bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduction of Europium Ions in SrAl2O4 Glass Composites Using Aluminum Nitride
Authors: Nakanishi Takayuki , Fushimi Koji , Hasegawa Yasuchika
Published: February 2020

Frozen sorbet technique has applied to the SrO-Al2O3-B2O3 glass system to prepare glass composites including Eu2+, Dy3+:SrAl2O4 (SA) microcrystals1. The glass composites show remarkable light-storage ability based on the natural properties of divalent europium in SA crystals, and this provide various photo-functionalities, such as long-persistent luminescence, photo-induced conductivity, and mechano-luminescence. Their unique optical properties of SA glass composites are expected to become novel light-storage materials for future energy applications.

To control the valence states of europium (Eu3+ or Eu2+) is one of the important factors for the development of photo-functional glasses2. Generally, industrially mass-produced glasses have been prepared by melting raw materials at high temperature in air (oxidizing atmosphere), and then the valence of multivalent ions is determined by redox equilibrium in glass melt. For some special applications, photo-functional glasses have been prepared under reduction atmosphere using H2 or CO gas to design low valence state of ions or metal formation in glasses. Low valance lanthanide ions, such as Eu2+, Yb2+, Sm2+, and Ce3+, for example, have been used as functional centers for laser materials, phosphors, and magnetic-optical memory devices. Considering the difficulty and safety in H2 or CO gases use, more convenient and simple glass preparation methods are strongly required.

Here, a new method for the reduction of Eu3+ to Eu2+ in SrO-B2O3-Al2O3-Eu2O3 (-AlN; reducing agent) system was proposed using a Frozen sorbet technique in air. Effective reduction of Eu3+ in SA crystals during the melting at 1500oC was demonstrated using differential thermal analysis (DTA), thermogravimetric analysis (TGA), and the optical properties. The reduction of Eu3+ to Eu2+ in AlN added glasses was proposed to proceed by the reaction of 2AlN + Eu2O3 + O2 (in air) → Al2O3 + 2EuO + N2. In this study, we have attempted to prepare the SA glass composites under various conditions using reducing agent; AlN for the frozen sorbet technique. Highly transparent SA glass ceramics were successfully synthesized and characterized using X-ray diffraction (XRD) and field emission-scanning electron microscopy (FE-SEM) with energy-dispersive X-ray analysis (EDX). The emission spectra and lifetime decays were observed using a steady-state and time-resolved spectrofluorophotometer system. Light-storage glass ceramics using the frozen sorbet method under oxidation control overcomes the limitation of Eu activated materials and the results of this study should be a significant contribution to the fields of inorganic chemistry and material design.

References

1. T. Nakanishi, Y. Katayama, J. Ueda, T. Honma, S. Tanabe, T. Komatsu, J. Ceram. Soc. Jpn., 119, 609 (2011).

2. T. Nakanishi, K. Watanabe, J. Ueda, K. Fushimi, S. Tanabe, Y. Hasegawa, J. Am. Ceram. Soc., 98, 423 (2015).
Application of Near Infra-Red Optical Probes in a Second Optical Window for Pathological Analyses in a Mouse Brain
Authors: Imamura Yukio , Yamada Sayumi , Tsuboi Setsuko , Jin Takashi
Published: February 2020

Light with near infra-red wavelength can pass through tissues in a body because of less light absorption and scattering. Especially, near-infrared fluorescence in a second optical windows (900-1400nm) is expected to be better for deep-tissue in vivo imaging by a low autofluorescence. Quantum dot (QD) is a nano-particle which functions as semiconductor, and emit near-infra red fluorescence emission with higher signal noise to ratio than other fluorescent chemical probes in visible region. We previously developed near infra-red QD from lead sulfate (PbS-QD) and reported the validity of this PbS-QD application from cultured cells to non-invasive in-vivo imaging in mice (Jin and Imamura, ECS journal (2016)). In this study, we examined whether PbS-QDs can be applied for medical diagnosis for pathogenesis. Mice (i.e, experimental animals) were administered by lipopolysaccharide (LPS,1.0mg/mouse) and induced a whole body inflammation (a mouse model of sepsis). In sepsis, patients are often suffering from the simultaneous-occurred blood coaugulation in the blood vessels, and aggravate the prognosis. To examine whether this was occurred, PbS-QD was injected from mouse tail vein after 20hrs of LPS administration. We found that LPS-treated mouse increased the thrombus-like structure along the brain blood vessels. Conversely, inhibitor of brain vascular thrombus reduced these structure. These findings suggest that our PbS-QDs may possibly visualize brain blood vessels in the pathological state for sepsis.
Scintillation Properties of Ga2O3 Crystal
Authors: Yanagida Takayuki , Okada Go , Kawaguchi Noriaki , Yanagida Satoko
Published: February 2020

