Symposium Organizers
Feng Bai, Henan University
Ying-Bing Jiang, Angstrom Thin Film Technologies LLC
Binsong Li, Tsinghua Innovation Center in Dongguan
Dong Qin, Georgia Institute of Technology
Symposium Support
Dongguan-RITS Innovation Center
Henan University
ED5.1: Photocatalysis I
Session Chairs
Tuesday PM, April 18, 2017
PCC North, 100 Level, Room 129 A
11:30 AM - *ED5.1.01
Interfacial Self-Assembly of Hierarchically Structured Nanoparticles with Photocatalytic Activity
Hongyou Fan 1 2
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 , University of New Mexico, Albuquerque, New Mexico, United States
Show Abstract
Design and engineering of the size, shape, and chemistry of photoactive building blocks enable the fabrication of functional nanoparticles for applications in light harvesting, photocatalytic synthesis, water splitting, phototherapy, and photodegradation. Here, we report the synthesis of such nanoparticles through a surfactant-assisted interfacial self-assembly process using optically active porphyrin as a functional building block. The self-assembly process relies on specific interactions such as π–π stacking and ligand coordination between individual porphyrin building blocks. Depending on the kinetic conditions, resulting structures exhibit well-defined one- to three-dimensional morphologies such as nanowires, nanooctahedra, and hierarchically ordered internal architectures. At the molecular level, porphyrins with well-defined size and chemistry possess unique optical and photocatalytic properties for potential synthesis of metallic structures. On the nanoscale, controlled assembly of macrocyclic monomers leads to formation of ordered nanostructures with precisely defined size, shape, and spatial monomer arrangement so as to facilitate intermolecular mass and energy transfer or delocalization for photocatalysis. Due to the hierarchical ordering of the porphyrins, the nanoparticles exhibit collective optical properties resulted from coupling of molecular porphyrins and photocatalytic activities such as photodegradation of methyl orange (MO) pollutants and hydrogen production. The capability of exerting rational control over dimension and morphology provides new opportunities for applications in sensing, nanoelectronics, and photocatalysis.
Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
12:00 PM - *ED5.1.02
Effects of Nano-Scale Surface Modifications on Photoelectrochemical Solar Fuel Production
Tsutomu Minegishi 1 2 , Kazunari Domen 1
1 Department of Chemical System Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan, 2 PRESTO, JST, Bunkyo-ku, Tokyo, Japan
Show AbstractSunlight driven fuel production is the key technology for the construction of sustainable energy society. Hydrogen has been regarded as a promising fuel derived from only water and renewable energy, and can be utilized in devices such as fuel cells and combustion engines. On the other hand, investigations about the hydrogen carriers such as ammonia and methylcyclohexane (MCH) also have arisen as one of the most important research issues.
Photocatalytic and photoelectrochemical (PEC) reactions are the promising way to produce fuels such as hydrogen and/or hydrogen carrier directly utilizing solar energy, and development of photocatalytic materials and construction of reaction sites are of crucial for these techniques. BaTaO2N (BTON) is one of the attractive photocatalytic materials owing to the relatively long absorption edge of <660 nm and a preferable band structure for water splitting. BTON photoanode prepared by particle transfer method shows relatively large photocurrent and stable water oxidation. [1] A solid solution of ZnSe and CuIn0.7Ga0.3Se2 (CIGS) with composition of (ZnSe)0.85(CIGS)0.15 is the recently reported promising candidate for photocathode because of a preferable absorption edge of ~900 nm with an outstanding onset potential of cathodic photocurrent, 0.9 VRHE.[2]
In the present study, PEC properties of surface modified particulate BTON photoanode and (ZnSe)0.85(CIGS)0.15 thin film photocathode on overall water splitting and/or overall MCH production were investigated in detail. BTON based photoanode sequentially modified with Co-species and Ir-species showed enhanced photocurrent contributing oxygen evolution. The improved PEC properties are due to both the enhanced charge separation by Co-species and high oxygen evolution activity of Ir-species. PEC hydrogen evolution reaction from water over (ZnSe)0.85(CIGS)0.15 based photocathode is clearly enhanced by introduction of multilayer structure. A surface modification with Pt and CdS enhanced both photocurrent value and an onset potential because of a modulated band diagram at solid-liquid interface and enhanced hydrogen evolution reaction. Furthermore, introduction of bilayer structure composed of In-rich and Ga-rich layer into the (ZnSe)0.85(CIGS)0.15 layer largely increased cathodic photocurrent under simulated sunlight. A cross-sectional electron beam-induced current (EBIC) mapping analysis clarified that the enhancement of the photocurrent is because of improved structural properties rather than of enhanced charge separation by varied band diagram.
[1] K. Ueda, T. Minegishi, J. Clune, M. Nakabayashi, T. Hisatomi, H. Nishiyama, M. Katayama, N. Shibata, J. Kubota, T. Yamada, and K. Domen, J. Am. Chem. Soc. 2015, 137, 2227−2230.
[2] H. Kaneko, T. Minegishi, M. Nakabayashi, N. Shibata, Y. Kuang, T. Yamada, and K. Domen, Adv. Funct. Mater. 2016, 26, 4570–4577.
12:30 PM - ED5.1.03
Ferroelectric Field Tuned Photoelectrochemical Water Splitting Using Graphene as Electrode
Xiaobo Chen 1 2 , Matthew Starr 1 , Yanhao Yu 1 , Jihye Bong 3 , Zhenqiang Ma 3 , Yong Qin 2 , Xudong Wang 1
1 Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States, 2 School of Physical Science and Technology, Lanzhou University, Lanzhou, Gansu, China, 3 Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States
Show AbstractPhotoelectrochemical (PEC) water splitting is a promising strategy for converting solar energy to chemical fuels. To accomplish efficient fuel production, the photoelectrode desirably need following characteristics: broad-band light absorption, rapid electron-hole separation and effective Faradic surface reaction. Prevailing strategies to promote the charge separation includes reducing the crystal size to the scale of the hole diffusion length; and increasing the carrier conductivity by morphology and crystallography control. Nevertheless, both strategies are restricted by the limit of synthesis procedures. Recently, permanent electric polarization (e.g., piezoelectric and ferroelectric potentials) were discovered to be an effective approach to tune the charge separation property of PEC electrodes beyond the limitation of structure and chemistry optimizations, known as piezotronics. The main challenge of this technology is how to sufficiently delivering free charges to the out circuit without screening out the electric polarizations. The trade-off between the charge collection and the electric polarization severely constrains the materials selection, film thickness and structural design of polarization-enhanced PEC electrodes, which synergistically jeopardizes the piezotronic enhancement.
Graphene is a two dimensional carbon material with unique electric and mechanical properties. The semimetal characteristic of graphene endows it a moderate free electron density, which is settled between metals and semiconductors. This unique property makes graphene a promising electrode selection for balancing the charge collecting and piezopotential screening in a piezotronic PEC system. Here, we demonstrated a ferroelectric polarization-enhanced PEC performance of TiO2 photoanode with graphene as the charge collection electrode sandwiched between the photoactive TiO2 and ferroelectric single crystalline lead magnesium niobate-lead titanate (PMN-PT). Both theoretical and experimental results show that the ferroelectric field is able to penetrate through graphene and further altering the depletion width and amplitude of photoactive TiO2. As a consequence, the photocurrent density and onset potential of TiO2 electrodes can be manipulated by controlling the polarization condition of PMNPT. By poling PMNPT with forward bias, the light current density increased from 0.08 mA/cm2 to 0.12 mA/cm2 at potential of 0 V vs. Ag/AgCl, and the onset potential decreased from -0.82 to -0.91 V. Reversely, backward bias induced a reduction of photocurrent density from 0.08 mA/cm2 to 0.06 mA/cm2 at potential of 0 V vs. Ag/AgCl, and an increase of onset potential from -0.82 to -0.74 V versus RHE. This study suggests graphene is a promising electrode material for piezotornic-enhanced PEC cells for its good conductivity and low charge density.
12:45 PM - ED5.1.04
Twin Defects Control the Shape of Ternary Silver Halide Nanocrystals for Photocatalytic Reactions
Bo Yin 1 2 , Xing Huang 3 , Rohan Mishra 4 1
1 Institute of Material Science and Engineering, Washington University in St. Louis, St. Louis, Missouri, United States, 2 Chemistry, Washington University in St. Louis, St. Louis, Missouri, United States, 3 Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, United States, 4 Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, Missouri, United States
Show AbstractSilver halide particles with small clusters of reduced silver metal on their surface are active photocatalysts for both the degradation of organic molecules and the reduction of carbon dioxide to produce methanol and ethanol. We demonstrate that the anion composition of ternary silver bromoiodide, AgBr1-xIx, nanocrystals determines their shape through the introduction of twin defects as the nanocrystals are made more iodide-rich. AgBr1-xIx nanocrystals grow as single-phase, solid solutions with the rock salt crystal structure for anions compositions ranging from 0 ≤ x < 0.38. With increasing iodide content the morphology of the nanocrystals evolves from cubic to truncated cubic to hexagonal prismatic. Structural characterization indicates the cubic nanocrystals are bound by {100} facets whereas the hexagonal prismatic nanocrystals possess {111} facets as their top and bottom surface. Our observations are consistent with a growth model in which the presence of multiple twin defects parallel to a {111} surface enhances lateral growth of the side facets, which changes the nanocrystal shape. Using these ternary silver bromoiodide nanocrystals of different controlled morphologies, we are able to study the facet-dependence of photocatalytic reactions, such as CO2 reduction.
ED5.2: Nanocrystal I
Session Chairs
Tuesday PM, April 18, 2017
PCC North, 100 Level, Room 129 A
2:30 PM - *ED5.2.01
Gold Nanocages as Photothermal Transducers for Controlled Release and Sensing Applications
Younan Xia 1
1 , Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractGold nanocages are hollow nanostructures with ultrathin (<2 nm) and porous walls. They have strong, highly tunable optical absorption in the visible and near-infrared regions, making them excellent photothermal transducers for a range of applications, including controlled release for drug delivery and optical sensing for detection and actuation. In this talk, I will start with a brief update on the recent progress in synthesis, including the preparation of gold nanocages as small as 15 nm in size, together with well-defined pores at the corner sites. I will then illustrate how gold nanocages can be integrated with other functional materials such as smart polymer, phase-change materials, and pyroelectric polymers for an array of technologically important applications.
3:00 PM - *ED5.2.02
Nanoscale Optical Interactions in Precise Assemblies
Paul Weiss 1
1 CNSI, Chemistry & Biochemistry, Materials Science & Engineering, University of California, Los Angeles, Los Angeles, California, United States
Show AbstractWe use molecular design, tailored syntheses, intermolecular interactions, and selective chemistry to direct molecules into desired positions to create nanostructures with controlled environments and dimensionality, to connect functional molecules to the outside world, and to serve as test structures for measuring single or bundled molecules and assemblies. We have developed and applied new multimodal nanoscale analysis tools based on the scanning tunneling microscope (STM) to measure structure, function, and spectra simultaneously. We are particularly interested in the interactions of photons with precisely assembled structures. The measured results of photoexcitation include photoconductivity and regioselective reaction. We apply this method to optimize molecules and materials for energy conversion and storage. Related imaging spectroscopies we have developed give access to the cooperative action of assembled molecular motors and the identification and orientations of parts of molecules such as amyloid-forming oligopeptides without averaging and without the need to crystallize the biomolecular assemblies. Concepts from sparsity and compressive sensing are developed and applied to guide efficient data acquisition and to accelerate data analysis and information assembly.
3:30 PM - ED5.2.03
Permanent Excimer Superstructures by Supramolecular Networking of Metal Quantum Clusters
Sergio Brovelli 1 , Angelo Monguzzi 1 , Beatriz Gonzalez 1 , Francesco Meinardi 1
1 , University of Milano Bicocca, Milano Italy
Show AbstractMetal quantum clusters are an important class of functional nanomaterials with growing applicative potential as size-tunable biocompatible luminescent probes for molecular theranostics and optoelectronic technologies. Here, we demonstrate for the first time that the optical properties of gold clusters (Au8), and in particular the energy separation between the emission and absorption spectra (Stokes shift), can be tuned by control of the inter-particle distance imposed by the capping ligands leading to the formation of inter-cluster excimers. Based on this newfound motif, we demonstrate a strategy for overcoming the intrinsic limitation to the use of molecular excimers in single-particle applications, that is, their nearly zero collisional formation probability in ultra-diluted solutions. To this aim, we use Au8 clusters as building blocks for fabricating permanent excimer-like colloidal superstructures (Au8-pX) held together by a network of hydrogen bonds between the capping ligands. In the ground state, unexcited clusters behave as individual photophysical entities, whilst optical excitation results in the formation of inter-cluster excimers featuring long-lived Stokes-shifted luminescence with no corresponding excitation transition. The obtained supramolecular architectures effectively represent a new aggregation state of matter conveying the photophysics of excimers into self standing individual particles that find their natural application as non-resonant emitters in cellular imaging and integrated photonic nanotechnologies. Importantly, in vitro confocal imaging experiments reveal the strong ability of Au8-pXs in scavenging cytotoxic reactive oxygen species responsible of premature cellular death, thereby further enhancing their potential for bio-medical applications.
Reference
Santiago-Gonzalez, B., Monguzzi, A., Azpiroz, J. M., Prato, M., Erratico, S., Campione, M., Lorenzi, R., Pedrini, J., Santambrogio, C., Torrente, Y., De Angelis, F., Meinardi, F. & Brovelli, S. Permanent excimer superstructures by supramolecular networking of metal quantum clusters. Science 353, 571-575 (2016).
3:45 PM - ED5.2.04
ALD-Grown Secondary Electron Emission Layer Studies for Microchannel Plates for Photodetection
Omkar Shende 1 2 , Anil Mane 1 , Jeffrey Elam 1
1 , Argonne National Laboratory, Lemont, Illinois, United States, 2 , Princeton University, Princeton, New Jersey, United States
Show AbstractRecent developments in the fabrication processes for microchannel plates (MCPs) using thin film functionalization methods, especially atomic layer deposition (ALD), allow precise and separate control over both resistive and electronic, namely secondary electron emission (SEE), properties of an MCP. By controlling the SEE material, thickness, and microstructure, it is possible to enhance the MCP’s SEE characteristics. These high gain MCPs can be used as electron multipliers in a variety of applications, including photodetectors, sensors, ToF mass spectrometers, in medical and scientific imaging, or any application where signal amplification is valued.
In particular, chemistries involving the oxides of magnesium and aluminum show promising results, yielding high gain values at coated thicknesses as low as 5-15 nm. We have assembled a high-vacuum-based MCP test setup to measure material parameters, including gain uniformity across samples via phosphor imaging on very short time scales (2 – 3 hrs). A systematic study of SEE layer thickness versus gain was performed using this newly assembled MCP test setup. Gain values on the order of 103 – 105 were observed and were shown to increase with secondary electron emission layer thickness, until a saturation point was reached for both Al2O3 and MgO coatings. Here, we present this behavior’s effects on MCP gain as a function of the thickness of precise ALD-grown SEE layer thickness.
4:30 PM - *ED5.2.05
Nanostructured Conjugated Polyelectrolyte Films—Properties and Applications
Kirk Schanze 1
1 , University of Texas, San Antonio, San Antonio, Texas, United States
Show AbstractConjugated polyelectrolytes (CPEs) are polymers that feature a pi-conjugated backbone that is functionalized with ionic charged units. These polymers feature the opto-electronic functionality characteristic of the conjugated backbone, with solubility in water. In addition, CPEs are polymer amphiphiles, and as such they undergo self-assembly to form nanostructured polyelectrolyte multilayer films at interfaces, and spontaneous self-assembly into nanoscale aggregates in aqueous solution. The talk will overview work which has characterized the structure and properties of the nanoscale CPE assemblies, and describe their application in hybrid solar cells and in light activated antimicrobials.
References:
Corbitt, T. S. et al. “Conjugated Polyelectrolyte Capsules: Light-Activated Anti-microbial Micro ‘Roach Motels’ “, ACS Appl. Mater. & Interfaces 2009, 1, 48-52, DOI: 10.1021/am800096q.
Fang, Z. et al. “Low Bandgap Donor-Acceptor Conjugated Polymer Sensitizers for Dye-Sensitized Solar Cells”, J. Am. Chem. Soc. 2011, 133, 3063-3069, DOI: 10.1021/ja109926k.
Parthasarathy, A. et al. “Conjugated Polyelectrolytes with Imidazolium Solubilizing Groups. Properties and Application to Photodynamic Inactivation of Bacteria”, ACS Appl. Mater. Interfac. 2015, 7, 28027-28034, DOI: 10.1021/acsami.5b02771.
5:00 PM - *ED5.2.06
Advanced Near-Infrared Fluorescence In Vivo Imaging—Seeing is Believing
Qiangbin Wang 1
1 , Chinese Academy of Sciences, Jiangsu China
Show AbstractFluorescent imaging in the second near-infrared window (NIR-II, 1.0~1.4 μm) is appealing in in vivo imaging due to minimal autofluorescence and negligible tissue scattering in this region, affording maximal penetration depth for deep tissue imaging with high feature fidelity. Herein, for the first time, we reported a new type of NIR-II QDs-Ag2S QDs and executed a series of in vivo imaging studies by using Ag2S QDs. The results show that, by using Ag2S QDs, the tissue penetration length can reach 1.5 cm, and the spatial and temporal resolution of the in vivo imaging can down to 25 µm and 50 ms, respectively, which are improved several to dozens of times in comparison with those using conventional fluorescence nanoprobes in the visible and the first near-infrared window (650-900 nm), facilitating in situ, real-time visualization of the biological events in vivo. With the advanced NIR-II fluorescence of Ag2S QDs, high signal to noise ratio imaging of tumor growth and angiogenesis, imaging-guided targeting drug-delivery and therapeutics, imaging-guided precision surgery of glioma, and stem cell tracking and regeneration in vivo, etc, have been achieved.
References
(1) Du, Y.; Wang, Q.; etc. J. Am. Chem. Soc. 2010, 132, 1470- 1471.
(2) Zhang, Y.; Wang, Q.; etc. ACS Nano 2012, 6, 3695-3702.
(3) Hong, G.; Wang, Q.; etc. Angew. Chem. Int. Ed. 2012, 51, 9818-9821.
(4) Li, C.; Wang, Q.; etc. Biomaterials 2014, 35, 393-400.
(5) Chen, G.; Wang, Q.; etc. Adv. Funct. Mater. 2014, 24, 2481- 2488.
(6) Chen, G.; Wang, Q.; etc. Biomaterials. 2015, 53, 265-273.
(7) Song, C.; Wang, Q.; etc. Adv. Funct. Mater. 2016, 26, 4192-4200.
5:30 PM - ED5.2.07
Phenoxazone-Based Pigments Isolated from Cephalopods Enhance Light Scattering in Bio-Derived Nanostructured Materials
Sean Dinneen 2 , Margaret Greenslade 2 , Leila Deravi 1
2 , University of New Hampshire, Durham, New Hampshire, United States, 1 , Northeastern University, Boston, Massachusetts, United States
Show AbstractCephalopods are arguably the most sophisticated, phototonic marine animals, as they possess the ability to rapidly adapt their dermal color and texture to their surroundings using both structural and pigmented coloration. While it is known that their pigmented chromatophore organs facilitate this process, the role of the pigments themselves in potentiating color change is not well understood. We hypothesize that the pigments, which are localized within nanostructured granules in the chromatophore, contribute to the scattering of light within the dermal tissue to enhance the color displayed during actuation. To test this, we first extracted the phenoxazone-based pigments from the chromatophore organ. We next extrapolated their complex refractive index (RI) from experimentally determined real and approximated imaginary portions of the RI and found that they possess uniquely high values (~1.99). Mie theory was used to calculate the absorbance and scattering cross-sections (cm2/particle) of the pigments across a broad diameter range at λ = 589 nm, where we observed that the pigments were more likely to scatter attenuated light than absorb it at particle sizes greater than 200 nm. These results are used inform the design of bio-inspired flexible displays built to efficiently absorb, scatter, and reflect all wavelengths of light using pre-packaged photonic nanoparticles.
5:45 PM - ED5.2.08
Energetic Alignment and Charge Transfer Excitation in Nanoassembly of Qyantum Dot and Metalorganic Dye
Svetlana Kilina 1
1 , North Dakota State University, Fargo, North Dakota, United States
Show AbstractRecent studies show organic or inorganic dyes retain as efficient hole mediators to quantum dots (QDs). Although the mechanism is yet to be determined, there exists an inclination in science and engineering communities to interpret the experimental charge transfer based on the energetic alignment between QD and dye. Here, we use the density functional method to simulate Cd33Se33 QD/tris(2,2’-bipyridine)Me(II) dye nanocrystal composite with different metal ion, Me=Cd, Cr, Fe, Os and Ru. Our results show: (1) the highest occupied molecular orbital (HOMO) energy level of dye is deep inside the valence band (VB) of QD; (2) increasing the electronegativity of metal ion reduces the energy separation between HOMO of dye and VB edge, on the contrary, the energy separation between LUMO of dye and CB edge is increased; (3) A substitution of Ru(II) ion with Cr(II) or Os(II) ion brings the dye states closer to the VB edge due to a smaller metal-ligand interaction in these two dyes than the other dyes. In addition, there is a significant increase of charge transfer (CT) characters in Cr(II) or Os(II) dye-functionalized Cd33Se33 QD upon photoexcitation. We further use the embedded fragment potential model to expand the QD’s electrostatic potential as multipole terms included in dye’s Hamiltonian, and found the dipole energies between QD and these two dyes are relatively larger than the other dyes, while the energy gaps between these two dye’s HOMOs and VB edge are relatively smaller than the other dyes, which collectively increases the resonant interaction between tris(2,2’-bipyridine)Me(II) dye and QD’s surface states, thus increases the probability of charge-transfer excitation.
ED5.3: Poster Session I
Session Chairs
Wednesday AM, April 19, 2017
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - ED5.3.01
Solution-Based Self-Assembly and Nanoengineering of Multifunctional Nanoparticle Coatings
Kaifu Bian 1 , Zaicheng Sun 2 , Huimeng Wu 1 , C. Jeffrey Brinker 1 2 , David Burckel 1 , Hongyou Fan 1
1 , Sandia National Laboratory, Albuquerque, New Mexico, United States, 2 Chemical and Biological Engineering, University of New Mexico, Albuquerque, New Mexico, United States
Show AbstractOptical coatings/films are widely used in consumer electronics, semiconductor devices, and high-performance glass and ceramic materials. Presently most of these films are manufactured using complicated and costly processes such as sputter deposition and chemical vapor deposition (CVD), which requires high temperature and/or high vacuum. Seeking a simpler and less expensive fabrication process, we have developed a rapid and versatile self-assembling process that employs nanotechnology to overcome the limitations of the conventional CVD and sputtering. In our method, multifunctional nanoparticles are synthesized and then assembled into three-dimensional ordered arrays forming optical films at an interface with the aid of polymers. The versatility of our method can be further expanded by combining it with top-down micro-fabrication methods such as lithography to achieve coatings of hierarchical structures and desirable functions at multiple length scales. As an example, a near infrared reflector with improved performance, comparing with traditional CVD or sputtered counterparts, was developed by quarter wave stacking of self-assembled nanoparticle films. Theoretical modeling shows very good consistency with our experimental results and addresses key manufacturing challenges.
Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
9:00 PM - ED5.3.02
Construction of Enhanced Photocurrent Generation Systems by Nanocomposite Layers of Silver Nanoparticles and Dyes
Katsuhiko Kanaizuka 1
1 , Yamagata University, Yamagata Japan
Show AbstractConstruction of artificial photo-excited electron-transfer systems on electrodes is one of the important issues for the creation of high performance solar cells, electroluminescent displays, catalytic devices, and so on. Metal nanoparticles (NPs) e.g., Ag, Au, Cu, and their alloys, have received much attention as light-harvesting materials due to the plasmonic effect. In addition, photo-excited efficiencies of molecules localized near metal NPs are remarkably improved by the near-field effect (enhanced electric fields caused by localized surface plasmon resonance). In this study, we have constructed porphyrins – Ag NPs composite layers on a transparent indium-tin oxide (ITO) electrode by using a bottom-up method and have evaluated their photocurrent generation.
An ITO electrode was immersed in a methanol solution of 3-mercaptopropyl trimethoxysilane (MPTS) to form self-assembled monolayers (SAMs) on the surface. Ag NPs (ca. 10 nm) were fixed on the ITO/MPTS film via thiol residues. 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrins, CPP, was embedded on the ITO/MPTS/Ag NPs electrode by its simple immersion into a chloroform solution of CPP. In addition, we also prepared ITO/CPP and ITO/Ag NPs/CPP. We measured atomic force microscope (AFM), UV-vis absorption spectra, cyclic voltammetry (CV), and photocurrent generation of these hybrid films. AFM was used for observation of surface morphology of Ag NPs of the electrodes. Photocurrent generation was measured in a 0.1 M Na2SO4 aqueous solution. The photocurrent was remarkably enhanced in the case of ITO/MPTS/Ag NPs/CPP. This enhancement is probably caused by near-field effect of Ag NPs.
9:00 PM - ED5.3.03
Pyrolysis of Self-Assembled Iron Porphyrin on Carbon Black as Core/Shell Structured Electrocatalysts for Highly Efficient Oxygen Reduction in both Alkaline and Acidic Medium
Yujiang Song 1
1 , Dalian University of Technology, Dalian China
Show AbstractWe report simple carbonization of evaporation-induced self-assembled iron(III) porphyrin (FeP) layers uniformly coated on carbon black, leading to an unprecedented core/shell structured nonprecious metal electrocatalysts (NPMEs) composed of N-doped graphene-like layers uniformly coated on carbon. The thickness of graphene-like shell can be readily adjusted up to about 6.6 nm by varying the amount of FeP loaded on carbon. Interestingly, the obtained NPME exhibited one of the highest oxygen reduction reaction (ORR) activity in both alkaline (half-wave potential of 0.87 V vs. RHE) and acidic (half-wave potential of 0.75 V vs. RHE) medium. In particular, the core/shell structured NPME demonstrated a remarkable durability in acidic conditions superior to that of commercial Pt/C, which likely comes from exposure of inner active sites after the outermost layer is consumed. Furthermore, the core/shell NPME displayed direct 4e and indirect 4e process toward ORR in alkaline and acidic medium, respectively. This study pointed out a new avenue for the design of high-performance NPMEs in both alkaline and acidic media, which may have potential applications in polymer electrolyte membrane fuel cells (PEMFCs), metal-air batteries, and electrolyzers.
9:00 PM - ED5.3.04
Graphene Quantum Dots in High Performance Organic Photovoltaic Devices
Zheling Zhang 1 2 , Xiaogang Xue 1 , Xiaoling Zhang 2 , Jian Zhang 1
1 School of Material Science and Engineering, Guilin University of Electronics and Technology, Guilin China, 2 School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing China
Show AbstractIn the past few years, there has been an ongoing enthusiasm on graphene quantum dots (GQDs) and study the new phenomena from GQDs, e.g. quantum confinement and edge effects. These dots are usually biocompatible, strongly luminescent and well dispersed in various solvents, showing bright promise for integration into devices of bioimaging, photovoltaic and light emitting applications [1]. It’s also can be applied in organic photovoltaic devices. For example, comparing with traditional hole extraction layer (HEL), the self-assembly of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) organogel films incorporating with GQDs and other similar combonations as the HEL can increase the device’s power conversion 26% [2].
Here we synthesis a series of amino-group modified GQDs by the widely used thermal route. These modified GQDs can help reduce the work function of transparent electrodes and can be applied in organic photovoltaic devices as electron transport layer.
Acknowledgement: This research was financially supported by the National Natural Science Foundation of China (61564003), and the Guangxi Natural Science Foundation (2015GXNSFGA139002).
Reference
[1] Mitchell Bacon, Siobhan J. Bradley, and Thomas Nann, Graphene Quantum Dots , Part. Part. Syst. Charact. 2014, 31, 415–428
[2] Jung Kyu Kim, Sang Jin Kim, Myung Jin Park, Sukang Bae, Sung-Pyo Cho, Qing Guo Du, Dong Hwan Wang, Jong Hyeok Park, Byung Hee Hong , Surface-Engineered Graphene Quantum Dots Incorporated into Polymer Layers for High Performance Organic Photovoltaics. Sci. Rep. 5, 14276; doi: 10.1038/ srep14276 (2015).
9:00 PM - ED5.3.05
Highly Stable Transparent Electrode Based on Copper Nanowire@Graphene Core@Shell Nanostructure
Yumi Ahn 1 , Donghwa Lee 1 , Youngu Lee 1
1 , Daegu Gyeongbuk Institute of Science and Technology, Daegu Korea (the Republic of)
Show AbstractTransparent electrodes (TEs) have been known and well-studied as an essential element of various optoelectronic devices. Vacuum-deposited Indium tin oxide (ITO) has been widely used in a variety of optoelectronic devices because of low sheet resistance and high optical transmittance. However, it has critical drawbacks such as brittleness, high production cost, high processing temperature, and low optical transmittance in near-infrared (NIR). Recently, silver nanowire (AgNW) TE showed outstanding physical performances such as high electrical conductivity, high transparency, and excellent flexibility. However, the mass production of AgNWs is limited due to its scarcity and high price. Copper is one of the earth-abundance elements. Copper is 80 times cheaper than silver. Furthermore, the electrical conductivity of copper (58.5 x 106 S/m) is as high as the electrical conductivity of silver which has the highest electrical conductivity (62.1 x 106 S/m). Thus, a copper nanowire (CuNW) has been considered as a promising alternative to AgNW. Recently, some research groups have proven the great performance of CuNW TE such as excellent optical transparency, electrical conductivity, and mechanical flexibility. However, it still has a long-term stability issue which makes it difficult for practical use. For instance, CuNW TEs are easily oxidized when exposed to air even at room temperature, leading to a sharp increase of their sheet resistance values. Thus, it is necessary to prevent the oxidation of CuNW in order to enhance the long-term stability of CuNW TE. To enhance the long-term stability of CuNW based TEs, we developed a CuNW@G core@shell nanostructure by a low temperature plasma enhanced chemical vapor deposition (LT-PECVD) process at temperatures as low as 400 °C for the first time. Furthermore, we have fabricated highly stable and conductive TEs based on a copper nanowire@graphene (CuNW@G) core@shell nanostructure. The CuNW@G core@shell nanostructure was systematically characterized by SEM, TEM, XRD, RAMAN, and XPS measurements. The CuNW@G TE exhibited excellent optical and electrical properties comparable to conventional ITO TE. In addition, the CuNW@G TE exhibited highly enhanced oxidation and chemical stability because of excellent moisture and gas barrier property of the graphene shell layer. The sheet resistance of the CuNW-G TE increased slightly less than 9% even after 30 days in air while that of the CuNW TE increased over 1800 times within 2 days. Furthermore, polymer solar cells with CuNW@G TE exhibited higher power conversion efficiency than those with CuNW TE because of significantly enhanced anti-corrosion property.
