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 AM, 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
Tuesday PM, April 18, 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 AM, 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.
12:00 PM -
OPEN DISCUSSION
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
Wednesday PM, April 19, 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 modifica