant 671881 PANDORA
NM03.12: Health Effects of 1D Nanomaterials II
Session Chairs
Juan Beltran-Huarac
Alessandro Ponti
Wednesday PM, November 29, 2017
Hynes, Level 3, Room 310
1:30 PM - *NM03.12.01
Physico-Chemical Properties of Carbon Nanotubes Driving Molecular Initiating Events (MIEs) of Adverse Outcome Pathways (AOPs)
Ivana Fenoglio 1 , Arianna Marucco 1 , Ida Kokalari 1
1 Department of Chemistry, University of Torino, Torino Italy
Show AbstractCarbon nanotubes (CNTs) are among the most promising products of nanotechnologies. They are candidates for a wide range of applications such as alternative forms of energy production, energy storage, innovative materials in aerospace and automotive. The presence of CNTs in several products has increased in the last decades, and with it the probability of exposure of workers and consumers. A large number of studies suggest that CNTs might drive severe adverse health effects. On the other hand, CNTs have been used or proposed in medicine e.g. as carriers for drugs or as scaffolds for tissues regeneration. This apparent paradox is explained by the fact that CNTs are not a single substance, but a growing family of very different materials possibly eliciting different biological responses. As a consequence, also the hazard associated with the exposure of humans to the different forms of CNTs may be different.
The knowledge of the physico-chemical properties associated to the molecular initiating events (MIE) of the different adverse outcomes is a pre-requisite for the assessment of the toxicological profile of CNTs. This knowledge also opens the way to the definition of Structure Activity Relationships (SARs), that in turn acts as substrate for a safe-by design approach.
Several studies addressed the applicability of the fiber paradigm to this class of nanomaterials. However, other physico-chemical properties appear to modulate the interaction of CNTs with cells, such as contaminants, defects and surface reactivity. I this contribute we present an overview of the state-of-the-art in the field focusing in particular on the role of the interface processes occurring between CNTs and other elemental carbon nanomaterials in the biological environment.
2:00 PM - *NM03.12.02
Human Health Risks of 1D Nanomaterials and Innovation Risk Management by Control Banding
Keld Alstrup Jensen 1
1 , National Research Centre for the Working Environment, Copenhagen Denmark
Show AbstractWhile 1D nanomaterials (NM) are of great technological interest, they also often possess physicochemical characteristics; such as nanosize dimensions, high aspect ratios, high specific surface areas, and slow dissolution rates; which can classify them as materials of inhalation toxicological concern. Whereas 5 µm is the accepted lower length limit for a mineral or man-made fibre of concern in a regulatory context, this concept is challenged by results from a decade of NM toxicological research. Moreover, chemical surface functionalization may alter the potential hazard of 1D materials in both positive and negative direction and the role of chemical functionalization is yet not fully understood.
The potential risk of 1D NM is naturally strongly dependent on the nature and likelihood of the potential exposure. Workplace studies have shown already from early nanosafety studies that 1D NM may be released to the air in different work-operations. Normally, the greatest risk of inhalation exposure is observed during preparation of synthesis equipment, sample harvesting and dry powder handling processes. Aerosolization of fibres to room air has also been reported as a result of probe-sonication of hydrous dispersions. Therefore, there is amble evidence that researchers and technical staff may risk exposure during syntheses, recovery and handling of 1D NM.
It is critical that proper risk identification and management is ensured during innovation and upscaling of new 1D NM productions and downstream industrial application. Control Banding tools offer such an approach and may be used in the lack of proper measurements with or without support from additional analysis of material dustiness. In this paper, the general hazard properties and exposure characteristics are reviewed and specific 1D NM will be analyzed to demonstrate recommended risk management levels using the NanoSafer Risk Assessment and Management web-tool platform (www.nanosafer.org).
NM03.13: Characterization
Session Chairs
Wednesday PM, November 29, 2017
Hynes, Level 3, Room 310
3:30 PM - NM03.13.01
Band Alignment and Thermalization Dynamics of Photoexcited Single GaAs0.7Sb0.3 and GaAs0.7Sb0.3/InP Nanowires
Iraj Shojaei 1 , Samuel Linser 1 , Giriraj Jnawali 1 , Howard Jackson 1 , Leigh Smith 1 , Xiaoming Yuan 2 , Philippe Caroff 2 , Hoe Tan 2 , Chennupati Jagadish 2
1 Department of Physics, University of Cincinnati, Cincinnati, Ohio, United States, 2 Department of Electronic and Materials Engineering, The Australian National University, Canberra, Australian Capital Territory, Australia
Show AbstractUltrafast time-resolved pump-probe measurements at 10K obtained from single zinc-blende GaAs0.7Sb0.3 core-only and GaAs0.7Sb0.3-InP core-shell nanowires exhibit a 5ps lifetime for core-only nanowires and a remarkable longer lifetime (~1800ps) for core-shell nanowires. At 300K similar measurements exhibit the same 5 ps lifetime for core-only nanowires but only a factor of ten longer lifetime (~55ps) for the core-shell nanowires. These results suggest that band alignment of the core-shell nanowire may be Type II with less than a 30 meV band off-set. Carrier density and thermalization dynamics which emerge from fitting wavelength-dependent lineshapes from pump-probe measurements using Transient Rayleigh scattering (TRS) theory provide supporting evidence for the Type II band alignment for the core-shell nanowires. The carrier density of core-only nanowires drops to 40% of the initial value in 20ps compared to nearly 2 ns for core-shell nanowires. Our fitting results reveal an equal initial carrier temperature of 400K for both core-only and core-shell nanowires, but substantially different thermalization dynamics for the two structures. For instance, the carrier temperature in core-only nanowires decreases from 400 K to 200K in 20ps while for core-shell nanowires the carrier temperature decreases to 150K in 2ns. We model the energy loss mechanisms of carriers based on the phonon scattering with longitudinal optical and acoustic phonon emission.
We acknowledge the financial support of the NSF through grants DMR 1507844, DMR 1531373 and ECCS 1509706, and the Australian Research Council.
3:45 PM - NM03.13.02
Advanced Functionalization of Carbon Surfaces
Antonio Setaro 1
1 , Freie Universität Berlin, Berlin Germany
Show AbstractA. Setaro, M. Gläske, M. Adeli, R. Haag, and S. Reich
Technological applications of single walled carbon nanotubes are thwarted by the big functionalization dilemma: Either one works in the noncovalent approach, which preserves the quantum optoelectronic features of the tubes but is intrinsically weak and can easily disassemble, or one covalently attaches the desired functionality, ensuring strong and stable attachment but disrupting the emission and transport quantum features of the tubes.
Here we show how to overcome these limitations, introducing a new covalent functionalization that even improves the optoelectronic features of the tubes. The flaw of standard covalent methods is the conversion of a fraction of the sp2 carbon atoms into sp3 ones, disrupting the extended pi-network. On the contrary, our method preserves and even regenerates the pi-conjugation: We show emission from covalently functionalized tubes, even at high degrees of functionalization, safeguarding the quantum features of the tubes [1]. This breaks the dogma that covalent functionalization disrupts the quantum features of carbon nanotubes.
Moreover, by simple chemical substitution, we can add virtually any functionality onto the tubes. This gives an unprecedented degree of sophistication to the functionalization, fully integrating the added groups within the nanotubes structure and not only relying on weak non-covalent interactions. As an example, we show the result of incorporation of molecular switches and nanoplasmonic particles into a novel class of hybrids [1].
[1] A. Setaro, M. Adeli, M. Glaeske, D. Przyrembel, T. Bisswanger, G. Gordeev, F. Maschietto, A. Faghani, B. Paulus, M. Weinelt, R. Arenal, R. Haag, and S. Reich, Preserving π-conjugation in covalently functionalized carbon nanotubes for optoelectronic applications, Nature Communications 8, 14281 (2017).
4:15 PM - NM03.13.04
Advanced Synthesis and High Resolution Transmission Electron Microscopy Characterization of Nanomaterials Confined Inside Nanotubes
Thang Pham 1 , Zhenglu Li 1 , Wu Shi 1 , Patrick Stetz 1 , Seita Onishi 1 , Steven Louie 1 , Christian Kisielowski 2 , Alex Zettl 1
1 , University of California, Berkeley, Berkeley, California, United States, 2 , Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractNovel properties may arise when lowering the dimensionality of materials because of the quantum confinement effect and the reducing of neighbor atoms. In this talk I will present different approaches to grow nanomaterials (metal, metal oxides, chalcogens and metal chalcogenides) inside boron nitride and carbon nanotubes (NTs). The spatial confinement of NT’s cavity promotes and stabilizes the formation of nanostructures with new phases and geometries. The encapsulation of nanotube walls protects the core materials from the chemical oxidation with the environment, which has been shown to have detrimental effects on the structure integrity and physical properties of the nanomaterials. The encapsulated materials are very mobile and they rotate, twist and shuttle inside nanotube channels. The nanomaterials filled nanotube system resembles the nanoscaled test-tube, which enables various in-situ studies of nanomaterials growth and interactions.
4:30 PM - NM03.13.05
Dopant Distribution Analysis Core-Shell Nanowires by Atom Probe Tomography
Yasuo Shimizu 1 , Bin Han 1 , Wipakorn Jevasuwan 2 , Kotaro Nishibe 2 , Yuan Tu 1 , Koji Inoue 1 , Naoki Fukata 2 , Yasuyoshi Nagai 1
1 , The Oarai Center, Institute for Materials Research, Tohoku University, Ibaraki Japan, 2 , International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba Japan
Show AbstractSemiconductor nanowires (NWs) have been extensively studied due to their substantial potentials as one-dimensional electronic devices [1]. Core-shell NWs, a combination of Ge and Si, have attracted considerable attention due to the band offset between Ge and Si. In Ge/Si and Si/Ge core–shell NWs, the dopant atoms can be selectively introduced into either the core or shell region [2]. The elemental distribution affects the electronic property of individual core-shell NWs, thus it is required to reveal the distributions of doped and host atoms. In this meeting, we report on atom probe tomography (APT) study of p-type B dopant atom distribution in core-shell NWs using Ge and Si as host atoms.
All NWs were grown on a Si(111) substrate. Nanocolloidal Au particles 3 nm in diameter were used as the catalyst for Ge or Si core-NW growth. For the Ge/Si core–shell NWs [Sample 1], the Ge core was grown at 320 °C for 30 min using 10 sccm of GeH4 source gas followed by the introduction of an additional 10 sccm of GeH4 at 500 °C for 1 min to increase the diameter of the Ge core region. A B-doped Si shell was grown at 700 °C for 1 min using 19 sccm of SiH4 and 1 sccm of B2H6 (1%) as source gases. Two kinds of Si/Ge core–shell NWs were prepared. For the first, a B-doped Si core was grown by introducing 19 sccm of SiH4 (100%) and 1 sccm of B2H6 (1%) at 700 °C for 2 min. Then, 10 sccm of GeH4 was introduced at 500 °C for 2 min to form the Ge shell [Sample 2]. For another kind of Si/Ge core–shell NWs [Sample 3], the B2H6 (1%) flux, growth temperature, and time were changed to 0.2 sccm, 600 °C, and 30 min, respectively for the growth of B-doped Si core. For applying the individual NW to APT analysis, the NWs were transferred from a Si substrate to a TEM mesh and were picked up by FIB combined with SEM (Helios NanoLab600i, FEI), enabling us to select desired NWs. APT analysis was performed using a laser-assisted atom probe (LEAP4000X HR, Cameca Instruments, Inc.).
Our APT reveals that B atoms were precisely doped into the Si regions of Ge/Si [Sample 1] and Si/Ge core–shell [Samples 2 & 3] NWs, and did not diffuse into the Ge regions. In Sample 1, the B atoms were randomly distributed along both the radial direction and the growth axis in the Si shell. In the Si/Ge core–shell NWs, the B distributions were controlled by the growth temperature and B2H6 flux. The B atoms piled up in the outer region of the Si core and the B concentration gradually increased from the top to the bottom of the NW along the growth axis when the growth temperature and B2H6 flux were higher. However, the B atoms were randomly distributed and the B concentration remained constant along the growth axis when the growth temperature and B2H6 flux were decreased [3].
This work was supported in part by JSPS KAKENHI Grant No. 15H05413.
[1] C. M. Lieber, MRS Bull. 36, 1052 (2011).
[2] N. Fukata et al., ACS Nano 6, 8887 (2012).
[3] B. Han et al., Nanoscale 8, 19811 (2016).
4:45 PM - NM03.13.06
Mapping the Built-In Potential at InGaP/InP Nanowire Tunnel Diodes
Ibeth Cordoba 1 , Xulu Zeng 2 , Daniel Wolf 3 , Axel Lubk 3 , Magnus Borgstrom 2 , Karen Kavanagh 1
1 , Simon Fraser University, Burnaby, British Columbia, Canada, 2 , University of Lund, Lund Sweden, 3 , IFW-Dresden, Dresden Germany
Show AbstractWe present a comparison of the structure and built-in potential of (p+)InGaP/(n+)InP nanowire (NW) tunnel diodes, as a function of the growth order of the junction. The NW heterostructures were grown via vapour-liquid-solid (VLS) Au catalysis, using metal-organic vapour phase epitaxy (MOVPE). The n-type InP was doped using S or Sn-based precursors (H2S, TESn) while the p-type InGaP with diethyl-Zn. The Ga, and dopant gas flows were switched at the same instance during growth. Excellent tunnel diode current-voltage (I-V) characteristics were obtained via externally-deposited lithographic contacts, when the structure was InGaP/InP/Au,[1] while back to back diode characteristics were observed for the reverse order structure, InP/InGaP/Au. Zn-doping of InGaP results in a high density of twinning faults, which likely degrade the transport, but were similar in density for both diodes. The change in composition and dopant type caused a 20% decrease in diameter of the InGaP compared to the InP NW sections, likely due to the Au alloy equilibrium shape. To better understand the reasons for the differences in electrical properties, we carried out imaging of the junction potential gradients via electron holographic tomography (EHT). In spite of strong dynamical scattering effects due to the twinning faults, 3D reconstructions of the morphologies and the potential gradients were obtained. EHT measured a p−n depletion width of 25 nm in the working diode while this width extended to over 100 nm in the non-working diode, explaining the lack of tunneling. EHT also revealed a smaller potential step in the InP/GaInP/Au NW of 0.3 V after thickness and mean inner potential (MIP) normalization, in contrast to 1.0 V in the GaInP/InP/Au NW. In this work we will present further investigations into the effects of charging induced by the electron beam on the NW when the p or n part is contacting the amorphous carbon support, which could overshadow the built-in potential at the p-n junction. [1] Gaute Otnes, Magnus Heurlin, Xulu Zeng, and Magnus T. Borgstrom, Nano Letters 2017, 17, 702−707. Acknowldegements: Canadian NSERC. CFI, and 4DLabs, Swedish Research Council, and the European Research Council under the European Union's Horizon 2020 Research and Innovation Programmes.