9:00 PM - ED5.3.06
Low Dimensional Multilayered Nanostructures for Plasmonic Applications
Ezgi Abacioglu 1 , Alpan Bek 1
1 , Middle East Technical University, Ankara Turkey
Show AbstractOptical properties of materials can be enhanced by tailoring their plasmonic properties. Plasmons are collective electron oscillations inside metals that can be coupled with light. Forming surface plasmon polaritons, this coupling creates strong optical and electrical fields within nanostructures. Plasmon resonance frequency is affected by intrinsic and morphological features of nanostructures; therefore, design holds great importance. Since they support the production of complex hybridized resonances, 1D coaxial nanowires of several metal-dielectric layers are promising in this manner. In addition, noble metals are generally preferred for plasmonic applications since their resonance frequency is in the visible and near-IR region. Scattering peaks of multilayered nanostructures depend on the thicknesses of the layers, i.e. thin coaxial nanowires exhibit strong plasmon mixing. Thus, dielectric and metal layers should be deposited as thin films. In this study atomic layer deposition (ALD) technique is used to fabricate coaxial nanowires. ALD is an important thin film deposition technique consisting of sequential surface reactions. Due to its self-limiting nature it has the best conformality compared to other thin film techniques, especially for high aspect ratio nanostructures. In this work high aspect ratio silver nanowires that are synthesized by polyol process are used as core nanostructures. On core Ag nanowires, oxides of titanium or aluminum are deposited as spacer dielectric layer which is succeeded by silver deposition. As the multilayered low dimensional plasmonic structures bear hybrid plasmon modes due to mixing, some of these modes are found to be subject to very low attenuation, thus long range, and long lifetime. We expect beneficial qualities as light management interfaces from the resultant nanostructures in thin film photovoltaic devices. The material properties, process optimization and optical characterization of these structures will be discussed in this context.
9:00 PM - ED5.3.07
Porphyrin-Based Composites Controllable Self-Assembly and Photodynamic Therapy Research
Jiefei Wang 1 2 , Yong Zhong 1 2 , Feng Bai 1 2
1 , Henan University, Kaifeng, AE, China, 2 , Key Laboratory for Special Functional Materials of the Ministry of Education, Kaifeng, Henan, China
Show AbstractPhotodynamic therapy is a kind technology of oxygen molecules participate in and photosensitizer mediated and produce biological effects. Porphyrin-based photosensitizers has attracted much attention on account of higher singlet oxygen productivity and very low toxicity, but most of them have a poor water solubility. Here we adopted an acid-base neutralization micelle confinement self-assembly method to simultaneously achieve the self-assembly of zinc porphyrin (ZnTPyP) and the hydrolysis condensation of tetraethoxysilane (TEOS), and one pot obtained core-shell type and blend type porphyrin @ SiO2 composite nanomaterials. The nanocomposite materials have realized on HeLa cells target recognition after further modification of BSA and folic acid and have good fluorescent tags learned from a confocal laser scanning microscope imaging. The cells were irradiated by laser irradiation at 660 nm and a power density 100 mW/cm2 for different time shown a very good kill efficiency and without dark toxicity and a good time- and concentration-dependent.
9:00 PM - ED5.3.08
3D Core-Shell Porous Structures for Photoelectrochemical Water Splitting
Kiwon Kim 1 , Jun Hyuk Moon 1
1 Chemical and Biomolecular Engineering, Sogang University, Seoul, Seoul, Korea (the Republic of)
Show AbstractPhotoelectrochemical cells which convert solar energy into hydrogen are a promising energy conversion technology for substituting fossil fuel and producing hydrogen. For photoelectrochemical cell photoanode, BiVO4 has become the top performer among the metal oxide due to its visible light absorption up to 520nm and relatively negative energy level. This advantage, however, is compensated by high electron-hole recombination property of BiVO4. Here, we fabricate 3D BiVO4-based core-shell inverse opal structure for photoelectrochemical water splitting application. The core-shell morphology and crystallinity of core-shell oxides are characterized. The electrode film and BiVO4 shell thicknesses are controlled and then, the effect of them on the water splitting efficiency is evaluated. Our heterojunction inverse opal structure exhibit the improvement of light harvesting and charge separation efficiencies compared to 1D planar bilayer electrode.
9:00 PM - ED5.3.09
Enhanced Optical Stability of All-Inorganic Perovskite Nanocrystals Embedded in Polymer
Yuan Chih Chang 1 , Fu-Song Ye 1 , Ing-Chi Lue 1
1 Department of Materials Science, National University of Tainan, Tainan Taiwan
Show AbstractCesium lead halide (CsPbX3, X=Cl, Br, I) perovskite nanocrystals prepared by solution process have shown great potential as a new class of optoelectronic material. Because they have high luminescence quantum yields, broad emission spectra tunablility, narrow emission bandwidth, and short radiative lifetimes. But their application is hindered by a low chemical and structural stability. In order to enhance their stability we introduce polymethylmethacrylate (PMMA) into the synthesis of the CsPbX3 perovskite nanocrystals. It is found that CsPbX3 perovskite nanocrystals can be stabilized by PMMA with the formation of ligand shell, and can also be embedded in the PMMA film to prevent them from the attack of water in the ambient environment. We can fabricate polymer composite films with different colors by using CsPbX3 nanocrystals with different compositions. In addition, we successfully attached the CsPbBrI2 nanocrystal-embedded PMMA films onto the commercial white LED chips to make them warmer. Finally we studied the durability of the CsPbBrI2 nanocrystal-embedded polymer films, and found their optical performance could maintain for more than one week in the ambient condition and could be operated at 70 degree Celcius without degradation.
9:00 PM - ED5.3.10
Synthesis and Characterization of Novel Copper-Manganese Based Oxides
Chun-Yi Lu 1 , Tri-Rung Yew 1
1 Materials Science and Engineering, National Tsing Hua University, Hsinchu, Choose a State or Province, Taiwan
Show AbstractOxide materials have played an important role in optoelectronic and sensing devices benefited from their various optical and electrical properties. In this work, earth-abundant cupric oxide and manganese dioxide were used according to the Gibbs free energy rule and fabricated into copper-manganese based oxide materials via a standard ceramic process. By varying the molar ratio of cupric oxide to manganese dioxide and ceramic processing conditions, different phases of Cu-Mn based multi-element oxides were formed and characterized to study their potential applications.
The prepared copper-manganese based oxides were fabricated into targets, followed by the oxide films deposition using RF sputtering. Thin film deposition parameters such as ambient pressure, working power, post-annealing temperature were optimized and the structural, electrical and optical properties of the oxide thin films were characterized. The morphological, compositional and structural properties of the films were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX) and X-ray diffraction (XRD), respectively. The electrical and optical properties of the thin films were also measured by Hall-effect measurement system and ultraviolet-visible spectroscopy (UV-Vis), respectively.
9:00 PM - ED5.3.11
Hierarchical TiO2-Based Nanostructures for Photoelectrochemical Water Splitting
Luca Mascaretti 1 , Simona Ferrulli 1 , Beatrice Bricchi 1 , Piero Mazzolini 1 3 , Carlo Casari 1 3 , Valeria Russo 1 , Roberto Matarrese 2 , Isabella Nova 2 , Giancarlo Terraneo 4 3 , Andrea Li Bassi 1 3
1 Micro and Nanostructured Materials Laboratory, Department of Energy, Politecnico di Milano, Milano Italy, 3 Center for Nanoscience and Technology - IIT@Polimi, Istituto Italiano di Tecnologia, Milano Italy, 2 Laboratory of Catalysis and Catalytic Processes, Department of Energy, Politecnico di Milano, Milano Italy, 4 Laboratory of Nanostructured Fluorinated Materials (NFMLab), Department of Chemistry, Materials, and Chemical Engineering “Giulio Natta”, Politecnico di Milano, Milano Italy
Show AbstractTitanium dioxide (TiO2) is one of the most studied materials for both photocatalytic and photoelectrochemical (PEC) water splitting, nonetheless it presents some limitations, such as poor absorption of visible light and low quantum efficiency. Recent innovative approaches towards the extension of its absorption range consist in the hydrogenation or reduction of TiO2, leading to the so-called black titania [1], and in the combination of TiO2 with noble metal nanoparticles, which exhibit plasmonic effects [2]. In both cases, remarkable enhancement for the water splitting reaction have been obtained, even though the comprehension of the involved mechanisms still presents some open issues. In addition, hierarchical TiO2 nanostructures, combining large surface area and anisotropic morphology, are object of intense research for the development of more efficient photoanodes [3].
In this work we present an explorative combined approach aimed at extending to the visible range the photoresponse of a TiO2 photonaode with optimized morphology and structure. First, hierarchical TiO2 nanostructures were prepared by Pulsed Laser Deposition (PLD) controlling both the deposition atmosphere and the post-annealing atmosphere with the aim to achieve hydrogenation or reduction of the material. This was performed by using an oxygen-poor deposition atmosphere and/or by annealing in a Ar/H2 mixture. Second, an investigation on plasmonic-enhanced water splitting was undertaken by studying the synthesis of Au nanoparticles (NPs) with PLD and exploring different strategies to efficiently combine them with the aforementioned hierarchical TiO2 nanostructures: growth of Au nanoparticles on top or below the TiO2 film, or dispersion of Au NPs in TiO2 by a co-deposition approach. SEM, Raman spectroscopy, XRD and UV-vis-NIR spectroscopy were employed as characterization techniques, whereas photocurrent measurements under solar simulator illumination with a three-electrode cell were employed to assess the materials photoresponse.
We discuss how the structure and consequently the photoresponse of hierarchical TiO2 can be tuned by playing with the deposition and annealing atmospheres. In particular, a thermal treatment in Ar/H2 results in the appearance of an optical absorption tail towards the visible region, and the material photoresponse is significantly enhanced after Ar/H2 annealing if an oxygen-poor deposition atmosphere is employed (i.e. Ar/O2 mixture) and if it is preceded by thermal sintering in air. Furthermore, we show how PLD permits to achieve dispersion and size control of Au NPs from few nm to about 20 nm. A detailed investigation of the plasmonic and photoelectrochemical properties of the Au/TiO2 films is currently being carried out.
[1] X. Chen et al. Chem. Soc. Rev. 2015, 44, 1861-1885.
[2] S. C. Warren, E. Thimsen Energy Environ. Sci. 2012, 5, 5133-5146.
[3] F. Di Fonzo et al. Nanotechnology 2009, 20, 015604; R. Matarrese et al. Chem. Eng. Trans. 2014, 41, 313-318.
9:00 PM - ED5.3.12
Tunable-Photoluminescence 2D Materials Quantum Dots
Bedanga Sapkota 1 , Abdelkrim Benabbas 1 , Paul Champion 1 , Meni Wanunu 1 2
1 Department of Physics, Northeastern University, Boston, Massachusetts, United States, 2 Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts, United States
Show AbstractBedanga Sapkota†, Abdelkrim Benabbas†, Paul Champion†, and Meni Wanunu*,†,‡
†Department of Physics, Northeastern University, Boston, Massachusetts 02115 United States
‡Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts 02115 United States
Graphene quantum dots (GQDs) have garnered an increasing interest for bioimaging and biotargeting applications, due to merits such as their optical properties, reduced toxicity, small size that is commensurate with biomolecules, and ease of functionalization. However, despite their mild chemical composition, toxicity is GQD-size dependent. It is well known that ultra-small particles are able to enter mitochondria (<6 nm) and nucleus (<10 nm), and these can produce physical cytotoxic effects. Here, we report on GQD synthesis with mean diameters that are controllable in the range 15-35 nm. These quantum dots maintain strong visible light fluorescence (mean quantum yield of 0.64) and a high two-photon cross section (6,500 Göppert-Mayer units). Furthermore, by virtue of their mesoscopic size, the quantum dots exhibit good cell permeability into living epithelial cells, while they do not enter the cell nucleus. We also report on synthetic routes to metal dichalcogenide quantum dots (MDCQDs). To date, very few works have been reported on MDCQDs such as MoS2 and WS2, all of which involve complicated preparation steps and have resulted in low-quantum yield materials. Here, we employ a straightforward sonication method to prepare water-soluble MoS2 QDs. Further, we obtain eight-fold enhancements in their quantum yield by passivating their surface with amine groups. We demonstrate peptide binding to these particles using fluorescence resonance energy transfer (FRET). Finally, we demonstrate strong antimicrobial activity of MoS2 nanosheets (NS).
Acknowledgement: This work was supported by NSF grant EFMA-1542707.
9:00 PM - ED5.3.13
A Quantitative Analysis of the Reduction Pathways of a Salt Precursor in the Synthesis of Metal Nanocrystals
Tung Han Yang 1 2 , Younan Xia 1 3 4
1 The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, United States, 2 Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu Taiwan, 3 School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, United States, 4 School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractMetal nanocrystals have received ever increasing interest owing to their fascinating properties for a variety of applications, including catalysis, electronics, photonics, sensing, and medicine. A typical synthesis involves the reduction of a salt precursor. Despite the remarkable progress, it is still unclear how the salt precursor is reduced to atoms for their evolution into nuclei, seeds, and then nanocrystals. It has been challenging to resolve such a process due to the lack of characterization tools. Specifically, the salt precursor can be reduced to an atom in the solution phase, followed by its deposition onto the surface of a growing nanocrystal. Alternatively, the precursor can adsorb onto the surface of a growing nanocrystal, followed by reduction through an autocatalytic surface growth process. With Pd as a typical example, here we design a set of kinetic experiments to shed light on the reduction pathway undertaking by a salt precursor during the growth of metal nanocrystals. Based on the quantitative analysis, we demonstrate that the pathway has a strong dependence on the reduction kinetics involved. We found that the precursor was reduced on the surface of a growing nanocrystal through an autocatalytic surface growth process under a slow kinetic whereas it was reduced in the reaction solution at faster reaction rates. Most significantly, we also demonstrate the switching of reduction pathway by manipulating the reaction parameters such as the type of precursor used and the reaction temperature, to modulate the reaction kinetics. This work represents a major step forward toward the achievement of a quantitative understanding of the reduction pathways of a salt precursor in the synthesis of metal nanocrystals.
9:00 PM - ED5.3.14
Optical Properties of Nano-Structured Semiconductors Fabricated by Ion Implantation
Angelica Hernandez 1 , Yuriy Kudriavtsev 1 , Georgina Ramirez 1
1 , CINVESTAV, Mexico City, FDM, Mexico
Show AbstractGermanium and silicon crystals were implanted with Ge+ ions at 25 and 50 keV, respectively and high ion dose (1x1016 ions/cm2). A subsequent thermal annealing was carried out with nitrogen and oxygen atmospheres in order to determine its effect in the optical properties. The annealing time and temperature were optimized in each case.
Structural characterization was performed by using Raman spectroscopy. The obtained results show the vibrational modes of the implanted element and the implantation matrix as the presence of germanium and silicon oxides as well as the crystalline properties of the lattice before and after annealing. The implanted elements were re-arranged into the crystal lattice due to the thermal process. Formation of a near surface binary layer was confirmed, among other.
A SIMS depth profile of the as implanted and thermally treated samples were obtained in order to study diffusion of the elements along the totally amorphized and the partially amorphized layer (caused by ion implantation). Of special interest is the concentration of the oxygen in the border between the amorphized layer and the crystal since the defects may act as a traps for oxygen.
The optical properties of the as implanted and thermally treated samples were studied at excitation wavelength of 325 nm at room temperature. The white light emission was observed in the as implanted samples and the PL intensity increased after the annealing. The de-convolved PL spectra reveal that several mechanisms gather in the photon-emission process. The spectrum can be considered a mixture of photonic effects that include the formation of nano-crystals and recombination of electrons in the oxygen vacancies of the germanium oxides.
Due to its technological importance, the fabrication of germanium and silicon-based luminescent materials has been explored through the development of several techniques which involve chemical and physical mechanisms. However, the ion implantation is an undoubtedly favorable cost-effect technique to fabricate nano-structured materials with optical properties in an uncomplicated and strongly controllable process.
9:00 PM - ED5.3.15
Tip-Enhanced Photovoltaic Effects in Pd Substituted PZT Thin Films
Shalini Kumari 1 , Dhiren Pradhan 1 , Ashok Kumar 2 , Ram Katiyar 1
1 , University of Puerto Rico, San Juan, Puerto Rico, United States, 2 , National Physical Laboratory (CSIR), Delhi India
Show AbstractDriven by the worldwide requirement for inexhaustible energy and clean fuel sources, considerable research attempts have been focused towards solar energy harvesting considering various photovoltaic (PV) effects. Ferroelectric materials have recently attracted much attention as promising candidates for use in photovoltaic devices, and for the coupling of light absorption with other functional properties. Breaking of strong inversion symmetry due to spontaneous polarization in these materials develop a desirable separation of photo-exited carriers and produces voltages higher than its band gap. However, a big challenge faced by ferroelectric-photovoltaic devices is to overcome the very low output photocurrent. Theoretically, it has been proposed by some research groups that metallic defects and/or doping/substitutions of transition metals and/or metal ions can reduce the band gap of ferroelectric materials which is the basic requirements for their applications in photovoltaic devices. We have synthesized Palladium substituted PZT (Pb(Zr0.20Ti0.80)0.70Pd0.30O3-δ (PZTP30)) thin films on ITO coated glasses and La0.67Sr0.33MnO3 (LSMO) coated LSAT (100) substrates utilizing pulsed laser deposition technique. X-ray diffraction showed that the PZTP30 thin films on ITO coated glass are polycrystalline and exhibit a random orientation with strong (101) diffraction peak whereas in the XRD spectrum of LSAT/LSMO/PZTP30, only (00l) diffraction peaks are visible, indicating a (00l) oriented growth of the films. The existence of ferroelctricity and switching of polarization are confirmed from the band excitation Piezo Force Microscopy (PFM) in PZTP30 thin films. XPS studies confirmed the existence of Pd in thin films. The frequency dependent dielectric constant and loss tangent of LSAT/LSMO/PZTP30 films show almost constant dielectric constant around 3000 and relatively low loss tangent (<0.2) at frequencies below 10 kHz. Well saturated ferroelectric loop with remanent polarization ~40 μC/cm2 confirmed the presence of ferroelectricity in this material. Optical properties were investigated by UV-visible spectrometer of PZTP30 films on glass/ITO, it exhibits 60% transmittance at 600 cm-1, with a reduction of only 30% compared with pure ITO/glass substrate. A decrease in direct-Eg value was observed from 3.8 eV to 3.1 eV as the thickness of the films increased from 5 nm to 400 nm. A decrease in indirect-Eg value was also observed from 3.4 eV to 2.2 eV as the thickness of the films increased from 5 nm to 400 nm. The tip induced photovoltaic studies were carried out on PZTP30 thin films using c- AFM measurements and significant amount of current were observed when the blue drive was on. The structural, dielectric, ferroelectric, tip induced photovoltaic, and bulk photovoltaic properties will be discussed in details.
9:00 PM - ED5.3.16
A Systematic Study of the Effect of CdS Shell Thickness on the Complex Index of Refraction of CdSe/CdS Core/Shell Nanocrystal Solids
Mayank Puri 1 , Dana Dement 1 , Vivian Ferry 1
1 , University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractA deep understanding of the factors that affect the complex index of refraction of quantum dot (QD) solids is essential towards tailoring QD-containing photonic and optoelectronic devices, such as photovoltaic cells and LEDs. This is particularly true for carrying out computational models on these systems, where knowledge of the complex index is a requirement. We have undertaken a systematic study on the effect of CdS shell thickness on the index of CdSe/CdS core/shell QD films, using spectroscopic ellipsometry to derive the complex refractive index directly from fabricated films. This data set ultimately allows us to control optical interactions inside these materials with greater precision.
Measuring the complex index of QD solids is made challenging by multiple variables including the QD chemical composition, shape, size and packing, as well as the supporting ligand identity and surface coverage. The use of CdSe/CdS heterostructures provides many advantages over plain CdSe QDs, including increased quantum yield and stability, as well as the ability to tune the size and shape of the QD through the thickness of the CdS shell, resulting in synthetic control over optical properties such as emission wavelength, Stokes shift and non-blinking behavior.
We have successfully synthesized zinc-blende CdSe QDs on a multigram scale through a reproducible non-hot-injection synthesis, yielding monodisperse particles with an average diameter of 3.5 nm and standard deviation of 10%. The large scale of this synthesis is critical to allow us to maintain the same CdSe core particles while systematically varying the thickness of the CdS shell, leading to a family of spherical CdSe/CdS QDs of varying diameters dependent only on the monolayers of CdS shell grown. We have realized 3, 5 and 9 monolayers of CdS growth, producing a range of CdSe/CdS particle sizes from 3.5 nm to 9.4 nm and emission wavelengths ranging from 585 nm to 637 nm.
Dip-coating a solution of the CdSe/CdS QDs onto an Al2O3 surface forms thin films with thicknesses ranging from 10 nm – 40 nm, depending on the coating conditions. Variable angle spectroscopic ellipsometry measurements on films containing CdSe/CdS QDs with 5 monolayers of CdS shell provides refractive index, n, and extinction coefficient, k, values of 1.92 and 0.075, respectively, at 500 nm, with appropriate dispersion throughout the full spectrum characterized. The ellipsometry model includes a Cauchy fit at energies below the band gap and multiple Loretz oscillators to model the QD absorption features. Importantly, quantum confinement is observed in the ellipsometry data, where the first excitonic peak of the CdSe/CdS QDs is visible. A systematic trend between the CdS shell thickness and the solid index will be presented and ultimately this systematic study will inform the development of computational models incorporating CdSe/CdS QDs, and enable the design of tailored optoelectronic devices using nanophotonic elements.
9:00 PM - ED5.3.17
Development of Al3+ and Fe3+ Co-Doped TiO2 Compact Films and their Application in Hybrid Solar Cells with a Mixed Tin-Lead Perovskite and Sb2S3 Photoabsorbing Nanoparticles
Jose Garcia Cerrillo 1 , Claudia Martinez-Alonso 2 , Asiel Neftalí Corpus Mendoza 1 , Araceli Hernandez-Granados 1 , Paola Moreno Romero 1 , Omar-Armando Castelo-Gonzalez 1 , Hailin Zhao Hu 1
1 Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Mexico (UNAM), Temixco Mexico, 2 Facultad de Química, Universidad Autónoma de Querétaro, Querétaro, Querétaro, Mexico
Show AbstractPerovskite-based photovoltaic technology is promising in terms of competitive performance and cost, as intensive and exciting research and development have recently demonstrated. Although their entrance into the photovoltaic market is imminent, perovskite solar cells still have many fundamental issues to be addressed, like the interfacial processes that occur between the perovskite absorber and the electron selective contact, in particular titanium dioxide (TiO2) compact layers. The surface morphology and chemistry of this electron transport layer (ETL) could influence the charge recombination phenomena, whereas its electrical conductivity is related to the device charge collection. In this work, co-doping with aluminum (Al3+) and iron (III) (Fe3+) is explored as a means to enhance the charge transfer and transport characteristics of the TiO2 compact layer, which is integrated into planar and mesoscopic devices employing an associated photoabsorber, e.g. a tin-lead organohalide perovskite and antimony sulfide (Sb2S3) nanoparticles. The effect of three co-dopant Al3+/Fe3+ molar ratios (1.0/0.4, 0.7/0.7 and 0.4/1.0) as well as individual impurifications is analyzed in terms of the photovoltaic parameters delivered by complete hybrid devices. It is concluded that the localization of dopants on the surface of the ETL improved the transference of electrons coming from the associated absorber and their distribution in the inner TiO2 structure facilitated their transport until reaching the charge collector, as reflected in an enhanced solar cell energy conversion efficiency.
9:00 PM - ED5.3.18
A Porphyrin Protein Maquette-Based Photovoltaic Device
David Officer 2 , Christopher Hobbs 3 , Nicholas Roach 3 , Rhys Mitchell 3 , Klaudia Wagner 3 , Pawel Wagner 2 , Jonathan Barnsley 1 , Keith Gordon 1 , Goutham Kodali 4 , Christopher Moser 4 , P. Leslie Dutton 4
2 ARC Centre of Excellence for Electromaterials Science and the Intelligent Polymer Research Institute, University of Wollongong, Wollongong, New South Wales, Australia, 3 Intelligent Polymer Research Institute, University of Wollongong, Wollongong, New South Wales, Australia, 1 Department of Chemistry, University of Otago, Dunedin, Otago, New Zealand, 4 Department of Biochemistry & Biophysics, The University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractThe emulation of photosynthesis, the efficient and sustainable utilization of solar energy using renewable materials to produce hydrogen and oxygen from water or convert carbon dioxide into a chemical feedstock represents one of the great scientific challenges of the 21st Century. Creating photosynthetic-like processes in devices could not only provide a new generation of economical photovoltaic devices but also lead to sustainable hydrogen production through water splitting as well as fuel and food production through carbon dioxide fixation.
The challenge in building a useful ‘artificial photosynthetic’ assembly is not in simply mimicking the natural photosynthetic apparatus but utilizing new materials to create and, if possible, improving the structural properties and functionality of the biological system. In 1994, Dutton et al. developed the methodology for the facile production of de novo synthetic protein helices (maquettes), structurally simpler analogs of natural redox proteins, which have proved extremely useful for the study of porphyrin behaviour and interactions in proteins.1 It has been demonstrated that not only is a maquette bound porphyrin more efficiently photo oxidized than a free porphyrin but also that light induced electron transfer between the porphyrin complex and an acceptor is faster and higher yielding. As the maquettes can be assembled on a variety of surfaces such as gold or titanium dioxide, they provide a unique platform on which to build and study a light harvesting reaction center replica.
Over the last 10 years, we have developed syntheses of single porphyrins and porphyrin arrays and utilized the resulting materials as light harvesters in dye sensitized solar cells bound through carboxyl based linkers to titanium dioxide.2 However, the introduction of porphyrins into water soluble maquettes requires the development of amphiphilic porphyrins and porphyrin arrays. We have synthesized and incorporated carboxylated porphyrins and amphiphilic porphyrin dimers into maquettes. As a first step in the practical application of these artificial photosynthetic reaction centers, we have bound a porphyrin maquette to titanium dioxide in a dye sensitized solar cell (DSSC) to create the first artificial protein based dye sensitized solar cell. The current–voltage characteristics of the porphyrin maquette DSSC exhibits an excellent fill factor of 0.73, an open circuit voltage of 652 mV, photovoltaic current density of 2.69 mA cm−2 and power conversion efficiency of 1.28%, which remarkably is more than 50% of the value for the DSSC directly sensitised with five times more of the porphyrin itself.
1. B. M. Discher, R. L. Koder, C. C. Moser, P. L. Dutton, Curr. Opin. Chem. Biol. 2003, 7, 741.
2. A. J. Mozer, M. J. Griffith, G. Tsekouras, P. Wagner, G. G. Wallace, S. Mori, K. Sunahara, M. Miyashita, J. C. Earles, K. C. Gordon, L. Du, R. Katoh, A. Furube, D. L. Officer, J. Am. Chem. Soc. 2009, 131, 15621.
9:00 PM - ED5.3.19
Nitrogen-Doped Carbon Nanodots for Photoacoustic Imaging and Photothermal Therapy
Songeun Beack 1 , Changho Lee 1 , Woosung Kwon 2 , Shi-Woo Rhee 1 , Chulhong Kim 1 , Sei Kwang Hahn 1
1 , POSTECH, Pohang Korea (the Republic of), 2 , Sookmyung Women's University, Seoul Korea (the Republic of)
Show AbstractMultifunctional nanoparticles have been widely investigated for biomedical applications, such as imaging, therapy, and drug delivery. Especially, photo-activated nanoparticles have received attention as theranostic agents because of their heat-generating abilities after laser irradiation. Unfortunately, photostability and safety issues have been critical problems. Here, we designed nitrogen (N)-doped carbon nanodots (N-CNDs), which have strong absorption in the near-infrared region, high photostability, and excellent biodegradability, by regulating their N-doped content. Optimized N-CNDs not only can be utilized as a new photoacoustic (PA) imaging agent but also as a superior photothermal therapy (PTT) agent in vivo because of their strong optical absorption at a specific wavelength. We used N-CNDs to perform in vivo/ex vivo noninvasive PA imaging of sentinel lymph nodes via local delivery and performed PTT for cancer ablation therapy. Finally, biodegradation and renal clearance were demonstrated by performing whole-body PA monitoring and a degradation test.
[Keywords] Carbon nanodot; Heat generation; Photoactivate nanoparticle; Photoacoustic Imaging; Photothermal therapy
9:00 PM - ED5.3.21
Microwave—Assisted Synthesis and Characterization of SnS Nanoparticles with Different Morphologies
Evelyn B. Diaz-Cruz 1 , Concepcion Arenas 2 , Hailin Zhao Hu 1
1 , UNAM, Temixco, Morelos Mexico, 2 , Escuela Nacional de Estudios Superiores, Leon, Guanajuato, Mexico
Show AbstractThe metal sulfide semiconductor nanostructures have attracted much attention in recent years due to their exceptional physico-chemical properties. Tin sulfide (SnS) has been reported with a direct optical band gap of 1.1–1.3 eV. This material exhibits excellent properties such as high absorption coefficient, high mobility, non-toxic nature and low cost, which makes it widely used in near-infrared detectors, photovoltaic materials and electrochemical capacitors. Various methods are available in the literature for the synthesis of SnS, however the synthesis of nanoparticles by microwave (MW) irradiation has the advantage of being effective, economical and environmentally friendly. Furthermore, the performance of nanomaterials in different fields of applications, depends largely on their morphology and 3D architecture. For example, morphologies of wires or rods are desirable for solar cell applications, and for hydrogen storage it is expected to be porous materials. During the microwave reaction process, the types of sulfur precursor and solvent are very important to the structural and morphological properties of SnS nanoparticles. In this work SnS nanoparticles under microwave irradiation were synthesized with thioacetamide and tin chloride as raw materials in different solvents. Different washing processes with ethanol, deionized water and ammonia were also conducted to improve the product purity. The reaction temperature was varied between 100 and 200°C. The crystal phase, morphology, binding energy and optical properties of the as-synthesized SnS products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectra (XPS), UV–vis diffuse reflection spectroscopy (UV–vis DRS), respectively. The obtained products gave an orthorhombic phase of SnS (PDF: 39-0354). The SEM results show that with water as solvent a morphology of spherical like flakes of 1 – 2 µm in diameter was obtained, while with ethylene glycol (EG) the morphology of the products was of square plates of 1 – 1.5 µm in diameter. The setting temperature generates an effect on the thickness of the plates obtained in EG; at lower temperatures plates of 150 nm were obtained, and at higher temperatures the plates were much thinner (10 – 20 nm). Finally, the asymmetrical nanowire morphology of MW synthesized Bi2S3 could be obtained by controlling the tin source and type of solvent, which is interested for their application in hybrid solar cells.