Ionizing radiation detectors are used in many kinds of non-destructive investigations. Many of such applications use a scintillation detector which consists of scintillator and photodetector. A scintillator is a type of the luminescent material that converts a high energy ionizing radiation photon/particle to hundreds of visible photons via energy migration from the host matrix to emission centers. Scintillators have been playing an important role in many scientific and industrial fields, including astrophysics, particle physics, medical imaging, security, nuclear plants, and well-logging. Although insulator materials doped with rare-earth or transition metal ions are commonly used in practical applications, semiconductor crystals have also attracted attentions due to their intrinsically high light yield and fast decay time without doping of any emission centers.

In this work, optical and scintillation properties of well-known Ga2O3 semiconductor material are investigated. Under UV excitation, photoluminescence (PL) emission peak appeared around 380 nm with the quantum yield of 6%, and fast decay of 8 and 793 ns were observed. In contrast, X-ray induced scintillation spectrum also showed an intense emission band around 380 nm, which of decay curve was reproduced by two exponential decay components with the time constants of 8 and 977 ns. The pulse height spectrum of 137Cs g-rays measured using measured Ga2O3 showed a clear photoabsorption peak with a light yield of 15000 ± 1500 ph/MeV. This high light yield was the highest value among the semiconductor scintillators reported.
High Electroluminescence of ZnS:Cu Phosphor with a CNT-Incorporated Dielectric Layer
Authors: Yu SeGi
Published: February 2020

High brightness was obtained for alternating current-driven inorganic ZnS:Cu powder electroluminescence (EL) devices by incorporating carbon nanotubes in a barium titanate (BaTiO3) based dielectric layer. The inorganic EL devices were consisted of four layers: a top electrode, a dielectric layer, an emitting layer, and an ITO layer which was pre-coated on the glass substrate. As an emitting material, ZnS:Cu power of particle size 9 µm (green emission) was mixed with the cyanoethyl pullulan polymer (CEP), as an organic binder, and the dimethyl formamide (DMF) organic solvent. The emitting solution was spin-coated on the ITO glass at the fixed speed of 1200 rpm. The BaTiO3 power were mixed with a CNT-CEP binder, which was also spin-coated on the emitting layer. In order to optimize the EL performance, the concentration of CNTs were varied by controlling the mixing ratio of CNTs—0, 0.0018, 0.0039, 0.0071, 0.011 and 0.014 wt%. Finally, a 500-nm-thick aluminum top electrode was thermally evaporated onto the dielectric layer. Up to 50% higher brightness was obtained for the CNT concentration of 0.011 wt%. The high brightness might be caused by the high dielectric constant of the CNT-incorporated BaTiO3 dielectric layer, thanks to the micro-capacitor effect. [Z. M. Dang et al., Small 12, 1688 (2016).] Roughly speaking, the higher concentration of the CNT yielded to the higher brightness, until a certain concentration, here, between 0.011 and 0.014 wt%. It implies that too high concentration of CNTs might lead to the formation of the unwanted percolation network of a leakage current within the dielectric layer. Finally, the role of the chlorine was investigated by inclusion of chlorobenzene into the CNT-containing dielectric layer. [J.-Y. Kim et al., Adv. Mater. 25, 2308 (2013).] Based on the above results, incorporation of CNTs within the dielectric layer enhanced the brightness (and the efficiency, possibly) of the ZnS:Cu-based EL device, which would help to extend the potential applications of EL devices.
X-Ray Excited Luminescence of Terbium Doped Sodium Aluminium Phosphate Glass
Authors: Kawaguchi Noriaki , Kuro Tomoaki , Okada Go , Yanagida Takayuki
Published: February 2020

Luminescent materials which convert high energy photons to visible light are used for medical X-ray radiography. These materials contain luminescent centers with high efficiency, for example trivalent Tb ions in oxysulfide gadolinium ceramic. Generally, luminescent materials for X-ray radiography exhibit slower decay times than scintillators for photon-counting applications, however they also exhibit low afterglow.