NM03.14: Poster Session III: Energy, Devices and Applications, Health Effects and Characterization
Session Chairs
Thursday AM, November 30, 2017
Hynes, Level 1, Hall B
8:00 PM - NM03.14.01
Design of Block Co-Polymers for Sub-10 nm Directed Self-Assembly Lithography
Natsuko Ito 1 2 , Gregory Blacut 3 , Austin Lane 3 , Yusuke Asano 1 2 , Yasunobu Someya 3 7 , Xiao Min Yang 4 , Stephen Sirard 5 , Christopher Ellison 6 , C. Grant Willson 1 3
1 Chemistry, The University of Texas at Austin, Austin, Texas, United States, 2 , JSR Corp., Minato-ku, Tokyo, Japan, 3 Chemical Engineering, The University of Texas at Austin, Austin, Texas, United States, 7 , Nissan Chemical Industries, ltd., Chiyoda-ku, Tokyo, Japan, 4 , Seagate Corp., Fremont, California, United States, 5 , Lam Research Inc., Fremont, California, United States, 6 Chemical Engineering and Materials Science, The University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractDirected self-assembly (DSA) of block co-polymers (BCPs) is a next-generation lithography technique that shows promise for extending Moore’s Law into the 10 nm regime and below. The minimum size of the features that can be produced by BCPs is controlled by the interaction parameter (χ) and the degree of polymerization (N). We have developed silicon containing BCPs for sub-20 nm line-and-space lithography. These BCPs were synthesized by living anionic polymerization, thermally annealed in thin films between neutral layers to generate the requisite perpendicular orientation [1, 2]. The silicon-containing blocks provide excellent development contrast under both oxidizing and reducing reactive ion etching (RIE) conditions. The developed patterns work well as masks for transfer of the developed patterns into useful substrate materials [3]. Through optimizing the design of the block copolymers and the “hybrid” DSA process [1], we have now obtained 10 nm full pitch gratings.
Recently we have studied silicon containing BCPs that incorporate a poly(2-vinylpyridine) block as a path to achieving still higher χ. For example, we have synthesized poly(4-pentamethyldisilylstyrene-block-2-vinylpyridine) (PDSS-b-P2VP) and found that this material has a χ parameter that is significantly higher than that of the BCP used for 10 nm lithography, meaning that even smaller feature sizes should be possible. Neutral top coats and cross-linked surface treatment layers were identified for PDSS-b-P2VP using the island and hole techniques that have been described previously [5]. While the materials and the processes are not yet fully optimized, we have succeeded in demonstrating 8 nm full pitch finger print patterns that are oriented perpendicular to the substrate. These are the smallest patterns we have managed to document in our system to date.
1. Blachut, G., et al. Chem. Mater (2016), 28(24), 8951-8961.
2. Bates C. M., et al. Science (2012), 338(6108), 775.
3. Azarnouchea, L., et al. J. Vac. Sci. Technol. B (2016) 34 (6), 061602/1-061602/10.
4. Lane A. P., et al. “Directed Self-Assembly and Pattern Transfer of 5 nm Block Copolymer Lamellae,” in review by ASC Nano (2017)
5. Maher, M. J., et al. Chemistry of Materials (2014), 26(3), 1471-1479.
8:00 PM - NM03.14.02
One-Dimensional Nanomaterials for Energy Storage
Liqiang Mai 1
1 , Wuhan University of Technology, Wuhan China
Show AbstractOne-dimensional nanomaterials can offer large surface area, facile strain relaxation upon cycling and efficient electron transport pathway to achieve high electrochemical performance. Hence, nanowires have attracted increasing interest in energy related fields. We designed the single nanowire electrochemical device for in situ probing the direct relationship between electrical transport, structure, and electrochemical properties of the single nanowire electrode to understand intrinsic reason of capacity fading. The results show that during the electrochemical reaction, conductivity of the nanowire electrode decreased, which limits the cycle life of the devices.1 We have fabricated hierarchical MnMoO4/CoMoO4 heterostructured nanowires by combining "oriented attachment" and "self-assembly".2 The asymmetric supercapacitors based on the hierarchical heterostructured nanowires show a high specific capacitance and good reversibility with a cycling efficiency of 98% after 1,000 cycles. Then, we designed the general synthesis of complex nanotubes by gradient electrospinning, including Li3V2(PO4)3, Na0.7Fe0.7Mn0.3O2 and Co3O4 mesoporous nanotubes, which exhibit ultrastable electrochemical performance when used in lithium-ion batteries, sodium-ion batteries and supercapacitors, respectively.3 In addition, we have successfully fabricated a field-tuned hydrogen evolution reaction (HER) device with an individual MoS2 nanosheet to explore the impact of field effect on catalysis.4 We also constructed a new-type carbon coated K0.7Fe0.5Mn0.5O2 interconnected nanowires through a simply electrospinning method. The interconnected nanowires exhibit a discharge capacity of 101 mAh g-1 after 60 cycles, when measured as a cathode for K-ion batteries.5 Our work presented here can inspire new thought in constructing novel one-dimensional structures and accelerate the development of energy storage applications.
Reference
[1] L. Q. Mai, Y. J. Dong, L. Xu, C. H. Han. Nano Lett. 2010, 10, 4273;
[2] L. Q. Mai, F. Yang, Y. L. Zhao, X. Xu, L. Xu, Y. Z. Lou. Nature Commun. 2011, 2, 381;
[3] C. J. Niu, J. S. Meng, X. P. Wang, C. H. Han, M. Y. Yan, K. N. Zhao, X. M. Xu, W. H. Ren, Y. L. Zhao, L. Xu, Q. J. Zhang, D. Y. Zhao, L. Q. Mai. Nature Commun. 2015, 6, 7402;
[4] J. H. Wang, M. Y. Yan, K. N. Zhao, X. B. Liao, P. Y. Wang, X. L. Pan, W. Yang, L. Q. Mai. Adv. Mater. 2017, DOI: 10.1002/adma.201604464;
[5] X. P. Wang, X. M. Xu, C. J. Niu, J. S. Meng, M. Huang, X. Liu, Z. A. Liu, L. Q. Mai. Nano Lett. 2017, 17, 544.
8:00 PM - NM03.14.03
Surface Treatments for CMOS Compatible InAs Nanowires on Si(111) by MBE
Daya Dhungana 1 , Nicolò Sartori 1 , Anne Hemeryck 1 , Filadelfo Cristiano 1 , Sebastian Plissard 1
1 , CNRS, LAAS-CNRS, Université de Toulouse, Toulouse France
Show AbstractBottom up (BU) integration of high electron mobilities III-V nanowires (NWs) on Silicon (Si) hold promises for improved Field Effect Transistors (FETs).1 However, full CMOS compatibility requires fully vertical NWs with high uniformity and self-catalyzed growth on Si within the framework of available thermal budgets. One of the biggest and unaddressed challenge so far, for all III-V integration, remains the thermal budget during the Back-End-of-Line (BEOL) process, where 450 °C is the maximum.2 This limits the InAs NWs integration to Front-End-of-Line (FEOL) where thermal budget is 1100 °C 2 despite having one of the highest electron mobility. Furthermore, differences exist between two conventional epitaxial systems: Molecular Beam Epitaxy (MBE) and Metal Oxide Vapor Phase Epitaxy (MOVPE), with better results from MOVPE systems.3,4 The research efforts remain on achieving high yields of vertical NW arrays, since high lattice mismatch with Si and strong native oxide hinders the growth. The BEOL compatibility remains out of the scope in this scenario. The aim of this study is to address this for InAs NWs thus making them fully CMOS compatible.
At first two reproducible surface treatments have been developed with the combination of chemical and in-situ surface preparations. The chemical treatment involves removing the native oxide with the help of hydrofluoric acid (HF 5%). The following in-situ treatment involves a Hydrogen Plasma or Hydrogen Gas preparation. The final step is an in-situ Arsenic annealing before growth. Thus two surfaces are available: one involving gas treatment and one involving plasma treatment. Finally, InAs NWs are grown on Si(111) by solid source Molecular Beam Epitaxy (MBE). The process never crosses the BEOL thermal budget of 450 °C. These nanowires are characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
Fully CMOS compatible InAs nanowires with very low diameter (~30 nm) and high aspect ratio (~50) have been observed on the optimized surfaces. The two surface treatment mechanisms will be discussed in detail. The effects of growth parameters on the NW morphology for these two surfaces will be detailed with complete statistics. Furthermore, the nucleation mechanisms: Vapor-Liquid-Solid (VLS) and/or Vapor-Solid (VS) observed during growth will be presented. This study unlocks the possibility to add new functionalities on CMOS.
(1) Tomioka, K.; Yoshimura, M.; Fukui, T. Nature 2012, 488 (7410), 189–192.
(2) Thelander, C.; Agarwal, P.; Brongersma, S.; Eymery, J.; Feiner, L. F.; Forchel, A.; Scheffler, M.; Riess, W.; Ohlsson, B. J.; Gösele, U.; Samuelson, L. Mater. Today 2006, 9 (10), 28–35.
(3) Tomioka, K.; Motohisa, J.; Hara, S.; Fukui, T. Nano Lett. 2008, 8 (10), 3475–3480.
(4) Hertenberger, S.; Rudolph, D.; Bichler, M.; Finley, J. J.; Abstreiter, G.; Koblmüller, G. J. Appl. Phys. 2010, 108 (11).
8:00 PM - NM03.14.04
Metal-Transition in NdNiO3-δ Nanowires
Marcia Escote 1 , Midilane Medina 1 , Bruna Ramirez 1 , Paula Ferreira 1 , Alessandra Zenatti 1
1 , UFABC, Santo André Brazil
Show AbstractRNiO3 (R = Pr, Nd, Sm, etc.) compounds are one of the few oxides that allowed a direct relation between the structure and the physical properties.[1,2] In fact, all compounds RNiO3 (R≠La) exhibit a metal-insulator (MI) transition, in which MI temperature (TMI) could be tuned by the choice of the rare earth ion.[2] This work describes the synthesis and characterization of NdNiO3-δ nanowires synthesized by electrospinning technique via polymeric precursor solution. This precursor solution consists of a mixture of neodymium nitrate, nickel nitrate and poly(vinyl pyrrolidone) (PVP), which was electrospun to produce Nd-Ni nanowires. These fibers were produced by applying an electric voltage of 20 kV between the collector and the needle tip (20 cm). Then, electrospun samples were then collected, annealed at 350 and 800 °C in oxygen atmosphere. X-ray diffraction, Raman spectroscopy, scanning electron microscopy (SEM) and electrical resistance measurements (ρ(T)) were used to characterize the NdNiO3-δ (NNO) nanowires. SEM images revealed a granular fiber microstructure of NNO nanostructures, with a large distribution of fiber diameters that vary from 50 to 150 nm. The NNO nanowires also exhibit granular characteristics with an average grain diameter of ~ 50 nm. The X-ray diffraction patterns of the NNO nanofibers indicated that these samples exhibited a high degree of crystallinity and their Bragg reflections can be indexed to a monoclinic-distorted (P21/n symmetry) and orthorhombic-distorted (Pbnm symmetry) perovskite structure. Low intense peaks can also be observed ~ 43°, and were identified as belonging to NiO. Raman spectra of these nanowires presents five vibrational modes in ~ 97.9; 140.8; 178.0; 396.2 and 430.6 cm-1, the intense lines at 97.9 and 400-430 cm-1 can be attributed to possible monoclinic symmetry presented by these nanowires as described in literature.[3] Although, such symmetry is observed (T < TMI) toward the metallic to insulator transition by Raman results.[3] ρ(T) measurement as a function of temperature for the NNO nanofiber revealed a linear curve above TMI ~ 200 K and a typical insulator behavior below such temperature. Such feature is addressed as a metal-insulator transition (MI), which is usually observed in NNO bulk samples.
REFERENCES
1. M. L. Medarde, J. Phys.: Condens. Matter 997, 1679 (1997)
2. Lacorre P, Torrance J, Pannetier J, Nazzal A, Wang P, Huang T., Journal of Solid State Chemistry 91, 225-237 (1991).
3. M. Zaghrioui, A. Bulou, P. Lacorre, and P. Laffez, Physical Review B 64, 081102 (2001).
8:00 PM - NM03.14.05
Magnetic Assembly and Soldering of Multi-Segment Metallic Nanowires
Jirui Wang 1 , Junwei Su 1 , Fan Gao 1 , Hongwei Sun 1 , Zhiyong Gu 1
1 , University of Massachusetts Lowell, Lowell, Massachusetts, United States
Show AbstractMetals are known to have unique thermal, electrical, mechanical, and catalytic properties. Thus, metallic nanowires are promising building blocks for a variety of applications such as electronics and photonics, sensors or biosensors, as well as energy conversion and storage devices. Whereas many different methods have been utilized to synthesize metallic nanowires with different characteristics, including chemical reduction, lithography, electrophoresis, VLS growth and self-assembly, electrodeposition has been shown to be an excellent fabrication method to grow nanowires with single composition or multi-composition. Even though electrodeposition is a well-established method, there are still several challenges that need to be overcome to use this technique for the fabrication of more complex nanostructures, such as multi-segment nanowires, to satisfy device applications. In this study, pure tin (Sn) nanowires or multi-segment nanowires such as tin-nickel-tin (Sn-Ni-Sn) and tin-gold-nickel-gold-tin (Sn-Au-Ni-Au-Sn) nanowires were successfully synthesized through a template assisted electroplating method. The porous polycarbonate membrane with nanosized pores was used as a template. One side of the membrane was coated with a layer of silver (Ag) by thermal evaporator in order to seal the bottom of the membrane and form an electrical conductive layer. The nanopores were filled by Sn electrolyte and Sn nanowires grew along the pores in template. For multi-segment nanowires, the electrolyte was changed in sequence to obtain Sn-Ni-Sn or Sn-Au-Ni-Au-Sn nanowires. During the electrodeposition process, the current density was controlled depending on the type of metals electrodeposited. The length of each segment was controlled by different electrodeposition time. After synthesizing the nanowires, the template was dissolved in dichloromethane and the nanowires were released into the solution. Followed by three cycles of dichloromethane and ethanol rinsing, respectively, the nanowires were stored in the ethanol at room temperature. 2D micro patterns on Si/SiO2 substrate were fabricated by lithography, and these multi-segment nanowires with two solder ends were connected into 2D or 3D structures on micro patterns by self-assembly method, such as magnetic field assisted assembly, with effective electrical and thermal connection. These assembled ordered 2D or 3D structures can be used for various applications such as sensors/biosensors or phase change materials (PCMs).