Symposium Organizers
Feng Bai, Henan University
Ying-Bing Jiang, Angstrom Thin Film Technologies LLC
Binsong Li, Tsinghua Innovation Center in Dongguan
Dong Qin, Georgia Institute of Technology
Symposium Support
Dongguan-RITS Innovation Center
Henan University
ED5.4: Solar Cell
Session Chairs
Wednesday AM, April 19, 2017
PCC North, 100 Level, Room 129 A
9:30 AM - *ED5.4.01
Hot Carrier Transfer in Nanoparticles—Quantum Dots to Perovskites
David Ginger 1
1 , University of Washington, Seattle, Washington, United States
Show Abstract
Inorganic quantum dots offer many advantages, such as size-dependent energy levels, and easily-altered surface chemistry, that provide avenues through which one can tailor photoinduced charge generation and recombination in energy harvesting and conversion devices. In this talk, we discuss the size-, and wavelength-dependence of hot carrier transfer from colloidal quantum dots to organic acceptors. By tailoring quantum dot size and excitation wavelength we are able to selectively excite quantum dots with long wavelength excitation, while probing the resulting charge transfer and recombination events using a combination of steady-state, and ultrafast photoinduced absorption spectroscopy to show that the rate of ultrafast hole transfer off the quantum dots increases with increasing photon energy. Finally, we compare and contrast hot carrier dynamics and charge transfer behavior across diverse materials including traditional chalcogenide quantum dots, and emerging colloidal perovskite nanoparticles.
10:00 AM - *ED5.4.02
Ultrasensitive and Fast Monolayer WS2 Phototransistors Realized by SnS Nanosheet Decoration
Zhiyan Jia 1 , Jianyong Xiang 1 , Fusheng Wen 1 , Zhongyuan Liu 1 , Yongjun Tian 1
1 State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinghuangdao, Hebei, China
Show AbstractTwo-dimensional chalcogenides monolayers are strong candidates for next-generation flexible and transparent optoelectronics. Due to the intrinsic ultrathin thickness and limited optical absorption, however, their responsivity is normally low. Here we develop a simple and low-cost method to fabricate high-performance monolayer WS2 phototransistors with dramatically enhanced responsivity and extended spectral response range, by virtue of surface decoration with liquid-phase exfoliated SnS nanosheets (NSs). The decorated phototransistors show a much enhanced responsivity of ~2 A/W and an ultrahigh light/dark signal-to-noise ratio of 106 under a 457 nm excitation, exhibiting a significant increase of 3 orders of magnitude in responsivity and an increase of 100 fold in signal-to-noise ratio as compared with pure WS2 devices. Our photodetector also exhibits a respectable response speed with a rise and decay time of 51 ms and 98 ms, respectively. After optimal surface decoration of narrow bandgap SnS NSs, an emergent optical responsivity in the near infrared regime (1064 nm) is also observed. The results open a facial and economical way towards tailoring the optoelectronic properties of two-dimensional materials.
10:30 AM - ED5.4.03
Bottom-Up Approaches for Precisely Nanostructuring Hybrid Organic/Inorganic Multi-Component Composites for Organic Photovoltaics
Yang Qin 1
1 , University of New Mexico, Albuquerque, New Mexico, United States
Show AbstractNanostructuring organic polymers and organic/inorganic hybrid materials and control of blend morphologies at the molecular level have become the prerequisites for organic photovoltaics (OPVs) that are widely perceived as low-cost alternative energy sources. To achieve all-around high performance, multiple organic and inorganic entities, each designed for specific functions, are commonly incorporated into a single device. Current state-of-the-art approaches to morphology control in these multi-component systems typically involve physical blending and optimization via thermal/solvent annealing. Such trial-and-error approaches are however highly system dependent, lack controllability on the molecular level and generally lead to morphologies at only thermodynamically meta-stable states. We present herein our efforts in developing a versatile toolbox employing supramolecular chemistry that is capable of precisely nanostructuring multi-component organic/inorganic hybrid materials through self-assembly processes. Specifically, we show that well-defined core-shell composite nanofibers (NFs) containing precisely placed conjugated polymers, inorganic quantum dots and fullerene derivatives, can be obtained through cooperation of orthogonal non-covalent interactions including conjugated polymer crystallization, fullerene aggregation, hydrogen bonding interactions and metal-ligand coordination.1-4 OPV devices applying these NFs display much improved efficiencies and stability over their conventional bulk heterojunction (BHJ) counterparts.
1. Li, F.; Yager, K. G.; Dawson, N. M.; Yang, J.; Malloy, K. J.; Qin, Y.* Macromolecules 2013, 46, 9021.
2. Li, F.; Yager, K. G.; Dawson, N. M.; Jiang, Y.-B.; Malloy, K. J.; Qin, Y.* Chem. Mater. 2014, 26, 3747.
3. Li, F.; Yager, K. G.; Dawson, N. M.; Jiang, Y.-B.; Malloy, K. J.; Qin, Y.* Polym. Chem. 2015, 6, 721.
4. Li, F.; Dawson, N.; Jiang, Y.-B.; Malloy, K. and Qin Y.* Polymer 2015, 76, 220.
10:45 AM - ED5.4.04
A Bio-Inspired and Self-Assembled Water Oxidation Photoelectrode Based on Moth-Eye Photonic Architecture
Florent Boudoire 1 2 , Artur Braun 1 , Jakob Heier 1 , Rita Toth 1 , Edwin Constable 2
1 , Empa-Swiss Federal Laboratories for Materials Science and Technology, Duebendorf Switzerland, 2 Chemistry, University of Basel, Basel Switzerland
Show AbstractTechnology for solar fuel production is now waiting for major breakthroughs in materials science. Metal oxides play an important role as photoelectrode materials for water splitting for solar hydrogen fuel production in photoelectrochemical cells because of their environmentally benign nature and low cost and high abundance. Iron oxide is a highly controversial material for that purpose, because its conductivity in the bulk and at the surface are rather limited. We found a way around this limitation by designing an electrode architecture based on spheroidal shaped heterostructures from iron oxide and tungsten oxide. Specifically, with a vesicle formation process we synthesize tungsten oxide spheroidal cores with sub-micrometer size and coat them with a nano-sized ultrathin film iron oxide. This electrode architecture has an enhanced conductivity. Moreover, it has photonic properties with which allow us to tune its optical absorption by simple processing parameters, such as the spin coating speed. It turns out that our electrode works similar to the moth eyes in nature. The practical outcome is that the photocurrent density is doubled alone by the mesoscale structuring.
F. Boudoire, R. Toth, J. Heier, A. Braun, E. C. Constable, Photonic light trapping in self-organized all - oxide microspheroids impacts photoelectrochemical water splitting, Energy Environ. Sci., 2014, 7, 2680 - 2688.
ED5.5: Nanocrystal II
Session Chairs
Wednesday PM, April 19, 2017
PCC North, 100 Level, Room 129 A
11:30 AM - *ED5.5.01
Rational Design of Photoactive Titania Nanostructures
Yadong Yin 1
1 , University of California, Riverside, Riverside, California, United States
Show AbstractWe discuss our recent efforts in the design and architectural control of titania nanostructures and their applications. We first review the synthesis, crystallinity control, and photocatalysis of TiO2 porous nanostructures by discussing several methods for changing the structures from amorphous to crystalline and subsequently ways for enhancing the crystallinity. We also discuss the photocatalytic applications of the TiO2 nanoshells and the methods for improving their catalytic activities. We will also report a new color switching system based on reversible redox reaction that could be initiated by photocatalytic response of TiO2 nanocrystals. The excellent performance of the new color switching system promises their potential applications as attractive rewritable media to meet our society’s increasing needs for sustainability and environmental conservation.
12:15 PM - ED5.5.03
Enhancing Photocatalytic Performance by Tailor-Made Iron Oxide Nanoshells in Advanced Oxidation Process
Wenjing Xu 1 , Yadong Yin 1
1 , University of California, Riverside, Riverside, California, United States
Show AbstractPhotoactive catalysts have been found to be able to significantly enhance the performance of advanced oxidation processes (AOPs) for removing pollutants from contaminated water. Among all the photocatalysts, magnetic iron oxide has attracted intensive attention for the effective conversion between Fe2+ and Fe3+, good stability and fast recycling of the catalysts by magnetic separation. However, the fast diffusion of Fe2+ from the surface of the catalysts has largely impeded the recycling performance of the catalysts. Therefore, the confinement and enrichment of the iron ions is crucial for the practical application. Here, we demonstrate a surface protection method for solution phase chemical conversion of colloidal nanostructures that allows for preservation of overall particle morphology despite large volume changes. Benefiting from the hollow shell structure, the catalyst shows excellent photocatalytic performance in the AOP for the degradation of rhodamine B, which can be attributed to the efficient enrichment and confinement of Fe2+ in the nanocavity of the shell structure and effective recycling between Fe2+ and Fe3+. The confinement effect of the nanocavity can effectively prevent the loss of iron ions and promote the decomposition of H2O2 for the generation of ●OH. As a result, the Fe3O4 nanoshells with the nanocavity structure exhibit a much higher activity of the UV light-driven AOPs than the solid counterparts.
12:30 PM - ED5.5.04
Morphology Dependence of Photocatalytic Methane Oxidation in Shape-Controlled BiVO4 Microcrystals
Wenlei Zhu 1 , Alicia Yang 1 , Meikun Shen 1 , Bryce Sadtler 1
1 Chemistry, Washington University in St. Louis, St louis, Missouri, United States
Show AbstractMethane is the primary component of natural gas. The transportation of methane gas is an obstacle due to its low energy density (0.0364 megajoule/liter) and low flash point (85.1K). Photocatalysis provides a route to convert methane into an energy dense fuel, such as methanol, using only sunlight, water, and a photocatalyst as inputs. We are studying the activity and selectivity of different morphologies of bismuth vanadate microcrystals for photocatalytic methane oxidation. Bipyramidal bismuth vanadate microcrystals with {120} and {021} surface facets are more stable, more active, and more selective for methane to methanol conversion compared to platelet particles that expose {010} crystal facets as their top and bottom surface. Initial tests demonstrated that oxidative other than reductive reaction are preferred on {120} and {021} surface facets. Photocatalytic conversion of methane with the bipyramidal bismuth vanadate microcrystals shows more than 88% selectivity towards methanol formation. Compared to other crystal morphologies, such as thick and thin platelets, the bipyramids exhibit 50% more mass activity and specific activity. Therefore, our studies show that by tuning the morphology of BiVO4 we can successfully control the oxidation level of methane.
12:45 PM - ED5.5.05
Ultrathin Dielectrics as the Carrier Blocking Layer for Amorphous Selenium (a-Se) MISIM Photodetectors of High Signal Contrast
Cheng-Yi Chang 1 , Jian-Siang Lin 1 , Jye-Yow Liao 1 , Fu Ming Pan 1
1 Department of Materials and Science Engineering, National Chaio Tung University, Hsinchu Taiwan
Show AbstractAmorphous selenium (a-Se) has long been used as a photoconductor for image sensing applications because of its appealing photoelectric properties. Lateral a-Se metal-semiconductor-metal (MSM) device structure allows efficient photon absorption, low operation voltage and short response and fall times. In this study, we fabricated MSM and metal-insulator-semiconductor-insulator-metal (MISIM) photodetectors using an 1-mm thick a-Se layer as the photoconductor. In the MISIM devices, various ultrathin dielectrics (< 10 nm) were deposited between the a-Se layer and the electrodes as the blocking layer by different deposition methods. The dielectrics included thermally grown Al2O3, Inductively coupled plasma-chemical vapor deposited silicon nitride (Si3N4), and atomic layer chemical vapor deposited (ALD) Al2O3 and HfO2. The MISIM structure greatly reduce the dark current of the photodetector. The MISIM photodetector with the ALD-HfO2 blocking layer exhibits the best dark current suppression with a dark current reduction by 3 orders of magnitude compared with the MSM detector. The enormous dark current reduction is mainly ascribed to charge trapping in deep traps in the dielectric layers. Carriers photogenerated in the a-Se layer can move through the ultrathin blocking layer via Fowler-Nordheim (F-N) tunneling and are collected by the electrodes without severe loss. As a result, the photocurrent density degradation due to the presence of the blocking layer is much less distinct than the dark current suppression, leading to a very high signal contrast (density ratio of the photocurrent to the dark current) for the MISIM photodetectors. The photodetector with the ALD-HfO2 blocking layer exhibits a signal contrast of 20000 at 15 V/mm. This study demonstrates that the MISIM structure effectively improves the image quality of a-Se photodetectors and has a great potential for low illumination imaging applications.
ED5.6: Photocatalysis and Nanostructures
Session Chairs
Wednesday PM, April 19, 2017
PCC North, 100 Level, Room 129 A
2:30 PM - *ED5.6.01
Interfacing Nanomaterials for Solar-to-Fuel Conversion
Peidong Yang 1 2 , Dohyung Kim 1 2
1 , University of California, Berkeley, Berkeley, California, United States, 2 , Kavli Energy Nanosciences Institute, Berkeley, California, United States
Show AbstractArtificial photosynthesis, which stores solar energy into chemical bonds, is considered as a future technology towards sustainability. Regarding its primary function, an artificial photosynthetic system is comprised of two main components at the nanoscale: the light harvesting component that captures photons and the catalytic conversion unit that can utilize charge extracted to produce value-added products. Just like natural photosynthesis, where all the functional components are elaborately arranged, artificial photosynthesis requires exquisite control over how functional nanomaterials are combined. In this talk, interfacing photo- and catalytically active nanomaterials for photocatalytic and photoelectrochemical reduction of carbon dioxide will be presented. One approach will involve photoactive molecular complexes interfaced with plasmonic nanostructures for enhanced CO2 photocatalytic activity and long term stability. Heterogenization of photoactive units into nanoscale metal-organic frameworks allowed spatial confinement of an ensemble of CO2 reducing molecular complexes to be interfaced with plasmonic nanoparticles. The other approach utilizes inorganic nanomaterials as components that can capture light and convert CO2. Nanoparticle electrocatalysts are integrated with silicon nanowire photocathodes for photoelectrochemical reduction of CO2 in aqueous media. Besides the well-known advantages of nanowire geometry for light-harvesting, we show that the one dimensionality of the nanowire geometry allows unique assemblies of nanoparticles to maximize performance of the overall system.
3:00 PM - *ED5.6.02
Scattering-Enhanced Absorption in Catalysts
Yugang Sun 1
1 , Temple University, Philadelphia, Pennsylvania, United States
Show AbstractIn recent years, generation of hot carriers in transition metal catalysts through photoexcitation has been demonstrated to be a promising approach capable of significantly lowering activation temperature of the catalysts, which could have widespread impact on substantially reducing the current energy demands and improving selectivity of heterogeneous catalysis. Due to unique LSPR, plasmonic nanoparticles made of Au, Ag, Cu, and Al can strongly absorb light at the resonance frequencies, where the absorption cross-sections of the nanoparticles are much larger than their corresponding physical cross-sections due to the strongly enhanced electromagnetic field near the nanoparticle surfaces. Such strong absorption, in particular in the visible region of the spectrum, leads to generation of hot carriers in plasomonic nanoparticles, on which chemical transformations can be directly driven by the hot carriers. Despite of the promise, plasmonic metal nanoparticles are not good catalysts for a wide range of important reactions. In comparison, platinum-group metals (PGMs) such as Pt, Pd, Ru or Rh are very good catalytic materials and possess LSPRs in the UV region, which represents a significant disadvantage for photocatalysis due to the poor overlap with the solar spectrum. Although increasing size of PGM nanoparticles shifts LSPR absorption to the red, it increases cost and reduces surface area, and thus catalytic activity. In this presentation, a new light absorption model to modulate the absorption beak of supported small Pt nanoparticles in the visible spectral region by adjusting their dielectric environment instead of changing their size. In this model, Pt nanoparticles can absorb the scattered light in the near field of the dielectric surface of a spherical SiO2 support, thereby exhibiting well-defined visible-light absorption peaks and driving photocatalytic reactions. This new model provides an unprecedented opportunity to efficiently generate hot carriers in photo-illuminated Pt nanoparticles with solar energy.
ED5.7: Photoactivie Polymer Materials
Session Chairs
Wednesday PM, April 19, 2017
PCC North, 100 Level, Room 129 A
4:30 PM - ED5.7.01
Enhanced Visible Light Photocatalytic Activity of BiVO4 Photoelectrodes Produced By Magnetron Co-Sputtering
Jonatan Pérez-Alvarez 1 , Osmary Depablos-Rivera 1 2 , Roberto Mirabal Rojas 1 2 , Sandra Rodil 1
1 , Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Mexico City, Mexico City, Mexico, 2 , Posgrado en Ciencia e Ingeniería de Materiales, Universidad Nacional Autónoma de México, Mexico City, Mexico City, Mexico
Show AbstractThe monoclinic bismuth vanadate (m-BiVO4) belongs to the functional materials group used as photoelectrodes for water splitting under visible light. The m-BiVO4 is chemically stable, and its bandgap and flat band values are suitable for the hydrogen generation. Usually, photoelectrodes are produced from samples synthesized as powders since they provide large surface area; however, the efficiency of the system has not yet achieved the predicted values expected for m-BiVO4; for this reason we proposed the synthesis and evaluation of the m-BiVO4 electrodes deposited directly as thin films. The vanadate films were prepared by dual magnetron co-sputtering using two individually driven targets (Bi2O3 and V) under an Ar:O2 atmosphere and the monoclinic phase was obtained after annealing at 400°C for 2 h in air. Only those films grown using the V target power about 5.5 times larger the power applied to the Bi2O3 crystallized into the m-BiVO4 phase. Then, films of different thicknesses were deposited under these conditions in FTO substrates. The photocurrent density (JA) of the m-BiVO4 films was measured by linear scan voltamperometry in NaSO4 0.5 M solution, and the values at 1.23 V vs. NHE were between 0.14 and 0.30 mA/cm2 when they were irradiated with a visible-light lamp (520 nm at 11 W/cm2); it was observed that the JA values depend of the thickness. Later on, we found two methods to improve the photocurrent values: chemical treatment using 1.0 M KOH solution during 40 min, and electrochemical treatment applying a potential scan from 0 to 1.3 V for 40 cycles (1 cycle per minute). The maximum JA values at 1.23 V vs. NHE were reached in the films with thickness around 200 nm, and the values were 1.68 and 1.22 mA/cm2 after the chemical and the electrochemical treatments, respectively. The structural changes that could explain the increase in the photocurrents as a consequence of both treatments were evaluated using X-ray diffraction, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and impedance spectroscopy. The SEM results showed changes in the surface morphology after the treatments, the films looked more porous. The XPS analysis indicated that the oxidation states corresponding to residual phases, such as vanadium oxides, were eliminated after the treatments; this means that the residual phases were removed and hence the treated films contained almost the pure m-BiVO4 phase.
Acknowledgement: The research leading to these results has received funding from the BisNano project (125141) and the CONACYT (251279).
4:45 PM - ED5.7.02
Photophysics of New Nanomaterials for Organic and Hybrid Solar Cells
Alberto Privitera 1 , Lorenzo Franco 1
1 Department of Chemistry, University of Padova, Padova, Veneto, Italy
Show AbstractDespite Organic Solar Cells (OSCs) have received a rising interest in the last years thanks to their flexibility, biocompatibility and ease in large area-fabrication, a significant economic development has not been observed yet because of their weak conversion efficiency and their low stability.1 The concept of incorporating nanostructured architectures as additional components in OSC active layers has demonstrated to be a new paradigm to increase solar cells performances.2 The need to synthesize tailored nanostructures and to study their photophysical interactions with common photovoltaic materials, such as semiconducting polymer P3HT and fullerene derivative PCBM, is fundamental for the fabrication of high performance devices.
We investigated three families of nanoparticles that have revealed highly promising properties for the photovoltaics: (1) CdSe colloidal Quantum Dots (QDs), (2) Carbon Quantum Dots (CQDs), a class of nanoparticles with a size below 10 nm mainly composed of carbon atoms, and (3) hybrid organic inorganic perovskite nanoparticles (HOIP NPs).
Firstly, we studied a prototypical active layer consisting in binary blends of PCBM and CdSe/CdS core-shell QDs capped with different ligands with the purpose to demonstrate that QDs not only influence the morphology of the active layer, as it is often reported in literature, but also its photophysics. In addition to this, we rationalized the influence of the length and the nature of QDs ligands on the electron transfer process, which is central in solar cells.
Secondly, taking advantage of the previous results, we proposed two new materials for the solar cells. In particular, we synthesized N-doped CQDs functionalized with different thiophene-containing groups and HOIP NPs with different stabilizing ligands. Their good processability allowed us to investigate the photoinduced interactions with PCBM through the combined use of optical and EPR spectroscopy. The comprehension of the multiple effects of these nanostructures embedded in organic solar cells materials allowed us to determine the main photophysical processes that occur within Quantum Dots Solar Cells and to suggest the application of these materials in next-generation solar cells.
References
1) L. Lu, et al. Chem. Rev., 2015, 115, 12666–12731.
2) G. H. Carey, et al., Chem. Rev., 2015, 115, 12732–12763.
5:00 PM - *ED5.7.03
Interface Engineering in Organic and Hybrid Photovoltaic Cells with Photoactive Nanomaterials
Jian Zhang 1
1 College of Material Science & Engineering, Guangxi Key Laboratory of Information Materials, Guilin University of Electrical Technology, Guilin China
Show AbstractOrganic solar cells (OSCs) and organic-inorganic hybrid perovskite solar cells (PSCs) have attracted large attention in photovoltaic community due to potential low cost and flexibility. Especially, PSCs had exhibited high power conversion efficiency (PCE) >20% and rapid progress in the past few years. In both OSCs and PSCs, interface engineering at the electrode/semiconductor interface by introducing proper interface materials is crucial for higher performance.
Photoactive nanomaterials, including TiOx and ZnO, have been widely used in OSCs and PSCs as interface materials due to the solution processability and low cost. The interface materials in OSCs and PSCs could improve the device performance by enhancing light absorption, carrier transportation and carrier extraction. In our lab, room-temperature processed TiOx layer was introduce into inverted OSCs as cathode interfacial materials, the PCE of PTB7:PC71BM OSCs with TiOx/PEI layer is improved up to 8.72% from 7.38% of OSCs with TiOx. A wide temperature tolerance, water-free and solution-processed MoOx was synthesized and used as anode interface layers in OSCs. The MoOx thin films possess the suitable morphology and electronic properties for application in OSCs, and show wide temperature tolerance from room temperature to 250°C. The OSCs with the solution processed MoOx thin films show high PCE of 7.40% and good environment stability. Graphene oxide derivatives with higher work function, Uv-O3 treated GO and chlorinated GO, were synthesized and used as anode interface materials in OSCs. The PCE of OSCs with 10-30% enhancement was achieved by using these high work function GO derivatives. The application of the photoactive nanomaterials in PSCs as interface materials is studied and will be introduced in the presentation.
Acknowledgement: This research was financially supported by the National Natural Science Foundation of China (61564003), and the Guangxi Natural Science Foundation (2015GXNSFGA139002), and the Guangxi Bagui Scholar program.
References (12 pt)
D. Yang, L. Zhou, L. Chen, B. Zhao, J. Zhang,* C. Li,* Chem. Comm., 2012, 48, 8078.
. Yang, W. Yu, L. Zhou, J. Zhang,* C. Li,* Adv. Energy Mater. 2014, 4, 1400591.
C. Xu, P. Cai, X. W.Zhang, Z. L. Zhang, X. X. Xue, J. Xiong,* J. Zhang,* Sol. Energy Mater. Sol. C. 2016, accepted.
D. Yang, P. Fu, F. Zhang, N. Wang, J. Zhang,* C. Li,* J. Mater. Chem. A 2014, 2, 17281.
5:30 PM - ED5.7.04
Plasmonic Nanoprobes as Labelling Agents in Optical Nanoscopy
Emiliano Cortes 1 , Paloma Huidobro 1 , Hugo Sinclair 1 , Stina Guldbrand 1 , William Peveler 2 , Timothy Davies 1 , Simona Parrinello 1 , Frederik Görlitz 1 , Chris Dunsby 1 , Mark Neil 1 , Yonatan Sivan 3 , I.P. Parkin 2 , Paul French 1 , Stefan Maier 1
1 , Imperial College London, London United Kingdom, 2 , University College London, London United Kingdom, 3 , Ben-Gurion University, Beer-Sheba Israel
Show AbstractThe diffraction limit has ceased to be a practical limit to resolution in far-field microscopy, following the demonstration of STED, RESOLFT and localisation microscopies and the subsequent development of a plethora of super-resolved microscopy techniques [1,2].
In particular, stimulated emission depletion (STED) nanoscopy, which builds on the advantages of laser scanning confocal microscopy, is a powerful technique for super-resolved imaging in complex biological samples. STED nanoscopy uses stimulated emission to turn off the spontaneous fluorescence emission of dye molecules, typically overlapping a focused excitation beam with a “doughnut” shaped beam that de-excites emitters to the ground state everywhere except for the area within the centre of the doughnut, thus providing theoretically diffraction-unlimited resolution in the transverse plane by reducing the full-width half-maximum (FWHM) of the point spread function.
The scaling of resolution with the square root of the depletion beam power means that relatively high-power lasers are typically used for STED nanoscopy. In practice, however, the use of high-power irradiation can result in problems such as photobleaching of the fluorophores and phototoxicity. Furthermore, high power lasers can add cost and complexity to STED microscopes and so the requirement for high power depletion beams presents challenges for parallelizing STED measurements, limiting the potential for faster super-resolved imaging [3].
In order to reduce the required intensity of the depletion beam, we recently proposed the use of plasmonic nanoparticles (NPs) whose localized surface plasmon resonances (LSPRs) are spectrally tuned to the depletion beam wavelength [4, 5, 6]. Here, we demonstrate this extension of NP-STED to smaller, anisotropic particles by synthesizing new plasmonic-probes based on 26x8 nm fluorescently-labelled AuNRs and show that we can achieve a resolution improvement of ~50% using STED microscopy at low depletion intensities (1.5 MW/cm2) for which a control experiment using fluorescent beads without plasmonic enhancement presents a much weaker (<10%) improvement in resolution. These new plasmonic nanoprobes for STED are ~2000 times smaller in volume compared to the nanoparticles we reported previously [7] and we have used them to label adult neural stem cells for STED microscopy at low depletion powers. We also note that the reduction (~1000x) in the amount of metal of these NP means that we no longer detect the unwanted background light from gold luminescence [7].
[1] S. W. Hell, et al., Optics Letters, 1994. 19(11): p. 780-782. [2] E. Betzig, et al., Science 2006. 313, 1642–1645. [3] B. Yang, et al., Opt. Express 2014. 22(5), 5581–5589. [4] Y. Sivan, et al., ACS Nano, 2012. 6(6): p. 5291-5296. [5] Y. Sivan, Applied Physics Letters, 2012. 101(2): p. 021111. [6] Y. Sonnefraud, et al., Nano Letters, 2014. 14(8): p. 4449-4453. [7] E. Cortes, et al., ACS Nano, 2016, 10 11): p. 0454–10461.
5:45 PM - ED5.7.05
Free Electron Photogeneration in Plasma-Synthesized ZnO Nanocrystals
Benjamin Greenberg 1 , Gunnar Nelson 2 , Eray Aydil 1 , Uwe Kortshagen 1
1 , University of Minnesota, Minneapolis, Minnesota, United States, 2 , Creighton University, Omaha, Nebraska, United States
Show AbstractFundamental understanding of ultraviolet (UV) photogeneration and subsequent transport and recombination of charge carriers in ZnO nanocrystals (NCs) is pertinent to the design of detectors, solar cells, and photocatalysts. Typically ZnO NCs are produced by colloidal synthesis and then used in colloidal dispersions or in thin films cast from dispersions. Manipulating the photogenerated free electron density (ne) and lifetime requires understanding and controlling the interactions between the NCs and chemical species in contact with their surfaces, which may include solvents, surface ligands, reducing agents (hole quenchers), and ambient gases.
We study ZnO NCs synthesized in a nonthermal plasma and manipulate their chemical environment in order to elucidate the determinants of ne under UV exposure. Specifically, we synthesize ~10 nm ZnO NCs in a low-pressure radio-frequency diethylzinc/oxygen/argon plasma and then deposit them directly onto a substrate via supersonic inertial impaction, creating a porous thin film of intimately connected NCs. This unique ZnO NC network contains no solvents, ligands, or reducing agents; the NC surfaces are terminated primarily in OH groups, and each NC interacts only with ambient gases, trace organic byproducts of the synthesis (which can be removed by heating), and neighboring NCs. We illuminate the NCs with a UV lamp (100 mW/cm2 centered at 380 nm), and we determine ne from the localized surface plasmon resonance (LSPR) features in the infrared absorption spectra of the NC films measured under an N2 atmosphere. The as-deposited NCs exhibit no LSPR, but after a two-second UV exposure, an LSPR emerges at 2000 cm-1, indicating that ne rises to 6 × 1019 cm-3. Air exposure quenches the LSPR within seconds, and subsequent UV illumination under N2 restores the LSPR; both processes are completely reversible. Electron photogeneration can also occur under air, and the readily modifiable ligand-free surfaces allow wide-range tunability of ne and electron lifetime. Using atomic layer deposition, we coat the NC surfaces with Al2O3 layers with thicknesses ranging from 1 to 8 nm, and thus we tune photogenerated ne in air from ~1017 to ~1020 cm-3 and the lifetime from seconds to days. The mechanism(s) of electron photogeneration will be discussed; possibilities include desorption of OH or O2- and formation of metallic Zn0 or H+ donors. The absence of ligands also enables electrical resistivities on the order of 1 Ωcm after illumination, making these films promising candidates for applications requiring electron transport across the NC network.
This work was supported by the National Science Foundation through the University of Minnesota MRSEC under Award Number DMR-1420013 and by the ARCS Foundation. Part of this work was carried out in the College of Science and Engineering Characterization Facility, University of Minnesota, which has received capital equipment funding from the NSF through the UMN MRSEC program.
ED5.8: Poster Session II
Session Chairs
Thursday AM, April 20, 2017
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - ED5.8.01
Stress-Induced Phase Transformation, Consolidation, and Optical Coupling of Quantum Dots
Kaifu Bian 1 , Binsong Li 1 , Sheng Liu 1 , Ting Luk 1 , Igal Brener 1 , Michael Sinclair 1 , Zhongwu Wang 2 , Tobias Hanrath 3 , Hongyou Fan 1
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 , CHESS, Ithaca, New York, United States, 3 , Cornell University, Ithaca, New Mexico, United States
Show AbstractQuantum dots are promising building blocks for important applications including photovoltaic, light emission, transistors and bioimaging due to their unique size- and shape-dependent optical and electronic properties. The ability to tune optical and electronic properties of quantum dots by engineering their size, shape, and composition has proved to be a versatile way to interrogate structure–property relationships in quantum dots. Here we present a new method to engineer quantum dot assemblies and to probe their structure-property relationships through stress-induced phase transformation and their exchange coupling during high-pressure compression. We show that under hydrostatic pressure, the unit cell dimension of a 3-dimensional (D) ordered quantum dot superlattice can be manipulated to shrink and swell reversibly, allowing fine-tuning of interparticle separation to probe optical coupling in the supertlattice. Further, beyond a threshold pressure, quantum dots are forced to connect with neighboring dots to form new classes of chemically and mechanically stable 1-3D nanostructures including nanorods, nanowires, nanosheets, and nanoporous networks which cannot be achieved by traditional top-down or bottom-up methods. Moreover, through in situ high-pressure synchrotron-based x-ray scatterings and optical absorption measurements, we discovered Hall-Petch-like size-dependent elastic stiffness and size-dependent pressure coefficient of energy gap in quantum dots. Stress-induced phase transformation and exchange coupling provides new insights for fundamental understanding of chemical and physical properties of quantum dots.
Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
9:00 PM - ED5.8.02
Effect of Plasma Modification on Surface Chemical Analysis and Photocatalytic Properties of Zinc Oxide
Yu-Ting Chiang 1 , Chia-An Li 1 , Kun-Dar Li 1
1 Department of Materials Science, National University of Tainan, Tainan Taiwan
Show AbstractIn this research, the effects of plasma modification on the zinc oxide nanostructures and the photocatalytic properties were explored. ZnO is a semiconducting material having a wide direct energy gap and a large exciton binding energy at room temperature that allows for short wavelength radiation and ultraviolet light absorption. Due to the remarkable performance in electronics, optics and photonics, ZnO nanostructures had been extensively investigated for the applications in solar cells, light-emitting diodes, and photocatalytic elements. Over recent years, many researches had showed promising improvement in the photocatalytic activities of metal oxide semiconductors by creating defects on the surface of the catalyst. In the present study, ZnO nanocrystal arrays were first grown by hydrothermal method with ZnO seed layer, and then followed by a plasma modification. To characterize the microstructure, surface morphology, chemical states of oxygen near the surface and photocatalytic properties, ZnO nanocrystals were evaluated by XRD, SEM, X-ray photoelectron spectroscopy, and photocatalytic degradation of methyl blue. From the experimental results, it showed that the two major effects were induced during plasmas treatment, including the sintering and sputtering effects. Based on the XPS analysis, it was observed that the oxygen vacancies of ZnO nanocrystals were increased with plasmas modification. And, accordingly, the photocatalytic properties of ZnO nanocrystals were distinctly enhanced after plasmas treatment. More detailed influence of plasmas modification on the surface chemical analysis and photocatalytic properties was discussed. The results from this study proved that the presence of surface defects in ZnO nanocrystals was crucial for its efficient photocatalytic activity.
9:00 PM - ED5.8.03
Synthesis and Photoelectrochemical Properties of Mesoporous Materials Embedded with Metallic Nanoparticles
Nelly Couzon 1 , Mathieu Maillard 1 , Laurence Bois 1 , Arnaud Brioude 1
1 , University of Lyon, Villeurbanne France
Show AbstractMesoporous oxide films filled with nanoparticles exhibit enhanced photocatalytic properties due to a controlled porosity and the presence of light absorbing metallic catalyzers. However, the exact mechanism of improvement is yet to be clarified as several phenomena occur concomitantly like charge carrier, surface catalysis, plasmon enhancement, and exciton relaxation. To understand this mechanism, we chose to study nanostructured electrodes made of metallic nanoparticles inside a semi-conductor oxide (TiO2-Ag) with a control of porosity and particle dispersion as an improved photocatalytic system. We performed electrochemical experiments in a three electrode configuration under various ranges of light irradiation, from UV to visible, to determine the variations of redox potentials and photocurrent and thus getting insights on the photochemical mechanism and material structure influence.
We demonstrate the importance of illuminations on mesoporous film TiO2-Ag electrochemical properties. Light absorption not only induces a photocurrent but also modifies the redox potential of silver nanoparticles, as observed by a shift in position and intensity during cyclic voltammetry measurements. In particular, we clearly observed a shift of almost 200mV to more positive potential on the reduction peak of silver ions while irradiating sample.
Silver nanoparticles are also modified due to electrochemical Ostwald ripening and diffusion of silver through the electrolyte during irradiation. These two phenomena are more or less pronounced depending on the wavelength, and lead to a decrease of intensity of the oxidation/reduction peak of silver. We point out that this aging phenomenon can also be reduced, working on short cycling time with an on/off alternation illumination.
9:00 PM - ED5.8.04
Electrical and Optical Properties of Novel Tin-Nickel Based Oxide
Yuying Chu 1
1 Materials Science and Engineering, National Tsing Hua University, Hsinchu Taiwan
Show AbstractMetal oxide materials exhibit potential in many applications on optoelectronics, such as thin film transistors (TFT), transparent conductive oxide (TCO) thin film, and optical sensors. It is interesting to study noble oxide materials for various potential applications.
In this work, earth-abundant tin oxide and nickel oxide were used to form tin-nickel based oxide materials. The tin-nickel based oxide material was prepared as a target and then sintered at a high temperature about 1000oC. The tin-nickel oxide materials were characterized by XRD analysis. The target was used to deposit tin-nickel oxide thin films. Thin film deposition parameters such as post-annealing temperature and time were varied to optimize the structural, electrical and optical properties of the oxide thin films. The morphological, compositional and structural properties of the films were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX) and X-ray diffraction (XRD), respectively. The electrical and optical properties of the thin films were also measured by Hall-effect measurement system and ultraviolet-visible spectroscopy (UV-Vis), respectively to study the potential applications.
9:00 PM - ED5.8.05
Radiative Defects, Emission and Structure of ZnO Nanocrystals Obtained by Electrochemical Method
Tetyana Torchynska 1 , Georgiy Polupan 1 , Brahim El Filali 1 , Lyudmula Shcherbyna 2
1 , Instituto Politecnico Nacional, Mexico City, FDM, Mexico, 2 Photoelectronics, 4V. Lashkaryov Institute of Semiconductor Physics at NASU, Kiev, Kievskaya, Ukraine
Show AbstractThe radiative defects, emission and structure of ZnO nanocrystals (NCs) have been studied using the scanning electron microscopy (SEM), Energy dispersion spectroscopy (EDS), X-ray diffraction (XRD) and photoluminescence (PL) techniques. ZnO NCs were prepared by etching the zinc sheets in an electrolyte and annealing after etching within the temperature range of 200 - 400oC in ambient air.
None monotonous variation of the crystal lattice parameters has been revealed at the XRD study of ZnO NCs annealed at different temperatures: i) decreasing the inter-planar distances in NCs annealed within the temperature range 200 - 360oC and ii) increasing the inter-planar distances in NCs annealed at 360-400oC. It was shown using EDS that the oxygen dissolution in ZnO NCs rises essentially at 400oC annealing. The correlation of the behaviors of orange, yellow, green and blue PL bands with the structural XRD parameters in ZnO NCs have been presented and discussed.
The study of PL thermal decays within the range of 10-300K permits to estimate the activation energies of PL intensity thermal decay processes for the defect related PL bands in ZnO NCs and to analyze the nature of donor-acceptor pairs (DAPs) responsible for the optical transitions. PL intensity varying the orange, yellow, green and blue PL bands by a controllable way is important for the future application of ZnO NC films in “white” light emitting device structures.
9:00 PM - ED5.8.06
Enhanced Self-Enhanced Self-Cleaning Surface by Atomic Layer Deposition of Photoactive TiO2 Nanocomposite
Joseph Jiang 2 1 , Charles Fan 3 1 , Jiajie Sun 4 , Hongxia Zhang 1 , Ying-Bing Jiang 1 4 , Hongyou Fan 2 4
2 , Sandia National Labs, Albuquerque, New Mexico, United States, 1 , Angstrom Thin Film Technologies LLC, Albuquerque, New Mexico, United States, 3 , Albuquerque Academy, Albuquerque, New Mexico, United States, 4 , University of New Mexico, Albuquerque, New Mexico, United States
Show AbstractSelf-cleaning surface can be achieved by two opposite strategies: super hydrophobicity or super hydrophilicity. The first strategy typically relies on modifying a surface with organic ligands so that the surface is “non-stick”; The second strategy typically uses a photocatalytic coating such as TiO2 to break the bonding between the dirt and the surface, followed by rinsing away the dirty with sheeting water between the super hydrophilic TiO2 surface and the dirt. In the first strategy, the organic ligands are not stable thereby the self-cleaning property may degrade year-by-year; In the second strategy, the coating is inorganic and robust, therefore most commercial self-cleaning surfaces are based on this strategy. However, the use of second self-cleaning strategy is limited due to the limited efficiency of photocatalytic reactions, which requires sufficient sunshine as well as proper atmospheric moisture. In this work, to improve the self-cleaning property, a composite structure with TiO2 nanocrystals included in hydrophilic silica nanopores was introduced. The silica nanopores was fabricated by sol-gel dip-coating process, and the pure TiO2 and doped TiO2 nanocrystals were deposited within nanopores using atomic layer deposition process. The distribution of ALD TiO2 within nanopores was investigated using Ti-mapping function in a transmission electron microscope, and the crystallinity and the crystal phase were studied using electron energy filter and electron diffraction mode. The ALD parameters and the best doping conditions were optimized by the guidance of above results. It was found that the hydrophilic nanopores in our composite structure can help trapping atmospheric moisture and make it concentrate in the TiO2 surface vicinity – which is critical for the photocatalytic dirt decomposing process, thereby the self-cleaning property has been improved significantly.
9:00 PM - ED5.8.07
Spontaneous Self-Assembly of Silver Nanoparticles into Lamellar Structured Silver Nanoleaves
Qiangbin Wang 1
1 , Chinese Academy of Sciences, Jiangsu China
Show AbstractUniform lamellar silver nanoleaves (AgNLs) were spontaneously assembled from 4 nm silver nanoparticles (AgNPs) with p-aminothiophenol (PATP) as mediator under mild shaking at room temperature (RT). The compositions of the AgNLs were verified to be ~1 nm Ag25 nanoclusters and PATP molecules in quinonoid model. The underlying assembly mechanism was systematically investigated and a two-step reaction process was proposed. Firstly, the 4 nm AgNPs were quickly etched to ~1 nm Ag25 nanoclusters by PATP in the form of [Ag25(PATP)n]n+ (n < 12), which were then further electrostatically or covalently interconnected by PATP to form the repeated unit cells of [Ag25(PATP)n-1](n-1)+-PATP-[Ag25(PATP)n-1](n-1)+ (abbreviated as Ag25-PATP-Ag25). Secondly, these Ag25-PATP-Ag25 complexes were employed as building blocks to construct lamellar AgNLs under the directions of the strong dipole-dipole interaction and the π-π stacking force between the neighboring benzene rings of PATP. Different reaction parameters including the types and concentrations of ligands, solvents, reaction temperature, ionic strength, and pH, etc, were carefully studied to confirm this mechanism above. Finally, the preliminary investigations of the applications for AgNLs as “molecular junctions” and SERS properties were demonstrated. We expect that this convenient and simple method can be in principle extended to other systems, or even mixture system with different types of NPs, and will provide an important avenue for designing metamaterials and exploring their physicochemical properties.
9:00 PM - ED5.8.08
Remarkably Enhanced Photocatalytic Activity in Bi1-xBaxFeO3 Prepared by Sol-Gel Method
Chenlan Zhang 1 , J.R. Cheng 1
1 School of Materials Science and Engineering, Shanghai University, Shanghai China
Show AbstractAs a typical multiferroic material,BiFeO3 (BFO),has exhibited photocatalytic activities under visible light irradiation,thanks to its suitable band gap (2.2–2.8 eV) and good chemical stability.However,the low photocatalytic activity of BFO hinders its commercialization in photocatalytic field for the degradation of organic pollution.Therefore,an important task is to improve the photocatalytic activity of BFO for practical use.
In this paper,a series of nano particles of Bi1-xBaxFeO3 (for x = 0,0.01,0.03,0.05,0.10) by Ba2+ acceptor-doping at A-site were synthesized by a sol–gel method. XRD analysis confirms that Ba ions enter into the lattice,and TEM image shows that Ba2+ doping refines the grain whose different size in the range of 30-60 nm.Though testing the photocatalytic degradation of methyl orange(MO),the purpose of our study was to explore the impact of Ba ions on the pure phase BFO,involving the content of Ba ions on the microstructure and surface morphology of the BFO photocatalysts,and the final improvement of their photocatalytic efficiency.We found the optimum concentration of Ba2+ doping is x = 0.03.In this condition,Bi1-xBaxFeO3 has the highest visible light degradation ratio (81% after 3 hours),which is much higher than that of pure phase BFO (66% after 3 hours).
The smaller particle size which reduce the probability of recombination by reducing the time of charge carriers’ migration and the formation of Fe4+ or oxygen vacancies should make some influence on enhancement of catalytic efficiency.We also try to make a prediction that Ba2+ serves as an efficient dopant to influence photocatalytic ability through band gap modifications and the change of Fe-O-Fe bond angle by our first-principles calculations.
9:00 PM - ED5.8.09
Electrochemical Reduction of Hydrogen Carbonate Using Porous Diodes
Yevedzo Chipangura 1 , Allen Chaparadza 1
1 , College of St. Scholastica, Duluth, Minnesota, United States
Show AbstractThe electrochemical reduction of CO2 on metal electrodes is an intensively studied reaction. However, there has not been much attention for CO2reduction on photo based diodes. Aqueous hydrogen carbonate is carbon dioxide equivalent:
H2O +CO2 ↔ H2CO3 ↔ HCO3- + H+ ↔ CO32-+ 2H+
Here we report the electrochemical reduction of aqueous of hydrogen carbonate to formate using porous diodes fabricated using platinum deposited Sb doped SnO2 (n-type) and Li doped CuO (p-type) nanowires. XRD, TEM and ATR-UV-Vis were employed to characterize the nanowires. Typical current-voltage curves of such devices resemble the behavior of a typical diode except for one key difference; the areas near the p-n interface and the p-and n-regions are accessible to analytes. Photo electrochemical reduction efficiency measurements were measured using cyclic voltammetry, as a function of UV light intensity and wavelength. GC, HPLC, NMR and IR were used to quantitatively and qualitatively analyze the reduction products. 13C enriched hydrogen carbonate NMR and infrared spectroscopy confirmed the reduction of hydrogen carbonate to formate. The reduction rate of hydrogen carbonate was 0.0015 mol min-1 cm-2at a bias voltage of 1.65 V. The rate of reduction decreased with increasing lithium doping up to 20% and increasing antimony up to 10% (moles in synthesis) with respect to copper and tin respectively.
9:00 PM - ED5.8.10
Visible-Light Nanoscale Photoconductivity of Grain Boundaries in Self-Supported ZnO Platelets
Nastaran Faraji 1 , Clemens Ulrich 1 , Niklas Wolff 2 , Lorenz Kienle 2 , Rainer Adelung 2 , Yogendra Mishra 2 , Jan Seidel 1
1 Science, University of New South Wales, Sydney, New South Wales, Australia, 2 , University of Kiel, Kiel Germany
Show AbstractThe response of individual grain boundaries in two dimensional polycrystalline ZnO platelets to visible light illumination is studied using scanning probe based techniques on the nanoscale. While many previous studies report and discuss the UV responses of ZnO, we find that even in the visible range of light below the band gap, grain boundaries are sensitive to light, this can be attributed to defect accumulation at the grain boundaries and associated photoexcitation of carriers. These findings suggest that engineered grain boundaries can be used for novel optoelectronic applications based on conductive channels in an otherwise wide-bandgap transparent material.
9:00 PM - ED5.8.11
Visible Light Emission from Implanted III-V Semiconductors
Angelica Hernandez 1 , Yuriy Kudriavtsev 1 , Miguel Avendano 1
1 , CINVESTAV, Mexico City, FDM, Mexico
Show AbstractWe have investigated the formation of a near-surface binary layer in a GaAs implanted with Ge+ ions and its optical properties. Commercially available GaAs wafers were implanted with Ge+ ions at 25 keV by using an ion dose of 1x1016 ions/cm2 and subsequent thermally annealed in nitrogen atmosphere. The annealing time and temperature conditions were optimized in order to diminish the damage in the crystal lattice due to the implantation and also to induce the oxidation of Germanium.
Structural characterization was performed by using Raman spectroscopy. The obtained results show the vibrational modes of the implanted element and the implantation matrix as the presence of germanium oxides. The implanted elements were re-arranged into the crystal lattice due to the thermal process. The corresponding Raman spectra shows the transition from amorphous to crystalline GaAs.
A SIMS depth profile of the as implanted and thermally treated samples were obtained in order to study diffusion of the elements along the totally amorphized and the partially amorphized layer.
The optical properties of the as implanted and thermally treated samples were studied at excitation wavelength of 325 nm at room temperature. Visible light emission was observed in the as implanted samples and the PL intensity increased after the annealing. The de-convolved PL spectra reveal that several mechanisms gather in the photon-emission process. The spectrum can be considered a mixture of photonic effects that include the formation of nano-crystals and recombination of electrons in the oxygen vacancies of the germanium oxides as well as the band to band emission of the GaAs itself.
Due to its technological importance, the fabrication of germanium-based luminescent materials has been explored through the development of several techniques which involve chemical and physical mechanisms. However, the ion implantation is an undoubtedly favorable cost-effect technique to fabricate nano-structured materials with optical properties in an uncomplicated process.
9:00 PM - ED5.8.12
PhotoCatalytic Performance and Electronic Structures of SnO2 Nanoparticles Modified by Transition Metal Doping
Hangil Lee 1
1 , Sookmyung Women's University, Seoul Korea (the Republic of)
Show AbstractMetal-doped SnO2 nanoparticles (M@SnO2) were synthesized by applying a thermos-synthesis method, which first involved doping SnO2 with Sb and then with transition metals (M = Cr, Mn, Fe, or Co) of various concentrations to enhance a catalytic effect of SnO2. The doped particles were then analyzed by using various surface analysis techniques such as transmission electron microscopy, X-ray diffraction, scanning transmission X-ray microscopy, and high-resolution photoemission spectroscopy (HRPES). We evaluated the catalytic effects of these doped particles on the oxidation of L-cysteine (Cys) by using HRPES under UV illumination. The Cr- and Mn-doped SnO2 nanoparticles exhibited enhanced catalytic activities, which according to the various surface analyses were due to the effects of the sizes of the particles and electronegativity differences between the dopant metal and SnO2.
9:00 PM - ED5.8.13
Near Infrared Laser Triggered NO Generators for Reversal of Multidrug-Resistant Cancer
Ranran Guo 1 2
1 Macromolecular Science, Fudan University, Shanghai China, 2 , State Key Laboratory of Molecular Engineering of Polymers, Shanghai China
Show AbstractThe therapeutic implications of nitric oxide (NO) for diverse diseases have been proposed for years, while developing precisely controlled NO generation system with potential in clinical application remains emergent. Herein, an intelligent near infrared laser triggered NO generator is fabricated for treatment of multidrug resistant (MDR) cancer. Integrating photothermal (PTT) agents and heat-sensitive NO donors together, the generators could absorb 808 nm near infrared photons and convert them into ample heat, resulting in controlled NO releasing temporally and spatially. Then the generated NO molecules are demonstrated successfully realizing MDR reversal by inhibiting the expression of P-glycol protein. As a result, the intracellular drug accumulation is increased effectively, inducing high toxicity to MDR cancer cells in vitro. Owing to the surface modification with targeting ligands, the nanoparticles are able to selectively accumulated in tumor region, and the therapeutic effects of the generators are confirmed in a humanized drug-resistant cancer model. The experimental results indicate the nanoparticles possess excellent tumor suppressor function with minimal side effect under NIR laser irradiation. Therefore, this photo-thermal conversion based NO-releasing platform is expected to be a potential alternative to clinical MDR cancer treatment and may provide insights on other NO-relevant applications.
9:00 PM - ED5.8.14
The Coupling between Two Heterogeneous InAs Quantum Dot Families and Its Effect into Optical Properties
Debabrata Das 1 , Debiprasad Panda 1 , Subhananda Chakrabarti 1
1 , IIT Bombay, Mumbai India
Show AbstractIn this study, we present the coupling between InAs submonolayer (SML) and stranski krastanov (SK) quantum dots (QDs). Interaction between these two different dot families was manipulated by changing the capping layer thickness. Significant shift in photoluminescence (PL) peak was observed due to the coupling effect. The dynamics of the carriers in this mixed dot matrix was also modified, which was evident from the increasing activation energy with increasing thickness of the capping layer. Moreover, an ex situ annealing study at different temperatures was done to check the thermal stability of as grown samples. Annealing at lower temperatures, improved the crystal quality a bit, but higher annealing temperatures accelerated the defect formation, the signature of which was visible in PL spectrum of annealed samples. Reducing activation energy with increasing annealing temperature was also indicated the same statement.
Standard six stack 0.3 monolayer (ml) InAs/InGaAs SML matrix was overgrown by 2.7 ml InAs SK QDs, with varying GaAs capping layer thickness (2.5, 5, 7.5 nm). Corresponding PL peaks are at 1081, 1076 and 1078 nm, respectively, which were blue-shifted than normal SK QD PL peak (1138nm). For 2.5 nm capping thickness there was no signature of SML peak, but rests with higher capping thickness depicted significant SML peak to the left of SK PL peak. This was due to better interaction for lower GaAs barrier, which eventually promoted a new downward transition path via SK higher excited states. Here the SML ground energy state and SK higher excited state were in resonating condition and most of the electrons, excited within SML QDS, had diffused into the SK dots and recombined. The influence of this additional recombination path was inversely proportional to the barrier thickness. Corresponding activation energy (167, 176 and 200 meV for 2.5, 5 and 7 nm capping thickness respectively) was also indicated the same assertion. Post growth annealing blue shifted the PL peaks, afforded to the reduction of dot size through In outdiffusion. DST, Riber acknowledged.
9:00 PM - ED5.8.15
Magnetically Rewritable and Thermally Reversible-Showing Photonic Crystal Paper
Huiru Ma 1 2 , Lin Ma 1 , Lidong Zhou 1 , Jianguo Guan 1 3
1 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, Hubei, China, 2 Department of Chemistry, School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan, Hubei, China, 3 International School of Materials Science and Technology, Wuhan University of Technology, Wuhan, Hubei, China
Show AbstractAbstract: Magnetically responsive photonic crystals(MRPs) are promising as photonic paper(PP) and ink[1] for calligraphy to information encryption,[2] saving display[3] and identification mark[4] due to their rapid, reversible color changes, self-displaying without power consumption, reduced eye-fatigue and low power consumption. In this work, we have demonstrated an external magnetic field (H)-aided phase inversion method to fabricate a novel kind of multifunctional PP by evaporating the dimethyl formamide solution with cellulose acetate (CA), poly(ethylene glycol) (PEG) and magnetic photonic nanochains under H. In the as-obtained PP, the porous CA is embedded with PEG and oriented photonic nanochains. The as-obtained PP may rapidly and reversibly switch its structural color from the natural brown color when H is exerted perpendicular or parallel to the film surface, corresponding to its writing and erasing functions. Moreover, the structural color can be covered by the crystallized PEG (opaque solid) when it cools below to the melting point (Tm) of PEG, and also be recovered above Tm, corresponding to the case that PEG is transformed into transparent liquid from opaque solid. For the PP, the self-displaying time (td) largely prolongs with increasing the PEG molecular weight or decreasing temperature. The CA content used in the film-forming process has strongly influences on the pore sizes, and thus td of the PP. When the CA content is 30 wt% or more, the PP can repetitively show and hide its structural color for multiple recycles with the brightness almost remaining. Our results suggest that this novel multifunctional PP shows extensive applications ranges from color display, the rewritable signage to anti-counterfeiting labels.
Acknowledgement
This work was financially supported by the National Natural Science Foundation of China (51303143, 21474078, 51573144 and 51521001).
Reference
[1] M. Wang, L. He, Y. Hu, Y. Yin, J. Mater. Chem. C, 2013, 1, 6151.
[3] R. Xuan and J. Ge, J. Mater. Chem., 2012, 22, 367.
[2] W. Luo, H. Ma, F.Mou, M.Zhu, J.Yan and J. Guan, Adv. Mater., 2014, 26, 1058.
[4] H.Hu, H. Zhong, C. Chen and Q. Chen, J. Mater. Chem. C, 2014, 2, 3596.
9:00 PM - ED5.8.16
Surface-Coated Responsive Polymer Superparamegnetic Nanoparticles for Photonic Crystal Sensors
Ke Chen 1 2 , Wei Luo 1 , Huiru Ma 1 2 , Min Long 1 , Zhen Wu 3 , Jianguo Guan 1 3
1 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, Hubei, China, 2 Department of Chemistry, School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan, Hubei, China, 3 International School of Materials Science and Technology, Wuhan University of Technology, Wuhan, Hubei, China
Show AbstractPhotonic crystal (PC) sensors provide a simple yet powerful detection strategy that is well-suited to the development of low-cost and low-power sensors.[1] However, most of the so far developed PC sensors suffer from long equilibration time, low local sensitivity and short durability due to the contained bulk polymer matrix, and need large quantities of analytes.[2] Besides, the periodic structure of PCs may be deteriorated by impurities like ionic species during the solidification process, degrading the sensing properties.[3] Herein, a new sensing motif was developed by dynamically assembling superparamagnetic Fe3O4 colloidal nanocrystal cluster (CNC)@responsive polymer core-shell nanoparticles into 1D PC nanochains under a fixed external magnetic field (H). The volume change of the responsive polymer layers induced by analytes changes the interparticle distance within the 1D PC and thus the corresponding reflection peaks. For example, uniform pH responsive Fe3O4@PVP@P(HEMA-co-AA) nanoparticles were fabricated by a hydrogen bond-guided template polymerization method, where monomers HEMA, AA are highly concentrated within the PVP shells of uniform Fe3O4@PVP CNC particles.[4,5] The PC array formed under H diffracts different visible light at different pH buffer solutions. This method shows a rapid response and high sensitivity of pH due to the tens-of-nm-thick responsive polymer shell. Moreover, it can further detect small quantities of solution with trace analytes toward real-time local sensing with greatly improved detection precision. In addition, as the responsive nanoparticles are small enough to pass through microchannels and then form periodical structures under H on demand, they can be used in different micro areas that previous PC sensors cannot. Finally, these nanoparticles without H can keep stable for a long time in aqueous solution. The as-proposed MRPCs based surface-coated responsive polymer particles would have great application prospects for sensing.
Acknowledgement
This work was financially supported by the National Natural Science Foundation of China (51303143, 51573144, 21474078 and 51521001),the Natural Science Foundation of Hubei Province (2014CFB163 and 2015CFA003), the Top Talents Lead Cultivation Project of Hubei Province.
Reference
[1] R. Macfarlane, B. Kim, B. Lee, R. Weitekamp, C. Bates, S. Lee, A. Chang, K. Delaney, G. Fredrickson, H. Atwater, R. Grubbs, J. Am. Chem. Soc., 2014, 136, 17374.
[2] Z. Cai, D. H Kwak, D. Punihaole, Z. Hong, S. Velankar, X. Liu, S. Asher, Angew. Chem. Int. Ed., 2015, 54, 13036.
[3] M. Chen, L. Zhou, Y. Guan and Y. Zhang, Angew. Chem. Int. Ed., 2013, 52, 9961.
[4] W. Luo, H. Ma, F. Mou, M. Zhu, J. Yan and J. Guan, Adv. Mater., 2014, 26, 1058.
[5] Z. Feng, Z. Wang, C. Gao, J. Shen, Chem. Mater., 2007, 19, 4648.
9:00 PM - ED5.8.17
1D Flexible Photonic Nanochains-Based Magnetically Responsive Photonic Crystals
Yun Liu 1 , Guanghao Zhu 1 2 , Huiru Ma 1 2 , Juanjuan Pan 1 , Fenghe Fu 1 , Jianguo Guan 1 3
1 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan China, 2 Department of Chemistry, School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan, Hubei, China, 3 International School of Materials Science and Technology, Wuhan University of Technology, Wuhan, Hubei, China
Show Abstract1D magnetically responsive photonic crystals (MRPCs) have attracted great research interest for their potential applications in energy-efficient displays, erasable photonic paper/ink, sensors, camouflage, etc.[1,2] The so far reported MRPCs only include two types of uniform superparamagnetic colloidal nanocrystal cluster (CNC) particles or 1D rigid peapod-like structures in liquid. The former exhibits adjustable 1D periodically ordered nanochains and structural colors by changing applied magnetic field (H), while the latter swiftly makes rotation orientation under H, displaying a structural color almost independent of the intensity of H.[3]
In this work, we have prepared flexible Fe3O4@polyvinylpyrrolidone (PVP)/poly(N- isopropyl acrylamide) (PNIPAM) photonic nanochains through hydrogen bond-guided UV-light initiated template polymerization under H. In this protocol, the uniform superparamagnetic Fe3O4@PVP CNCs, which were obtained by a solvothermal approach reported previously,[4] are linearly aligned into 1D nanochains under the application of H. They strongly absorb poly(acrylic acid) (PAA) and then monomer NIPAM around each chain through the hydrogen bond interaction of PAA with PVP and NIPAM, respectively. Subsequently, they act as templates for the UV-initiated polymerization of NIPAM to form individual pod-like Fe3O4@PVP/PNIPAM nanochains. The as-obtained nanochains are flexible, evidenced by a bent shape without H. The interparticle space and chain length can be adjusted by the intensity and applied time of H used in the chain forming process, while the flexibility is determined by the crosslinking degree of the included PNIPAM.
Upon the application of H, the as-obtained flexible nanochains orient along the H direction in two successive ways of deflection orientation and stretch orientation, depending on the intensity of H. With increasing H, the position of the diffracted peak remains unchanged, but the intensity gradually increases. With these unique optical properties, the obtained flexible nanochains could be used for the detection of magnetic field distribution and intensity through brightness of visual color.
Acknowledgement
This work was financially supported by the National Natural Science Foundation of China (51303143, 51573144, 21474078, and 51521001), the Natural Science Foundation of Hubei Province (2014CFB163 and 2015CFA003), the Top Talents Lead Cultivation Project of Hubei Province.
Reference
[1] M. Wang and Y. Yin, J. Amer. Chem. Soc, 2016, 138, 6315–6323.
[2] H. Ma, M. Zhu, W. Luo, W. Li, K. Fang, F. Mou and J. Guan, J. Mater. Chem. C, 2015, 3, 2848–2855.
[3] M. Wang, L. He, Y. Hu and Y. Yin, J. Mater. Chem. C, 2013, 1, 6151–6156.
[4] W. Luo, H. Ma, F. Mou, M. Zhu, J. Yan and J. Guan, Adv. Mater. 2014, 26, 1058–1064.
9:00 PM - ED5.8.18
Self-Oriented Magnetochromatic Photonic Crystal Balls
Yali Tan 1 , Lin Ma 1 , Huiru Ma 1 2 , Zhuozhi Ruan 1 , Juan Bian 3 , Jianguo Guan 1 3
1 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, Hubei, China, 2 Department of Chemistry, School of Chemistry, Chemical Engineering and Life Science, Wuhan University of Technology, Wuhan China, 3 International School of Materials Science and Technology, Wuhan University of Technology, Wuhan, Hubei, China
Show AbstractOne-dimensional (1D) photonic crystal (PC) microspheres are intrinsic anisotropy in optical properties and the structural color displayed only along the direction parallel to nanochains can be maintained only when an external magnetic field (H) is applied.[1,2] This feature sometimes greatly limits their application prospects. In this work, by using a combined technique of micropipet injection and UV photopolymerization in the presence of H, we have prepared self-oriented magnetochromatic PC balls, poly(N-isopropylacrylamide) balls with both oriented Fe3O4 PC nanochains and a droplet containing superparamagnetic Fe3O4@polyvinylpyrrolidone (PVP) colloidal nanocrystal cluster (CNC) particles[3] asymmetrically encapsulated. The as-obtained PC balls have a unique asymmetrical heterostructure with biphases of liquid and solid, and show remarkably distinguished properties from the present developed photonic crystal microspheres.[4] Firstly, they can self-orient without the help of H in water and show a single bright structural color originating from the outer shells containing parallel oriented nanochains. Secondly, upon applying H along the parallel oriented chains, the structural color can be magnetically tunable as the superparamagnetic Fe3O4@PVP CNC particles dispersed in the droplet are arranged into 1D periodic structures with the interparticle distance magnetically adjustable. Thirdly, the balls in viscous liquid can further display various structural colors in a wide angle range when H is applied perpendicular to its self-oriented direction as the 1D periodic structures formed in the droplet are perpendicular to that in the shells. These remarkable properties endow the PC balls with excellent potential applications, such as structural color printing, switchable signage, stimulus-response color display, and anti-counterfeiting devices.