 In this study, we researched about X-ray excited luminescence characteristics of sodium aluminium phosphate glass which is lower melting point than oxysulfide gadolinium ceramic. Tb doping concentrations of sodium aluminium phosphate samples were 0.3, 1.0, 3.0 and 10%, respectively. As a result of X-ray excited luminescence, emission peaks at wavelengths of around 480, 540, 580 and 620 nm were observed from each samples. Intensity of X-ray excited luminescence were increased with increasing of Tb doping concentration. Decay curves of samples were also evaluated by using X-ray induced afterglow characterization system [1] which was developed by our laboratory. Slow decay curves with time range of 20 milliseconds were successfully observed.

[1] T. Yanagida, Y. Fujimoto, T. Ito, K. Uchiyama, K. Mori, "Development of X-ray induced afterglow characterization system" Appl. Phys. Exp., 7 062401 (2014).
(Invited) Polymeric Materials in LEDs: Outlook and Challenges
Authors: Piquette Alan , Tchoul Maxim , Linkov Alexander
Published: February 2020

In traditional lighting technologies, such as discharge and incandescent lamps, polymers were unsuitable materials because of the high temperatures and/or ultraviolet light. In solid state lighting (SSL), however, polymers and polymer-based composites are ubiquitous. They are used in housing materials, adhesives, encapsulants, lenses, flexible substrates, light-weight heat sinks, and in various other applications. Virtually all SSL products have some form of polymer present in their make-up. In this presentation, we will discuss the use of polymers in LED-based lighting, highlighting the challenges and outlook. The primary focus will be on their applications as encapsulants and adhesives.

The most abundantly used technology in producing white light with LEDs is based on phosphor conversion. It has been estimated that >75% of the white LED market relies on phosphor conversion.[1] Whether the phosphor is present as a powder, polycrystalline ceramic, single crystal, or thin-film, polymers are often used to either glue the conversion layer to the LED chip, encapsulate the phosphor particles, or both. For these applications, optical silicones are the usual choice. Even though silicones have many desirable properties, there are three main challenges that limit their performance as adhesives or encapsulants: (i) low thermal conductivity, (ii) low refractive index, and (iii) long term photo-thermal stability. The Department of Energy (DOE) SSL R&D Plan lists LED encapsulation as a key issue and R&D priority.[2]

In this talk, we will briefly present the history of polymer encapsulants for LEDs, leading up to the use of state-of-the-art optical silicones. We will discuss the associated limitations of these materials in terms of losses and how LED performance could improve with advancements in polymer and polymer-composite technology.

References:

[1] Company estimates based on McKinsey & Company, Lighting the Way: Perspectives on the Global Lighting Market, 1st ed. (2011).

[2] DOE SSL Program, "R&D Plan," prepared by Bardsley Consulting, SB Consulting, SSLS, Inc., LED Lighting Advisors, and Navigant Consulting, Inc., May 2015; http://energy.gov/eere/ssl/downloads/solid-state-lighting-rd-plan.
Printing of Enzyme Electrodes on Nonwoven Fabric for Flexible Biofuel Cells
Authors: Hsieh Yunchen , Ogawa Yudai , Kato Yuto , Kai Hiroyuki , Nishizawa Matsuhiko
Published: February 2020