8:00 PM - NM03.14.07
Wafer-Scale Growth of Close-Packed Single Crystalline Ferroelectric Nanorod Arrays on Silicon
Min Gyu Kang 1 , Seul-Yi Lee 1 , Deepam Maurya 1 , Christopher Winkler 1 , Hyun-Cheol Song 1 , Robert Moore 1 , Mohan Sanghadasa 2 , Shashank Priya 1
1 , Virginia Tech, Blacksburg, Virginia, United States, 2 , U.S. Army Aviation and Missile Research, Redstone Arsenal, Alabama, United States
Show AbstractOne-dimensional (1-D) ferroelectric nanostructures are promising for enhanced ferroelectric and piezoelectric performance at nanoscale, however, their synthesis at wafer scale using industrially compatible process has been challenging. In order to advance the nanostructure – based electronics, it is imperative to develop silicon-compatible growth technique yielding high volumetric density and ordered arrangement. Here we provide major breakthrough in addressing this need and demonstrate ordered and close-packed single crystalline ferroelectric nanorod arrays, of composition PbZr0.52Ti0.48O3, grown on commercial grade three inch silicon wafer. La0.67Sr0.33MnO3 seed template was found to drive the growth of vertical PZT nanorods by minimizing the surface energy, self-screening of physical vapor during deposition, and by reducing the crystallization energy. PZT nanorods covering the full three inch wafer exhibited independent ferroelectric domain switching and enhanced piezoelectric and ferroelectric performance compared to thin films of similar dimensions. Sandwich structured architecture utilizing 1-D PZT nanorod arrays and 2-D reduced graphene oxide thin film electrodes was fabricated to provide electrical connection for practical electronic devices. Using this structure, the macroscopic ferroelectric behavior of the nanostructures was characterized for the first time. Combined these results offer clear pathway towards integration of ferroelectric nanodevices with commercial silicon electronics.
8:00 PM - NM03.14.08
Confined Crystallization of α-Fe2O3 and TiO2 Nanotubes for Application to Energy Storage Devices
Hochul Nam 1 , Seonhee Lee 1 , Changdeuck Bae 1 , Hyunjung Shin 1
1 , Sungkyunkwan University, Suwon Korea (the Republic of)
Show AbstractThe one-dimensional (1-D) nanostructures (e.g., nanotubes, nanowires, nanorods, and so on) are emerging and promising candidates for a wide range of applications such as photovoltaic cells, sensors, lithium ion batteries and catalysts. Due to their unique geometries and properties, 1D nanostructures have gained considerable interests over past few decades. Atomic Layer Deposition (ALD) combined with the template-directed method can successfully fabricate pinhole-free and conformally coated nanotubes with a capability to control sub-nanometer thicknesses. We report on the wall thickness-dependent crystallization behaviors of ALD-grown Fe2O3 and TiO2 nanotubes (NTs) and the electrochemical performance as an anode for lithium ion battery. The microscopic structures of Fe2O3 and TiO2 NTs were characterized by high-resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD). Elongated grains along the tube walls were observed, and over 10 nm in wall thickness, interestingly, growth with preferred orientation was observed for both NTs. Moreover, we successfully optimized the wall thicknesses of Fe2O3 and TiO2 NTs-based anode for Li-ion batteries. Constructing the conductive TiN electrodes on the active tubular anodes by ALD enhanced the charge transfers, and improved the cycling performance. The initial reversible charge capacity of α-Fe2O3/TiN NTs was at 952mAh/g, and this value has been retained 673mAh/g after 30cycles, which corresponds to 70.7% of the initial specific capacity. The α-Fe2O3/TiN NTs also exhibited improved lithium-ion storage capacity.
KEYWORDS
Atomic layer deposition, Template-directed synthesis, α-Fe2O3, TiO2, Nanotubes, 1-D nanostructures, Anode materials, Li-ion batteries
8:00 PM - NM03.14.09
Structural and Mechanical Properties of Boron Nitride Nanotubes in High Temperature Environment
Xiaoming Chen 2 , Christopher Dmuchowski 1 , Cheol Park 3 , Catharine Fay 3 , Changhong Ke 1
2 , Xi’an Jiaotong University, Xi’an China, 1 , State University of New York at Binghamton, Binghamton, New York, United States, 3 , NASA Langley Research Center, Hampton, Virginia, United States
Show AbstractBoron nitride nanotubes (BNNTs) are a type of one-dimensional tubular nanostructure that is composed of hexagonal B-N bonding networks. As a low density material, BNNTs possess a number of unique structural and physical/chemical properties. For example, BNNTs reportedly possess very high Young’s modulus and tensile strength, extraordinary thermal conductivity, and superior thermal and chemical stabilities. The unique light and strong characteristics together with their extraordinary chemical and thermal stability are promising to enable BNNTs to excel in high temperature applications, such as reinforcing additives for metal and ceramic nanocomposites that are typically involved with extreme thermal processing and/or working conditions. However, the structural stability and mechanical integrity of BNNTs in high temperature environment remain not well understood. In this paper, we present an extensive study of the impacts of high temperature exposure on the structural and mechanical properties of BNNTs with a full structural size spectrum from nano- to micro- to macro-scale by using a variety of in situ and ex situ material characterization techniques. Atomic force microscopy (AFM) and high resolution transmission electron microscopy measurements reveal that the structures of individual BNNTs can survive at up to 850 °C in air, and the findings are consistent with in situ Raman spectroscopy measurements. The AFM-based nanomechanical compression measurements demonstrate that the mechanical integrity of BNNTs remain largely intact after being thermally baked at up to 850 °C in air. The studies demonstrate that BNNTs are structurally and mechanically stable materials in high temperature environments, which enables their usages in high temperature applications.
8:00 PM - NM03.14.10
Sb@Nitrogen-Doped Carbon Coaxial Nanotubes as a High-Rate and Long-Life Anode Material for Na-Ion Batteries
Wen Luo 1 2 , Feng Li 1 , Jean Gaumet 2 , Pierre Magri 2 , Liqiang Mai 1 3
1 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan China, 2 Laboratoire de Chimie et Physique: Approche Multi-échelles des Milieux Complexes, Université de Lorraine, Metz France, 3 Department of Chemistry, University of California, Berkeley, Berkeley, California, United States
Show AbstractAntimony (Sb) is an attractive anode material for sodium-ion batteries (SIBs) with a high theoretical capacity of 660 mAh/g. However, the rapid capacity fading caused by large volume expansion during sodiation greatly hinders its practical applications at present.[1] Recently, one dimensional (1D) nanostructure electrode materials are believed to provide opportunities to improve the performance of SIBs due to their unique geometric properties, such as high surface and volume ratio and the short electron diffusion pathway.[2] In this work, we designed and constructed unique 1D Sb anchored in nitrogen-doped carbon coaxial nanotubes (Sb@N-C) hybrid material through a facile coating of conductive polymer (polypyrrole, PPy) on Sb2S3 nanorods, followed by in-situ carbonization-reduction strategy.
Since Sb2S3 is a representative highly anisotropic material with layered structure which can be facilely fabricated into various 1D nanostructures.[3] Employing Sb2S3 nanorod as template, this novel nanoarchitecture can inherit well 1D structures meanwhile combine the advantages of internal hollow space and outside conductive carbon coating. In-situ high temperature XRD studies demonstrate the facile transformation from Sb2S3@PPy to high-crystallized Sb. The achieved Sb@N-C hybrid materials manifest superior electrochemical sodium storage properties including high specific capacity, excellent rate capability and ultra-long cycling stability. Specifically, it delivers a high specific capacity of 470 mAh/g at 100 mA/g after 300 cycles. Furthermore, a stable capacity of 290 mAh/g can be retained at 2.0 A/g even after 2000 cycles. More importantly, a high capacity of 320 mAh/g/ can be achieved at a large current density of 10 A/g. The excellent sodium storage performance indicates the promising potential of Sb@N-C for advanced SIBs.
References：
[1] Luo W, Zhang P, Wang X, et al. J Power Sources, 2016, 304: 340-345.
[2] Mai L, Tian X, Xu X, et al. Chem. Rev., 2014, 114(23): 11828-11862.
[3] Cademartiri L, Ozin G A. Adv. Mater., 2009, 21(9): 1013-1020.
Acknowledgement: Our work was supported by the National Natural Science Fund for Distinguished Young Scholars (51425204) and the Programme of Introducing Talents of Discipline to Universities (B17034).
8:00 PM - NM03.14.11
Performance Enhancement for Silver Nanowire-Based Flexible Transparent Conductive Films
Liwen Zhang 1
1 Department of Materials Science and Engineering, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen, Guangdong, China
Show AbstractTCFs on the basis of silver nanowires (AgNWs) with excellent performance are an promising candidate to replace the brittle transparent metal oxide. However, further improving the performance of AgNW-based TCFs is still highly desired. By introducing SiO2 hollow nanospheres (SiO2-HNSs) into the film, the contact resistance and visible light transmittance were both significantly improved. Typically, a AgNW/SiO2-HNS-based TCF with a sheet resistance of ca. 33 Ω/sq and transmittance of ca. 98.0% (excluding substrate) could be obtained. By electroplating metals (Ag, Ni, and Cu) on silver nanowires, the conductivity could be decreased greatly with slightly transmittance sacrifice. In this situation, a Ni/AgNWs-based TCF possesses an excellent sheet resistanc of ca. 9.8 Ω/sq at a transmittance of ca. 95.3% (excluding substrate). Very importantly, the thermal stability was improved in both two methods. To be specifically, the Ni/AgNWs-based TCF can withstand as high as 400 oC with no obvious conductivity change.
8:00 PM - NM03.14.12
Vertical InGaAs Nanowire Photodiode Array on Si
Kohei Chiba 1 , Akinobu Yoshida 1 , Katsuhiro Tomioka 1 , Junichi Motohisa 1
1 , Graduate School of Information Science and Technology, and Research Center for Integrated Quantum Electronics (RCIQE), Hokkaido University, Sapporo Japan
Show AbstractOptical interconnection and Si photonics, in which various photonic devices are integrated on a Si platform, has been attracting much attention to overcome issues in electrical connection in modern VLSI technologies. Si is transparent in the telecommunication wavelength band and is suitable for passive photonic components, but at the same time, Ge or III-V semiconductors are required for active components, and they should be integrated on the Si platform. In this context, InGaAs nanowires (NWs) have been shown to be suitable for heterogeneous integration on Si because their small footprint accommodates mismatches in lattice constant and crystal structures between InGaAs and Si. Furthermore, control of InGaAs alloy composition allows control of emission and detection wavelength of active components from infrared to far-infrared regions, including telecommunication band (1.33 ~ 1.55 µm). In this study, we demonstrate photodiodes (PDs) using vertical InGaAs NW arrays directly grown on Si. By controlling the alloy composition in InGaAs, the absorption edges was able to be tuned at around 1.55 μm.
p-Si(111) substrates partially masked with 20 nm-thick SiO2 for NW growth were prepared by thermal oxidation, electron-beam lithography, and wet chemical etching. InGaAs NWs with axial p-i-n structure were grown by selective-area MOVPE [1], using trimethylgallium (TMGa), trimethylindium (TMIn), and arsine (AsH3). Silane (SiH4) and diethylzinc (DEZn) were used as n-type and p-type dopants. The growth temperature was 670°C. To control the absorption edge at around 1.55µm, the composition of In in the vapor phase (ratio of TMIn supply over sum of TMIn and TMGa supply) was set at 41%, because the In content in InGaAs NW is known to be larger than that in the vapor phase under the employed growth conditions. For the fabrication of NW PDs, the NW array was buried with benzocycrobutene (BCB) and etched with RIE to expose the top parts of the NWs for electrode contacts. Then, to make contacts, an ITO layer was sputtered onto the NW array for transparent electrodes, and Al was deposited on the backside of the substrate. The device was annealed in N2 at 400°C for 15 min.
In the I-V characteristic in dark, the device showed moderate rectifying properties, whose turn-on voltage was 0.5 V. Some devices showed noticeable leakage current under the negative bias. Nevertheless, the NW PDs showed clear photoresponse at zero bias. For example, photocurrent density of 80 μA/cm2 was obtained under an illumination at 1.55 μm with input power of about 2.5 mW/cm2. Furthermore, the photocurrent was increased at 1.5 µm, but the same device was insensitive to the light at 1.65 μm. This means that the InGaAs NWs have an absorption edge at the wavelength slightly longer than 1.55 μm and successful operation of NW PDs on Si substrates.
[1] K. Tomioka, M. Yoshimura, T. Fukui, Nature 488, 189 (2012).
8:00 PM - NM03.14.13
Silver Nanowire Decorated Antibacterial Fabrics
Doga Doganay 1 , Akin Kanicioglu 2 , Sahin Coskun 1 , Gulcin Akca 2 , Husnu Unalan 1
1 Department of Metallurgical and Materials Engineering, Middle East Technical University, Ankara Turkey, 2 Department of Medical Microbiology, Gazi University, Ankara Turkey
Show AbstractModification of conventional textiles with antibacterial agents received considerable attention with the intention of protection against epidemics and creation of a sterile environment. Silver has been a long known material by its significant antibacterial activity. Nanoparticles were the most frequently investigated morphology of silver for this purpose. In this work, conventional cotton fabrics were decorated with polyol synthesized silver nanowires (Ag NWs). A simple dip and dry method, which is also well suited for large-scale deposition, were used for the decoration of different amounts of Ag NWs onto fabrics. Scanning electron microscopy analysis revealed the homogeneous deposition of Ag NWs onto cotton fabric fibers without any pretreatment step. Antibacterial activities of these fabrics against standard test strains of Staphylococcus aureus (S. aureus,) ATCC#25923 as Gram-positive coccus, Escherichia coli (E. coli), ATCC#25922 as Gram-negative bacilli, Bacillus cereus (B. cereus) ATCC#14603as Gram-positive bacilli and spore-forming bacteria were investigated via agar disc diffusion technique and the inhibition zones of the samples were measured. A minimum of 10 samples was tested for each bacteria. An inhibition zone of 15 mm was observed for the fabrics at each Ag NW loaded against tested bacterial strains investigated in this work, whereas bare cotton fabrics as control samples have not shown any antibacterial efficacy as expected. The results obtained herein showed a highly promising antibacterial activity of Ag NW decorated fabrics against a broad range of bacteria.
8:00 PM - NM03.14.14
Magnetic Field Effect on a Single Dopant States in Silicon Cylindrical Truncated Nanowire
Mohamed El-Yadri 2 , Elmustapha Feddi 2 , N. Aghoutane 2 , Mostafa Sadoqi 1 , Gen Long 1 , Sunil Kumar 3 4
2 Group of Optoelectronic of Semiconductors and Nanomaterials, Mohammed V University in Rabat, Rabat Morocco, 1 , Saint John's University, Jamaica, New York, United States, 3 Mechanical and Aerospace Engineering, New York University, Brooklyn, New York, United States, 4 Mechanical Engineering, NYU-ABU DHABI, ABU DHABI United Arab Emirates
Show AbstractThis work reports on theoretical investigation of an applied magnetic field effects on the confined donor impurity in a (Si) hollow cylindrical shell Nanostructures. The charges are assumed to be completely confined to the interior of the shell with rigid walls in the presence of a uniform magnetic field applied parallel to the shell axis. Within the framework of the effective-mass approximation and by using a simple variational approach, we have computed the donor binding energies as a function of the shell size in order to study the behavior of the electron-impurity attraction for a very small thickness under the influence of magnetic field. Our results show that the binding energy is more pronounced with increasing the magnetic field and decreasing the QD sizes. Our results are in good agreement with previous theoretical reports and can offer an alternative way to the tuning of correlated electron-impurity transitions in optoelectronic devices.