Acknowledgement
This work was financially supported by the National Natural Science Foundation of China (51303143, 21474078, 51573144 and 51521001), the Natural Science Foundation of Hubei Province (2014CFB163 and 2015CFA003) and the Top Talents Lead Cultivation Project of Hubei Province.
Reference
[1] J. Ge, H. Lee, L. He and Y. Yin, J. Am. Chem. Soc., 2009, 131, 15687–15694.
[2] J. Kim, Y. Song, L. He, H. Kim, Y. Yin and S. Kwon, Small, 2011, 7, 1163–1168.
[3] W. Luo, H. Ma, F. Mou, M. Zhu, J. Yan and J Guan, Adv. Mater., 2014, 26, 1058–1064.
[4] J. Wang, Y. Hu, R. Deng, W. Xu, Z. Nie and J Zhu, Lab Chip, 2012, 12, 2795–2798.
Symposium Organizers
Feng Bai, Henan University
Ying-Bing Jiang, Angstrom Thin Film Technologies LLC
Binsong Li, Tsinghua Innovation Center in Dongguan
Dong Qin, Georgia Institute of Technology
Symposium Support
Dongguan-RITS Innovation Center
Henan University
ED5.9: Photoactive Biomaterials
Session Chairs
Ying-Bing Jiang
Xinhe Zheng
Thursday AM, April 20, 2017
PCC North, 100 Level, Room 129 A
9:30 AM - *ED5.9.01
Gallium Oxyhydroxide Containing Composites for Biointerface Studies
Albena Ivanisevic 1
1 , North Carolina State University, Raleigh, North Carolina, United States
Show AbstractGallium Oxyhydroxide, GaOOH, is a scintillator – it luminesces when exposed to radiation. The size of the material can range from 10 nm particles to 500 nm long rod structures. The work to be presented in this talk seeks to address the possibility of using GaOOH as the inorganic component in organic/inorganic composite biomaterials. Of particular importance is the ability to withstand varying pH environments, and to avoid the leaching of toxic ionic species. Lysine has shown to reduce the leaching of ionic species, when particles of inorganic molecules are cross-linking agents for the amino acid. The talk will address the aqueous stability of both AlOOH and GaOOH in a lysine environment. The optical and size characteristics observed in nanostructured forms of the mixed composition AlxGa1-xOOH material system is of interest, due optical tunability providing a distinct advantage in optoelectronic devices containing these organic/inorganic hybrids. Immobilizing phosphonic group containing organic dyes on the surface of GaOOH, AlOOH and mixed compositions of AlGaOOH using surface bonding sites, and possible covalent attachments mechanisms, seeks to provide an improvement in the long term stability of the inorganic/organic interface for biological applications. The final part of the talk will focus on GaOOH as an additive to a biological gel. This inorganic-organic interface provides a multifunctional platform for biological studies. Currently in the literature, cell behavior and cellular responses have been studied through many different material platforms. Specifically, researchers are interested in the effects of various stimuli, including mechanical properties, on cell fate. There is a need for a platform under which multiple stimuli and their effects can be studied. Data will be presented to demonstrate the creation a composite material with variable stiffness and scintillating properties to modulate cell behavior.
10:00 AM - ED5.9.01
Formation of Silicon Nanocrystals in Silica Films via Double Implantation
James Gaudet 1 , Peter Simpson 1
1 , University of Western Ontario, London, Ontario, Canada
Show AbstractThermal Silica films (285 and 2400 nm) grown on Si (100) wafer were subjected to Si+ ion implantation in high doses (1016 - 1017cm-2), first at 450 keV then at 90 keV. Si nanocrystals (nc) were formed using high temperature annealing in an inert atmosphere and a hydrogen containing atmosphere was used to passivate un-bonded Si orbitals. Photoluminescence (PL) Spectroscopy and Time-Resolved PL (TRPL) data were used to probe the Si-nc. A crude model of the depth-dependent stoichiometry and density was calculated for these films based on simulation data from the SRIM 2013 software package. This suggested an equal or lower concentration of Si at depths corresponding to the 450 keV implant than at depths corresponding to the 90 keV implant which would imply, at most, an equivalent proportion of the largest nc at the greater depth. However, PL intensity from the largest nc increases with increasing 450 keV dose (with 90 keV dose held constant). Previous studies have concluded that double implantation results in higher PL intensity than the two implants conducted individually, and we postulate that this is due to the damage done to the 90 keV implant region by the 450 keV implant. XANES data shows a diminishing marginal increase in bulk/nano-structured Si with increasing 450 keV dose. Positron annihilation spectroscopy was used to quantify the presence of vacancy-type defects and to identify the relative proportions of silica and silicon as a function of depth. This suggested an even less dense 450 keV implanted region than the model based on SRIM data, and lends further support to the role of the double implant. The ability to engineer the defect structure of thin films with large implant doses opens the possibility of creating application-tailored thin film/nc devices of technological interest.
10:30 AM - ED5.9.03
Relations between Morphology and Photoluminescence Properties in Single Colloidal Nanoplatelets
Zhongjian Hu 1 , Ajay Singh 1 , Jennifer Hollingsworth 1 , Han Htoon 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractAtomically flat colloidal semiconductor nanoplatelets (NPLs) as free-standing quasi quantum well nanostructures have attracted great research attentions due to their fascinating optical properties and appealing potential for numerous applications. Here, we investigated how the morphology affects the photoluminescence properties in single CdSe/Cd(Zn)S NPLs. We showed that, while the emission is analogously red shifted with shell growth independent of the shell quality, the blinking behavior is strongly affected by the shell quality. From CdSe core NPLs with dominant large intensity blinking not accompanied by significant change in lifetime (B-type blinking), the growth of rough CdS shell leads to blinking associated with lifetime (A-type blinking). The growth of smooth shells, on the other hand, greatly reduces the occurrence of A-type blinking. The variations in the blinking behavior in these NPLs was explained in terms of the nonradiative traps on the surfaces and/or in the shell. Low temperature spectral experiments further revealed a narrower linewidth in the smooth shell NPLs relative to the rough shell NPLs.
10:45 AM - ED5.9.04
Fluorescence Enhancement in Quantum Dot Coupled Plasmonic Nanocup Structures
Akshit Peer 1 2 , Zhongjian Hu 3 , Ajay Singh 3 , Rana Biswas 1 2 , Jennifer Hollingsworth 3 , Han Htoon 3
1 , Iowa State University, Ames, Iowa, United States, 2 , Ames Laboratory, Ames, Iowa, United States, 3 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractQuantum dots (QDs) coupled with metal plasmonic nanostructures have been studied intensely as the basis for understanding the fundamental light-matter interactions and cooperative phenomena such as plasmon assisted lasing, super radiance and entanglement.
Here we develop plasmonic periodic nanocup structures that show high electric field intensity enhancement by factor >100 inside the nanocups, and couple them with semiconductor nanocrystals to investigate their quantum optical properties. The gold-coated plasmonic structures were fabricated using soft-lithography approach. The PDMS stamp having periodic nanocones with period (a) ~750 nm was stamped on polystyrene-coated glass substrate to create nanocups, followed by thin gold film deposition. Conventional ways of fabricating hole array structures involve advanced microelectronics facilities and procedures, and are difficult to implement for larger area samples. We demonstrate a particular simpler method to fabricate a subwavelength array structure using simple soft lithographic procedures that does not require any nanofabrication facilities, and may be easily achieved in a workbench without high vacuum facilities.
Optical measurements on these structures revealed the extraordinary transmission peak at λ~700-720 nm, close to the structure period, which occurs due to excitation of surface plasmon modes on both surfaces of the metal film and their coupling to each other. The transmission was enhanced ~ 2.5X as compared to the area fraction of the film occupied by the nanocups. Scattering matrix simulations employing tapered nanocups on gold-coated polystyrene film demonstrated a similar behavior exhibiting extraordinary transmission peak at a wavelength close to the structure period. Highly photoactive copper indium sulphide (CIS) QDs dispersed in 9:1 solution of o-dichlobenzene and hexane were coated on plasmonic nanocup cavity by solution drop-casting. The spectral emission of CIS QDs (λpeak ~ 700-710 nm) overlaps with the plasmon resonance wavelength of the nanocup structure. Photoluminescence lifetime measurements after excitation with 405nm pulsed diode laser show highly multi-exponential decay with shortest and longest lifetimes ~10ns and ~400ns respectively, compared to QD average lifetime ~400ns on flat glass substrate. The average lifetime is enhanced by factor ~2, and the enhancement can be >40 when the shortest lifetime component is compared. We utilize FDTD simulations to calculate the Purcell factor of the dipole emitter resting at the bottom of the nanocup. The lifetime enhancement is a result of the high electric field intensity which promotes the radiative decay rate within the nanocup cavity. These results provide an insight into investigating the nanocup structures as potential candidates for super-radiance and plasmon assisted lasing.
ED5.10: Photocatalysis II
Session Chairs
Thursday PM, April 20, 2017
PCC North, 100 Level, Room 129 A
11:30 AM - *ED5.10.01
Engineering of Semiconducting Heteronanostructures for Solar Energy Conversion
Shu-Hong Yu 1
1 Department of Chemistry, Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei China
Show AbstractSteering the photo-induced charge-flow based on unique bandgap alignment in semiconductor heterojunctions is critical for photocatalysis applications. Thus, design rational synthesis approach to construct novel heterostructures for efficient band engineering is highly desired. Herein, we report our recent progress on design and synthesis of semiconducting metal sulfide heteronanostructures (-ZnS-CdS-ZnS-, Cu1.94S-ZnS) as well as ternary semiconductor-(semiconductor/metal) nanoarchitecture for solar energy conversion. Through using our synthesized unique ultrathin ZnS nanorods as the template, we further prepared a series of ternary multi-node sheath heteronanorods, realizing enhanced full-spectrum absorption and efficient charge separation for solar energy conversion. In addition, self-coupled Cu2−xS heteronanostructure polymorphs (Cu1.94S-CuS) can also be synthesized by a facile one-pot chemical transformation route, showing much enhanced photoelectrochemical performance. These emerging semiconducting heteronanostructures show promising application potential for solar energy conversion.
12:00 PM - *ED5.10.02
Tailoring Titania Nanostructures for Solar Cell Applications
Peter Muller-Buschbaum 1
1 , Technical University of Munich, Garching Germany
Show AbstractTitania nanostructures are successfully used in hybrid solar cells. Tailoring of the titania nanostructures is achieved by a block copolymer assisted sol-gel synthesis. Different morphologies are installed by the choice of the weight ratios used in the sol-gel synthesis. In particular porous nanostructures are of interest, with pore sizes of several tens of nanometers. Such foam-like titania films have high mechanical stability and provide a percolating network for charge transport. Complex functional stacks are build-up by combining porous films with for example disc-shaped titania nanoparticles. Moreover, hierarchical titania foams are realized by a combination of polymer / colloidal tempating and artificial structuring is demonstrated via combining nano imprint lithography with block copolymer assisted sol-gel templating. Different deposition techniques such as spin coating, spray coating and printing are discussed.
12:30 PM - ED5.10.03
Hierarchical Micropost Array for Enhancement of Photoactive TiO2 for Catalytic Microreactor Applications
Duncan Ashby 1 , Yibo Jiang 1 , Kenneth Ply 1 , Vinh Nguyen 1 , Bryan Woo 1 , Phillip Christopher 1 , Masaru Rao 1
1 , University of California, Riverside, Riverside, California, United States
Show AbstractInterest in TiO2 microfluidic reactors for applications in optoelectronic microfluidic devices has grown considerably over the past decade. Advantages of microfluidic devices over traditional bulk reactor systems include increased surface area to volume ratio, reduced diffusion length, and greater uniformity of irradiation, which can translate to enhanced performance on a miniature scale. TiO2-based photocatalysts have been functionalized for novel use in water purification, water-splitting, and photochemistry. However, low volumetric throughput remains a critical limitation in many applications, as does the difficulty associated with integrating TiO2 uniformly within complex microfluidic device geometries.
As we have reported earlier, growth of nanoporous TiO2 (NPT) within Ti-based microfluidic devices may provide a new means for addressing these issues. Using this approach, NPT is grown in situ, directly from the Ti channel surfaces, using a peroxide-based oxidation process. The advantages of this approach include: a) conformal coverage of complex geometries that would be difficult, if not impossible to coat uniformly using conventional sol-gel or thin-film deposition routes; b) reticulated, open-framework porosity that provides higher surface area than dense films, and greater fluidic accessibility than nanoparticle-based films; and c) potential for fabrication of robust, large-area photocatalytic devices that can provide volumetric throughputs approaching those required for commercial feasibility. However, while this approach shows promise, the photocatalytic performance of NPT falls behind that of P25 nanoparticles. Therefore, we propose that introducing a novel high-density, high-aspect-ratio micropost array to serve as a scaffold for NPT oxidation will yield significant performance enhancements to overcome the majority of microreactor limitations.
Herein, we present our recent efforts to increase the photon absorption efficiency via inclusion of a micropost array fabricated using advanced titanium microfabrication techniques. Using a Taguchi design of experiments study, optimal NPT growth conditions were determined based upon methylene blue degradation efficiency and SEM image contrast analysis. Factors such as NPT pore size and crack density were used to quantitatively evaluate the morphological differences between the growth conditions. Our studies identified the key oxidation parameters responsible for photocatalytic performance. These ideal growth conditions were applied to the micropost array to form NPT in situ and demonstrated a notable improvement in photocatalytic response compared flat NPT films. Collectively, these results represent important steps towards our goal of developing robust, high-performance multi-scale photocatalytic microreactors via complex channel geometries for increased mass and photon transfer efficiency.
ED5.11: Quantum Dots
Session Chairs
Thursday PM, April 20, 2017
PCC North, 100 Level, Room 129 A
2:30 PM - *ED5.11.01
Design and Synthesis of New Non-Blinking Structure, Composition and Shape-Controlled Quantum Dots
Jennifer Hollingsworth 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractThe synthetically accessible “structural toolbox” available for tuning photophysical properties of semiconductor nanocrystals has been dramatically expanded in recent years. Once largely dependent on size or quantum-confinement effects for the direct manipulation of properties like the color of light emitted by a quantum dot (QD), synthetic tuning of shape and compositional complexity has afforded access to additional variables and, thereby, opportunities for exquisite refinement and optimization of photophysical phenomena, as well as for introduction of new and nonlinear properties. Supporting the development of novel photoactive nanostructures has been advances in both the ability to correlate functionality with specific structural features and to synthesize intentionally designed structures. Here, I will describe three examples of advances in function that have involved leaps in understanding of structure-function correlations aided by advances in synthetic control. (1) Next-generation non-blinking “giant” QDs (gQDs): New degrees of thermal and photostability were achieved with demonstrated fine control over gQD internal structure, while structure-function correlations have been advanced to the point of being able to determine quantum yields for individual gQDs. (2) Two-color blinking suppression: Ultrastable excitonic and multi-excitonic dual emissions were realized by synthetically tuning size, composition and/or shape. (3) Automated synthesis of complex nanoscale heterostructures: Our ability to rapidly optimize and develop functional nanostructures is unpinned by availability of software control over otherwise time-consuming, multistep syntheses.
3:00 PM - *ED5.11.02
Syntheses of Nanoparticles and Nanowires Using Charged Nanoparticles Spontaneously Generated in the Gas Phase during Chemical Vapor Deposition
Nong-Moon Hwang 1 , Woong-Ryeol Yu 1
1 , Seoul National University, Seoul Korea (the Republic of)
Show AbstractIt has been shown that charged nanoparticles tend to be generated spontaneously in the gas phase in many chemical vapor deposition processes. Further it has been shown that these charged nanoparticles can be the building block in the growth of nanowires or films, whose phenomenon is called non-classical crystallization. These charged nanoparticles can be captured to produce quantum dots of individual nanoparticles on the substrate. The capturing behaviour depend on the electric bias applied to the substrate. Further these charged nanoparticles can grow into nanowires by the electrostatic self-assembly without catalytic metal particles on the substrate. In the presence of catalytic metal particles, these charged nanoparticles undergo Coulomb interact with the catalytic particles, facilitating the growth of nanowires. Charged nanoparticles were shown to be generated in many systems such as diamond, silicon, Si3N4, GaN, and ZnO. The size distribution of charged nanoparticles depended on the processing condition. Nanoparticles of diamond, silicon, Si3N4 nanoparticles could be produced on the substrate. The growth of SiC nanowires from charged nanoparticles was relatively easily achieved but the growth of diamond nanowires was not successful. The easy or difficulty in the growth of nanowires by charged nanoparticles is attributed to the difference in the crystal structure between SiC and diamond. Although the nanowire growth by charged nanoparticles produces a smooth surface, sometimes it produces a pearl-necklace shaped chain-like structure. This difference appears to be attributed to the presence or absence of charge.
3:30 PM - ED5.11.03
Reversible, Tunable, Electric Field-Driven Aggregation and Assembly of Silver Nanocrystals
Yixuan Yu 1 , Christine Orme 1 , Dian Yu 1
1 , Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractOrdered ensembles, or superlattices, of ligand-stablized nanocrystals are emerging materials that can find appliations in solar cells, photodetectors, light emitting devices, field effect transitors, memory devices, and beyond. Despite the fact that nanocrystal superlattices have been intensively studied for more than two decades, their fabrication methods are still limited to manipulating the solvents in which they are dispersed. One can either let solvents to evaporate to increase the concentration of nanocrystals to the point where entropy driven self-assembly, also known as Kirkwood-Alder transition, takes place; or change the composition of the solvent to decrease the nanocrystal solubility to a point below the nanocrystal concentration, leading to nanocrystal aggregation and self-assembly. These methods often run into a dilemma where fast fabrication results in disorder or poorly ordered superlattices and a highly ordered superlattice often requires a fairly long fabrication time. For example, it would take a few days or weeks for solvent evaporation or destabilization methods to generate 3 dimensional superlattices (also known as colloidal crystals). The lattice constant of the superlatties is dictated by the size of nanocrystals and length of capping ligands.
In this work, we report, for the first time, the use of electric fields to reversibly drive silver nanocrystal aggregation and assembly to superlattices, without changing solvent volume or composition. We show that this method only takes 30 min to produce 3-dimensional colloidal crystals, rather than days or weeks. This method offers a mean to control the lattice constants and degree of preferential orientation for superlattices, and can greatly suppress the uniaxial superlattice contraction associated with solvent evaporation. In-situ small angle X-ray scattering experiments indicated that nanocrystal superlattices were formed while solvated, not during drying.
3:45 PM - ED5.11.04
Interface Chemistry of Colloidal Quantum Dots in Photonic Applications
Weon-kyu Koh 1 , Heejae Chung 2 , Kyung-Sang Cho 1 , Dongho Kim 2
1 , Samsung Advanced Institute of Technology, Suwon Korea (the Republic of), 2 , Yonsei University, Seoul Korea (the Republic of)
Show AbstractColloidal quantum dots (QDs) have great potential in conventional display applications of light emitting diodes (LEDs) and lasers, as well as new area of photonic applications such as single photon emitters in quantum cryptography and communication. While there have been extensive research and development of colloidal QDs in display applications from understanding carrier dynamics to realizing electroluminescence devices and QD-based ultrahigh density TV, intrinsic challenge of QD application is still remained in engineering their interface chemistry. Single QD spectroscopy is useful in understanding the role of interface in multi-shell QD structures. CdSe and InP-based QDs will be discussed to compare their probability density plots and Auger ionization efficiencies determined by analyzing their photoluminescence blinking dynamics.
- reference: Nanoscale, 2016,8, 14109-14116
ED5.12: Carbon Dots
Session Chairs
Thursday PM, April 20, 2017
PCC North, 100 Level, Room 129 A
4:30 PM - *ED5.12.01
Construction of Theraonstic Agent Based on Fluorescent Carbon Dots
Zaicheng Sun 1
1 , Beijing University of Technology, Beijing China
Show AbstractCarbon dots, as a rising fluorescent materials have attracted continuously attention for potential applications in LED, solar cells, sensor, bioimaging and photocatalyst. However, its photo luminescent quantum yield (PL QY) is still quite low, especially emission in long wavelength region like red light. Herein, we proposed increasing the PL QY by doped carbon dots with N or S, N. The PL QY of carbon dots dramatically rises up after doping with N. It can reach over 90%. The carbon dots prepared via bottom-up route show excitation independent emission. In order to extend the absorption in the visible light region, S element is further introduced into the carbon dots to form S, N co-doped carbon dots. Due to the introduction of S and N, there is another S state was introduced into the band gap. That results in the new emission at red light region. Blue, green and red light emissions were obtained from carbon dots. Due to the excellent biocompatibility and low cytotoxicity, we further conjugated the cisplatin with carbon dots to obtain the theranostic agent. We explored to adding more function onto the carbon dots, like self-targeting and therapeutic function to construct the nanomedicine integrating with targeting, bio-imaing and therapy function together.
5:00 PM - *ED5.12.02
Metal/Semiconductor Hetero-Nanocrystals—Surface/Interface Control and Photocatalysis Applications
Jiatao Zhang 1 , Muwei Ji 1 , Liu Huang 1 , Jingwen Feng 1 , Xinyuan Li 1
1 School of Materials, Beijing Institute of Technology, Beijing, Beijing, China
Show AbstractThe key iusses of Metal/seminconductor binary cooperative nano-system is the coherence between near field enhancement from localized SPR effect and exciton bohr radius related quantum confinement effect at the nanoscale. To achieve flexible coupling between Plasmon and excition and then enhance optoelectronic applications, the synergistic tailoring of shape, size, composition, crystallization, hetero-interface and the distance between two nanoscopic components comparable to the characteristic length of plasmon/exciton interactions are key materials issues. By controlling soft acid-base coordination reactions between cation molecular complexes and colloidal nanostructures, we showed that chemical thermodynamics could drive nanoscale monocrystalline growth of the semiconductor shell on metal nano-substrates and the substitutional heterovalent doping in semiconductor nanocrystals. We have demonstrated evolution of relative position of Au and II-VI semiconductor in Au-Semi from symmetric to asymmetric configuration, different phosphines initiated morphology engineering and synergistic control of surface/interface and doing, which can further lead to fine tuning of plasmon-exciton coupling. Therefore, different hydrogen photocatalytic performance, enhanced photovoltaic and electrical properties have been achieved further which lead to the fine tuning of plasmon-exciton coupling.
5:30 PM - ED5.12.03
Optical Properties of Metal-Semiconductor Janus Nanoparticles Templated on Genetically and Morphologically Manipulated Bacteriophage
Joshua Plank 1 , Tam-Triet Ngo-Duc 1 , Elaine Haberer 1
1 , University of California, Riverside, Riverside, California, United States
Show AbstractIn recent years, viruses have been investigated as versatile, hierarchical templates with site-specific affinity. Peptides displayed via genetic or chemical modification can facilitate the selective synthesis of one or more inorganic materials on viral surface proteins, while viral structure can control the long-range assembly of these materials. In particular, the M13 bacteriophage, measuring approximately one micron in length and 6 nm in diameter, has been studied extensively. This virus is composed of five structural proteins including the p3 located at its proximal tip and the p8 found along its length. Each of these proteins can be modified to create a comparatively low-symmetry template with peptide affinity for two different materials. Moreover, using simple chemical exposure, this filamentous template can undergo a shape transformation to form 150 nm rods or 60 nm spheres, while maintaining peptide affinity. The capacity for extreme modification of morphology combined with the asymmetric placement of the p3 and p8 on the viral surface make the M13 bacteriophage a potentially powerful scaffold for metal-semiconductor Janus particle assembly. Unlike core-shell metal-semiconductor structures in which the core material is isolated from the surrounding environment (and therefore chemically inactive), two-faced particles preserve the chemical activity of both materials. Exposure of both the metal and semiconductor to the surrounding environment is beneficial for photocatalytic processes as it allows for electron/hole exchange between catalyst and reactant. In this work, Au-ZnS matchstick- and dumbbell-shaped Janus particles were synthesized using the shape-modified M13 bacteriophage as a template and the optical properties of the resulting materials were characterized. Using genetic modification, peptides with an affinity for ZnS and Au were displayed on the p3 and p8 coats, respectively. The phage was converted from its filamentous to spheroidal form by gently mixing the phage solution with chloroform under ambient conditions. ZnS and Au were then chemically synthesized on the template in aqueous solution to create metal-semiconductor Janus particles. The crystallinity, crystal structure, size, morphology, and composition of the synthesis products were examined using transmission electron microscopy, electron diffraction, and energy dispersive spectroscopy. The optical properties, including metal-semiconductor junction effects, were evaluated with UV-visible absorption spectroscopy and fluorescence spectroscopy. Our studies demonstrate the feasibility of using the M13 bacteriophage as a means of assembling optically-active matchstick and dumbbell-shaped metal-semiconductor Janus particles.
5:45 PM - ED5.12.04
Nucleation and Growth of CdS Quantum Dots by SAXS, WAXS and MD
Andreas Magerl 1 , Dirk Zahn 1 , Alexander Krach 2 , Richard Weihrich 3
1 , University of Erlangen-Nurnberg, Erlangen Germany, 2 Chemistry, University of Regensburg, Regensburg Germany, 3 Materials Resource Management, University of Augsburg, Augsburg Germany
Show AbstractWith a novel free-liquid jet setup featuring a Y-shaped micromixer for turbulent flow the very early stages of nucleation and growth of fast forming quantum dots like CdS in liquid media become experimentally accessible [1].
Key advantages of this device compared to conventionally capillary-based stopped-flow cells are:
1) access to a so far unexplored early time regime down to 20 µs,
2) high time resolution down to 10 µs,
3) chemical reaction times between 20 µs and 3000 µs are accessible by variation of jet velocity and the position of the probe along the jet,
4) decoupling of chemical reaction time and measurement time,
5) missing friction between liquid and container wall provide for well-defined chemical reaction times,
6) no radiation damage in the sample, and
7) no background scattering from container walls.
With synchrotron X-ray scattering as a probe we have measured the nucleation and growth of quantum dots in aqueous solution and report here on CdS as a prototype example [2, 3].
SAXS data show a non-classical two-step pathway with a surprising stability of a structurally relaxed cluster with a diameter of 2.5 nm. This relaxation together with a likely interface restructuring [4] is at the origin of an energy barrier which makes an agglomeration into larger units a slow process. Ab initio theoretical calculations support the amorphous-like nature of the primary clusters and reveal further an activation energy of about 0.4 eV for cluster attachment. WAXS data confirm, that the particles at this early stage are not yet crystalline.
References
[1] A. Schiener, S. Seifert, and A. Magerl, The stopped-drop method: a novel setup for containment-free and timeresolved measurements, J. Synchrotron Rad., 23, (2016) 545-550
[2] A. Schiener, T. Wlochowitz, S. Gerth, T. Unruh, A. Rempel, H. Amenitsch, and A. Magerl, Nucleation and growth of CdS nanoparticles observed by ultrafast SAXS, MRS Proceedings, (2013) 572.
[3] A. Schiener et al., In situ investigation of two-step nucleation and growth of CdS nanoparticles from solution, Nanoscale 7, (2015) 11328-11333
[4] Zobel, M., Neder, and R. B., Kimber, S. A. J., Science 347, (2015) 292-294
Acknowledgment
Work supported by the DFG priority program SPP 1415
ED5.13: Poster Session III
Session Chairs
Friday AM, April 21, 2017
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - ED5.13.01
Pressure-Directed Folding and Unfolding Self-Assembly of New Classes of Multi-Dimensional Nanostructures
Kaifu Bian 1 , Binsong Li 1 , Leanne Alarid 1 , Hattie Schunk 1 , Huimeng Wu 1 , Wenbin Li 2 , Ju Li 2 , Zhongwu Wang 3 , Hongyou Fan 1
1 , Sandia National Laboratory, Albuquerque, New Mexico, United States, 2 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 , CHESS, Ithaca, New York, United States
Show AbstractNaturally occurring responsive systems such as folding and unfolding in self-assembled DNA bundles prove natural designs are hierarchical, with structures and property on multiple scales through interactions of subunits or building blocks. Mimicking these designs in fabrication of active materials requires a clear picture of energy landscaping that governs local interactions such as hydrogen bonding, van der Waals interactions, dipole-dipole interaction, capillary forces, etc, which will provide correct thermodynamic end points as well as facile kinetics for precise control of hierarchical structure for responsive functions. To date, fabrications of active and responsive nanostructures have been conducted at ambient pressure and largely relied on these specific chemical or physical interactions. Using our recently developed stress-induced assembly (SIA) as an artificial actuator, we can emulate natural folding and unfolding processes to explore energy landscaping that govern local interactions. Through SIA, we can design new classes of active materials with controlled structure and function and investigate new properties resulting from the folding and unfolding processes. We show that under a hydrostatic pressure field, the unit cell dimension of a 3D ordered nanoparticle arrays can be manipulated to reversibly shrink and swell during compression and release of pressure, allowing precise tuning of interparticle symmetry and spacing, ideal for controlled investigation of distance-dependent energy couplings and collective chemical and physical property such as surface plasmon resonance. Moreover, beyond a threshold pressure, nanoparticles are forced to contact and sinter, forming new classes of chemically and mechanically stable 1-3D nanostructures that cannot be manufactured by current top-down or bottom-up methods. Depending on the orientation of the initial nanoparticle arrays, 1-3D ordered nanostructures (Au, Ag, etc.) including nanorods, nanowires, nanosheets, and nanoporous networks can be fabricated. The SIA method mimics embossing and imprinting manufacturing processes and opens exciting new avenues for the study of responsive behaviors of active materials during compression (folding) and pressure release (unfolding). Exerting stress-dependent control over the structure of nanoparticle or building block arrays provides a unique and robust system to understand collective chemical and physical characteristics of nanocrystal superlattices.
Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
9:00 PM - ED5.13.02
PEALD-Grown AlN Films with Sharp Interface and Good Uniformity on Silicon Substrates
Xinhe Zheng 1 , Sanjie Liu 1 , Caixia Hou 1 , Jin Wang 1 , Meiling Li 1 , Yingfeng He 1
1 , University of S&T Beijing, Beijing China
Show AbstractPolycrystalline AlN thin films are deposited on Si(100) substrates by remote plasma-enhanced atomic layer deposition (PEALD). A forming gas of Ar/N2/H2 with volume ratio of 1:3:6 and trimethylaluminum (TMAl) precursors are used as nitrogen plasma source and metal source, respectively. The self-limiting growth window is optimized using precursor dose, deposition temperature (Td) and purging times. The clearly-resolved fringes are observed from x-ray reflectivity (XRR) measurements on AlN films grown at optimized growth conditions (Td=300 °C, 0.1s TMA dose/30s plasma/15s purge), which reveals that the interface where the AlN films and substrates meet is perfectly smooth. TEM analysis shows that no interface layer is observed between the two materials. Also, the thickness within the entire film is extracted using a two-layer model to fit the experimental XRR data. The thickness displays a good uniformity. The deposition rate is estimated to be 2.1 Å/cycle, which is a little higher than the reported value. The achieved AlN films could open up new avenues of research in a use of AlN as the template to support GaN growth and AlN-based devices on silicon substrates.