Enzymatic biofuel cells (EBFCs) are lightweight and eco-friendly power sources that employ enzymes as catalysts and sugar as fuel for redox reactions at ambient temperatures. Due to their lightness and biocompatibility, EBFCs recently attract a great deal of attention and have been applied to a wide range of medical, implantable, and wearable devices [1-5]. We previously developed an iontophoresis skin patch with a built-in EBFC for enhancing drug delivery through skin by ionic current generated by the EBFC. The electrodes of the EBFC in the skin patch were made by multi-step fabrication. Carbon fabric was immersed in the dispersion of carbon nanotubes (CNTs) to make electrodes, followed by immobilization of enzymes onto them. Fructose dehydrogenase (FDH) was immobilized on an anode, and bilirubin oxidase (BOD) on a cathode to form a complete EBFC. In this study, we developed ink of CNTs and enzyme that can be printed onto nonwoven fabric that works as a flexible substrate. This material simplifies the fabrication process of CNT/enzyme electrodes, and enables patterning of the electrode with an arbitrary shape.

To prepare the CNT/enzyme ink, CNT and additives of different roles were first mixed in aqueous solution and dispersed by sonication: CNTs as a highly-conductive scaffold for enzyme immobilization, polyvinylimidazole (PVI) as a binder, trehalose as a stabilizer of enzymes during freeze-drying, and 1-pyrenebutyric acid N-hydroxysuccinimide ester (PBSE) for non-covalent immobilization of enzymes to CNTs. Next, FDH as an enzyme catalyst for an anode was added to the mixture above to complete the CNT/enzyme ink. The CNT/enzyme ink was cast on nonwoven fabric in 1 cm2 size to form an anode. Finally, the cast electrode was freeze-dried for 6 hours. After freeze-drying, the fabricated FDH anode had highly porous structures as observed by scanning electron microscopy, and it could be preserved for longer time after freeze-drying because of trehalose.

The performance of the printed FDH anode and the effects of the additives were evaluated. The FDH anode was immersed in a stirred buffer solution containing 200 mM fructose and measured by typical cyclic voltammetry (CV) at 10 mV/s. The FDH anode generated current density of 2 mA cm-2 with fructose as fuel. Though the printed ink was originally aqueous dispersion, the printed shape was kept intact after rehydration, while without PVI the printed electrode readily dissolved in buffer solution. CV of the anode in the presence and absence of PBSE indicated that PBSE was essential for high power density.

[1] Enzymatic Fuel Cells from Fundamental to Applications (Eds: H. R. L uckarift, P. Atanassov, G. R. Johnson), Wiley, New Jersey, 2014

[2] W. Gellett, et al., Electroanalysis.,
22, 727, (2010)

[3] G. Valdés-Ramírez, et al., Electrochem. Commun., 47, 58, (2014)

[4] S. Cosnier, et al., Electrochem. Commun., 38, 19, (2014)

[5] Y. Ogawa, et al., Adv. Healthc. Mater., 4, 506, (2015)

Figure 1
High-Energy Density Metal-Free Biobatteries Powered By Soft Drinks
Authors: Zhu Zhiguang , Zhang Y-H Percival
Published: February 2020

More and more portable electronics urgently require better batteries featuring high-energy density, good safety, and low environmental impacts. Enzymatic fuel cells are a promising micro-power source for small electronics. However, incomplete oxidation of sugars mediated by few redox enzymes and low faraday efficiency result in low energy storage densities. Here we demonstrate the complete oxidization of sucrose, glucose, and fructose at the anodic compartment of biobatteries via a synthetic 15-enzyme pathway. The biobatteries generated maximum power densities from 0.65 to 0.98 mW cm-2. Also, a nitrogen-doped activated carbon cloth was used as a flexible cathode to achieve oxygen reduction reaction faster than that catalyzed by platinum-coated membrane electrode assembly. Biobatteries comprised of 15 enzymes oxidize sucrose, fructose and glucose simultaneously, generated nearly 24 electrons per hexose with faraday efficiencies of approximately 95%. Metal-free biobatteries powered by commercial soft drinks whose energy-storage density was ~400 Ah kg-1 of drinks exhibited maximum power densities of up to 0.55 mW cm-2, implying that soft drinks could be perfect fuels for bioelectricity generation.
Electrochemical and Power Performance of Microbial Fuel Cells: A Novel Numerical Approach
Authors: Falcucci Giacomo , Nastro Rosa Anna , Cigolotti Viviana , Minutillo Mariagiovanna , Jannelli Elio
Published: February 2020

In this work, a novel numerical approach for the simulation of electrochemical and power performance of Microbial Fuel Cells (LBM) for waste-water treatment is proposed.