8:00 PM - NM03.14.15
Rutile TiO2 Nanowire-Array Integrated 3D Honeycomb Monoliths for Catalysis Applications
Son Hoang 1 , Xingxu Lu 1 , Andrew Binder 2 , Todd Toops 2 , Pu-Xian Gao 1
1 , University of Connecticut, Storrs, Connecticut, United States, 2 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractRutile TiO2 nanowire arrays have received significant interests for a variety of applications, including catalysis, photo(electro)catalysis, and photovoltaics. However, rutile TiO2 nanowire arrays have found no commercial success so far due to the lack of a scalable synthetic approach. Here we report a scalable solvothermal method for the integration of rutile TiO2 nano-arrays onto several types of 3D-channeled monolithic substrates with tunable morphology and mesoporosity. The TiO2 nanowire array based monolithic catalysts hold promises as an exceptional catalyst support for catalysis applications, including diesel oxidation catalysts (DOCs). Here, we report Pt-Pd bimetallic supported TiO2 nanowire array DOC catalysts that exhibited full conversion of CO and unsaturated hydrocarbons in simulated exhausts at a temperature below 200 oC. Notably, the catalysts were not suffered from S-poisoning effects. The catalysts also showed remarkable mechanical, thermal/hydrothermal stability, and mass-transfer properties thanks to their unique mesoporous-macroporous hybrid structures. The catalysts show great potentials for low-temperature DOCs as well as other industrial catalysis applications.
8:00 PM - NM03.14.16
Visible Light Driven Nanowire Motor in Ionic Solution with Chemical Modification
Xiaojun Zhan 1
1 , The University of Hong Kong, Hong Kong Hong Kong
Show AbstractElectrophoresis nanowire motors’ speed will descend as the ionic strength increase in the solution, typically stops at less than 100 μs/cm.1,2 This intrinsic defect limits the application of this type of nanowire nano/micro-motor in ionic physiological environment and other ionized fuel solution severely. Based on previous experiment and simulation reports on janus motor, the electrophoretic mechanism is widely studied and different composite structures have been raised up.3,4 Interestingly, the surface area of the motor haven't been explored intensely which is the area that the motor generate force for movement. Typically, the ion conductive polymer has been widely used in surface engineering to modify the catalytic electrode, solar cell and battery system to improve the performance.5When polystyrene sulfonate (PSS) is coated onto the surface of silicon nanowire motor (SNM), the surface environment and motion model have been changed. Both numerical simulation and experimental study demonstrate the function of the PSS coating, increasing the ion tolerance, and illustrate the property changes when electrolyte is added into the solution. Furthermore, silicon-based nanowire nano/micro-motors harvest energy from visible light to enhance the chemical reaction and finally convert it into mechanical movement, which provides promising light control to fulfill complex and tough task in the future.6
References
Paxton. Journal of the American Chemical Society 128.46 (2006): 14881-14888
Moran, Jeffrey L., and Jonathan D. Posner. Physics of Fluids 26.4 (2014): 042001.
Wang, Joseph, and Kalayil Manian Manesh. . Small 6.3 (2010): 338-345.
Kline, Timothy R. Angewandte Chemie International Edition 44.5 (2005): 744-746.
Shi, Ye, et al. Nano Letters (2017).
Dai, Baohu, et al. Nature Nanotechnology, (2016): 1087-1092.
8:00 PM - NM03.14.17
Control of Bending Structures in MnAs/InAs Heterojunction Nanowires
Ryutaro Kodaira 1 , Tetsuro Kadowaki 1 , Shinjiro Hara 1
1 , Hokkaido University, Sapporo Japan
Show AbstractHeteroepitaxial structures between semiconducting nanowires (NWs) and magnetic materials are of high interest for future spintronic devices. We have been demonstrating the synthesis of vertical ferromagnetic MnAs nanoclusters (NCs)/semiconducting InAs heterojunction NWs by selective-area metal-organic vapor phase epitaxy, which is a catalyst-free bottom-up fabrication method. [1] These heterojunction NWs provide new possibilities and versatility in the creation of novel nanospintronic devices, e.g., spin-NW-transistors. It is crucial to control the MnAs NC formation and improve the size uniformity of heterojunction NWs for such NW devices. Here, we present the MnAs/InAs heterojunction NW formation and discuss controllability of bending structures in the heterojunction NWs.
We obtained zinc-blende-type InAs NW arrays as a template selectively grown at 580 oC on GaAs (111)B substrates covered with a SiO2 mask with circular openings. During the NiAs-type MnAs NC growth performed after the InAs NW growth, we only supplied the organometallic Mn source diluted in H2. For the NC growth, the growth temperature was set to 490 and 580 oC, and the growth time was 1 and 5 min. Most of the heterojunction NWs were grown straight in the <111>B direction of the substrates. But, in addition, some NWs bending at around the vicinity of NCs were occasionally observed, and such NWs tended to bend toward one of the six ridge directions which are between two {0-11} facets of host hexagonal InAs NWs. When NCs were grown at 490 oC for 1 min, the bending NWs were tilted toward the parts where the NCs were partly formed from the sidewall surface of the host NWs into the inside of them. These results indicate that the nucleation of NCs possibly starts from one of the six ridges, which is consistent with our previous studies. [1] For the NCs grown at 580 oC for 1 min, on the other hand, the NCs completely penetrated the host NWs at the middle parts of the NWs, and then, formed atomically abrupt heterointerfaces between MnAs and InAs. The number of bending NWs with NCs grown at 580 oC was much smaller than that at 490 oC. It was possible that the bending NWs were formed, in particular, at 490 oC owing to incomplete heterointerface formation and lattice mismatch between MnAs and InAs. For the NCs grown at 580 oC for 5 min, we observed that additional NCs were formed next to the NCs formed in the middle parts of the host NWs. It appeared that the NCs with additional NCs were polycrystalline. It was indicated that the number of bending NWs with the NCs grown for 5 min tended to increase compared with the NCs grown for 1 min, possibly owing to the overgrowth of additional NCs after the complete heterointerface formation at 580 oC. We conclude that it is necessary for growing straight heterojunction NWs in the <111>B direction to form complete heterointerfaces and single crystalline NCs on {111}B facets of the host NWs. [1] Jpn. J. Appl. Phys. 55, 075503 (2016); 56, 06GH03 (2017)
8:00 PM - NM03.14.18
Fabrication of Ferroelectric HfO2 Nanowire Capacitors by MOCVD
Hironori Fujisawa 1 , Yohei Takeuchi 1 , Seiji Nakashima 1 , Masaru Shimizu 1
1 , University of Hyogo, Himeji Japan
Show AbstractOne-dimensional nanowires and nanotubes of various functional materials have extensively been studied for novel electronic applications. In particular, multi-shell nanowires with functional materials have a great potential for novel electronic devices. We have developed metalorganic chemical vapor deposition (MOCVD) technique for the functional nanowires with ferroelectric shell and ZnO core, for example, PbTiO3/ZnO and Pb(Zr,Ti)O3/ZnO nanowires. In this study, we demonstrate ZnO/HfO2/ZnO-multishell nanowire capacitors in which HfO2 and ZnO can be acted as a dielectric/ferroelectric and an electrode, respectively.
ZnO nanowires were grown on Pt/SiO2/Si by vapor-solid (VS) growth via MOCVD using Zn(C2H5)2 and O2 as the precursor and oxidizing gas, respectively. Typical growth temperatures and reaction pressures for ZnO NW template were 700−750 oC and 2−5 Torr, respectively. Average diameter, length, and aspect ratio of ZnO nanowires were 110 nm, 10 µm, and 90, respectively. Amorphous HfO layer was prepared on ZnO nanowire template at 200oC by MOCVD using Hf(O-t-C4H9)4 and O2. Field emission scanning electron microscopy (FE-SEM) revealed that ZnO nanowires were uniformly covered with 10-20 nm-thick HfO2 layer because of the capability of conformal growth by MOCVD. HfO2 layer was annealed at 600-1000oC and 300 s in N2 for crystallization. By annealing at 600-800oC, ferroelectric orthorhombic phase was observed by XRD while paraelectric monoclinic phase was dominant by annealing above 800oC. After annealing, HfO2/ZnO nanowires were covered with ZnO top layer by MOCVD at a low growth temperature of 200oC. ZnO top layer was grown in the form of thin films at 200oC, and ZnO/HfO2/ZnO NW capacitors can be achieved.
At the meeting, details of electrical and structural property of the ZnO/HfO2/ZnO nanowire capacitors will be discussed.
8:00 PM - NM03.14.19
Nanobelt-Like One-Dimensional Silver/Nanocarbon Hybrid Materials for Flexible and Wearable Electronics
Joong Tark Han 1 2 , Joon Young Cho 2 , Jun Yeon Hwang 3 , Hee Jin Jeong 1 , Seung Yol Jeong 1 , Seon Hee Seo 1 , Geon-Woong Lee 1
1 , Korea Electrotechnology Research Institute, Chgangwon Korea (the Republic of), 2 Department of Electro-functionality Materials, University of Science and Technology, Changwon Korea (the Republic of), 3 , Korea Institute of Science and Technology, Wanju Korea (the Republic of)
Show AbstractLow dimensional metallic nanostructures have received considerable attention due to their potential applications in printed electronics, wearable electronics, catalysis and sensors. Usually, most synthetic processes of metallic nanostructures were assisted by organic/inorganic or polymeric materials to control their shapes to one-dimension or two-dimension. However, these additives have to be removed after synthesis of metal nanostructures for applications. Here we report a straightforward method for the low-temperature and additive-free synthesis of one-dimensional nanobelt-like silver nanostructures templated by nanocarbon (NC) materials via bio-inspired shape control by introducing supramolecular 2-ureido-4[1H]pyrimidinone (UPy) groups into the NC surface. The growth of the Ag nanobelt structure was found to be induced by these UPy groups through observation of the selective formation of Ag nanobelts on UPy-modified carbon nanotubes and graphene surfaces. The synthesized NC/Ag nanobelt hybrid materials were subsequently used to fabricate the highly conductive fibres (>1000 S/cm) that can function as a conformable electrode and highly tolerant strain sensor, as well as a highly conductive and robust paper (>10000 S/cm after thermal treatment).
8:00 PM - NM03.14.20
An Investigation into the Effects of POSS Functionalization of CNTs on Microstructure and Thermo-Mechanical Behavior of CNT/Polymer Nanocomposites
Seyed Morteza Sabet 1 , Hassan Mahfuz 1 , Andrew Terentis 1 , Majid Nezakat 2 , Javad Hashemi 1
1 , Florida Atlantic University, Boca Raton, Florida, United States, 2 , University of Saskatchewan, Saskatoon, Saskatchewan, Canada
Show AbstractSurface modification of carbon nanotubes (CNTs) is a promising method to control the properties of a CNT/polymer system. Recently, research studies have directed towards chemical attachment of polyhedral oligomeric silsesquioxane (POSS) nanostructures to the CNT surface. POSS-modification of CNTs may affect both the quality of CNT dispersion in the matrix and the interactions between polymer chains and nanotubes at the interphase region. The goal of the current study is to investigate these effects. Accordingly, nanocomposites containing POSS-modified CNTs as well as as-received CNTs and POSS were fabricated by diffusion of 0.25, 0.5 and 1.0 wt% nanoparticles into a vinyl ester (VE) resin. Similar fabrication parameters were considered in manufacturing of all nanocomposites. The state of nanoparticle distribution/dispersion in VE matrix was observed. Optical microscopic studies showed that both POSS/VE and CNT/VE nanocomposites possess agglomeration of nanoparticles. This was more extensive in CNT/VE system. However, CNT-POSS/VE systems showed a fine-textured microstructure with homogeneous distribution of CNT-POSS nanoparticles into VE resin. This indicates that the exfoliation of CNTs improved due to POSS functionalization. Scanning electron microscopy (SEM) of fracture surfaces revealed apparent de-bonding of agglomerates from the matrix in both POSS/VE and CNT/VE system, which is in agreement with the observed drop in their fracture strain. On the other hand, SEM studies of nanocomposites containing POSS-modified nanotubes revealed formation of a 3D network of well-dispersed CNT-POSS nanohybrids. Moreover, in-depth SEM analysis indicated the occurrence of a fracture mechanism with enhanced interactions between individual CNTs and VE matrix due to POSS linkages. This stiff and flexible network of individual CNTs is suggested to be responsible for enhancement in elastic modulus, glass transition and thermal decomposition temperatures of CNT-POSS/VE nanocomposites.
8:00 PM - NM03.14.21
Silver-Coated Gold Nanorods as a Promising Agent in Treating Cancer-Related Infections
Junyan Zhang 1 , Mian Wang 1 , Di Shi 1 , Thomas Webster 1
1 , Northeastern University, Boston, Massachusetts, United States
Show AbstractCancer is the second most deadly disease in the US and can easily lead to life-threatening infections to patients due to their weaker immune system. Moreover, the increasing prevalence of antibiotic-resistant pathogens due to overuse of antibiotics has posed an even greater challenge in treating cancer patients. Therefore, it is of great importance and necessity to research alternative approaches to combat infections, especially those happening to cancer patients.
Silver nanoparticles have been proven to be an efficient antimicrobial agent and hence have been widely researched for diverse medical applications. However, silver nanoparticles have been found to cause DNA damage, chromosomal aberrations and cell cycle arrest in a dose-dependent manner. Therefore, in order to employ the super antimicrobial properties of silver nanoparticles, more studies need to be conducted either to reduce the amount of silver nanoparticles, or to combine with other antimicrobial agents.
Silver-coated gold nanoparticles of various shapes have been synthesized and investigated in recent decades. Among them, Ag/AuNRs have attracted much interest. The Au-Ag bimetallic material has been demonstrated to share similar optical properties as with gold nanoparticles. However, its potential as a promising antimicrobial agent has not been studied yet, even though intense research has proven the super antimicrobial properties of silver nanoparticles.
In this study, silver-coated gold nanorods were synthesized and characterized. Then, their antimicrobial properties were tested on different bacteria species and their growth was suppressed with increasing concentration. Furthermore, the fluorescence assays on P. aeruginosa showed much less bacteria and no formation of a biofilm compared with the control group. Finally, the cytotoxicity of the silver-coated gold nanorods was investigated and no obvious toxicity was found up to a concentration of 25 μg/mL. Therefore, the silver-coated gold nanorods were effective in treating bacteria at a concentration when there was very little cytotoxicity towards healthy mammalian cells.
8:00 PM - NM03.14.22
Biodegradable and Stretchable Triboelectric Nanogenerator Based on Conductive Nanocomposite
Ha Ryeon Hwang 1 , Suk-Won Hwang 1
1 NBIT, Graduate School of Converging Science and Technology, Korea University (KU-KIST), Seoul Korea (the Republic of)
Show AbstractExisting electronic devices have been encountering with long-term power sources as a critical obstacle since a battery has a limited capacity and durability. Although countless achievements have been announced over the last decade, these breakthroughs were not appropriate to transfer into commercial batteries with the promised improvements in cost, efficiency and energy storage. Alternatively, recent researches have been focused on energy harvesting systems, e.g., triboelectric nanogenerators (TENGs) which operates based on a simple principle known as triboelectric effect and electrostatic induction to convert ambient mechanical movements into electrical energy. TENG can be defined as a biomechanical energy harvester in that it enables converting natural body movements such as walking, bending of elbows and swing of arms into electrical power, and utilized as a long-term power source.