9:00 PM - ED5.13.04
Fabrication and Characterization of Platinum Coated with Solution Processed Graphene
Yinghe Zhang 1
1 , Helmholtz Association of German Research Centre, Hamburg Germany
Show AbstractFabrication and Characterization of Platinum Coated with Solution Processed Graphene
Y. Zhanga, T. Hasanb, S. Kuroiwac
a Helmholtz Association of German Research Centre, Germany
b Cambridge Graphene Centre, Cambridge University, UK
c Applied Chemistry, Waseda University, Japan
Dye-sensitized solar cells (DSSCs) are an attractive alternative to conventional silicon-based solar cells, largely due to its simple fabrication process and low-cost materials. However, the cost of platinum counter electrode and its dissolution in the I3−/I− electrolyte are drawbacks of the well-established platinum counter electrode based DSSCs. Graphene is a promising candidate for platinum substitution or coating due to the high surface area, low charge transfer resistance and corrosion resistance. In this work, graphene ink is produced by liquid phase exfoliation of pristine graphite. The Pt counter electrode and graphene ink coated on Pt counter electrode are made by various coating methods. N719 is used as the dye in our devices. The coatings are characterized by scanning electron microscopy and Raman spectroscopy. Performance of the devices is compared under a solar simulator. We find that graphene coated Pt counter electrode based DSSCs show efficiency as high as 1.25±0.10%, with 0.71 V open circuit voltage, 0.358 fill factor and 210.36±14.38 Ω series resistance. The device efficiency is 6 times (0.19±0.05 %) higher than that of pure Pt electrode using the same device structure. Our results indicate graphene ink have the potential to be a viable, low cost counter electrode material for DSSCs.
References:
1. Sanedrin, R. G., D. G. Georganopoulou, S. Park, C. A. Mirkin, Adv. Mater., 2005, 17, 1027
9:00 PM - ED5.13.05
Hybrid Silicon Honeycomb/Polymer Solar Cells with Enhanced Efficiency Using Surface Etching
Ruiyuan Liu 1 2 , Teng Sun 1 , Baoquan Sun 1
1 Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu, China, 2 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractSilicon (Si) nanostructure-based photovoltaic devices are attractive for their excellent optical and electrical performance, but show lower efficiency than their planar counterparts due to the increased surface recombination associated with the high surface area and roughness. Here, we demonstrate an efficiency enhancement for hybrid nanostructured Si/polymer solar cells based on a novel Si honeycomb (SiHC) structure using a simple etching method. SiHC structures are fabricated using a combination of nanosphere lithography and plasma treatment followed by a wet chemical post-etching. SiHC has shown superior light-trapping ability in comparison with the other Si nanostructures, along with a robust structure. Anisotropic tetramethylammonium hydroxide etching not only tunes the final surface morphologies of the nanostructures, but also reduces the surface roughness leading to a lower recombination rate in the hybrid solar cells. The suppressed recombination loss, benefiting from the reduced surface-to-volume ratio and roughness, has resulted in a high open-circuit voltage of 600 mV, a short-circuit current of 31.46 mA cm-2 due to the light-trapping ability of the SiHCs, and yields a power conversion
efficiency of 12.79% without any other device structure optimization.
9:00 PM - ED5.13.06
Block Copolymer Templated Nanostructured Metal Oxides through Atomic Layer Deposition
Charles Fan 3 , Kaifu Bian 1 , Ying-Bing Jiang 2 , Hongyou Fan 1 2
3 , Albuquerque Academy, Albuquerque, New Mexico, United States, 1 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 , University of New Mexico, Albuquerque, New Mexico, United States
Show AbstractDesign and engineering of metal oxide materials with controlled nanostructures present important applications in nanoelelctronics and catalysis. Here we report a simple atomic layer deposition process to prepare uniform metal oxide nanostructures using self-assembled block copolymer polystyrene-b-polyvinylpyridine (PS-PVP) as the structure-directing scaffold. PS-PVP self-assembles in mixture of organic and water forming varied mesostructures such as micelles, tubes, and vesicles. These mesostructures have hydrophilic external interface that can further react with metal oxide precursors. Atomic layer deposition (ALD) was carried out to the hydrophilic interface of the mesostructures to grow metal oxide layers. Different oxides including TiO2 and SiO2 have been demonstrated at varied processing conditions. By altering ALD cycles, thickness of the metal oxide layer can be fine tuned. The capability of exerting rational control over dimension and composition of nanostructured metal oxides through ALD processes provides new opportunities in nanoelectronics and catalysis.
Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
9:00 PM - ED5.13.07
Nitrodopamine-PEG Grafted Iron Oxide Nanocubes for Magnetic Resonance Imaging Probe
Bibek Thapa 1 2 , Daysi Diaz 1 2 , Nitu Kumar 1 2 , Yuxuan Wang 4 , Huadong Zeng 3 , Juan Beltran-Huarac 5 1 2 , Brad Weiner 1 2 , Gerardo Morell 1 2
1 , University of Puerto Rico, San Juan, Puerto Rico, United States, 2 , Molecular Sciences Research Center, San Juan, Puerto Rico, United States, 4 Center for Electrochemical Engineering Research, Ohio University, Athens, Ohio, United States, 3 Advanced Magnetic Resonance Imaging Spectroscopy, University of Florida, Gainesville, Florida, United States, 5 Harvard T. H. Chan School of Public Health , Harvard University, Cambridge, Massachusetts, United States
Show AbstractAdvancement of next-generation medical imaging applications of iron oxide nanoparticles (IONPs) as a novel magnetic resonance imaging (MRI) probe principally depends on their higher MR relaxivity, steric stability in aqueous and physiological envoronment, and non-toxicity to the targeted cells. For this, the engineering of monodisperse and anisotropic-shaped iron oxide nanoparticles and their successful functionalization via irreversible or non-fouling binding of biocompatible polymers are the key scientific importance. Here, we report the investigation of engineered anisotropic-shaped iron oxide nanocubes grafted with nitrodopamine-PEG (ND-PEG) as a potential T2 magnetic resonance imaging (MRI) probe. In this work, we synthesized highly crystalline 12 nm-sized iron oxide nanocubes and functionalized with nitrodopamine-PEG (ND-PEG) via subsequent ligand exchange and graft to method. X-ray diffraction (XRD) pattern and Fourier-transform infrared (FTIR) spectrum confirm the formation of magnetite (Fe3O4) phase of nanocubes. These grafted nanocubes show excellent steric stability in aqueous at different pH, phosphate buffer saline (PBS) and other cell growth media, and good cytocompatibility on CCRF-CEM: T lymphoblast, A549 and MDA-MB-468 human cancer cell lines over 2 mM of iron concentration. Evaluation of in vitro cellular uptake kinetics, analysis of cellular morphology and quantification of cellular internalization of nanocubes are carried out by flow cytometry technique. The magnetic measurements of these nanocubes exhibit high saturation magnetization of 74 emu/gm and the transverse relaxivity (r2) is observed to be 247 mM-1Sec-1 in aqueous solution. The mechanism of this enhanced relaxivity is discussed in details based upon shape anisotropy of nanocubes. Further, we have demonstrated the relaxivity measurements and T2-weighted MR phantom images on aqueous, pooled human platelet lysate (pHPL) and CCRF-CEM: T lymphoblast cancer cell lines to mimic in vivo environment. This study allows an opportunity to explore the optimum relaxivity and biological properties of nanocubes by tuning the molecular weight of PEG and size of nanocubes in order to exploit them as magnetic resonance (MR) probe for tumor targeting.
9:00 PM - ED5.13.08
Path Programmable Droplet Manipulations on a Light-Responsive Surface
Surjith Kumaran 1 , Sinoj Abraham 1 , Carlo Montemagno 1
1 , University of Alberta, Edmonton, Alberta, Canada
Show Abstract
Microfluidics is a quickly growing, highly interdisciplinary field at the interface of physics, engineering, chemistry and biology and it provides a versatile platform for user-defined, high-throughput biochemical assays and analytical applications. [1] Even though microfluidics harnessed for fluid manipulation, but most suffer from disadvantages such as unintended flow patterns caused by particular boundary effects, channels of fixed geometry and the lack of reconfigurability, becomes a serious obstacle to the development of next generation of programmable microfluidics. The recent emergence of digital microfluidics, a liquid-handling technology that manipulates liquids in discrete droplets in integrated microfluidic devices with an array of electrodes coated with dielectric material requires highly complicated fabrication process. In contrast, droplets are manipulated on two-dimensional surfaces using light stimuli has enormous interest due to it can be applied with spatio-temporal precision without the need for any reagents, and it can also be triggered non-invasively from outside of the system.
In this presentation, we demonstrate programmable surfaces aims towards the alternative to microfluidics using photo-switchable smart surfaces. The idea is to integrate synthesized of surface grafted light-responsive polymer [2] on the surface, which can alter the interfacial wettability by the introduction of light. The photochemical generation of the gradient of surface wettability as a result of spatially controlled changes of chemical structures resulted in a gradient in surface tension that induces a net mass transport of liquids, which affords a driving force for liquids and biological cells. Our approach has an advantage over traditional microfluidics that the complete surface wettability can be erased by irradiation of particular wavelength light allowing for dynamic use in various applications in a single substrate.
References:
[1] D. B. Weibel and G. M. Whitesides, Curr. Opin. Chem. Biol., 2006, 10, 584-591.
[2] Montemagno, C. D.; Sinoj, A.; Surjith K.; US Patent WO/2016/029307.
9:00 PM - ED5.13.09
Selective Area Atomic Layer Deposition of Platinum on Patterned Peeling Graphene
Weier Lu 1 , Song Cheng 1 , Bo Chen 1 , Yang Xia 1
1 , Chinese Academy of Sciences, Beijing China
Show AbstractAs an effective catalyst, platinum (Pt) have been widely used in fuel cells and hydrogen technologies. Among them, preparation of Pt nanostructures with various morphologies is a key strategy for increasing their catalytic mass, and electron transport. Atomic Layer Deposition (ALD) has received growing attention to fabricate ultra-thin films, but the precise control is of increasing interest for its ability to restrict the growth areas during the deposition process.
As a chemically inert monolayer film, graphene is a perfect platform for the selective area deposition. Nucleation on pristine graphene only occurs on the step edges, defects and Moiré pattern areas. And while pretreated by hexamethyldisilazane (HMDS) and enhancing the deposition temperature, the nucleation can be dramatically suppressed.
Here we present a gold film assisted peeling method to pattern the graphene which utilizes the relative strong adhesion between gold and graphene and removes the graphene contact with gold by just peeling off. This peeling method gives out a smoother edge of patterned graphene than traditional reactive ion etching (RIE) method. Then the patterned graphene is used as a mask for selective area deposition of Platinum nanowires. This patterned graphene assisted approach would be a promising way for the selective area Atomic Layer Deposition.
9:00 PM - ED5.13.10
Heterovalent-Doped Quantum Dots—Synthesis, Doped Impurities Control and Their Dispersion in Bulk Polymer for LSC Applications
Jiatao Zhang 1 , Qilin Wei 1 , Qiumei Di 1
1 , Beijing Institute of Technology, Beijing China
Show AbstractLuminescent solar concentrators (LSCs) are photovotatic devices consisiting of a large-area platform of a transparent material serving as a low-loss waveguide impregnated with fluorophores such as emitting ions or quantum dots (QDs). In this work, two fundamental scientific problems on LSCs were studied. Firstly, Heterovalent-doped CdS QDs, such as CdS: Ag and CdS: Cu QDs with high dopant luminescence efficiency were synthesized by cation exchange reactions, which results in substitutional heterovalent doping in deep positions of QDs. The doped fluorescence and doped level (n-, and p- type) have been tailored well. Secondly, doped CdS QDs were dispersed in bulk-size polymethyl methacrylate (PMMA) matrix via in-situ polymerization. The composites retained well optoelectronic properties of doped CdS QDs and is a promising material for further using in LSCs.
9:00 PM - ED5.13.11
Synthesis of Nanostructures with Controllable Plasmonic Resonance by Deposition of Metals onto Porous Silicon
Hanna Bandarenka 1 , Kseniya Girel 1 , Sergey Zavatski 1 , Andrei Panarin 2 , Sergei Terekhov 2 , Vitaly Bondarenko 1 , Bruno Azeredo 3
1 , Belarusian State University of Informatics and Radioelectronics, Minsk Belarus, 2 , Stepanov Institute of Physics of NAS of Belarus, Minsk Belarus, 3 Polytechnic School, Arizona State University, Tempe, Arizona, United States
Show AbstractThe results of our work on nanostructures with controllable plasmonic resonance which are synthesized by deposition of highly ordered arrays of metallic nanoparticles or nanovoids on porous silicon are presented.
Reported data implies that a morphology and a dopant type of the porous template as well as a combination of silver with copper or nickel and variation of the metal deposition regimes allow to manage a spectral position of the plasmonic resonance of the final nanostructures from near UV to IR ranges. Such nanostructures demonstrate a high photoactivity to be efficiently used in surface enhanced Raman scattering (SERS) and photovoltaic cells.
SERS spectroscopy provides detection and study of organic molecules in a number of sensing applications ranging from medical diagnostics to forensic science. Here the potential of the using porous silicon as a template to improve detection limit, reproducibility and shelf life of the SERS substrates is highlighted. The best SERS substrates are based on the silvered mesoporous silicon with an average pore diameter of 50 nm. The detection limit of such substrates is found to reach pico- and femtomolar concentrations depending on the types of the photoactive structure and analyte molecule. The deviation of the SERS intensity in the range of a single substrate or a batch of substrates does not exceed 7 %. The shelf life of the SERS substrate proved up to date is one year.
The developed technique of the formation of plasmonic nanostructures in macroporous silicon with pore sizes varying between 500 and 2000 nm is shown to improve the efficiency of photovoltaic cells. An incident light excites surface plasmon-polaritons in the plasmonic nanostructured film on macroporous silicon. They lead to the concentration of an electromagnetic field in the surface layer and the resonant scattering of light in the direction of the semiconductor layer. As a result, the absorption coefficient of the photovoltaic cell is significantly increased and most of the light energy is converted into an electrical energy. The light is shown to absorb in the film of a few microns’ thickness while the thickness of the semiconductor absorber free of plasmonic film has to be one-two orders of magnitude higher. Furthermore, the developed surface of macroporous silicon provides an increase of the absorbing surface area. Thus, it is possible to decrease the dimensions of the photovoltaic cell.
Summarizing, the utility of plasmonic nanostructures based on metallized porous silicon in the SERS spectroscopy and photovoltaics shows much promise and is worthy of further intensive study.
This work is supported in parts by the Belarusian State Research Program “Photonics, opto- and microelectronics” (task # 1.4.01) and the Belarusian Republican Foundation for Fundamental Research (grant # T16-099).
9:00 PM - ED5.13.13
Porphyrin Controllable Self-Assembly and Photocatalytic Structure-Activity Relationship Study
Yong Zhong 1 2 , Jiefei Wang 1 2 , Feng Bai 1 2 , Kaifu Bian 3
1 , Henan University, Kaifeng China, 2 , Key Laboratory for Special Functional Materials of the Ministry of Education, Kaifeng, Henan, China, 3 , University of New Mexico, Albuquerque, New Mexico, United States
Show AbstractNanocrystals synthesized from the noncovalent selfassembly of molecular precursor exhibit unique electronic and optical properties stemming from the molecular building blocks. Abilities to control the size and shape of nanocrystals in order to tune functional properties are an important grand challenge. Here we developed an interfacial self-assembly driven microemulsion (μ-emulsion) process and acid-base neutralization micelle confinement self-assembly method to synthesis multilevel nanocrystals using the optically active precursor porphyrin oil soluble four phenyl tin porphyrin (SnTPP) and hydrochloric acid soluble four pyridyl zinc porphyrin (ZnTPyP) as building block relies on one or more noncovalent interactions. Then these multilevel nanocrystals were used to photocatalytic degradation of organic pollutants, photosplitting water hydrogen production, photocatalytic reduction of precious metals under visible light and exhibit collective optical properties revealed an exciting morphology structure-activity dependence and good recycling performance. When the multilevel porphyrin nanocrystals used as photocatalytic template,well-defined hollow metal nanostructures and interconnected nanoporous framework with high surface area for enhanced catalytic performance/mass transport for methanol/ formic acid oxidation were also synthetized.
9:00 PM - ED5.13.14
Evidence for Small Polaron Formation Leading to Intrinsic Photoexcited Charge Trapping in α-Fe2O3
Scott Cushing 1 2 , Lucas Carniero 1 2 , Michael Zuerch 1 , Hung-Tzu Chang 1 , Stephen Leone 1 2 3
1 Chemistry, University of California, Berkeley, Berkeley, California, United States, 2 Chemical Sciences, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 3 Physics, University of California, Berkeley, Berkeley, California, United States
Show AbstractWhile progress has been made in overcoming trap states and poor oxidation kinetics in hematite, intrinsic recombination and transport issues still limit the material's performance. In this presentation, we investigate the role that small polaron formation plays in the localization and trapping of photoexcited carriers in hematite (α-Fe2O3). Ultrafast transient extreme ultraviolet (XUV) spectroscopy measures a sub-5 fs shift in charge density from the oxygen to the iron atom following optical excitation. Small polaron localization of the photoexcited electrons begins on a 100 fs time scale as measured by a splitting of the Fe M2,3 edge, and the polaron signature continues to increase until 2-3 ps. The kinetics reproduce the sub-100 ps lifetimes commonly attributed to trap or mid-gap states in hematite. However, the splitting of the Fe M2,3 edge only matches predictions of polaron localization, and not the pre-edge absorption or bleach expected for mid-gap trap states. The polaron formation rate and probability are found to vary with excitation wavelength. This trend agrees with the fact that the incident photoconversion efficiency does not necessarily increase with the visible light absorption in the t2g conduction band, suggesting that excited state transport is limited by excitation-wavelength dependent small-polaron trapping. This presentation gives insight into the intrinsic transport issues that limit hematite, and more generally, into the impact of small polaron formation on photoconversion efficiencies in metal oxide photocatalysts.
9:00 PM - ED5.13.15
Novel Route for the Preparation of Bi2O3 Nanostructures with Photocatalytic Activity
Karen Valencia Garcia 1 2
1 Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Mexico City Mexico, 2 Posgrado en Ciencia e Ingenieria de Materiales, Universidad Nacional Autonoma de Mxico, Mexico City Mexico
Show AbstractBi2O3 is considered as a good photocatalysts because it can absorb in the visible light, although its photocatalytic efficiency depends on the nanocrystalline structure. In the micrometric size regime, Bi2O3 presents large particles [1,2], while nanostructured Bi2O3 have been grown showing different morphologies like nanosheets, nanorods or nanowires, which are preferable because its surface area is increased, and the electron-hole are well separated and as consequence the photocatalytic activity is tremendously improved [3,4]. In this work, Bi2O3 in the nanometric regimen were prepared by a simple chemical precipitation method, using ethylenediamine-solvent as a precipitating and capping agent to reduce the particle size. The influence of the relation HNO3/ethylenediamine on the crystalline structure, morphology and photocatalytic activity was investigated. The characterization of the as prepared samples by X-ray diffraction and thermal analysis, showed that the crystalline structure is completely amorphous and additional calcination process at 600°C was required to get the monoclinic a-Bi2O3 phase. The scanning electron microscopy analysis showed that the microsheets samples were reduced to nanosheets when the HNO3/ethylenediamine was increased and, after the calcination, nanostructures of α-Bi2O3 were obtained. The adsorption capacity in dark condition and the photocatalytic activity under UV light of the annealed a-Bi2O3 were studied using Methyl-orange dye solutions and the degradation was measured as a function of pH solution. The optimal pH was found at 5, where it was found that the dye was completely degraded using the a-Bi2O3 nanostructures obtained using a high HNO3/ethylenediamine ratio. A possible mechanism of the microsheet-nanosheet transition guided by the addition of the ethylenediamine is given.
Reference
R. Irmawati, M.N. Noorfarizan Nasriah, Y.H. Taufiq, S.B. Abdul Hamid. Characterization of bismuth oxide catalysts prepared from bismuth trinitrate pentahydrate: influence of bismuth concentration 93-95 (2004) 701-709.
Guiyu Cai, Lingling Xu, Bo Wei, Jixin Che, Hong Gao, Wenjun Sun. Facile synthesis of β-Bi2O3/Bi2O2CO3 nanocomposite whit high visible-light photocatalytic activity. Elsevier. 120 (2014) 1-4.
Xiang Ying Chen, Hyun Sue Huh, Soon W. Lee. Controlled synthesis of bismuth oxo nanoscale crystals (BiOCl, Bi12O17Cl2, α-Bi203, and (BiO)2CO3) by solution-phase methods.Journal of Solid State Chemistry. 180 (2007) 2510-2516.
Waseem Raza, M.M. Haque, M. Muneer, T. Harada and M. Matsumura, Synthesis, characterization and photocatalytic performance of visible light induced bismuth oxide nanoparticle. 648 (2015) 641-650.
Acknowledgments: CONACYT 251279.
9:00 PM - ED5.13.16
Silver@Anatase TiO2-Coated Light-Diffusing Polymer Optical Fibres by Atmospheric-Pressure Plasma-Enhanced CVD for Antibiotic Degradation and Water Decontamination
Kamal Baba 1 , Miguel Quesada-Gonzalez 1 2 , Nicolas Boscher 1 , Simon Bulou 1 , Patrick Choquet 1
1 Materials Research and Technology Department, Luxembourg Institute of Science and Technology (LIST), Esch-sur-Alzette Luxembourg, 2 Materials Chemistry Research Centre, Department of Chemistry, University College London (UCL), London United Kingdom
Show AbstractTitanium dioxide (TiO2), one of the most important photocatalytic materials, has met a wide range of applications, including self-cleaning surfaces, environmental purification, water splitting and photovoltaic applications. Many attempts to enhance the photoactivity of TiO2, including doping and noble-metal nanoparticles loading, have been investigated in order to enhance the visible response of the material and/or reduce the photo-induced electron-hole pair recombination probability.
Numerous methods have already been investigated for the formation and deposition of TiO2 thin films. Due to their undeniable industrial advantages, such as low temperature, low cost, easy implementation and in-line process capabilities, low-temperature atmospheric-pressure plasma processes have become the most promising ‘next generation’ candidate system for replacing thermal chemical vapour deposition or wet chemical processes for the deposition of functional coatings.
In this work, anatase TiO2 thin films with embedded Ag nanoparticles (Ag NPs) were deposited on polymer and silicon substrates using an atmospheric-pressure microwave plasma discharge. The careful selection of the titanium precursor and Ag NPs concentration and distribution allows the deposition of well adherent, dense and crystalline Ag-TiO2 nanocomposite thin films with a visible light activity thanks to the surface plasmon resonance effects. The photocatalytic activity of the deposited films was demonstrated by monitoring de degradation of stearic acid or methylene blue and sulfamethoxazole (a common antibiotic) under UV and visible light by FTIR and UV-Vis spectrophotometry.
Finally, light-diffusing polymer optical fibres were coated using the developed method for the elaboration of a water decontamination reactor for the removal of antibiotics.
9:00 PM - ED5.13.17
Earth Abundant Zn-Sn Based Oxide Ferroelectric Nanostructures as Effective Solar Cell Materials
Anuja Datta 1 , Sohini Kar-Narayan 1
1 , Department of Materials Science, University of Cambridge, Cambridge United Kingdom
Show AbstractFerroelectric (FE) perovskite-type materials have generated interest as potential absorbers in next generation solar cells since they exhibit spontaneous polarization that facilitates electron-hole separation and that drives charge carriers to opposite ends,[1] as required for efficient cell performance. However, typically wide band-gaps in most oxide FE materials restrict their full range absorption of the solar spectrum. Recent reports have shown that the low conversion efficiencies can be overcome by large (above-band gap) photovoltages in complex oxides, opening up a vast and exciting area of ferroelectric-photovoltaics (PV) research.[1,2] Moreover, optical band-gaps of many FE perovskite oxides are strongly dependent on lattice constants and could be appropriately tuned by doping and alloying in thin-films or through nanostructuring. Lead-free perovskite FEs based on earth abundant elements, such as ZnSnO3, are theoretically predicted and experimentally reported to possess large remnant and high spontaneous polarization.[3-6] Nevertheless, the bulk bandgap is ~ 3.8 eV for undoped ZnSnO3, but band-gap modifications may be expected in this material to impart high mobility due to their high dielectric constants, when substituted in either Zn-site or O-site.[3,4] However, the experimental investigations are restricted due to the cost of growing epitaxial thin-films by physical techniques and low scalability associated with these processes, thereby detailed knowledge of the structural and dimensional effects on the FE as well as PV properties is lacking, with incomplete understanding of the photo-carrier mechanisms at small length scales. Here we will discuss the effects of site-specific doping on band gap tuning in ZnSnO3 nanostructures synthesized by a facile solvothermal process. Band gap tuning is also studied by introducing strain through lattice mismatch in core-shell structures with ZnSnO3 as the core and ZnO and SnO2 as the shell materials. Detailed structural, optical, electrical and photoconductivity studies are conducted to understand the effects of substitution and lattice strain on modifying the band structure and the results are discussed in terms of the efficacy of using earth abundant and non-toxic ZnSnO3 based materials as a future solar cell material.
[1] K. T. Butler, J. M. Frost, A. Walsh, Energy Environ. Sci. 2015, 8, 838.
[2] C. Paillard, X. Bai, I. C. Infante, M. Guennou, G. Geneste, M. Alexe, J. Kreisel, B. Dkhil, Adv. Mater. 2016, 28, 5153.
[3] B. Kolb, A. Kolpak, Chem. Mater. 2015, 27, 5899.
[4] K. P. Ong, X. Fan, A. Subedi, M. B. Sullivan, D. J. Singh, Apl. Mater. 2015, 3, 062505.
[5] A. Datta, D. Mukherjee, C. Kons, S. Witanachchi, small 2014, 10, 4093.
[6] D. Mukherjee, A. Datta, C. Kons, M. Hordagoda, S. Witanachchi, P. Mukherjee, Appl. Phys. Lett. 2014, 105, 212903.
9:00 PM - ED5.13.18
Characterization of Titanium Dioxide Thin Films Prepared by Dip-Coating Method Followed with Hydrothermal Treatment
Zhen-Yu Lin 1 , Jia-Zheng Lin 1 , Kun-Dar Li 1
1 Department of Materials Science, National University of Tainan, Tainan Taiwan
Show AbstractBy virtue of the unique properties, including the wide band gap, low cost, high-efficiency photocatalysis and non-toxic nature, anatase titanium dioxide (TiO2) has been studied extensively in the last few decades for the potential applications in solar cells, fuel cells and photocatalytic systems. One of the most widely used synthesis techniques is the sol-gel hydrothermal method due to its reproducibility, low temperature processing, small particle size and morphological control. In order to accelerate and tailor the crystallization process, in this research two-steps sol-gel coating process was proposed to prepare the TiO2 thin films for photocatalytic applications. First, a TiO2 seed layer on the silicon (100) substrate was coated by dip-coating method with the precursor solution contained TiO2. Then, in the next step TiO2 crystals were formed on the top of TiO2 seed layer by hydrothermal treatment. To further change the crystallinity and morphology of TiO2 films, a heat treatment was also applied by atmospheric furnace. From the experimental results of XRD and SEM analyses, it showed that while the number of the dip-coating cycles for seed layers was increased, sharp peaks of anatase TiO2 were revealed distinctly. It was assumed that the uniformity and thickness of TiO2 seed layers might be improved with increasing the number of the dip-coating cycles. Furthermore, after the hydrothermal treatment followed by heat treatment was implemented, different morphologies of TiO2 crystals would be formed on the TiO2 seed layer. More detailed characterizations for TiO2 nanostructures during different stages of processing were discussed in this study. These results provided useful information for a better control over the morphology and nanostructure of TiO2 thin-films prepared by sol-gel synthesis, and their influences on the efficiency of the photocatalysis for advanced applications.
9:00 PM - ED5.13.19
Photoluminescent Silicon Nanoparticles—Synthesis, Stabilization, Size-Dependent Properties and Applications beyond Optoelectronics
Chenxi Qian 1 , Wei Sun 1 , Geoffrey Ozin 1
1 , University of Toronto, Toronto, Ontario, Canada
Show AbstractPhotoluminescent crystalline silicon nanoparticles, with their extra benefit of being compatible with the existing silicon electronics, are considered as more environmentally-friendly alternatives to other semiconducting nanocrystals containing heavy metals. Previously our group has reported intensively on the synthesis and stabilization of silicon nanocrystals, their size-dependent properties and optoelectronic applications. Some of the latest results will be presented here.
But people may still ask, what’s new in this field beyond optoelectronics that can be achieved? It is known that silicon, with its earth-abundant, non-toxic and low-cost feature, has long been crowned as king in the solar energy conversion realm. However, in terms of making fuels from sunlight and CO2, the best performers are usually made from rare and expensive elements, such as noble metals.
Herein we report the observation that hydride-terminated silicon nanocrystals with diameters around 2 to 5 nanometers, can function as a heterogeneous reducing agent for converting gaseous carbon dioxide selectively to carbon monoxide, with rates up to the scale of mmol h-1 g-1. The large surface area and broadband visible to near infrared light harvesting of the material play key roles in this conversion. This conceptually distinct strategy for making fuels directly from sunlight is proven practical by our observation.
9:00 PM - ED5.13.20
Electrodeposition of Single-Crystalline ZnO Nanorods on Graphene for Tin Oxide-Free Photoanodes
Claudia Villarreal 1 3 , Derek Vi 2 , Annie Wong 2 , Ashok Mulchandani 2
1 Materials Science and Engineering, University of California, Riverside, Riverside, California, United States, 3 Materials Science and Engineering, Instituto Tecnologico de Costa Rica, Cartago Costa Rica, 2 Chemical Engineering, University of California Riverside, Riverside, California, United States
Show AbstractDue to its good optoelectronic properties, graphene is a promising transparent conductor alternative to replace the traditional fluorine or indium-doped tin oxides (FTO, ITO), which are brittle, costly, possibly toxic and produced from conflict minerals. In comparison, graphene is a carbon-based flexible film that could be synthesized from a variety of organic and waste materials. Despite the hundreds of reports on graphene photoanodes, the majority of them use graphene only as an additive or interlayer, and keep using FTO or ITO as the transparent conductor. We explore the application of graphene obtained by chemical vapor deposition as the transparent conductor in tin oxide-free photoanodes for dye sensitized solar cells (DSSCs) using ZnO as the wide bandgap semiconductor.