Our model is based on the accurate description of the MFC internal phenomena by means of the Lattice Boltzmann Method, a numerical approach based on an optimized formulation of Boltzmann's Kinetic Energy, which has been successfully applied to phenomena of technical and engineering interest in recent years.

Employing a multi-component LBM solver, an accurate prediction of wastewater flow through the reactor chamber is achieved; within the LBM framework, a novel methodology has been developed to account for the different types of anode materials in MFC reactors (carbon fiber brushes or solid porous media). The direct conversion of organic substrate into e
- and H
+ through microbs metabolism has been modeled according to dedicated experimental activity. The electrochemical characteristics of anode and cathode electrodes have been included and their effects on internal species transport and charge transfer is accurately simulated.

The very good agreement between our results and the experiments in literature highlight the reliability and versatility of LBM applied to MFC implementations.

Figure 1
(Keynote) Recent Advance in Sensor Technologies for Mobile Healthcare
Authors: Lowe Christopher
Published: February 2020

This talk will discuss the motivation behind the global interest in introducing mobile healthcare systems, including the myriad constraints felt by healthcare systems in both developed and developing nations, high population growth, disease prevalence and the rapid rise in mobile phone penetration in developing nations. The concept of lifetime diagnostic and disease management, the types of physiological and biochemical parameters to be measured and the challenges in making discrete and real-time measurements on patients using non-invasive, minimally invasive and invasive sensor technologies will be covered. Examples will be given from various acoustic and optical sensor technologies being developed in the speaker’s laboratory in Cambridge.
The Unusual Redox Properties of Fluoroferrocenes Revealed through a Comprehensive Study of the Haloferrocenes
Authors: Inkpen Michael , Du Shuoren , Hildebrand Mariana , White Andrew , Harrison Nicholas , Albrecht Tim , Long Nicholas , Long Nicholas
Published: February 2020

We report the synthesis and full characterization of the entire

haloferrocene (FcX) and 1,1′-dihaloferrocene (fcX2) series (X = I, Br, Cl, F; Fc =

ferrocenyl, fc = ferrocene-1,1′-diyl). Finalization of this simple, yet intriguing set of

compounds has been delayed by synthetic challenges associated with the incorporation of

fluorine substituents. Successful preparation of fluoroferrocene (FcF) and 1,1′-

difluoroferrocene (fcF2) were ultimately achieved using reactions between the

appropriate lithiated ferrocene species and N-fluorobenzenesulfonimide (NFSI). The

crude reaction products, in addition to those resulting from analogous preparations of

chloroferrocene (FcCl) and 1,1′-dichloroferrocene (fcCl2), were utilized as model

systems to probe the limits of a previously reported “oxidative purification” methodology. From this investigation and careful solution voltammetry studies, we find that the fluorinated derivatives exhibit the lowest redox potentials of each of the FcX and fcX2 series. This counterintuitive result is discussed with reference to the spectroscopic, structural, and first-principles calculations of these and related materials.
Ionic Liquid|Water Interface As an Electrochemical Reaction Field for the Formation of Novel Metal Nanostructure
Authors: Nishi Naoya
Published: February 2020

Electrochemistry at interface between two immiscible electrolyte solutions (ITIES) has been explored in the novel liquid-liquid two-phase system of water (W) and ionic liquids (ILs) since more than a decade ago [1,2]. One of several characteristics of ILs is the ability to disperse and stabilize metal nanostructures in ILs without addition of any capping reagents, which seems to result from the existence of ionic multilayers [3,4], a rigid interfacial structure, formed on the metal surface. This characteristic motivated us to study electrochemical deposition of metal at the IL|W interface utilizing electron transfer across the interface.