Here we introduce a stretchable, biodegradable conductive nanocomposite for triboelectric nanogenerator in a format of medical implants, via blending PLCL (Poly(lactide-co-caprolactone)) as a biodegradable elastomer and Fe nanowires for a dissolvable conductive filler, forming Fe nanowires network embedded in PLCL matrix. The motivation of materials selection is to produce electronic system that is ‘transient’ in this sense has novel strong advantages that cannot be addressed with established technologies, such as implantable biomedical systems that can be operational for clinically useful time period, then physically degrades or resorbs into the body. Therefore, all electronic constituents are designed to be dissolved/disappeared in water/biofluids at a well-controlled time frames after prescribed operation time is over.
Second, a manufactured, facile TENG operates based on a single electrode mode including a single electrification layer and single electrode, fabricated with PLCL as an electrification layer and PLCL-Fe nanowire composites for a conducting electrode. As a result, complete triboelectric nanogenerator can scavenge power/energy from diverse mechanical movements of the body, and potentially applicable for medical electronic implants in a self-operation mode.
8:00 PM - NM03.14.23
One Dimensional Rare Earth Metal Pyrochlores as Efficient Photocatalysts—Molecular Precursor to Nd2Sn2O7 Nanofibres
David Graf 1 , Yakup Gonullu 1 , Sanjay Mathur 1
1 , University of Cologne-Inorganic Chemistry, Cologne Germany
Show AbstractIn recent years, the upsurge of research in the field of heterogenous photocatalysts for the storage and production of renewable energy has risen significantly. The need to modify existing systems in their various parameters, morphologies and dimensionalities may lead to an overall improvement in the efficiency and stability of these entities. Highly crystalline and well-ordered binary oxides have been throughly studied in this area of research. A purpose driven examination of ternary oxides i.e. Pyrochlores present interesting absorption behaviour, the band gap energies and the efficient transfer of charged carriers.
This work encompasses the synthesis of heterobimetallic metal alkoxides with predefined metal-metal ratio relevant for the formation of the ternary rare earth metal oxide. The 1-Dimensional bimetallic oxides were fabricated using the amiable Electrospinning process. In order to elucidate the photocatalytic activity of the Nd2Sn2O7 nanofibres, methylene blue (MB) dye degradation under UV Illuminations were conducted. TiO2 in MB was used as reference in these studies.
8:00 PM - NM03.14.24
Fabrication of ZnO Quantum Dots–Decorated CNF Using Electrospun ZIF–8/PVA Nanofibers for High–Performance Electrochemical Capacitors
Gyeongseop Lee 1 , Jyongsik Jang 1
1 , Seoul National University, Seoul Korea (the Republic of)
Show AbstractSupercapacitors (SCs) have drawn great attention as an ideal power source for emerging industries including hybrid electric vehicles (HEVs) due to their attractive properties such as a high charge/discharge rate, long life cycle, and high power density. ZnO is considered a suitable candidate for an electrode material due to its good electrochemical activity, eco-friendliness, and low cost. However, the low rate capability and poor cyclic stability derived from large volume changes during the charge/discharge process limit the practical application of ZnO as an electrode material. To address these issues, a number of studies have suggested the use of ZnO composites with various carbon materials such as graphenes, reduced graphene oxides, and carbon nanotubes. However, these materials demonstrated inadequate performance because the active materials were not fully exploited for a number of reasons (e.g., bulk size of ZnO, weak adhesive force between ZnO and carbon). Hence, a novel design for ZnO-based SCs with enhanced electrochemical performance is still required.
A metal organic framework (MOF) has been reported as a precursor material for achieving a hybrid structure of well-dispersed metal oxide (MO) quantum dots (QDs) embedded in porous carbon matrices (MO QDs@carbon), which retains the initial characteristics of the parent MOF. Owing to their ideal structure as an electrode material, many groups have synthesized a variety of MO QDs@carbons and evaluated their electrochemical performance; however, despite structural advantages (e.g., quantum-sized MOs, strong adherence between MOs and porous carbon matrices), the conductivities of MO QDs@carbons proposed thus far have been too weak for application as an electrode material. As the low conductivities of MO QDs@carbons stem from the lack of connection between the particles, significant research efforts have been devoted to increasing the conductivity by linking these particles with various conductive materials.
Herein, we demonstrated a novel method for linking ZIF-8-derived ZnO QDs@carbon particles with electrospun CNF to obtain the synergistic effects of the porous nature of ZIF-8 and the conductive CNF networks. Specifically, ZnO QD-decorated CNFs (ZPCNFs) were simply fabricated by the carbonization of electrospun ZIF-8/PVA nanofibers, and in particular the oxygen-rich PVA nanofibers, which were utilized as a CNF precursor in this study, provided abundant oxygen sources to surrounding ZIF-8 during the carbonization process, resulting in the transformation of ZIF-8 to ZnO QDs@carbon particles on the surface of CNF. With the unique structural characteristics such as hierarchical porous structure and one-dimensional morphology, ZPCNF exhibited outstanding electrochemical performance with high capacitance (214 F g-1 at 0.5 A g-1), reliable rate capability (74% capacitance retention at 8 A g-1), and a long cycle life of over 5,000 cycles.
8:00 PM - NM03.14.25
Transformation of Pt-Cu Nanowires into “Crack-Tips” Enriched Pt-Cu Superlattice Nanoflakes for High-Performance Methanol Electrooxidation
Lijun Zheng 1 , Dachi Yang 1
1 , Nankai University, Tianjin China
Show AbstractMaximizing the surface ratio of the nanostructures and forming desirable crystallization is of great importance for the nanotechnology and applications in such as gas sensors and nanocatalysts. However, the synthetic art is still challenging. Herein, we have developed “crack-tips” and “superlattice” enriched Pt-Cu nanoflakes (NFs), via first anodic aluminum oxide (AAO) template-confined electrodeposition of cylindrical Pt-Cu nanowires (NWs), and a subsequently wet-chemical transformation. The Cu plays a crucial role both in forming “Pt-Cu-Pt-Cu” superlattices and in transforming NWs into NFs. The as-prepared Pt-Cu NFs are full of “crack-tips”, from which superlattices are observed forming with two Pt (111) and two Cu (111) alternate planes. As an example of application, we take Pt-Cu NWs nanocatalysts for methanol electrooxidation. Benefiting from the synergetic effects of “crack-tips” and “superlattice crystal”, the Pt-Cu NFs exhibit 4 times higher mass activity, 6 times higher specific activity and 6 times higher stability than those of the commercial Pt/C catalyst, respectively. Meanwhile, the Pt-Cu NFs show more enhanced CO tolerance than commercial Pt/C catalyst. To sum up, simultaneously introducing “crack-tips” and “superlattice” into the Pt-Cu NFs nanocatalysts enable to expose more catalytic active sites and weaken the Pt-CO bonds, which is promising to reduce Pt usage as well as to boost their electrocatalytic performance. Our strategy can be extended to design other more efficient electrocatalysts.
8:00 PM - NM03.14.26
Assembly of Novel Complex Li2SnO3 1D-Nanostructures by a Vapor-Solid Growth
Miguel Garcia-Tecedor 1 , Javier Bartolomé 2 , David Maestre 1 , Ana Cremades 1 , Javier Piqueras 1
1 , Univ Complutense de Madrid, Madrid Spain, 2 , Paul-Drude-Institute , Berlin Germany
Show AbstractLi-Sn-O compounds are emerging as alternative anode materials for Li-ion batteries. Among others, the Li2SnO3 has been prepared as ceramic material and scarcely as nanoparticles or thin films. However, fundamental properties and other aspects on the synthesis of Li-Sn-O nanostructures require further research in order to improve and broaden their applicability. In this work novel 1D nanostructures of Li2SnO3 have been fabricated by means of a catalyst-free vapor-solid growth using metallic Sn and Li2CO3 powders as precursors. Thermal treatments carried out at 700-900 oC during 2-10 hours lead to the growth of different structures, most of them showing branched and hierarchical appearance, as studied by scanning electron microscopy (SEM). Two types of branched structures have been observed, as well as nanowires and belts in a lower concentration. The as-grown structures consist of monoclinic Li2SnO3, as demonstrated by x-ray diffraction (XRD) and Raman spectroscopy measurements, although the presence of isolated Li doped SnO2 domains and/or structures cannot be totally discarded, especially in the case of the structures grown at higher temperatures. Transmission electron microscopy (TEM) observations show that the central trunk of most of the branched structures grows perpendicular to the (130) or (200) planes, while the lateral branches form 60o with the central trunk. The detection of Li in the structures was carried out by X-ray Photoelectron Spectroscopy (XPS) and Electron Energy Loss Spectroscopy (EELS). The luminescence of the nanostructures, scarcely studied so far, was analyzed by cathodoluminescence (CL) and photoluminescence (PL), and consists of a broad and complex emission in the visible range with three main bands centered around 2, 2.25 and 3 eV, which relative intensity varies as a function of the morphology of the branched-structure. The high luminescence intensity of some of these structures makes them potentially suitable for applications in light emitting devices.
8:00 PM - NM03.14.27
Al Doped TiO2 1-Dimensional Nanostructures
María Taeño 1 , David Maestre 1 , Ana Cremades 1 , Javier Piqueras 1
1 , Univ Complutense de Madrid, Madrid Spain
Show AbstractTiO2 is widely used in a wide range of applications in the fields of photocatalysis, solar cells, and gas sensing, among others. Controlling the chemical composition by doping, the morphology and dimensions of TiO2 nanostructures is essential in order to improve and broaden the applicability of this material. Al doping has recently demonstrated to improve the thermal stability of TiO2 nanoparticles, inhibiting the anatase to rutile transition, and modifying TiO2 optoelectronic properties. However, fabrication of aluminium doped TiO2 1-dimensional nanostructures is scarcely reported.
Al doped TiO2 elongated structures have been grown by a catalyst-free evaporation-deposition method using different precursors. The best results have been obtained for TiN and Al2O3 as starting materials, achieving the growth of nanowires, nano and microrods and belts with thermal treatments carried out at 900-940 oC during 5-15 h. The structural/microstructural characterization was performed by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy and dispersive x-ray spectroscopy (EDS). The nanostructures present rutile structure and high crystallinity. Most of the structures show a stepped appearance with terraced lateral faces. Nano and microrods are some microns long and hundred to several hundreds nm width. Some structures exhibit a bidimensional growth with nanometric thickness. The luminescence of the samples was analyzed by cathodoluminescence (CL), showing two main emissions, centered at 1,51 eV and 2,23 eV. The first emission is related to the presence of Ti3+ interstitials, while the second is associated with oxygen vacancies, generated due to the charge imbalance between Ti4+ and Al3+. The relative intensities of the bands change depending on the nanostructure considered and the thermal treatment, due to a different concentration of defects generated during growth.
8:00 PM - NM03.14.28
Synthesis of Core-Shell Rutile/Anatase Heterojunction Titanium Dioxide Nanofiber and Its Photocatalytic Performance
Kia-Chi Hsiao 1 , Ming-Chung Wu 2 , Wei-Fang Su 1
1 , National Taiwan University, Taipei Taiwan, 2 Department of Chemical and Materials Engineering, Chang Gung University, Taoyuan Taiwan
Show AbstractIn order to synthesize the high photocatalytic activity titanium dioxide the hydrothermal method and two-step calcination process are applied to fabricate the core@shell heterojunction titanium dioxide nanofibers. At the first step, the calcination have to be practice to prepare the high crystalline anatase and rutile phase titanium dioxide nanofibers. Subsequently, the wet impregnation method is utilized to coat the titanium dioxide nanoparticles at the surface of the as-prepared titanium dioxide nanofibers, and then the second calcination is carried out. By applying the characteristic of the lower phase transformation temperature of nanoparticles than it of nanofibers, the two types of core@shell heterojunction titanium dioxide nanofibers are fabricated completely (one is rutile nanofiber titanium dioxide as core material and anatase nanoparticles titanium dioxide as shell material, which is denoted as R@A TiO2 NFs; the other is the reverse structure and denoted as A@R TiO2 NFS.) The micro-raman scattering spectroscopy and Spherical-aberration Corrected Field Emission TEM are used to analyze these two type of core@shell heterojunction titanium dioxide nanofibers and help us realize the crystalline structure and internal microstructure transformation.
In our survey, the photodegradation of methyl orange and Kelvin probe force microscope are applied to frame the mechanism of the excited electron-hole pairs separation. The results of photodegradation exhibit that the A@R TiO2 NFs have the fastest degradation rate under not only UV-A but also UV-B irradiation, and the performance is beyond AEROXIDE® TiO2 P25 and pristine titanium dioxide nanofibers. The calculated reaction rate constant are 0.0133 min-1, 0.0333min-1 under UV A and UV B light source, respectively. After 150 min photodegradation, the degradation rate of Methyl orange are 99.78% and 87.46% under UV B and UV A irradiation. The results indicate that the heterojunction structure is benefit to electron-hole pairs separation.
For the comparison with photodegradation consequence of this two type structures, R@A TiO2 NFs and A@R TiO2 NFs, the A@R TiO2 NFs possesses much better performance that of R@A TiO2 NFs. This attribute to the fact that the excited electron would stay in the anatase phase, but the excited holes prefer to transport to rutile phase structure and boots the photodegradation ability of A@R TiO2 NFs.
8:00 PM - NM03.14.29
Systematic Study of Interdependent Relationship on Gold Nanorod Synthesis Assisted by Electron Microscopy Image Analysis
Seokyoung Yoon 1 , Byoungsang Lee 1 , Jaesub Yun 1 , Jeon Geon Han 1 , Jongseok Lee 1 , Jungheon Lee 1
1 , Sungkyunkwan University, Suwon Korea (the Republic of)
Show AbstractHere, we systematically investigated the independent, multiple, and synergic effects of three major components, namely, ascorbic acid (AA), seed, and silver ions (Ag+), on the characteristics of gold nanorods (GNRs), i.e., longitudinal localized surface plasmon resonance (LSPR) peak position, shape, size, and monodispersity. To quantitatively assess the shape and dimensions of GNRs, we used an automated transmission electron microscopy image analysis method using a MATLAB-based code developed in-house and the concept of solidity, which is the ratio between the area of a GNR and the area of its convex hull. The solidity of a straight GNR is close to 1, while it decreases for both dumbbell- and dogbone-shaped GNRs. We found that the LSPR peak position, shape, and monodispersity of the GNRs all altered simultaneously with changes in the amounts of individual components. For example, as the amount of AA increased, both the LSPR peak and solidity decreased, while the polydispersity increased. In contrast, as the amount of seeds increased, both the LSPR and solidity increased, while the monodispersity improved. More importantly, we found that the influence of each component can actually change depending on the composition of the GNR growth solution. For instance, the LSPR peak position red-shifted as the amount of AA increased when the seed content was low, whereas it blue-shifted when the seed content was high.