Our previous results with ZnO nanoparticles spread by doctor blade have shown that graphene DSSCs render similar efficiency but faster rates of charge recombination in comparison to FTO cells, due to graphene's high electro-catalytic activity towards triiodide reduction. We propose a carpet of vertically aligned ZnO nanorods (-NRs) grown in situ on graphene to improve the performance of tin oxide free-DSSCs. The ZnO NRs are expected to provide efficient light scattering and act as a passivating layer on graphene to prevent shunt current leakage. The NRs are grown by electrodeposition on graphene, resulting in a highly texturized film with preferential growth of single-crystalline NRS oriented in the c-axis, providing a fast freeway for electron transport from the sensitized surface towards the graphene collector. This method has the advantage of lower processing temperatures and shorter deposition times in comparison to hydrothermal and chemical vapor deposition.
We compare the charge transport within the materials and across the interfaces of the ZnO-NRs/graphene by testing solid state devices and DSSCs. Voltammetric measurements of illuminated DSSCs are performed to extract performance parameters, complemented with electrochemical impedance spectroscopy and open-circuit voltage decay. Equivalent circuit models are fitted to the experimental data to get estimations of the charge transfer kinetics and resistance elements of the cells. This integral electrochemical approach provides understanding of the fundamental performance limitations of the DSSCs and traces the route to optimize graphene 3D hybrid nanomaterials for photovoltaics.
The study of sustainable alternatives to FTO and ITO holds great relevance, as transparent conductors coated with wide bandgap semiconductors are photoanode platforms not only for DSSCs, but have been inherited into bulk heterojunction, quantum dot- and perovskite-sensitized solar cells, technologies that are rapidly changing the game of photovoltaics. Furthermore, the ZnO-NRs/graphene hybrid displays multi-transducing properties to convert optical, chemical and piezoelectric signals into electrical responses, which we are exploring as well.
9:00 PM - ED5.13.21
Engineering Gold Nanoconstructs for Photoactivatable Controlled Release of Antibiotics
Jingyi Chen 1 , Samir Jenkins 1 , Daniel Meeker 2 , Mark Smeltzer 2
1 Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas, United States, 2 Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States
Show AbstractDrug delivery systems with targeted capability and on-demand controlled release mechanism are particularly appealing for designing optimal medications in many disease treatments. Controlled release systems for drug delivery using nanocarriers have been developed and studied for more than three decades. Gold nanostructures have been used as drug delivery vehicles in chemotherapy because of their biocompatibility, facile surface modification, and robust optical properties. While drug molecules can be covalently immobilized on the nanoparticles’ surface, non-covalent interactions are particularly appealing because they minimize modification of the drug molecules, whose efficacy is then largely retained upon release. In this work, we have developed a controlled-release system for delivery of antibiotics based on gold nanoconstructs and demonstrated the synergistic effect of photothermal and antibiotic therapies. The gold nanoconstructs are capable of converting light into heat and triggering the release of the encapsulated antibiotics. Upon light irradiation, the photothermal effect of gold nanoconstructs can initiate an instantaneous release, and thus control of the release kinetics, demonstrating on-demand drug release. The surface of these gold nanoconstructs can be readily functionalized with specific moieties for targeting biomarkers at the pathological sites. We have demonstrated that an appropriate antibiotic (daptomycin) can be incorporated into gold nanoconstructs and that daptomycin-loaded gold nanoconstructs can be conjugated to antibodies targeting a species-specific surface protein (staphylococcal protein A) as a means of achieving selective delivery of the nanoconstructs directly to the bacterial cell surface. We demonstrated that laser irradiation at levels within the current safety standard for use in humans can be used to achieve both a lethal photothermal effect and controlled release of the antibiotic, thus resulting in a degree of therapeutic synergy capable of eradicating viable bacteria. The use of this nanoconstruct to synergize these therapeutic modalities was successfully demonstrated for the methicillin-sensitive S. aureus strain UAMS-1 in planktonic culture and more importantly for the methicillin-resistant S. aureus strain LAC in both planktonic culture and a clinically-relevant biofilm model. The system was initially validated using planktonic bacterial cultures and was subsequently shown to be effective in the context of an established biofilm, thus indicating that this approach could be used to resolve intrinsically-resistant biofilm infections. Further utilizing the optical properties of gold nanoconstructs, these systems can achieve theranostics through diagnosis via gold nanoconstructs as contrast-enhanced molecular imaging and multi-modal treatment via photothermal and antibiotic therapies.
9:00 PM - ED5.13.22
Enhanced Efficiency of Self-Organized TiO2 Nanotubes Films due to Secondary Materials—Towards Applications
Milos Krbal 1 , Hanna Sopha 1 , Jan Prikryl 1 , Jan Macak 1
1 , University of Pardubice, Pardubice Czech Republic
Show AbstractOver past 10 years, the self-organized TiO2 nanotube layers have attracted considerable scientific and technological interest motivated for their possible range of applications including photo-catalysis, solar cells, hydrogen generation and biomedical uses [1]. The synthesis of 1D TiO2 nanotube structure is carried out by a conventional electrochemical anodization of valve Ti metal sheet. The main drawback of TiO2 is its applicability in the UV light (wavelengths < 390 nm). In order to enhance the efficiency, TiO2 has been doped by N [2] or C [3] o to shift its absorption into the visible light.
Except of doping, one of the major issues to extend the functional range of nanotubes is to coat homogenously tube interiors by a secondary material. It has been shown that additional ultrathin surface coating of TiO2 by secondary materials such as Al2O3 [4], ZnO [5] or MgO [6] annihilates electron traps at the TiO2 surface and thus increases the photogenerated concentration of charge carriers. Recently, it has been demonstrated that just a single cycle of Al2O3 [7] or ZnO [5] deposited by atomic layer deposition (ALD) efficiently improve charge transport properties of the heterostructure while gradual passivation appears with increasing ZnO thickness due to stronger band-bending [5].
The presentation will focus in detail on the coating of the nanotube arrays by secondary materials using ALD. The deposited materials influence strongly photo-electrochemical properties of nanotube films. Experimental details and some very recent photocatalytic and sensing results will be presented and discussed.
References
1. J. M. Macak et al., Curr. Opin. Solid State Mater. Sci. 1-2 (2007) 3.
2. C. Burda et al., Nano Lett. 3 (2003) 1049.
3. S. Sakthivel et al., Angew. Chem., Int. Ed. 42 (2003) 4908.
4. R. Zazpe et al., Langmuir, in press, DOI: 10.1021/acs.langmuir.6b03119.
5. A. Ghobadi et al., Scientific Reports 6 (2016) 30587
6. H. Park, et al., Journal of Electroceramics 23 (2009) 146.
7. J-Y. Kim et al., Nanotechnology 25 (2014) 504003.
9:00 PM - ED5.13.23
Photoelectric Properties of Visible Light Photodetectors Based on Crystalline Selenium
Jye-Yow Liao 1 , Jian-Siang Lin 1 , Cheng-Yi Chang 1 , Fu Ming Pan 1
1 Materials Science and Engineering, National Chiao-Tung University, Hsinchu Taiwan
Show AbstractCrystalline selenium (c-Se) has attractive potential for ultra-high-definition imaging technology due to its high absorption coefficient over visible light region; c-Se has an absorption coefficient in red light region two orders of magnitude larger than Si and amorphous Se (a-Se). In this study, c-Se thin films was prepared by thermal annealing 500 nm-thick a-Se thin films at various temperatures, which were evaporated deposited on the ZnO capped ITO substrate. The 50 nm thick ZnO film is used as the hole blocking layer. Te was sputter-deposited on ZnO as an adhesion layer before the a-Se deposition. The photodetector fabricated with the a-Se crystallization temperature (Tc) at 200oC shows a larger photocurrent in both blue (465 nm) and red (620 nm) light than the one fabricated with Tc=110oC. This could be attributed to a larger grain size of c-Se prepared at Tc=200oC; the larger grain size results in less grain boundaries in the c-Se layer and thus lowers the recombination rate of photocarriers. However, the larger grain size leads to a rougher interface of the c-Se layer with the overlying Al electrode according AFM and SEM analyses. As a result, the photodetector fabricated with a higher Tc breaks down at a lower bias, likely resulting from strong electric field accumulation at sharp edges of the interface. Photodetectors fabricated with different Tcs have a comparable dark current, suggesting that the dark current has weak dependence of the grain size and the hole blocking layer must play the decisive role suppressing the dark current. For comparison, we also prepared a-Se photodetectors, and found that c-Se detectors exhibit better photoconduction in the red light region than the a-Se detectors by a factor of 3-10 depending on the electric field. In summary, this study suggests that the photoelectric performance of the c-Se photodetectors can be further improved by growth of larger c-Se grains with an optimized smooth interface with the electrodes and by suitable selection of hole blocking layer materials to reduce the dark current.
9:00 PM - ED5.13.24
Formation of Doped and Undoped ZnO Nanostructures by Liquid Phase Deposition
Eugene Chubenko 1 , Vitaly Bondarenko 1 , Bruno Azeredo 2
1 Micro- and Nanoelectronics Department, Belarusian State University of Informatics and Radioelectronics, Minsk Belarus, 2 Polytechnic School, Arizona State University, Tempe, Arizona, United States
Show AbstractZinc oxide (ZnO) for several decades remains one of the promising materials for applications in optoelectronics, energy conversion, sensing and imaging fields. The new spiral of the development of ZnO technology emerged with the advances of ZnO nanoparticles and nanostructures synthesis techniques. In contrast with other wide band-gap semiconductors (GaN or AlN) ZnO structures of nanometer dimension can be formed without any lithographic step directly on the substrate by chemical, sol-gel or electrochemical liquid phase deposition. Such methods allow simultaneous treatment of large area substrates and fabrication of ZnO nanostructures with high crystalline quality even at temperatures below 100 °C. However, for practical application the control of ZnO optical and electrical parameters by doping and quantum-confinement effect engineering are in demand. In this work we have investigated the influence of depositions parameters on the properties of doped and undoped ZnO nanoparticles and nanostructures fabricated by chemical hydrothermal and electrochemical techniques. Doping of ZnO was carried out during the deposition by addition of appropriate additives. Variety of metals was selected as dopants: aluminum, nickel, cobalt and erbium. Arrays of doped ZnO nanostructures with different sizes controlled by the temperature of the reacting medium were hydrothermally obtained on silicon and metal substrates. Preliminary hydrogenisation of the substrate surface was shown to improve ZnO crystal density. Fabricated ZnO nanocrystals demonstrated photoresponse in UV spectral range and enhanced conductivity compared to undoped ZnO samples. In the case of electrochemical deposition the most crucial factor is the cathodic current density which controls size and arrangement of ZnO nanostructures across the substrates. At low current densities the formation of ZnO nanostructures arrays occurs. Doping ZnO coatings with Er improve their optical properties while doping with magnetic Ni and Co enhances ZnO ferromagnetic characteristics. The demo samples of photovoltaic and photoelectrochemical devices, UV detectors and magnetic sensors based on the ZnO nanostructures were fabricated and studied.
This work was supported by the Belarus Government Research Programs “Photonics, opto- and microelectronics”, Grant 2.1.02, “Physical materials science, novel materials and technologies”, Grant 1.15 and 2.21.
9:00 PM - ED5.13.25
Enhancing Light Absorption in CZTS Solar Cell Using Plasmonics Back Scattering Nanostructures
Omar Abdelraouf 1 , Nageh Allam 1
1 Energy Materials Laboratory (EML), Department of Physics, School of Sciences and Engineering, The American University in Cairo, Cairo Egypt
Show AbstractCZTS (Cu2ZnSnS4) is an earth-abundant and low cost material, which make it a promising absorbing layer in thin film solar cell. The efficiency of CZTS solar cell has increased in last few years to reach only over 9% in 2016. However efficiency of CZTS solar cell should be enhanced more to be comparable with others high efficiency bulk photovoltaic. Another route for enhancing planar CZTS solar cell than material development is using plasmonic nanoparticles which could scatter or concentrate light at subwavelength scale for increasing sun light absorption in active layer.
In this paper, we explain the effect of using molybdenum plasmonic back scattering nanostructures on surface of back contact in CZTS solar cell. Using three dimensional optical model based on finite element method, we simulated many plasmonic nanoparticles to show which one will lead to improvements in light absorption, by tuning size and dimensions of many nanoparticles, results showed good enhancements in light absorption over planar CZTS solar cell. Furthermore, we studied effect of replacing molybdenum with titanium nitride (TiN) on light absorption enhancements. TiN material has low cost, and most important it has plasmonic properties similar to gold, which make it a good candidate for our work.
9:00 PM - ED5.13.26
Nanovectors Based on Glycosylated Materials for Targeting Anticancer Drug
Jose Andre-i Sarabia-Sainz 1 , Amed Gallego-Tabanico 1 , Erika Silva-Campa 1 , A. Burgara-Estrella 1 , A. Angulo-Molina 1 , Martin Pedroza-Montero 1
1 , University of Sonora, Hermosillo Mexico
Show AbstractThe targeted drug delivery is one of the main goals in medicine to ensure successful treatments of diseases. Therefore, the strategies depend on the reduction of dosage and tissue-specific treatments. In this work, we modified bovine serum albumin (BSA) with lactose obtaining a neoglycan (BSA-Lac). Subsequently, were synthetized and characterized nanovectors with the ability of drugs delivery specifically to liver cells. Results indicate that the BSA molecules were conjugated with 41 lactose, estimated by electrophoresis and confirmed by infrared spectroscopy and fluorescence. Using a water in oil emulsion method was obtained BSA-Lac nanoparticles with spheroid morphology and average size of 300-500 nm. Glycosylated nanovectors were specifically recognized by Ricinus communis lectins. The results indicate that the nanovectors could be aimed to the asialoglycoprotein receptors from liver cells and potentially used as transport anti-tumor drugs.
9:00 PM - ED5.13.27
Real-Time Characterization of Nanoparticle Interactions using MP-SPR
Annika Jokinen 1 , Niko Granqvist 1 , Janusz Sadowski 1
1 , BioNavis Ltd., Tampere Finland
Show AbstractSurface Plasmon Resonance (SPR) is commonly used method to measure molecular binding kinetics and affinities, however, the physical phenomenon is also applicable to measure interaction of nanoparticles and characterization of thin films [1]. Multi-parametric surface plasmon resonance (MP-SPR) utilizes full SPR angular spectral measurement at multiple wavelengths measuring binding kinetics in real-time and label free as well as characterizing simultaneously thickness and optical properties of solid supported thin films [1,2].
Nanoparticles are extensively studied for various applications such as sensors, electronics, photonics, solar cells, cancer diagnosis and therapy, drug delivery and biomedical imaging. However, characterization methods to better understand nanoparticles interaction kinetics and affinities are needed in the field. Functionalized gold nanoparticles (50nm) adsorption kinetics on self-assembled monolayer was studied using MP-SPR [3]. Recently, MP-SPR has been exploited to study also self-assembly kinetics of in situ deposited porphyrins, and thickness, and complex refractive indexes of CVD grown graphene and ALD deposited nanolaminates [4]. MP-SPR method is suitable to measure also non-metallic nanoparticles, cell uptake of mesoporous silica nanoparticles and DNA polyplexes were measured in real-time and label-free [5].
The MP-SPR method has shown good correlation with reference methods used in the studies such as QCM, Confocal microscopy, AFM and Raman, and with previous literature values for similar systems.
High sensitivity of the method enables characterization of even sub nanometer thick layers. Thus the non-invasive MP-SPR is proven to be an effective tool for nanoparticles interactions and nanoscale thin films characterization in air and in liquids.
References
[1]Albers, Vikholm-Lundin, Chapter4 in Nano-Bio-Sensing, Springer2010
[2]Granqvist et al., Langmuir 2013,29(27),2013,8561-8571
[3]Vikholm-Lundin et al. 2016, Applied Surface Science 378, 519–529
[4]Jussila et al., Optica 2016,3(2),151-158
[5]Suutari et al. 2016, Small, DOI: 10.1002/smll.201601815
9:00 PM - ED5.13.28
Morphological and Structural Study of Nanostructured SnS Obtained by a Liquid-Gas Reaction in a Closed System
Omar Castelo 1 , Jesus Fuestes-Rios 2 , Mérida Sotelo-Lerma 2 , Hailin Zhao Hu 1
1 Instituto de Energías Renovables, Universidad Nacional Autonoma de México, Temixco, Morelos, Mexico, 2 Departamento de Investigación en Polímeros y Materiales, Universidad de Sonora, Hermosillo, Sonora, Mexico
Show AbstractTin sulfide (SnS) is a promising material for photovoltaics applications acoording to the theorical calculation of its semiconductor and absorber properties. It is also an and abundant material on the crust of the Earth. In this work, nanostructured semiconductor SnS was obtained by passing hydrogen sulfide gas (H2S) through a non-aqueous solution of the tin salt without complexing agents or surfactants. The reaction system was completely closed, such that the excess of H2S could be neutralized, reducing the impact on the environment. The purity of the SnS products could be improved by choosing an adequate solvent as well as the washing process. The obtained SnS products showed a nanosheet morphology with a diameter of ~100 nm, identified by Scanning Electron Microscopy (SEM). As the concentration of the metal ions was increased in the solution, the tendency of the formation of agglomerates of a size of 200 to 500 nm was observed. The nanosheets presented a preferential growth in the (111) plane in orthorhombic phase (JCPDS file, 39-0354), determined by X-Ray Diffraction (XRD). The results of this work demonstrated the feasibility of controlling the crystallite size and shape of SnS nanoparticles with a low concentration of impurities by the method of liquid-gas synthesis in a closed system.
9:00 PM - ED5.13.29
Superaerophobic Electrode with Metal@Metal-Oxide Powder Catalyst for Oxygen Evolution Reaction
JinLing He 1
1 , Henan University, Kaifeng China
Show Abstract
Stable and highly-active oxygen evolution reaction (OER) electrode is the key for fast and robust O2 production, which is one of the essential points for various kinds of energy conversion system, such as water splitting, lithium-O2 battery and artificial photosynthesis. Here, we show superaerophobic electrodes with metal@metal-oxide powder catalysts, which demonstrate high and stable OER activity. The active-site-density of metal@metal-oxide catalysts is increased over one order of magnitude than those of pure metal oxides due to the large enhancement of electrical conductivity, revealing the substantial enhancement of electrochemical OER kinetics. Furthermore, the superaerophobic property of electrodes is favorable for fast O2 desorption, which improves electrochemical active surface area (EASA) during OER. The superaerophobic electrode with metal@metal-oxide powder catalysts provides the new insight for increase of active site density and EASA simultaneously, which are the key factors to determine the activity of OER electrode.
9:00 PM - ED5.13.30
Effect of Deposition Parameters on ZnO Nano-Islands Using Thermal Atomic Layer Deposition
Nazek El-Atab 1 , Farsad Chowdhury 1 , Ammar Nayfeh 1
1 , Masdar Institute of Science and Technology, Abu Dhabi United Arab Emirates
Show AbstractZnO has lately attracted considerable attention due to several favorable electronic and optical properties such as its wide bandgap of 3.37 eV at room temperature, good transparency, high electron mobility, strong room-temperature luminescence, etc. Moreover, Atomic Layer Deposition (ALD) has received great attention due to its ability to deposit very thin and conformal material layers. However, it is possible to grow islands instead of continuous and conformal layers using ALD during the first few cycles and under specific growth conditions and for specific materials where the growth per cycle can be less than a monolayer per cycle. The growth of ZnO nano-islands using thermal ALD has already been proven to be possible [1-2]. In this work, we study the effect of the deposition temperature, DI water precursor dose time, and pressure on the islands. In addition, the role of ZnO nano-islands seed layer for nano-pillar formation is investigated. The grown ZnO nano-islands using thermal ALD are characterized using Atomic Force Microscopy (AFM).
The ZnO nano-islands were initially deposited by 22 thermal ALD cycles at a temperature of 300 C, pressure of 80 mtorr, 50 ms ZnO dose, and 80 ms H2O dose. It was found that with increasing pressure increased the number of nano-islands on the surface. The thickness of the nano-islands varied between 1.6-2.2 nm with pressure. The width of the nano-islands varied between 15-35 nm with pressure. Moreover, with increasing temperature fewer nano-islands were detected on the surface. The thickness of the nano islands varied between 0.8-1.5 nm and width varied between 14-38 nm with temperature. In addition, with increasing H2O dosing time, surface coverage by ZnO nano-islands found to be decreasing. The thickness of the nano-islands varied between 0.7-0.9 nm with variation of H2O dosing time while their width varied between 20-30 nm. In addition, the possibility of growing ZnO nano-pillars using initially grown ZnO nano-islands as seed layers was studied. After depositing the nano-islands layer consisting of 22 cycles, islands of thickness around 1.5 nm and widths of around 20-nm were obtained. Annealing the nano-islands at 600C for 10 minutes in N2 atmosphere was performed afterwards. 200 cycles of ZnO were deposited at the same conditions as the seeds islands’ deposition which increased thickness of the nano-islands to 7-7.5 nm. However, the deposition of 200 cycles of ZnO on a Si substrate showed a continuous film which highlights the importance of ZnO seed layers for nano-pillar formation. The obtained results are promising for the fabrication of electronic devices with ZnO nanostructures such as solar cells with ZnO nano-pillars which can be used for light trapping and memory devices with ZnO nano-islands charge trapping layer [2].
[1] M. K. Wu et al., Materials Transactions, 51, 253 (2010)
[2] N. El-Atab et al., Electrochemical Society Meeting Abstracts, no. 16, 1454.
9:00 PM - ED5.13.31
Confinement Barrier Induced Enhancement in Thermal Stability of the Optical Response of InAs/InGaAs/GaAs Submonolayer Quantum Dot Heterostuctures
Debabrata Das 1 , Hemant Ghadi 1 , Sandeep Singh 1 , Subhananda Chakrabarti 1
1 , IIT Bombay, Mumbai India
Show AbstractIn this study the improvement in thermal stability of optical properties of InAs submonolayer quantum dot (SML QD) heterostructures was observed through the incorporation of AlGaAs barrier layer on either side of a dot in a well like structure (DWELL). Low temperature photoluminescence (PL) spectra showed a blue shift with less full width at half maxima, ascribed to the assimilation of AlGaAs barrier layers. The sample with confinement enhancing barrier showed the highest ground to ground transition energy with lowest dot size distribution. Ex situ annealing of as grown samples, followed by PL analysis, confirmed the improvement in thermal stability of the optical behavior. For the samples with symmetric AlGaAs layer, external annealing at higher temperatures could not change the downward transition energy effectively; whereas normal DWELL structures exhibited significant blue shift for the same.
Solid source molecular beam epitaxy was used to grow these structures (DWELL, DWELL with confinement enhancing barrier, and dot in a double well) on semi insulating GaAs (001) substrate, followed by rapid thermal annealing (650, 700, 750, and 800 °C for 30 seconds) of as grown samples and characterization processes (PL, XRD). Symmetric AlGaAs layer increased the carrier confinement, which was reflected in the higher activation energy (55, 107, and 110 meV) and Blue shifted PL peak (1052, 910, and 893 nm) for the corresponding samples. XRD results indicated that the addition of this barrier layer improved the crystalline quality with abrupt interfaces. Enhancement of thermal stability was also earned by this AlGaAs barrier layer. Due to lower mobility of In adatoms in AlGaAs matrix, outdiffusion of In became restricted between this symmetric barrier, on either side of the DWELL, and dot size became immune to the external annealing to some extent. As a result, there was no significant shift in PL peak energy for last two samples. Moreover annealing at higher temperature introduced defects into the overall heterostructure, which eventually reduced the activation energy of it. DST, Riber acknowledged.
Symposium Organizers
Feng Bai, Henan University
Ying-Bing Jiang, Angstrom Thin Film Technologies LLC
Binsong Li, Tsinghua Innovation Center in Dongguan
Dong Qin, Georgia Institute of Technology
Symposium Support
Dongguan-RITS Innovation Center
Henan University
ED5.14: Photocatalysis III
Session Chairs
Hongyou Fan
Ying-Bing Jiang
Yang Qin
Friday AM, April 21, 2017
PCC North, 100 Level, Room 129 A
9:00 AM - *ED5.14.01
Artificial Photosynthesis Using Powdered Metal Oxide and Sulfide Materials
Akihiko Kudo 1 2
1 Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, Tokyo Japan, 2 Photocatalysis International Research Center, Research Institute for Science and Technology, Tokyo University of Science, Tokyo Japan
Show AbstractWater splitting and CO2 fixation of uphill reactions can be regarded as artificial photosynthesis, because light energy is converted to chemical energy. In the present paper, we introduce various metal oxide and sulfide photocatalysts and photoelectrochemical cells aiming at artificial photosynthesis.
Rh and Sb-codoped SrTiO3 photocatalyst loaded with an IrO2 cocatalyst is active for water splitting into H2 and O2 under visible light and simulated sunlight irradiations as a single particle type of photocatalyst. This photocatalyst responds to 500 nm. SrTiO3:Rh of a H2-evolving photocatalyst and BiVO4 of an O2-evolving photocatalyst construct various types of Z-schematic photocatalyst systems with Fe3+/Fe2+, [Co(bpy)3]3+/2+, [Co(phen)3]3+/2+, and a conductive reduced graphene oxide (RGO) of electron mediators and even without an electron mediator. It is noteworthy that a sheet photocatalyst consisting of SrTiO3:Rh,La and BiVO4:Mo powders with a Au contacting layer shows a quite high activity.
Metal sulfide photocatalysts that are normally unstable for water splitting into H2 and O2 in the absence of an electron donor can be employed for Z-schematic photocatalyst systems for water splitting. Z-schematic photocatalyst systems composed of metal sulfides of H2-evolving photocatalysts with TiO2 and BiVO4 of O2-evolving photocatalysts with RGO and Co complexes of electron mediators show activity for water splitting into H2 and O2. These photocatalyst materials can also be employed for photoelectrochemical system for solar water splitting.
Ag/BaLa4Ti4O15 and Ag/KCaSrTa5O15 photocatalysts with wide bandgaps show activities for CO2 reduction to form CO and HCOOH in an aqueous medium without any sacrificial reagents. O2 evolved with a stoichiometric amount under UV irradiation indicating that water reacts as an electron donor. Thus, an uphill reaction of CO2 reduction accompanied with water oxidation was successfully achieved. CuGaS2-RGO/BiVO4 of a Z-scheme photocatalyst system is active for water splitting and CO2 reduction to CO under visible light irradiation without any sacrificial reagents. This is the first time to demonstrate CO2 reduction using water as an electron donor in a powdered photocatalyst system with visible light response.
9:30 AM - *ED5.14.02
Composition-Performance Correlation of Catalytically Functionalized SrTiO3 in Overall Water Splitting
Kai Han 1 , Bastian Mei 1 , Guido Mul 1
1 , University of Twente, Enschede Netherlands
Show AbstractStrontium Titanate (SrTiO3) is a semiconductor capable of inducing both half reactions of overall water splitting, yielding O2 and H2. Catalysts are required to enhance the rates in the SrTiO3 induced water splitting process. Ni_NiO core-shell particles are very effective catalytic entities, formed when impregnation of SrTiO3 with Ni(NO3)2 is followed by calcination, treatment in H2, and mild reoxidation in diluted O2. Hydrogen formation is proposed to be catalyzed by the Ni_NiO core-shell particles, while water oxidation occurs over the SrTiO3 surface1. More recently, Osterloh and coworkers2 suggest the core-shell model is not representing the active phase(s), but rather separate particles of Ni and NiO, which promote formation of hydrogen, and oxidation of water to oxygen, respectively.
In this presentation, transients in composition of Ni/NiO core/shell co-catalysts when deposited on SrTiO3 are discussed, by comparing state of the art analysis of the reaction in a Continuously Stirred Tank Reactor (CSTR) connected to a micro gas chromatograph equipped with a Pulsed Discharge Detector (PDD), and ex situ XPS and TEM data. We show that the composition and core shell morphology of the Ni/NiO catalyst is very dynamic, and not only prone to changes upon illumination, but also when subsequently maintained in aqueous slurry in dark conditions. NiOOH (Nickel Oxy Hydroxide) will be identified to be formed upon illumination, known from photo-electrochemical studies to be an excellent water oxidation catalyst. Oxidation of Ni by presumably NiOOH, yielding Ni(OH)2 particles, with residual Ni embedded, occurs when illumination is discontinued. When in close proximity to NiO/Ni(OH)2, Ni is thus a sacrificial electron donor. Several improvements of the performance (activity/stability) of NiOOH_SrTiO3, including functionalization with Pt, Fe and/or Mg will be discussed on the basis of structural and compositional changes.
1. K. Domen, A. Kudo, T. Onishi, N. Kosugi, H.J. Kuroda, J.D. Andrew, J. Phys.Chem., 1986, 90, 292.
2. T.K. Townsend, N.D. Browning, F.E. Osterloh, Energy Environ. Sci. 2012, 5, 9543
10:00 AM - ED5.14.03
Soft-Templating Strategies for Anisotropic Au Nanomaterials and Hollow Multi-Au@SiO2 Nanosystems
Hyojong Yoo 1 2
1 Chemistry, Hallym University, Chuncheon, Gangwon-do, Korea (the Republic of), 2 Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractSolubilization of specific anions into an aqueous CTAB (cetyltrimethylammonium bromide) or CTAC (cetyltrimethylammonium chloride) solution leads to the formation of rod-shaped micelles and becomes a key shape-directing factor to generate one-dimensional Au structures. Through this strategy, Au bipyramids and Au fibers are successfully synthesized in a controllable fashion. In addition, unique star-shaped Au multipod nanoparticles (GMN) and core-shell GMN@Pt or GMN@Pd nanoparticles with high surface area have been fabricated. The structural features of each branch in these nanoparticles are finely tuned. The catalytic performances are morphology-dependent and synergistically improved in the bicomponent nanosystems.
Spherical nanoparticles (multi-Au@SiO2 NPs) and nanowires (multi-Au@SiO2 NWs) with a core comprising multiple Au nanodots and silica shell are fabricated in high yields through reverse (water-in-oil) microemulsion-based methods. By simple treatments, york-shell multi-Au@SiO2 NPs and peapod-like one-dimensional Au nanoparticles array within hollow silica nanotubes (pp multi-Au@SiO2 NTs) can be successfully synthesized. These hollow multi-Au@SiO2 nanosystems can be used as efficient nanoreactors for fabrication of hybrid nanoparticles assembly and catalysis.
10:15 AM - ED5.14.04
Rapid Water Disinfection Using Vertically Aligned MoS2 Nanofilms and Visible Light
Chong Liu 1 , Desheng Kong 1 , Po-Chun Hsu 1 , Hongtao Yuan 1 , Yi Cui 1
1 , Stanford University, Stanford, California, United States
Show AbstractSolar energy is readily available in most climates and can be used for water purification. However, solar disinfection of drinking water mostly relies on ultraviolet light, which represents only 4% of the total solar energy, and this leads to a slow treatment speed. Therefore, the development of new materials that can harvest visible light for water disinfection, and so speed up solar water purification, is highly desirable. Here we show that few-layered vertically aligned MoS2 (FLV-MoS2) films can be used to harvest the whole spectrum of visible light (∼50% of solar energy) and achieve highly efficient water disinfection. The bandgap of MoS2 was increased from 1.3 to 1.55 eV by decreasing the domain size, which allowed the FLV-MoS2 to generate reactive oxygen species (ROS) for bacterial inactivation in the water. The FLV-MoS2 showed a ∼15 times better log inactivation efficiency of the indicator bacteria compared with that of bulk MoS2, and a much faster inactivation of bacteria under both visible light and sunlight illumination compared with the widely used TiO2. Moreover, by using a 5 nm copper film on top of the FLV-MoS2 as a catalyst to facilitate electron–hole pair separation and promote the generation of ROS, the disinfection rate was increased a further sixfold. With our approach, we achieved water disinfection of >99.999% inactivation of bacteria in 20 min with a small amount of material (1.6 mg l–1 ) under simulated visible light.