When we used AuCl4
- as the metal source dissolved in W and a reducing reagent dissolved in trioctylmethylammonium bis(nonafluorobutanesulfonyl)amide, which is a highly hydrophobic IL, spontaneous and simultaneous electron transfer-ion transfer reaction occurred and dendritic Au nanofibers were formed at the interface [5]. Similar dendritic nanofibers were formed at the IL|W interface of other highly hydrophobic ILs, although the fiber diameter depended on the ionic species of the ILs. On the other hand, when we used a conventional organic solvent, dichloromethane, instead of ILs, we obtained not nanofibers but micro-scale burr-like structures. In the present paper, the mechanism of the formation of such highly anisotropic nanostructure will be discussed and the application of this system to other nanostructures such as metal-polymer composites will be introduced.

[1] T. Kakiuchi and N. Nishi, Electrochemistry, 74 (2006) 942-948.

[2] Z. Samec, J. Langmaier, T. Kakiuchi, Pure Appl. Chem., 81 (2009) 1473-1488.

[3] N. Nishi, Y. Yasui, T. Uruga, H. Tanida, T. Yamada, S. Nakayama, H. Matsuoka, T. Kakiuchi, J. Chem. Phys., 132 (2010) 164705(1-6).

[4] N. Nishi, T. Uruga, H. Tanida, J. Electroanal. Chem., 759 (2015) 129-136.

[5] N. Nishi, T. Kakinami, T. Sakka, Chem. Commun., 51 (2015) 13638-13641.
Fast Near-Infrared Electrochromism of Redox-Active Plasmonic Copper Sulfide Nanoparticles
Authors: Nishi Hiroyasu , Asami Keisuke , Tatsuma Tetsu
Published: February 2020

Metal nanoparticles absorb and scatter light strongly on the basis of resonance of free electron oscillation with incident light, which is denoted as localized surface plasmon resonance (LSPR). Especially, gold and silver nanoparticles are known to exhibit LSPR in the visible and near-infrared (NIR) regions and applied to sensors,1 photovoltaics and photocatalysis,2 and photochromic materials.3 The LSPR properties such as resonant wavelength and intensity depend significantly on particle size and shape, local refractive index, and interparticle distance. Those are also dependent on electron density of the nanoparticles, which can be controlled electrostatically.4-6 However, it is difficult to induce large changes in resonant wavelength and intensity by the electrostatic means.

Here, we focus on plasmonic copper sulfide nanoparticles as an electrochromic material. Nanoparticles of copper sulfide, represented by Cu2-x
S, have sufficient holes to exhibit LSPR in the NIR region.7 In addition, copper valence can be controlled reversibly by chemical redox reactions,8 suggesting that reversible electrochemical tuning of their LSPR properties is possible. However, such a redox reaction-based control of LSPR has not been reported so far.

Covellite (CuS) nanoparticles were prepared by heating copper(I) chloride and elemental sulfur in a mixture of oleylamine and oleic acid under N2 atmosphere9 and deposited on an ITO electrode. The figure shows absorption spectra of the electrode at different potentials (vs. Ag|AgCl) in deuterated water containing 0.1 M Na2S. Broad absorption due to LSPR is observed in the NIR region at -0.6 V while that gradually disappears as the applied potential is shifted negatively, indicating that plasmonic copper(II) sulfide is reduced to non-plasmonic copper(I) sulfide.10 It is noteworthy that reductive disappearance and oxidative reappearance of LSPR can be repeated at least 12 cycles and the response time is a few seconds. These results indicate that copper sulfide nanoparticles can be applied to fast NIR electrochromic devices that are driven in a narrow potential range (~0.4V).

1. K. M. Mayer, J. H. Hafner, Chem. Rev.
2011, 111, 3828.

2. Y. Tian, T. Tatsuma, J. Am. Chem. Soc.
2005, 127, 7632.

3. Y. Ohko, T. Tatsuma, T. Fujii, K. Naoi, C. Niwa, Y. Kubota, A. Fujishima, Nat. Mater.
2003, 2, 29.

4. T. Ung, M. Giersig, D. Dunstan, P. Mulvaney, Langmuir
1997, 13, 1773.

5. A. H. Ali, R. J. Luther, C. A. Foss, Jr, Nanostruct. Mater.
1997, 9, 559.

6. H. Nishi, S. Hiroya, T. Tatsuma, ACS Nano
2015, 9, 6214.

7. J. M. Luther, P. K. Jain, T. Ewers, A. P. Alivisatos, Nature
2011, 10, 361.

8. P. K. Jain, K. Manthiram, J. H. Engel, S. L. White, J. A. Faucheaux, A. P. Alivisatos, Angew. Chem. Int. Ed.
2013, 52, 13671.