8:00 PM - NM03.14.30
Doping Effect of Cobalt into Tungsten Sulfide and Tungsten Oxide Core/Shell Nanotubes on Hydrogen Evolution
Xinjian Shi 1 , Xiaolin Zheng 1
1 , Stanford University, Stanford, California, United States
Show AbstractSulfides have been widely used material for hydrogen evolution and element doping is an effective way for the enhancement of their performance. Nevertheless, there is still a gap between the understandings of what and why for the enhanced performance, which is exactly necessary for guiding the future work. Here, we have carried out a study based on the doping effect to the sulfide, and investigate the different doping concentration to the absorption of H and de-sorption of H2 on the active sites, as well as the formation of S vacancy, through a facile and effective doping approach in a fabricated core/shell structured WS2/W18O49 nanotubes. The appropriately doped WS2 showed a 0.21V shift on the overpotential relative to the pristine WS2 at -10mA/cm2, with a much lower slope of Tafel plot (from 122mV/dec to 49mV/dec) indicating a great enhanced activity on H2 evolution.
8:00 PM - NM03.14.31
Fabrication of Microcapacitors from Single Walled Carbon Nanotube Films Using Laser Ablation Technique
Mete Batuhan Durukan 1 , Kamil Cinar 1 , Alpan Bek 1 , Husnu Unalan 1
1 , Middle East Technical University, Ankara Turkey
Show AbstractThe requirement for micropower sources and small-scale energy storage units increases in tandem with the technological trend towards to miniaturized electronic devices. While small batteries exists for current technology in microelectromechanical systems, personal and military wearable technology, biosensors and such, their short lifetime and limited power densities hinders further improvements in aforementioned systems.
Supercapacitors have high power densities coupled with their long operation time that can be counted even millions of cycles without losing their efficiency, are offered as a replacement for batteries for miniaturized electronic devices; yet, current structures are not suitable for microscale applications. Micro-capacitors, which contains micro sized supercapacitors are extensively researched to achieve integration of supercapacitors to such devices.
In this work, microcapacitors are fabricated via SWCNT buckypapers using vacuum filtration and consecutive stamping on glass substrates which are then patterned with laser ablation technique without any need for interdigitated contacts. Capacitive behaviour of SWCNT microcapacitors were investigated through cyclic voltammetry, galvanostatic charge discharge and impedance spectroscopy. A result of 3.5 mF.cm-2 areal capacitance was obtained through cyclic voltammetry with 10 mV/s scan rate using TBAPF6:PMMA:PC:ACN gel electrolyte. A detailed analysis on the capacitive behaviour wil be presented with the comparison of patterning and amount/thickness of the active material and buckypaper film.
8:00 PM - NM03.14.32
Multiwall Carbon Nanotubes Filled with Al4C3—Electron-Phonon Coupling and Doping Process
Newton Barbosa 1 , Mario Edson de Souza 1 , Marcos Allan dos Reis 1 , Manuel Vieira 2 , Sonia Simões 2 , Rômulo Angélica 1 , Mildred Dresselhaus 5 , Paulo Araujo 3 4
1 , Universidade Federal do Pará, Belém Pará Brazil, 2 , Universidade do Porto, Porto Portugal, 5 , Massachusetts Institute of Technology, Boston, Massachusetts, United States, 3 Physics and Astronomy, The University of Alabama, Tuscaloosa, Alabama, United States, 4 Center for Materials for Information Technology, The University of Alabama, Tuscaloosa, Alabama, United States
Show AbstractHere, the doping mechanism in multiwall carbon nanotubes filled with aluminum carbide (Al4C3-MWCNTs) was studied and interpreted relative to changes in their electronic and phononic structures. The samples were characterized via scanning electron microscopy (SEM), tunneling electron microscopy (TEM) and resonant Raman spectroscopy, through which the electron-phonon coupling mechanisms associated to the G-band and G'-band Raman modes were analyzed and connected to the doping mechanism in these multi-walled systems. We report evidences of strong electron-phonon coupling and doping of MWCNTs filled with Al4C3. SEM and TEM studies confirm that the Al4C3 are inside the innermost tubes in the MWCNT systems and resonant Raman scattering was used to show that electrons are being transferred from the Al4C3 nanoparticles to the innermost tubes. Moreover, our experimental results, which are endorsed by theoretical calculations, suggest some spectroscopic signatures inherent to the MWCNT systems filled with Al4C3: (1) the G-band and the G’-band are mainly composed of two peaks attributed to inner and outer tubes; (2) although the G-band frequencies do not change much when compared to the unfilled MWCNT systems, the FWHMs of the Ginner and Gouter are broader (narrower) and narrower (broader) for the unfilled (filled) MWCNT systems and the intensity of the Ginner peak is always greater than the intensity of the Gouter peak; (3) the G’-band is also composed of a G’inner peak and a G’outer peak and it is seen that the G’inner peak undergoes a blueshift in frequency and the G’outer peak undergoes a redshift in frequency when compared to the unfilled MWCNT systems; (4) there is an inversion in the G’inner and G’outer intensities for the filled MWCNT systems in comparison with the unfilled MWCNTs and both FWHM of the G’inner and G’outer peaks become slightly narrower when compared to the unfilled MWCNT G’inner and G’outer peaks. This work is supported by CNPq, CAPES and ELETRONORTE.
8:00 PM - NM03.14.33
Influence of the Flanking Residues in a Tripeptide Library in Sorting Out Metallic and Semiconducting Carbon Nanotubes
Shrishti Singh 1 , Andine Carine 1 , Jillian Smith-Carpenter 2 , Prabir Patra 1 , Isaac Macwan 1
1 , University of Bridgeport, Bridgeport, Connecticut, United States, 2 Chemistry, Fairfield Univeristy, Fairfield, Connecticut, United States
Show AbstractThe helicity (twist) of the CNTs is determined by differences in the chiral indices of a graphene sheet hence giving rise to both metallic and semiconducting types of CNTs with different electronic properties, bundled together as ropes in a typical mixture. This makes their separation from a mixture an expensive and exhaustive process. Hence, use of biomolecules to aid in their separation is of prime interest and is being thoroughly researched on. However, the use of biological molecules has two limitations: difficulty in dispersion of a mixture of CNTs due to their strong cohesive interactions and difficulty in determination of specific and selective biomolecules for differentiating between the types of the CNTs. In this study, the different events at the interface of tripeptides and varying chirality CNTs are quantified based on the interactions between a set of nine tripeptide constructs and the CNTs. It is also found that this technique is very closely related to a unique way that a tripeptide interacts with CNTs, which is based on the side chain of the flanking residues being hydrophobic, polar uncharged and polar negatively charged. Visual Molecular Dynamics (VMD) was used to construct a tripeptide library and analyze the interactions. Glycine formed the middle amino acid residue in each tripeptide construct as a previous study showed its selectivity for the metallic type of CNT. Hence, the role of glycine is justified and the effect of the flanking amino acid residues of glycine in their selectivity for either type of CNTs in the tripeptide construct is also substantiated. Hydrophobic residues with polar, negatively charged showed a higher adsorption stability for semiconducting type whereas polar, uncharged residues combined with two repetitive glycine residues showed the highest adsorption stability for metallic type in this study based on RMSD and interaction energy analysis. Threonine-Glycine-Glycine showed highest interaction energy of 9.8 kcal/mol with the metallic type and an average stability of 0.001 A per frame, whereas for the semiconducting type, Asparagine-Glycine-Glutamic Acid showed maximum stability of adsorption with an average RMSD value of 0.0002 A per frame and interaction energy of 10.2 kcal/mol. This study provides a very crucial insight into the use of a simple tripeptide library and projecting this idea towards using proteins in sorting of CNTs based on their electronic properties, which can be useful in developing CNT substrates for sensors. An insight into these interactions are useful in biotechnology to develop peptide-CNT systems whose applications include peptide based sensors and developing peptide sequences which can interact specifically with other inorganic molecules.
8:00 PM - NM03.14.34
Silver Nanowires and Carbon Nanotubes for Application in Flexible and Transparent Electrodes
Felipe Soares 1 , Sidney Lourenço 2 , Carlos Cava 3
1 Department of Physics, State University of Londrina (UEL), Londrina Brazil, 2 Department of Physics, Technological Federal University of Paraná (UTFPR), Londrina Brazil, 3 Department of Materials Science and Engineering, Technological Federal University of Paraná (UTFPR), Londrina Brazil
Show AbstractThe electrical and optical characterization of silver nanowires (AgNWs) made by polyol route and its mix with carbon nanotubes (CNTs) are presented in this work. Three ethylene glycol (EG) solutions were prepared: one with polyvinylpyrrolidone (PVP), other with sodium chloride (NaCl), and the other with silver nitrate (AgNO3). The first two were heated at a characteristic temperature and then mixed. The third is added slowly into the heated mixture. The concentration of each solution is a very important factor for the synthesis efficiency, as well as the temperature and time that the solution remained heated and stirred. Thus, an EG solution with dispersed silver nanowires and nanospheres were obtained. At the end of this process, the nanowires would had also adsorbed the PVP layer that allowed the growth in a single direction. The PVP layer electrically isolates the contact between the wires of the network, affecting the formation of conductive films. A washing procedure is necessary to remove the excess of PVP. The first step is to dilute the solution in acetone in order to decant the nanowires; then a sequence of dispersions in ethanol are followed by centrifugations. In each centrifugation, most of the PVP and silver nanoparticles remain in the supernatant, leaving only the AgNWs. The AgNWs were characterized by electron and atomic force microscopy. After the AgNWs production and characterization, the CNTs and AgNWs composites were studied concerning their ratio and deposited as a film onto a plastic substract. The optical absorption and four probe measuraments were performed in order to characterize the composite. The preliminary results showed to be promising regarding flexible and transparent electrodes.
8:00 PM - NM03.14.35
High Photocatalytic Performance of Ag/TiO2 Nanofibers Prepared by Combining the Hydrothermal Synthesis and Simple Heat-Treatment
Ting-Han Lin 1 , Po-Yeh Wu 1 , Yin-Hsuan Chang 1 , Ming-Chung Wu 1
1 , Chang Gung University, Taoyuan City Taiwan
Show AbstractA series of transition metal-doped TiO2 nanofibers (metal/TiO2 NFs) are prepared by combining the hydrothermal synthesis and a simple thermal treatment in air atmosphere without reduction procedure. The eleven types of transition metal precursors, including Ag, Au, Co, Cr, Cu, Fe, Ni, Pd, Pt, Y and Zn precursors, were separately doped into TiO2 NFs to obtain the doping effect on the photocatalytic performance. Consider the results of simple photocatalytic testing, Ag/TiO2 NFs was chosen to further study. Then, a systematical study was carried out to find the appropriate calcination condition and doping concentration for preparing high active Ag/TiO2 NFs. The crystal structure, microstructure, chemical composition, and optical property were characterized by XRD, Raman spectra, HRTEM, and UV/visible absorption spectrometer to discuss the doping effect on Ag/TiO2 NFs. For the photodegradation of methyl orange in UV irradiation, 0.5mol% Ag/TiO2 NFs calcined at 600oC exhibits the high visible-light photodegradation activity, even higher than Degussa P25. Moreover, 0.5mol% Ag/TiO2 NFs also has the capability in the photocatalytic hydrogen production (~500 μmol/g●hr). This synthesis of Ag/TiO2 NFs opened up new possibilities for large-scale and convenient fabrication of nanofibers by simply annealing the obtained product in air, and Ag/TiO2 NFs have the high practical potentials in wastewater treatment and clean energy.
8:00 PM - NM03.14.36
One-Dimensional Nanostructured Photoanodes with Staggered Bandgap for Efficient Solar Energy Conversion
Nageh Allam 1
1 , American University in Cairo, New Cairo Egypt
Show Abstract
Vertically oriented Ta–W–O nanotube array films were fabricated via the anodization of Ta–W alloy foils in HF-containing electrolytes. HF concentration is a key parameter in achieving well-adhered nanotube array structure. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance measurements confirm the staggered band-alignment between Ta2O5 and WO3, which facilitates the separation of charge carriers. The nanotubes made of Ta–W films containing 10% W showed 100-fold improvement in the measured photocurrent compared to pristine Ta2O5 upon their use to split water photoelectrochemically. This enhancement was related to the efficient charge transport and the red shift in absorption spectrum with increase of the W content, which was asserted by ultrafast transient absorption (TA) spectroscopy measurements. The TA measurements showed the elimination of trap states upon annealing Ta–W–O nanotubes and, hence, minimizing the charge carrier trapping, whereas the trap states remain in pristine Ta2O5 nanotubes even after annealing.
8:00 PM - NM03.14.37
Pure and Hierarchical Metallic MoS2 Nanotubes for Lithium-Ion Batteries
Yucong Jiao 1
1 , Northeastern University, Boston, Massachusetts, United States
Show AbstractMetallic 1T phase molybdenum disulfide (MoS2) is well-known for orders of magnitude higher conductivity than 2H semiconducting phase MoS2. Herein, for the first time, we designed and fabricated a novel porous nanotube assembled with vertically aligned 1T MoS2 nanosheets using the scalable hydrothermal method. This metallic nanotube has following advantages: (i) intrinsic high electrical conductivity that promotes the rate performance of battery and eliminates using of conductive additive; (ⅱ) hierarchical, hollow, porous, and aligned structure that assists the electrolyte transportation and diffusion; (ⅲ) tubular structure that avoids restacking of 2D nanosheets, therefore maintaining the electrochemistry cycling stability; (iv) shortened ion diffusion path that improves the rate performance. This 1D metallic MoS2 nanotube has been demonstrated to be a promising anode material for lithium-ion batteries. The unique structure delivers an excellent reversible capacity of 1100 mA h g-1 under a current density of 5 A g-1 after 350 cycles, and an outstanding rate performance of 589 mA h g-1 at a current density of 20 A g-1. Furthermore, attributed to the material’s metallic properties, the electrode with 100% pure material without any additive provides an ideal system for the fundamental electrochemical study of 1T MoS2. This study firstly revealed the characteristic oxidation peak at 1.5 V in cyclic voltammetry of 1T MoS2. This research shed light on fabricating metallic 1D, 2D or even 3D structure with 2D nanosheets as building blocks for various applications.
8:00 PM - NM03.14.38
Confinement Induced Ordering and Miniaturization in Dewetting of Thin Polymer Bilayers on Nano-Patterned Substrates with Complex Geometry
Nandini Bhandaru 2 , Anuja Das 1 , Rabibrata Mukherjee 1
2 Center of Nanosciences, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh, India, 1 , Indian Institute of Technology Kharagpur, Kharagpur India
Show AbstractDewetting of a thin polymer film on physically heterogeneous substrates is known to result in numerous ordered meso scale structures. This work reports the dewetting of a thin bilayer of Polystyrene (PS) and Poly(methylmethacrylate) (PMMA) on a topographically patterned non wettable substrate comprising array of pillars, arranged in a square lattice. With gradual increase in the concentration of PMMA solution (Cn–PMMA), the morphology of the bottom layer changes as: 1) aligned array of spin dewetted droplets arranged along substrate grooves at very low Cn–PMMA; 2) threads surrounding each pillar at intermediate Cn–PMMA; and 3) continuous bottom layer at higher Cn–PMMA. The morphology of the PS top layer depends largely on the nature of the pre-existing bottom layer, in addition to Cn–PS. An ordered array of PMMA core – PS shell droplets form right after spin coating when both Cn–PMMA and Cn–PS are very low. The bilayers with all other initial configurations evolve during thermal annealing, resulting in variety of ordered structures. Several unique morphologies are observed during the dewetting process including laterally coexisting structures of the two polymers confined within the substrate grooves, an array of core-shell and single polymer droplets arranged in an alternating order and more. These complex structures cannot be fabricated by any standard lithography technique. Under a certain condition, the partially dewetted bottom layer just covering the substrate grooves imparts stability to an intact top PS layer against dewetting. Apart from ordering, significant miniaturization and downsizing of dewetted feature periodicity and dimension as compared to dewetting of a single layer on a flat substrate is observed. With the help of a morphology phase diagram, we show that the ordering is achieved over a wide combination of Cn–PMMA and Cn–PS, though the morphology and dewetting pathway differs significantly with variation in the thickness of the individual layers.