11:15 AM - ED5.14.06
All-Optical Switching of Doped Semiconductor Nanocrystals
Benjamin Diroll 1 , Peijun Guo 2 , Robert Chang 3 , Richard Schaller 2
1 Center for Nanoscale Materials, Argonne National Laboratory, Lemont, Illinois, United States, 2 , Argonne National Laboratory, Lemont, Illinois, United States, 3 Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractEpsilon-near-zero materials may be synthesized as colloidal nanocrystals which display large magnitude sub-picosecond switching of infrared localized surface plasmon resonances. Such nanocrystals offer a solution-processable, scalable source of tunable metamaterials compatible with arbitrary substrates. Under intraband excitation, these nanocrystals display a red-shift of the plasmon feature arising from the low electron heat capacities and conduction band non-parabolicity of the oxide. Under interband pumping, they show in an ultrafast blueshift of the plasmon resonance due to transient increases in the carrier density. Combined with their high quality factor, large changes in relative transmittance (+86%) and index of refraction (+85%) at modest control fluences (<5 mJ/cm2), suggest that these materials offer great promise for all-optical switching, wavefront engineering, and beam steering operating at terahertz frequencies.
ED5.15: Photoelectric Conversion
Session Chairs
Ying-Bing Jiang
Chong Liu
Yang Qin
Friday PM, April 21, 2017
PCC North, 100 Level, Room 129 A
11:30 AM - *ED5.15.01
Low-Dimensional Inorganic Optoelectronic Nanomaterials and Micro/Nano Devices
Tianyou Zhai 1
1 , Huazhong University of Science and Technology, Wuhan China
Show AbstractLow-dimensional inorganic nanostructures have drawn great scientific and technical interest due to their interesting fundamental properties and possibilities of utilization in novel promising opto-electronical devices with augmented performance and functionalities. We have been carrying out a systematical study on the low-dimensional inorganic optoelectronic materials and micro/nano devices, including the ration design, structure and optoelectronic property relationship, and high-performance optoelectronic devices of low-dimensional organic materials. Some new result achieved in our group will be presented including (1) Developed several novel methods to synthesis inorganic nanomaterials with controlled size and morphologies through controlling the kinetics, thermodynamics and crystal engineering; (2) Investigated their optoelectronic properties including flexible optoelectronic devices, optimizing optoelectronic properties, and in-situ optoelectronic measurements.
References
[1] Zhai, T. Y.; Yao, J. N. One-dimensional Nanostructructures: Principles and Applications, John Wiley & Sons, 2013
[2] Zhai, T. Y. et al. Chem. Soc. Rev. 2016, 45, 2694; Prog. Mater. Sci. 2016, 83: 472; Adv. Mater. 2016, 28: 460; Adv. Mater. 2016, DOI: 10.1002/adma.201601977; Adv. Mater. 2016, revised; Adv. Funct. Mater. 2016, 26: 704; Adv. Funct. Mater. 2016, 26: 4405; Adv. Funct. Mater. 2016, 26: 4551; Adv. Funct. Mater. 2016, DOI:10.1002/adfm.201603804; Small. 2016, 12: 874; Small. 2016, 12: 1024; Adv. Mater. 2015, 22: 8035; Energy Env. Sci. 2015, 8: 3629; Adv. Funct. Mater. 2015, 25: 5885; NPG Asia Mater. 2015, 7: e213; Adv. Sci. 2015, 2: 1500023; Adv. Mater. 2014, 26: 3088; Adv. Mater. 2013, 25: 4625; Adv. Funct. Mater. 2013, 23: 5038; NPG Asia Mater. 2013, 5: e53; Adv. Mater. 2013, 25: 3017; Adv. Mater. 2012, 24: 3421; Adv. Funct. Mater. 2012, 22: 2682;.Chem. Soc. Rev. 2011, 40: 2986; Small. 2011, 7: 445; Energy Env. Sci. 2011, 4: 2586; Prog. Mater. Sci. 2011, 56: 175.
12:00 PM - ED5.15.02
Tuning the Energy Transfer Process in Mn2+-Doped Lead Halide Perovskite Nanocrystals
Jeffrey Pietryga 1 , Wenyong Liu 1 , Istvan Robel 1 , Victor Klimov 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractImpurity doping has been widely used to endow semiconductor nanocrystals (NCs) with novel optical, electronic, and magnetic functionalities. In this talk, we discuss a new family of doped NCs offering unique insights into the chemical mechanism of doping, as well as into the fundamental interactions between the dopant and the semiconductor host. Specifically, by elucidating the role of relative bond strengths within the precursor and the host lattice, we develop an effective approach for incorporating manganese (Mn) ions into nanocrystals of lead-halide perovskites (CsPbX3, where X = Cl, Br, or I). In a key enabling step not possible in, e.g., II-VI nanocrystals, we use gentle chemical means to finely and reversibly tune the NC band gap over a wide range of energies (1.8 - 3.1 eV) via post-synthetic anion exchange. We observe a dramatic effect of halide identity on relative intensities of intrinsic band-edge and Mn emission bands, which we ascribe to the influence of the energy difference between the corresponding transitions on the rate of reverse energy transfer from the Mn ion to the semiconductor host.
12:15 PM - ED5.15.03
Electrical Properties of Nanocrystalline Li-Doped SnO2 and Its Applications in CO2 Reduction
Allen Chaparadza 1
1 , The College of St. Scholastica, Duluth, Minnesota, United States
Show AbstractWide band gap, transparent semiconductor SnO2 is a normally n-type conductor and is widely used as sensor material as well as transparent electrode materials e.g. in solar cells and flat panel displays. Recent discovery of p-type doping with Li has opened exciting possibilities new classes of sensor as well as transparent nanoelectronic devices. Li-doping in SnO2 nanoparticles was explored through a gel-sol method of synthesis to examine the influence of reaction conditions such as pH, dopant concentration, and calcinations temperature. The doping was characterized using nuclear reaction analysis and the nanostructure with high-resolution electron transmission microscopy and X-ray diffraction techniques. Direct current conductivity of the nanocrystals measured from 25 to 350 oC showed Efros-Shklovskii Variable Range Hopping (ES-VRH) conduction mechanism at temperatures below 100 oC with a cross over to 2D-Mott Variable Range Hopping (M-VRH) conduction at temperatures above 250 oC. Using a compression technique, porous diodes consisting of n-type (antimony doped) and p-type (lithium doped) SnO2 nano-particulate films were prepared. Typical current-voltage curves of such devices resembled the behavior of a typical diode but for one key difference, owing to the porosity of the film areas near the p-n interface and the p- and n-regions are accessible to analytes. Their potential to photo electrochemically reduce carbon dioxide were investigated and had a reduction rate of hydrogen carbonate of 0.0015 mol min-1cm-2 at a bias voltage of 1.5 V.
12:30 PM - ED5.15.04
On the Possibility of Using Sintering to Synthesize Materials with Low Structural Defects for Opto-Electronic Applications
Amit Samanta 2 , Andrew Lange 1 , Selim Elhadj 2
2 , Lawrence Livermore National Laboratory, Livermore, California, United States, 1 , University of California, Davis, Davis, California, United States
Show AbstractThermal or laser based sintering of nanoparticles is important to emerging technologies, like additive manufacturing, or to established technologies involving material annealing. Since the final microstructure and the presence of atomic defects impacts the electrical, optical, and mechanical properties of a sintered material, it is important to optimize the processing parameters. We have studied the processing-structure-property relationship during the sintering of Au nanoparticles using in situ electron microscopy and atomic-level computational tools. Our results suggest that sintering of nanoparticles leads to the formation of a coherent particle without any residual dislocations or interfaces, both of which are detrimental for optoelectronic applications. In addition, using our simulated free energy landscapes and experimental results we are able to reconstruct a sintering mechanism map which illustrates that, in contrast to the classical notion of diffusion aided sintering, in nano-scale materials sintering is aided by extensive dislocation activity. Finally I will illustrate how this study helped us to prepare high quality ZnO think films from sintering of ZnO nanopillars.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
ED5.16: Organic Solar Cell
Session Chairs
Friday PM, April 21, 2017
PCC North, 100 Level, Room 129 A
2:30 PM - ED5.16.01
A Combined Experimental and Theoretical Study Into the Performance of Vanadium Dioxide Nano-Composites for Energy Saving Applications
Christian Sol 1 , Mark Portnoi 1 , Johannes Schlaefer 1 , Joseph Bear 2 , Tao Li 1 , Clemens Tummeltshammer 1 , I.P. Parkin 2 , Ioannis Papakonstantinou 1
1 Electronic & Electrical Engineering, University College London, London United Kingdom, 2 Chemistry, University College London, London United Kingdom
Show Abstract
In the built environment there is a increasing issue of heat management, with buildings expending significant energy resources to maintain comfortable living temperatures. In many parts of the world, this entails the use of both heating and cooling during daylight hours depending on ambient temperatures. Due to the variation in the desired temperature control, classical solutions can become counter productive in their aim of maintaining comfortable temperatures, therefore it is important to employ adaptive solutions that vary their functionality based on circumstance.
Here, we present a model for the design of thermochromic smart windows based on the phase change properties of vanadium dioxide (VO2) nanoparticles embedded in a dielectric film and use these simulations to guide measured results with simulation. In recent years vanadium dioxide has generated a broad range of interest due to its heat-mediated structural phase transition from a semiconductor to a metal, which occurs at a critical temperature that may be tuned via doping. The phase transition of vanadium dioxide significantly modulates its optical properties, with the high temperature metallic state absorbing considerably more infrared radiation than the lower temperature monoclinic state due to a reduction in band-gap energy; a window coated with a composite nanoparticle film may passively vary its transmission of infrared radiation based on the ambient temperature, in doing so reducing the temperature management energy-load. In comparison to thin film deposited VO2, VO2-dielectric composite films exhibit higher transmission of visible light and may be retrofitted to existing windows.
The model presented combines both finite-difference-time-domain (FDTD) and Monte Carlo ray-tracing to create a hybrid model capable of modelling both micro- and macroscopic properties of a material composite. Uniquely, the use of this technique enables us to model both specular and diffuse transmission, from which we can model the level of haze resulting from the nanoparticles, a property that is often overlooked but very important in nano-particulate window design. Guided by simulation, the nanoparticles are fabricated and a composite is formed to a desired concentration, after which optical measurements are performed and compared with simulated results.
2:45 PM - ED5.16.03
Population Inversion in Electrically Pumped Colloidal Quantum Dots with a Continuously Graded Layer
Jaehoon Lim 1 , Young-Shin Park 1 2 , Victor Klimov 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 Centre for High Technology Materials, University of New Mexico, Albuquerque, New Mexico, United States
Show Abstract
Since the first report on colloidal quantum dot (QD) lasing (Science, 2000), ceaseless efforts have been made over a decade to turn this effect into a practically applicable technology. The main difficulty in the QD lasing regime is ultrafast gain depletion by Auger recombination (Nano Lett., 2014) that requires short-pulse optical excitation for activating gain media. This has motivated numerous efforts on engineered QD heterostructures for suppressing Auger decay. One demonstrated approach involves smoothening the confinement potential (Nano Lett. 2009) that reduces the probability of the intra-band transition accompanying the Auger recombination event. This concept has been successfully exploited with so-called "giant" CdSe/CdS core/shell QDs (ACS Nano, 2013; Nano Lett., 2014), which demonstrates record-low lasing thresholds under pulsed excitation as well as dual-color lasing (Nano Lett., 2015). However, even these engineered QDs did not permit the use of more practical pumping methods such as continuous-wave optical excitation or electrical injection for achieving the lasing regime.
Here we realize for the first time population inversion in colloidal QDs by direct current electrical pumping, a critical milestone on the path to colloidal QD laser diodes. An important innovation in this work is a new class of type-I II-VI QDs with a continuously graded thick shell. To realize the confinement potential with a desired "smooth" spatial profile we utilize both the reaction kinetics and thermally induced atomic inter-diffusion. This strategy results in the graded interfacial region wherein the elemental profile smoothly vary in a radial direction over the distance of ~2.5 nm. Pump-power-dependent ensemble photoluminescence (PL) dynamics reveal a high average biexciton PL quantum yield (qXX) of ~50%, a two-orders of magnitude enhancement over core-only CdSe QDs with a comparable confinement energy (qXX = ~0.5%). It indicates a considerable suppression of Auger decay achieved by the continuous interface grading.
Another important element of this work is a new "current-focusing" p-i-n device architecture that achieves extremely high current densities (10−15 A cm-2) exceeding those in traditional light-emitting diodes by at least a factor of 10. This allows us to realize very large average per-dot excitonic occupancies up to 6. Clear evidence for the formation of high-order multiexcitons is the emergence of the 1P emission feature coexisting with the band-edge 1S feature. This observation indicates the presence of not only biexcitons but also triexcitons and even species with higher multiplicity. A comparison of electroluminescence spectra with optically-pumped lasing spectra suggests that excitation levels achieved in these specially designed devices based on continuously graded QDs are sufficient for realizing not only 1S lasing but also two-color 1S and 1P lasing.
3:00 PM - ED5.16.04
Liquid-Phase Laser Ablation for the Controlled Synthesis of Graphene Quantum Dots
Rosemary Calabro 1 , Wenjin Cao 1 , Yiyang Liu 1 , Doo Young Kim 1 , Dong-Sheng Yang 1
1 Chemistry, University of Kentucky, Lexington, Kentucky, United States
Show AbstractGraphene quantum dots (GQDs) have emerged as promising materials for catalysis, biosensing and imaging, and photovoltaics applications. Their optical properties can be influenced by the size of the particles and the functional groups present in surface defect states. GQDs are commonly produced by chemical oxidation where a large graphitic source material is broken down by harsh chemicals into smaller graphene pieces. These chemically synthesized GQDs (ChemOx-GQDs) often exhibit size and surface functional group inhomogeneity. This inhomogeneity complicates the understanding of the GQDs’ photoluminescence mechanisms. Therefore, an alternative method is desirable for producing GQDs with a better control of their sizes and functional groups while utilizing fewer chemicals and forming fewer side products. We report liquid-phase laser ablation synthesis of GQDs (LA-GQDs) by focusing a high-power nanosecond pulsed laser beam on a pellet of carbon sources immersed in water. The laser induces the formation of carbon plasma plumes, which are then condensed into the carbon dots by the surrounding water. Compared to chemical oxidation, the liquid-phase laser ablation synthesis has the advantages of controllable sizes and properties for the LA-GQDs, fewer reactants and byproducts, and fast purification of the products. The size and properties of the LA-GQDs could be tuned by selecting appropriate solvents, laser-ablation parameters, and precursor materials. Compared to the ChemOx-GQDs, the LA-GQDs show a blue shifted emission, a smaller size with a single graphene layer (rather than 3 or 4 layers), and a larger concentration of surface hydroxyl groups (instead of carbonyl and carboxylic groups). These differences are obtained by fluorescence, Fourier-transform infrared absorption, and x-ray photoelectron spectroscopic measurements, and atomic force and transmission electron microscopic measurements.
3:15 PM - ED5.16.05
Thin Film H:TiO2-Silicon Tandem Cell Structures
Helmut Karl 1 , Tanzia Chowdhury 1 , Daniel Gerblinger 1 , Marc Lindorf 1 , Thomas Kraus 1
1 , University of Augsburg, Augsburg Germany
Show Abstract
Since titanium dioxide (TiO2) was identified in 1972 by Fujishima for is capability to split water photoelectrochemically (PEC) into H2 and O2 increasing research effort was undertaken to reduce its large band gap of around 3.2 eV. Many techniques were investigated ranging from anion doping to elemental substitution and utilizing nonlinear effects by embedding plasmonic nanoparticles to name but few attempts. Hydrogen post-treatment of TiO2 powder with molecular and atomic H at elevated temperatures and pressures resulting in hydrogenated TiO2 (H:TiO2 or black titania) with increased absorption in the visible frequency spectrum of light and simultaneous improvement of PEC activity dragged interest on the properties and in particular on the stability of this material.
In the meantime it emerged also, that there might be no single compound which simultaneously fulfills all requirements for unassisted (i.e. without external applied electric fields) direct PEC water splitting, which are firstly band edge energy levels and quasi-Fermi energy level positions providing over potentials needed to enable hydrogen (HER) and oxygen evolution (OER) reactions, secondly a potential difference of more than 1.23 V, and thirdly chemical stability under highly photo corrosive working conditions. Coupling of H:TiO2 with Si in thin film tandem cell structures could be a route toward PEC water splitting devices.
In this work H:TiO2 thin films were grown in-situ by fully reactive sputtering of a metallic Ti target in an atmosphere of a mixture of Ar, H2 and O2 on silicon and silica substrates. The complete chemical separation of the parent substances allows maximization of the hydrogen concentration in the H:TiO2 thin films. We mapped the critical process parameters consisting of the sputter gas ratio and the RF-sputter power over a wide range for determining growth condition resulting in maximal hydrogen incorporation. Quantitative depth profiling of the H content in the H:TiO2 thin films was performed by helium elastic recoil detection analysis (He-ERDA) which revealed an H content of more than 2.7 at.%. The optical absorption coefficient and temperature dependent electrical conductivity will be discussed in context of the thermal stability and hydrogen content. The temperature dependent resistivity and Seebeck coefficient of H:TiO2 thin films were determined by consecutive temperature cycles up to 723K and show to be stable up to 673 K, above which a slight increase in the resistivity was observed. First H:TiO2-silicon-iridium tandem cell structures will be presented and their PEC properties discussed.
3:30 PM - ED5.16.06
NIR Quantum Dot Luminescent Solar Concentrators
Hunter McDaniel 1 , Matt Bergren 1 , Karthik Ramasamy 1 , Aaron Jackson 1 , Nikolay Makarov 1
1 , UbiQD, LLC, Los Alamos, New Mexico, United States
Show AbstractIn the near future, luminescent solar concentrating glass windows with quantum dot (QD) coatings will enable building-integrated, sunlight harvesting and revolutionize urban architecture by turning tinted windows into power sources. With this technology, buildings may eventually realize net zero energy consumption or even end up suppling the grid with electricity. Several companies are pursuing transparent organic photovoltaics as a sunlight-harvesting window solution but are far from an economically viable product due to cost issues. A much lower cost alternative is the luminescent solar concentrator (LSC), and although the concept has been perused academically, no companies have commercialized the idea due to the lack of a suitable fluorophore. UbiQD’s innovation is the development of a suitable fluorophore technology in CuInSexS2-x/ZnS (CISeS/ZnS) QDs and has the team to scale the technology and the industry relationships to bring an LSC product to market.
LSCs can play an important role in the emerging building-integrated photovoltaic (PV) industry as they provide semi-transparent windows that convert the energy-passive facades of buildings into distributed energy generation units, while simultaneously reducing the heat gain of the building. The technology works by tinting a window with a fluorophore which absorbs sunlight and subsequently luminesces monochromatic light. This light is guided through the window to the edge(s) where a small PV device converts the light into electricity. The LSC is semi-transparent, and filters visible light neutrally, so as not to impart unnatural color to the transmitted light. The key value proposition for UbiQD’s LSC-enabling, near-infrared (NIR) QDs are low-cost with negligible toxicity compared to QD alternatives. No other known QDs or organic dyes can achieve the cost and performance requirements to achieve a reasonable energy payback period without adding unnecessary health risks. UbiQD manufactures copper-, indium- and zinc-based QDs, while competitors utilize carcinogenic indium phosphide, cadmium- or lead-based materials that cost three- to ten-fold. In contrast to LSCs, typical “solar window” concepts utilize photovoltaic stacks that cover the entire window, whereas the LSC requires only a very narrow strip of PV along one edge of the window. The former approaches are intrinsically more expensive than LSCs because they require coating an entire window with a complex multi-layered PV.
In this presentation, UbiQD's progress towards deploying a commercial product will be discussed, including the preliminary results of a recently funded NSF SBIR project. Spefically, the current state of the art CISeS/ZnS NIR QDs (QY>50% at 1000nm peak emission) and efforts to integrate them into glass window architectures will be presented.
ED5.17: Photocatalysis IV
Session Chairs
Friday PM, April 21, 2017
PCC North, 100 Level, Room 129 A
4:15 PM - ED5.17.01
Monitoring the Formation of Conductive PbS Nanocrystal Superlattices at the Liquid/Air Interface in Real Time by X-Ray Scattering
Alexander Andre 1 , Santanu Maiti 1 , Jan Hagenlocher 1 , Frank Schreiber 1 , Rupak Banerjee 2 , Marcus Scheele 1
1 , University of Tubingen, Tuebingen Germany, 2 Department of Physics, Indian Institute of Technology Gandhinagar, Gandhinagar India
Show AbstractWe will present a real-time study of the surface-functionalization of PbS nanocrystals (NC) with the organic semiconductor tetrathiafulvalene dicarboxylic acid (TTFDA) at the liquid/air interface. Our analysis is carried out by in-situ grazing incidence small angle x-ray scattering (GISAXS) to monitor changes in the type and lattice constant of the superlattice of NCs during ligand exchange with TTFDA. We have previously demonstrated that TTFDA-functionalized PbS superlattices are conductive and mesocrystalline, which bears new possibilities of exploiting NCs for optoelectronic applications, since the properties of such materials will not only depend on the type, size and coupling of the NCs, but also on their orientation.[1–3] To this end, a detailed understanding of the formation pathway is mandatory.
We will compare the different kinetics for ligand exchange of NC monolayers to multilayers, extract typical times of diffusion for the organic semiconductor and discuss our results in the light of other recent real-time X-ray studies of NC assembly.[4,5] Guidelines for efficient ligand exchange of NCs at the liquid/air interface with large, bulky molecules will be provided.
References:
1. Andre, A. et al. Chem. Mater. 27, 8105–8115 (2015).
2. Scheele, M.,et al. Phys. Chem. Chem. Phys. 17, 97–111 (2015).
3. Scheele, M. et al. ACS Nano 8, 2532–2540 (2014).
4. Geuchies, J. J. et al. Nat Mater advance online publication, doi:10.1038/nmat4746 (2016).
5. Weidman, M. C. et al. Nat Mater advance online publication, doi:10.1038/nmat4600 (2016).
4:30 PM - ED5.17.02
Plasmonic Nanohemisphere Monolayers
Cagri Topal 1 , Hamzeh Jaradat 2 , Sriharsha Karumuri 1 , Alkim Akyurtlu 2 , Kaan Kalkan 1
1 Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, Oklahoma, United States, 2 Electrical and Computer Engineering, University of Massachusetts Lowell, Lowell, Massachusetts, United States
Show AbstractPlasmonic devices, such as chemical sensors, surface-enhanced Raman scattering (SERS) substrates, photocatalysts, and light-coupling layers in photovoltaics, are conveniently prepared by immobilization of metal nanoparticles (NPs) on a substrate. When NPs are synthesized directly on the substrate (e.g., vapor deposition, electrochemical reduction), the metal adatom surface diffusion length may be comparable or larger than the nanoparticle size. As a result, the NP can approach thermodynamic equilibrium and minimize the total surface energy resulting in the formation of a certain contact angle between the metal-ambient and substrate-ambient interfaces. The contact angle can be significantly less than 180°, meaning the metal wets the substrate. Hence, the particles may be truncated spheres rather than spheroids. Truncated nanospheres or specifically nanohemispheres (NHSs) offer distinct advantages in plasmonics over nanospheres owing to their higher diversity of localized surface plasmon modes due to broken symmetry. In the present work, monolayers of hemispherical Ag nanoparticles deposited by chemical reduction as well as thermal deposition reveal localized plasmon modes, whose resonances are sensitive to angle and polarization of the incident light. Using numerical simulations, the major resonances are assigned to dipoles parallel (visible) and perpendicular (ultraviolet) to hemisphere basal plane. The modes differ significantly in terms of energy, damping and couplings (i.e., particle-substrate and particle-particle). The perpendicular mode exhibits a 4-fold narrower linewidth due to reduced radiative damping and substrate coupling. On the hand, the parallel mode exhibits enhanced coupling with substrate and adjacent NHS due to higher field concentrations at the sharp edges (i.e., lightening rod effect) as we corroborate with numerical simulations. Unlike in a spherical dimer where the field intensity peaks in the middle of the gap, the maximum field in a NHS dimer gap occurs on the metal surface (i.e., at the edges), overlaying with the chemical enhancement. Hence, higher sensitivity molecular detection/sensing is anticipated with NHSs than nanospheres. Indeed, our SERS studies over the several years have shown that the monolayers of Ag NHSs possess enhancement factors large enough to capture conformational steps in single molecules of green fluorescent protein (GFP), azobenzene, hemoglobin, and photoactive yellow protein (PYP).
4:45 PM - ED5.17.03
TiO2 Film as Visible-Light Active Photocatalyst by Designing the Multilayer Structure with WO3 Film
Junjun Jia 1 , Kenta Taniyama 1 , Nanami Miyazawa 1 , Masaaki Imura 2 , Toshimasa Kanai 2 , Yuzo Shigesato 1
1 , Aoyama Gakuin University, Kanagawa Japan, 2 Thin Films Division, Nippon Electric Glass Co., Ltd, Wakasa, Mikata-Kaminaka, Fukui, Japan
Show AbstractTiO2 has been widely used in many industrial process due to its exceptionally efficient photoactivity, high chemical stability, and low cost. Due to its large band gap (Rutile: 3.0 eV; Anatase: 3.2 eV), TiO2 absorbs less than 5% of the available solar light photons. How to improve the photocatalytic ability in the visible region becomes important in the practical applications. On the other hand, WO3 photocatalyst is visible-light active as we have reported from 2000 [1-6], but WO3 is soluble under alkaline environment and shows poor corrosion resistance. In this study, we designed a multilayer structure of TiO2 and WO3 to improve the TiO2 photocatalytic ability in visible region and to avoid WO3 chemical instability, where TiO2 film was deposited on the WO3 film (TiO2/WO3) by reactive dc magnetron sputtering using W metal target and Ti metal target.
For WO3 depositions, the total gas pressure during sputter depositions was kept at 3.0 Pa, and the post-annealing temperature in air was 400 °C, where we have reported that this approach make WO3 perform higher photo-induced super hydrophilicity and oxidative decomposition activity of acetaldehyde under the irradiation of visible light than ones deposited on the substrate heated at 800 °C [6]. For TiO2 depositions, the total gas pressure during sputter depositions was kept at 3.0 Pa and the substrate temperature was kept at 200 °C. Meanwhile, in order to improve, we also study the effect of Pt nanoparticles on the photocatalytic ability of TiO2 in visible region by deposited Pt nanoparticles in the interface between TiO2 film and WO3 film.
The photocatalytic decomposition of acetaldehyde and CO2 generation were measured under the irradiation of visible light (Xe lamp with a 410-500 nm band pass filter, 1.0 mW/cm2). Our experimental results showed that the TiO2/WO3 multi-layer film could decompose acetaldehyde. It is considered that the holes generated in the WO3 film by the irradiation of visible light are transferred into TiO2 film to participate oxidative decomposition in TiO2/WO3 multi-layer film. In addition, when Pt nanoparticles were deposited in the interface between TiO2 film and WO3 film, the decomposition speed of acetaldehyde was obviously faster (about two times) than one of the TiO2/WO3 multilayer. Detailed mechanism was discussed in this talk.
[1] M. Ebihara, Y. Shigesato, et al., Proceedings of the 3rd ICCG (2000) 137.
[2] M. Kikuchi, Y. Shigesato, et al., Abstracts of the 21st IUPAC Symposium (2006) 496.
[3] M. Kikuchi, Y. Shigesato, et al., Proceedings of the 6th ICCG (2006) 365.
[4] A. Murata, Y. Shigesato, et al., J. Nanosci. Nanotechnol. Vol.12, No. 6 (2012) 5082.
[5] Masahiro Imai, Yuzo Shigesato, et al., J. Vac. Sci. Technol. A 30(3), (2012) 031503.
[6] Jyunya Takashima, Nobuto Oka, and Yuzo Shigesato, Jpn. J. Appl. Phys. 51 (2012) 055501.
5:00 PM - ED5.17.04
Spatially Resolved Charge Distribution and Its Impact on Plasmonic Property of Doped Metal Oxide Nanocrystals
Omid Zandi 1 , Ankit Agrawal 1 , Clayton Dahlman 1 , Delia Milliron 1
1 , University of Texas at Austin, Austin, Texas, United States
Show AbstractHighly doped metal oxide semiconductor nanocrystals (NCs) are emerging as a class of near-infrared (NIR) plasmonic materials. The tunability of the localized surface plasmon resonance (LSPR) absorption has led to applications in IR-selective smart windows and provides a compelling outlook for tunable catalysis, sensing, and optics. Such plasmonic NCs are often assumed defect free with homogenous free electron distribution throughout the NC volume. This assumption needs to be scrutinized further as it is well known that metal oxides possess deep surface trap states due to presence of surface hydroxyl groups or dangling bonds. In this work, we investigate the effect of surface states on electrochemical modulation of Sn:In2O3 (ITO) NCs LSPR as well as the sensitivity of LSPR to host surrounding medium.
The electrochemical modulation of LSPR has been demonstrated in several NC systems. The fundamental interplay between the injected charge and the LSPR response, however, has remained unexplored. In majority of previous studies, NCs were assumed to form an ideal capacitance at the electrolyte interface. Such a simple model, however, was shown to be unable to explain the electrochemical modulation behavior of Sb:SnO2 (ATO) NCs (zum Felde et al. J. Phys. Chem. B 2000, 104, 9388). Further, we have found contrasting results for ITO NCs with different doping levels. zum Felde et al. suggested a depletion model to explain the anomalous behavior of ATO NCs that accounts for surface sate-induced space charge formation at the NC-electrolyte interface. In this work, the validity and generality of this hypothesis was systematically investigated for ITO nanocrystals as a model system. To fully account for the NC geometry and doping, a series of highly monodisperse NCs with various doping level and sizes were synthesized and incorporated in uniform thin films. NC films were assembled in a custom-made ultrathin electrochemical device allowing in situ full spectra acquisition in the near to mid-IR range. In situ LSPR spectra acquired at various charging levels are consistent with a spatially depleted NC surface under open circuit. A consequence of depleted surface layer is constant carrier density versus reducing potential, which manifests as constant LSPR frequency. For lightly doped or smaller NCs (where depletion layer occupies the majority of the NC volume), the LSPR frequency exhibits a blue shift with reducing potential, indicating an increase in electron density. These experimental observations were quantitatively consistent with simulated potential and charge distribution using the Poisson’s equation for a nanocrystalline film as well as the full optical spectra modeled using the effective medium theory. These results provide the first experimental evidence of space charger layer formation on NC surfaces and its effect on plasmonic properties and are key to design efficient NC-based materials for electrochromic, sensing, catalysis and electronics.