8:00 PM - NM03.14.39
Spectral Variation Analysis for Silicon-Wire-Based Microring Resonators
Tsuyoshi Horikawa 1 2 , Akemi Shiina 2 , Keizo Kinoshita 2 , Tohru Mogami 2
1 , AIST, Tsukuba Japan, 2 , PETRA, Tsukuba, Ibaraki, Japan
Show AbstractPhotonic integrated circuits (PICs) using silicon photonics technology is a possible solution to overcome bandwidth bottleneck in data transmission between LSIs. In optical transceivers for LSI interconnect, silicon wire-waveguides are used for connection between integrated optical devices, and for resonance or interference in wavelength filtering devices, such as ring resonators. In the manufacture of PICs, it is a major concern to secure the reproducibility in the circuit performance because the fabrication variation in the waveguides affects the spectra of the wavelength filters in the PICs.
In this paper, we investigated the spectral variation for microring resonators consisting of silicon wire-waveguides, and found that there is a correlation between deviations for free spectral range and resonant wavelength. Theoretical analysis suggested that the fabrication deviation in the waveguide width arises these spectral changes. The wafer-level width distribution estimated from the observed correlation successfully reproduced the results of physical measurement.
This research was partly supported by the NEDO.
8:00 PM - NM03.14.40
Pre-Compression-Assisted Approach to Wavy Networks of Metal Nanowires Imparting Omnidirectional Stretchability and Transparency
Jun Beom Pyo 1 , Byoung Soo Kim 1 2 , Jonghwi Lee 2 , Jong Hyuk Park 1 , Sang-Soo Lee 1
1 , Korea Institute of Science and Technology, Seoul, SE, Korea (the Republic of), 2 Department of Chemical Engineering and Materials Science, Chung-Ang University, Seoul Korea (the Republic of)
Show AbstractFabrication of transparent conductors that are mechanically deformable or stretchable is challenging yet essential in developing smart textiles or soft electronic devices. So far, indium tin oxide (ITO), the most commonly used transparent conductive materials has been known to hardly exhibit long term stability under mechanical stress, and thus, investigations of novel transparent electrodes in curvilinear stretchable devices have been extensively growing. Network architecture of metal nanowires (NWs) including Ag NWs has been considered one of the strong candidates for the mission due to their superior transparency and conductivity. However, most previous studies have been focusing only on uniaxially stretchable conductors, and practical requirements as stretchable electronics cannot be fully satisfied with uniaxial performance.
Here we present novel design of Ag NW network-based transparent conductors capable of omnidirectional stretchability. We have developed a facile method to control the structure of wavy NW networks in an isotropic manner that releases applied strains so that the NWs sustain the conductive nanowire network. Strain tests and cyclic tests showed that samples prepared by our method including the pre-compression have high strain tolerance regardless of the direction of stretching while electrodes prepared via pre-straining method have strain tolerance only in the direction of a pre-strained direction. Our stretchable electrodes based on the wavy 2-D networks resulted in superior cyclic stability and greater expansion when involved in actuators as compliant electrodes. We anticipate our findings could potentially be applied to other metal NWs for stretchable optoelectronic applications.
8:00 PM - NM03.14.42
Electromigration Behaviors of Single-Crystalline Ge2Sb2Te5 Nanowire Evaluated by the Mean-Time-to-Failure Test
Shao-En Lo 1 , Chi-Jui Yeh 1 , Tsung-Eong Hsieh 1
1 , National Chiao Tung University, Hsinchu Taiwan
Show AbstractPhase-change memory (PCM) has been widely recognized as a promising candidate for next-generation non-volatile memory. PCM utilizes chalcogenides such as Ge2Sb2Te5 (GST) as the programming materials in which the signal recording is achieved by electrical heating. Accordingly, electromigration (EM) of chalcogenides becomes one of the crucial issues affecting the reliability of PCM. Recently, PCM containing chalcogenides in one-dimensional (1-D) form is proposed due the pursuit of miniaturization and performance enhancement of electronic devices. It is hence the motivation of this study to evaluate the EM behaviors of GST nanowires (NWs) so that a better understanding on the reliability of PCM in 1-D form can be secured.
First, the single-crystalline GST NWs were prepared by the vapor-liquid-solid method at the conditions of ambient pressure of 1 torr, vehicle gas flow rate of 50 sccm and temperature of 415°C. Afterward, the mean-time-to-failure (MTTF) tests under direct-current (DC) bias were performed and the data were analyzed in terms of the Black’s theory in order to explore the EM behaviors of GST NWs. The MTTF tests carried out at the temperature of 200°C and current densities ranging from 4x103 to 3.2x105A/cm2 found that the n value or, the current density exponent of Black’s equation, is equal to 0.98. Since n value is about equal to one, mass transport of GST NWs during EM process is hence mainly via the surface diffusion. Moreover, the MTTF tests performed at the current density of 6x104 A/cm2 and temperatures ranging from 200 to 300°C revealed the activation energy of EM is 1.23 eV. This indicates a better resistance to EM failure of GST NWs in comparison with the thin-film samples. Energy dispersive spectroscopy found that Te elements migrate to the anode side whereas Ge and Sb elements move toward the cathode side of GST NWs subjected to the DC bias. Scanning electron microscopy observed the occurrence of necking in cathode side of GST NWs which pronounces the EM failure, implying the dominance of electron wind force effect during the EM process. The necking is ascribed to the vacancy accumulation caused by surface diffusion, consequently escalating the Joule heating effect and eventually inducing the EM failure of GST NWs.
Keywords: Ge2Sb2Te5, Nanowires, Vapor-liquid-solid process, Electromigration.
*Corresponding author’ email: tehsieh@mail.nctu.edu.tw
8:00 PM - NM03.14.43
A Strategy to Fabricate Carbon Nanotube-Based Stretchable Electrodes for Wearable Energy Devices
Seungki Hong 1 2 , Kyungsik Do 1 2 , Sangkyu Lee 1 , Dae-Hyeong Kim 1 2
1 , Institute for Basic Science (IBS), Seoul Korea (the Republic of), 2 , Seoul National University, Seoul Korea (the Republic of)
Show AbstractCarbon nanotubes (CNTs) have many advantages including soft mechanical property, electrical conductivity, electrochemical activity, and large surface area that make them suitable candidate for soft current collector in wearable energy devices. However, their electrical conductivity is typically lower than that of metal conductors, and besides, complex modes of mechanical deformations including stretching and twisting usually lead to loss of contacts between CNT networks, and consequently deteriorate their electrical property. To address this issue, here we introduce a novel strategy to fabricate stretchable electrodes based on laterally-combed CNT networks and ink-jet printing method. Lateral combing of vertically-grown CNT networks maintains contact points between individual CNTs even under complex mechanical deformations. Additional electroplating of Nickel metal drastically increases electrical conductivity of stretchable CNT electrode. Moreover, the stretchable CNT electrodes can be patterned in various shapes including meandering serpentine design providing excellent deformability by using ink-jet printing method. The resulting stretchable electrode shows very low sheet resistance of 6 Ω per square with negligible resistance change under ~ 100 % of stretching and even after 1,000 repeated stretching cycles of the 50 % applied strain. Furthermore, we demonstrated an integrated wearable energy supplying system composed of energy harvesting (wireless power transmission coil and triboelectric generator), energy storage (supercapacitors and lithium ion battery) devices using the stretchable CNT electrodes. This novel strategy to fabricate stretchable CNT electrodes provides new opportunities in wearable and stretchable energy applications.
8:00 PM - NM03.14.44
Synergistic Coupling of Cobalt Nitrides and Iridium based Catalysts for Efficient Oxygen Evolution Reaction
Su-Ho Cho 1 , Ki Ro Yoon 1 , Ji-Won Jung 1 , Chanhoon Kim 1 , Jun Young Cheong 1 , Dooyoung Youn 1 , Il-Doo Kim 1
1 , Korea Advanced Institute of Science and Technology (KAIST), Daejeon Korea (the Republic of)
Show AbstractThe utilization and development of efficient water electrolysis for hydrogen production is currently limited due to the sluggish kinetic of the oxygen evolution reaction (OER). Carbon-supported nanomaterials are the most frequently used catalyst-support platform due to their high electrical conductivity and large surface area, and noble metal catalysts such as Ir and Ru are widely adopted as catalytic components for OER. Even though their excellent catalytic activity, low durability of carbon materials and high cost of noble metal catalysts are believed to hinder the use of these materials in practical applications. Herein, we report the use of metallic cobalt nitride (Co4N) nanofibers (NFs) as a highly stable and conductive catalyst supporting materials for the first time. One-dimensional (1D) Co4N NFs network can provide interconnected channels for electron transportation, efficient mass transport (OH-) between interfibers, and numerous surface area for catalysts loading due to its high surface-to-volume ratio, guaranteeing effective catalytic active sites. The Ir catalysts supported on Co4N NFs (Ir@Co4N NFs) exhibit the high OER activity and excellent stability in alkaline media comparable to commercial Ir/C catalyst. These results are attributed to the maximized exposure of catalytic active sites, synergistic charge compensation effect between Co4N and IrOx and cooperative OER catalysis of Co4N support by itself.
8:00 PM - NM03.14.45
Brush-Like Cobalt Nitride Nanorods Anchored Carbon Nanofiber Membrane: 3D Current Collector-Catalyst Integrated Cathode for Long Cycle Li-O2 Batteries
Ki Ro Yoon 1 , Kihyun Shin 1 , Su-Ho Cho 1 , Chanhoon Kim 1 , Ji-Won Jung 1 , Jun Young Cheong 1 , Hyuk Mo Lee 1 , Il-Doo Kim 1
1 , Korea Advanced Institute of Science and Technology (KAIST), Daejeon Korea (the Republic of)
Show AbstractOwing to the growing worldwide demand for global energy, the development of sustainable and renewable energy storage systems is essential. The Li-O2 batteries have the highest theoretical energy density (3,505 Wh kg-1) among currently known energy storage systems, but the critical challenges including high charging overpotential, low power density and low round-trip efficiency resulting in poor cycle life still remain unsolved. To achieve a high reversibility and long cycle life for lithium-oxygen (Li-O2) batteries, the irreversible formation of Li2O2, inevitable side reactions, and low conductivity of cathodes should be overcome. Especially, the development of efficient air cathode has a great significance for improving overall performance because the key reactions, i.e., oxygen reduction and evolution reaction (ORR/OER), occur at the cathode surface during cell operation.
In the present study, we suggest a new air cathode design, 1D catalyst (cobalt nitride (Co4N) nanorods)-current collector (carbon nanofiber (CNF) paper) monolithic 3D network, for a free-standing and flexible Li-O2 battery. Brush-like Co 4N nanorods are conformally anchored on highly conductive N-doped CNFs via hydrothermal growth of Co(OH)F nanorods followed by nitridation step. Co4N-decorated CNF (Co4N/CNF) cathode exhibited excellent electrochemical performance with outstanding stability for over 177 cycles in Li-O2 cells. We investigated the surface chemistry of electrodes via in-depth ex-situ observation and computational simulation. The results revealed that growth mechanism of main discharge products (Li2O2) and mediation of side reactions are largely governed by LiO2 adsorption energy and functional groups especially related to the oxidized carbons (epoxy and carboxyl groups), which have a strong influence on the Li-O2 cell performance. In detail, thin amorphous cobalt oxide layer (<10 nm) is formed on the surface of Co4N nanorods during cycling, which can facilitate reversible formation of Li2O2 and suppress unwanted side reactions. Furthermore, Co4N nanorods with metallic conductivity provide facile electron transport throughout the continuously networked CNFs, leading to significant reduction in overpotential gap (~1.23 V at 700 mAh g-1). The results demonstrate that hierarchically assembled conductive catalyst-current collector integrated cathode offer the most suitable surface chemistry with minimized side reactions, which is essential for enhanced Li-O2 cell performance. Moreover, pouch-type Li-O2 batteries using Co4N/CNF cathode stably operated even under 180° bending.
8:00 PM - NM03.14.46
Nano-Transplantation Printing of Crystallographic-Orientation-Controlled, Highly Ordered Single-Crystal Si Nanowires Applicable for Diverse Surfaces
Hyeuk Jin Han 1 , Jae Won Jeong 2 , Cheolgyu Kim 1 , Keon Jae Lee 1 , Taek-Soo Kim 1 , Yeon Sik Jung 1
1 , KAIST, Daejeon Korea (the Republic of), 2 , KIMS, Changwon Korea (the Republic of)
Show AbstractNanostructured inorganic semiconductors have gained much attention for their advantages in flexible electronic devices due to high flexibility and functionalities. Among the diverse semiconducting nanowires, single crystal silicon nanowires have been widely used because of their unprecedented usefulness in diverse applications. However, single crystal nanowire array fabrication requires complex assembly process, which limits its use in mass-production and wide applications. Here, we introduce a novel fabrication method for single-crystalline silicon nanowire based on nanotransfer printing and transplantation of nanowires on various non-conventional substrates including flexible plastic substrate. Nanopatterns at scale of 30 ~ 200 nm were transferred on single-crystal bare silicon wafer through nanotransfer printing after which two step sequential dry etching process define the silicon nanowires. The width and height of silicon nanowires are controlled by modulating the width of nanopatterns and controlling the etch depth at first vertical etching process, respectively. In addition, by employing specific crystallographic orientations of the wafer and controlling the angle between nanopattens and the particular axis of unit cell of silicon, crystallographic orientations of fabricated silicon nanowires are controlled. Fabricated nanowires were securely transferred onto various substrates through novel transplantation printing process which uses polymeric nano-forcep as transfer medium and solvent-assisted transfer process. The electrical characteristics of the nanowires were examined by fabricating Shocttky-junction field-effect transistor. The usefulness of the silicon nanowires has also been demonstrated by fabricating a piezoresistive strain sensor. Furthermore, the nanotransplantation printing process can be applied to fabricate various high-quality single-crystal semiconducting nanowires, and we expect that these nanostructures can be highly useful for high-performance future nanodevices.
8:00 PM - NM03.14.47
Fabrication of (Hf,Zr)O2 Nanowire Capacitors with a Multilayered Core-Shell Structure
Masaru Shimizu 1 , Yohei Takeuchi 1 , Hironori Fujisawa 1 , Seiji Nakashima 1
1 , University of Hyogo, Himeji Japan
Show AbstractInterest in the one-dimensional ferroelectrics, such as nanowires, nanorods and nanotubes has increased greatly from the view point of not only basic physics but also practical applications. Generally, the sol-gel process, hydrothermal process, electrospinning process and molten-salt process have been employed for synthesizing ferroelectric nanowires. We have already reported the fabrication of PbTiO3/ZnO and PZT/ZnO core-shell nanowire structures by the MOCVD (Metalorganic Chemical Vapor Deposition ) process.
In this paper, HfO2-based nanowire capacitors with a multilayered core-shell structure ((ZnO/(Hf,Zr)O2/ZnO) were experimentally studied for an application to ultrahigh density ferroelectric random access memories (FeRAMs). Recently, HfO2-based ferroelectric materials have attractive much attention because they exhibited good ferroelectric properties down to sub-10nm thickness, which is very appropriate for realization of ultrahigh density 3D-FeRAMs. Vertically allined nanowire capacitors are indispensable for realization of ultrahigh density 3D-FeRAMs.In 3D-FeRAMs, the nanowire typed capacitor could be fabricated without using the deep etching technique as for the trench-typed capacitor.
In our experiments, firstly, ZnO nanowires were grown on Pt/SiO2/Si at 700oC by MOCVD using Zn(C2H5) as a source precursor and O2 as an oxidizing gas. ZnO nanowires play very important roles as a psotive template and electrode. ZnO nanowires were very easy to grow on substrate vertically due to their strong anisotropic c-axis oriented growth (VS-growth). In the next stage, (Hf,Zr)O2 was deposited on ZnO nanowire positive templates by MOCVD using Hf(OC(CH3)3)4, Zr(OC(CH3)3)4 and O2 at 200oC. After annealing at 800oC in an air for 1min, X-ray diffraction pattern showed the orthorhombic (ferroelectric phase) (Hf,Zr)O2(111) peak. Finally, ZnO as a top electrode was deposited on (Hf,Zr)O2/ZnO core-shell nanowire structure at 200oC. ZnO/(Hf,Zr)O2/ZnO multilayered core-shell capacitor structures with diameters of 200-300nm and an aspect ratio of -50 were successfully fabricated solely by MOCVD.
8:00 PM - NM03.14.49
Confinement and Surface Effects on the Itinerant Ferromagnetism in Ni and Ni-Fe Nanowire Arrays—An Ab Initio Study
Ikram Ziti 1 2 , Mohammed Britel 2 , Chumin Wang 1
1 , Universidad Nacional Autonoma de Mexico, Mexico City Mexico, 2 , National School of Applied Sciences, Abdelmalik Esaadi University, Tanger Morocco
Show AbstractThere are growing interests on magnetic nanowires (NW), due to their potential applications in sensors, solar cells, biotechnology, and microelectronics. In particular, the tunable magnetic and chemical properties of nanowires make them an excellent vehicle for applying forces to cells [1]. In this work, we investigate the permanent magnetic moment of Ni and Ni-Fe NW arrays, as well as its dependence on the NW shape, diameter, interwire distance, and chemical composition, in order to analyze the confinement and surface effects on the itinerant magnetic properties. Nowadays, the DFT calculations are mainly based on plane-wave or atomic-orbital basis, and we firstly perform a comparative study of both approaches to address the magnetization of Ni NWs using eight different NW geometries [2]. In the second part, we analyze the quantum confinement effects on the permanent magnetic moments (µ) obtained from the difference between integrated spin-up and spin-down densities of states, for different NW diameters, interwire distances, and Ni-Fe alloys. The ab-initio results are compared with experimental ones and a good agreement is observed. Finally, the carbon functionalized Ni and Ni-Fe nanowires is further studied. In particular, we quantify the magnetic moment modifications as a function of the carbon layer thickness in comparison with the nanowire diameter. Moreover, the adsorption selectivity of these functionalized nanowires is addressed by means of ab initio molecular dynamics [3].
This work has been partially supported by UNAM-IN106317 and CONACyT-252943. Computations were performed at Miztli of DGTIC, UNAM.
[1] A. Hultgren, M. Tanase, C. S. Chen, G. J. Meyer, and D. H. Reich, Cell manipulation using magnetic nanowires, J. Appl. Phys. 93, 7554 (2003);
[2] I. Ziti, M. R. Britel and C. Wang, Atomic-orbital and plane-wave approaches to ferromagnetic properties of NixFe1-x nanowires, MRS Advances 2, 507 (2017).
[3] M. R. Arcos and C. Wang, Fluorine etching in porous silicon: An ab-initio molecular dynamics study, ECS J. Solid State Sci. & Technol. 6, P172 (2017).
8:00 PM - NM03.14.51
Probing the Wurtzite Band Structure and Carrier Dynamics in Single In0.65Ga0.35As and In0.65Ga0.35As/InP Nanowires
Samuel Linser 1 , Iraj Shojaei 1 , Giriraj Jnawali 1 , Howard Jackson 1 , Leigh Smith 1 , Amira Ameruddin 2 , Philippe Caroff 2 , Hoe Tan 2 , Chennupati Jagadish 2
1 Department of Physics, University of Cincinnati, Cincinnati, Ohio, United States, 2 Department of Electronic and Materials Engineering, The Australian National University, Canberra, Australian Capital Territory, Australia
Show AbstractWe use transient Rayleigh scattering (TRS) measurements to explore the band structure of single wurtzite In0.65Ga0.35As nanowires. We studied core-only InGaAs nanowires as well as strained core-shell InGaAs-InP heterostructures at 300 K and 10 K, with probe photon energies in the near-infrared from 0.79 to 1.16 eV. We observe an electronic transition in the 10 K core-shell spectra at 0.97 eV, a significantly higher energy than the fundamental bandgap energy of bulk zincblende In0.65Ga0.65As of similar composition. We observe a corresponding transition in the 10 K core-only spectra at 0.86 eV. This blue-shift is consistent with compressive strain in the InGaAs core of the core-shell nanowire. We report an order of magnitude enhancement in the 10 K carrier lifetimes of the core-shell nanowires (2100 ps) compared to the core-only nanowires (90 ps). Numerical modeling of our TRS spectra, accounting for valence band splitting of the wurtzite crystal phase, provides further insight into the cooling dynamics of the electron-hole plasma within a single nanowire after photoexcitation.
We acknowledge the financial support of the NSF through grants DMR 1507844, DMR 1531373 and ECCS 1509706, and the Australian Research Council.
8:00 PM - NM03.14.52
Enhancement of the Catalytic Activity of 1D Sodium Titanate Nanotubes in Biodiesel Production
Tatiana Klimova 1 , Mark Eugenii Martinez-Klimov 1 , Pedro Roquero Tejeda 1 , Antonio Gomez-Cortes 2 , Gabriela Diaz-Guerrero 2
1 Facultad de Química, Universidad Nacional Autónoma de México (UNAM), Ciudad de Mexico Mexico, 2 Instituto de Física, Universidad Nacional Autónoma de México (UNAM), Ciudad de México Mexico
Show AbstractOne dimensional sodium titanate nanotubes (STNT) synthesized by the Kasuga method have already been tested as catalysts for biodiesel production from vegetable oil and methanol giving good results. In the present work, we modified the above catalysts by the addition of different amounts of sodium carbonate in order to increase their basicity and, consequently, improve their performance in the transesterification reaction. Catalysts with sodium carbonate loadings between 1 and 10 wt. % were prepared. Hereinafter, these catalysts will be denoted as STNT-x, where x represents nominal Na2CO3 weight loadings in the samples. Synthesized catalysts were characterized by N2 physisorption, X-ray powder diffraction (XRD), FT-IR, scanning electron microscopy (SEM-EDX), transmission electron microscopy (TEM), and CO2 temperature-programmed desorption (CO2-TPD). The STNT reference had high sodium content (10.3 wt. %) and attractive textural characteristics (surface area of 222 m2/g and pore volume of 0.46 cm3/g). Addition of sodium carbonate to STNT resulted in a slight decrease in the specific textural characteristics of the STNT materials. However, all of them maintained a characteristic nanotubular structure and showed the presence of only the sodium trititanate crystalline phase (Na2Ti3O7). No agglomeration of sodium carbonate was detected by XRD. Addition of sodium carbonate to the STNT allowed us to obtain 1D nanostructured materials with a higher amount of sodium, which resulted in an increase in the total amount of basic sites and especially in the proportion of strong basic sites. Thus, STNT-3 and STNT-5 materials had about 18 – 19 % of strong basic sites, which represents a noticeable increase in comparison with the starting STNT reference (13 % of strong basic sites). Catalytic activity tests were performed in transesterification of soybean oil with methanol. Reactions were performed in a batch reactor, at 80 oC, 1 h reaction time, 1 wt. % of the catalyst, using methanol:oil molar ratio of 20:1. The best results were obtained with the catalysts containing 3 and 5 wt. % of sodium carbonate, which gave methyl esters (ME) yields of 90-91 %. In the same conditions, the reference STNT catalyst resulted only in a 53 % of ME yield. Such a strong increase in the catalytic activity of Na2CO3-containing sodium titanate nanotubes was attributed to a sinergetic effect between the impregnated sodium salt and 1D nanostructured STNT material.
8:00 PM - NM03.14.53
Preparation of ZnO Based One-Dimensional Heteroarchitecture via Non-Solvent Method for High Performance Photocatalysis
Chi Wang 1 , Jun Wu 1 , Chengzhi Luo 1 , Chunxu Pan 1
1 , Wuhan University, Wuhan China
Show AbstractAmong various photocatalysis, ZnO has been recognized as a kind of excellent materials for photocatalysis, because of its high photosensitivity, nontoxic nature, and large band gap. In this paper, we introduce two novel and facile methods for preparing the ZnO based one dimensional heteroarchitecture. The experimental results exhibit a great improvement on the separation efficiency of electrons and holes and photocatalytic properties.
1) Preparation of Au Nanoparticles Decorated ZnO/NiO Heterostructure via Non-solvent Method for High-Performance Photocatalysis. In this work, the heterostructure photocatalytic composite was prepared according to the process, i.e., a Zn layer upon Ni foam substrate is prepared by using a pulse electro-deposition, then the ZnO nanoneedle/NiO heterostructural composite is obtain via thermal oxidation, and at last, the composite is modified with the dispersively deposited Au nanoparticles (Au NPs) by ion sputtering. The surface plasmon resonance (SPR) effect of the Au NPs significantly enhances the light absorption. Meanwhile, the Au NPs form a Schottky barrier with ZnO nanoneedles and further inhibit the recombination of photo-generated electron-holes. In addition, due to the non-solvent conditions, the introduction of impurities is avoided, and it shows strong photocatalytic stability. The experimental results reveal that, the optimized Au/ZnO/NiO composite exhibits up to two times photocatalytic performance on RB degradation and higher stability than that of regular ZnO/NiO composite. The present experimental strategy can also be used for other noble metals, and it is expected to have important application prospects in the fields of environmental purification, solar cells and hydrogen generation, etc.
2) Preparation of 3D reticulated ZnO/CNF/NiO heteroarchitecture for high-performance photocatalysis. In this work, we introduce a novel facile two-step chemical vapor deposition (CVD) route as a straightforward protocol for preparing the ZnO/CNF/NiO heteroarchitectured composite, i.e., carbon nanofibers (CNFs) grew directly on porous Ni foam, and ZnO nanorods were seamlessly and uniformly grew from CNFs. The experimental results revealed this composite an excellent photocatalytic performance 2.5 times higher than that of regular ZnO/NiO composite. This is because of the following advantages: The 3D reticulated structure provides more nucleation sites for ZnO nanorods, in which the light would be reflected multiply, and thus increased the absorption efficiency of the light; Because CNFs formed two strong and compact hetero-interfaces with both ZnO nanorods and NiO substrate respectively, it provided barrier-free access to transport photo-induced carriers (electrons and holes) between ZnO and NiO as bridge during photocatalytic process, which therefore greatly improved the separation efficiency of the electrons and holes.
8:00 PM - NM03.14.54
Growth, Structural and Visible Emission Studies of InGaN Nanostructures on p-Si by Molecular Beam Epitaxy
Kiran Dasari 2 , Bibek Thapa 2 , Wojciech Jadwisienczak 3 , Jingzhou Wang 1 , Ratnakar Palai 2
2 Department of Physics, University of Puerto Rico at Río Piedras, San Juan, Puerto Rico, United States, 3 School of Electrical and Computer Sciences, Ohio University, Athens, Ohio, United States, 1 , Global Prior Art, Inc. , Boston, Massachusetts, United States
Show AbstractHigh indium content InGaN alloys are most studied semiconductor materials for the optoelectronic, spintronic, and solar cell applications. The growth of high-quality InGaN is still a great challenge due to the formation of high defect density, complex growth thermodynamics, and large lattice mismatch between InN and GaN. One dimensional (1D) structures such as, nanorods and nanowires offer defect-free, high crystalline InGaN due to minimal strain effect. The growth of InGaN directly on silicon substrate is very challenging and needs more attention. In this presentation, the growth of self-catalyzed nanorods of InxGa1-xN with different In-concentrations from 0.10 to 0.26 will be reported on p-Si (111) substrates at different growth temperatures from 600 °C to 900 °C by plasma-assisted molecular beam epitaxy. The growth of the nanorods monitored by in situ reflection high energy electron diffraction (RHEED) revealed the formation of the single crystalline growth along the c-axis. Highly crystalline growth of InGaN (000l) along the c-axis without any phase segregation and phase separation is confirmed from the x-ray diffraction (XRD) analysis. The vertically aligned nanowires are confirmed from the top-view and cross-sectional view of high resolution scanning electron microscopy (HRSEM). The length and diameter of the nanorods are found to be in the range of 200-290 nm and 10- 50 nm, respectively. X-ray photoelectron spectroscopy is used to study the elemental composition in the as-grown InGaN nanorods and revealed all the fundamental states of Ga, In, and N. Bright, and sharp near band emission (NBE) centered at 560 nm in the visible range has been revealed from the InGaN grown at 900 °C in the room temperature photoluminescence (PL). Selected InGaN nanorods samples were characterized using deep level transient spectroscopy (DLTS) to investigate the role of defects. The devices tested in this work had a Schottky contact with diameter of 5x10-3 mm2 formed by evaporation of gold for InGaN samples through a metal mask at room temperature. A eutectic InGa alloy is used onto the back side of the Si substrates to form the Ohmic contact or ring-shaped Ti/Au Ohmic contacts were evaporated through a metal mask. DLTS measurements were conducted using a Sula DDS-12 DLTS system equipped with a cryostat covering the temperature range from 10 K to 500 K. The identified DLTS energy traps were compared with other energy traps reported for III-Ns NRs in literature. Furthermore, the temperature dependent PL studies of InGaN on p-Si will be demonstrated to understand the influence of the growth temperature on the In-content fluctuations and optical properties of the InGaN on Si substrate. In addition, the high-resolution transmission electron microscopy and the temperature dependent PL will be implemented and studied for the better understanding of the growth and luminescent properties, and will be discussed in detail.