9. H. Nishi, K. Asami, T. Tatsuma, Opt. Mater. Express
2016, 6, 1043.

10. I. Kriegel, C. Jiang, J. Rodríguez-Fernandez, R. D. Schaller, D. V. Talapin, E. da Como, J. Feldmann, J. Am. Chem. Soc.
2012, 134, 1583.

Figure 1
Virus-Assisted Growth of Metal Alloy Nanostructure and Its Use an Electrocatalyst
Authors: Kim Kyuwon , Seo Yeji , Kang Inhak , Manivannan Shanmugam
Published: February 2020

We report an engineered M13 virus (MV) as a scaffolds to electrodeposit well dispersed Au–Pt alloy nanostructures at bio-template, which represents a new type of MV/R/Au–Pt hetero structure .Amine-functionalized sol–gel matrix (T)/MV/R composite is prepared and attachment of Au binding peptide sequences along the major coat protein of MV enables specific nucleation cites, where growth of Au–Pt alloy nanostructures occurred. The electrocatalytic activity of the Au–Pt catalyst towards methanol oxidation was investigated. At this bio-template, MV ensures a close contact between Au–Pt alloy nanostructures and R besides it facilitates the OH– rich environment to the catalyst. As a result, efficient electron transfer and the synergistic catalytic acivity for methanol oxidation were observed.
(Invited) Highly Efficient Visible Light Photocatalysis for Hydrogen Production
Authors: Hu Yun Hang
Published: February 2020

It is a great challenge to use visible light for photocatalytic processes. In this talk, I will highlight the efforts and findings in my group, with emphasis on (1) why the absorbed visible light by a photocatalyst makes negligible contribution to a photocatalytic process and (2) how to solve such an issue. Furthermore, an efficient visible light photocatalytic process for hydrogen production will be discussed.
(Invited) Electrocatalysts for Solar-to-Chemical Conversion
Authors: Min Byoung Koun , Hwang Yun Jeong
Published: February 2020

Solar-chemical production inspired from photosynthesis in nature has attracted much attention due to a need for developing sustainable technology for future energy as well as chemical resources. In this study, we demonstrate a highly efficient solar energy to chemical conversion device using CO2 and water as feedstock. Among many core technologies for the realization of this architecture electrocatalysts for both water oxidation and CO2 reduction are critically important because the overpotential for solar-chemical device operation and the product from CO2 are strongly dependent on the catalytic function of electrodes. To perform selective production of CO from CO2 in water nanostructured gold and silver electrocatalyst were successfully synthesized based on the method of oxidation and subsequent reduction cycle. In addition, water oxidation was very efficiently carried out by a stainless steel based electrocatalyst in low overpotential conditions. The details of the synthetic method and characterization of the electrocatalysts and the solar-chemical generation system will be discussed in the presentation.
(Invited) Latest Development in Design Strategies for Efficient Solar Water Splitting Photoelectrodes
Authors: Vayssieres Lionel
Published: February 2020

An overview of a decade of research on metal oxide semiconductor design [1], electronic structure [2] and applications for solar energy conversion and solar hydrogen generation [3-5] will be presented. Latest advances in design strategies [6] and nanodevice fabrication for efficient low cost solar (sea)water oxidation without sacrificial agents will be demonstrated. Visible-light active photocatalyst heteronanostructures based on non toxic and earth abundant materials engineered to efficiently drive aqueous chemical reactions at their interfaces have been fabricated and tested intensively. Their surface chemistry [7], structural, optical, electrical [8], photoelectrochemical, dimensionality effects [9] and interfacial electronic structure [10] along with their efficiency have been thoroughly investigated at synchrotron radiation facilities as well as in our laboratories. The most promising structures for low cost and large scale solar water splitting will be discussed [11].

References

[1]   L. Vayssieres, Appl. Phys. A
89, 1 (2007); Int. J. Nanotechnol. 4, 750 (2007); Int. J. Nanotechnol.
1, 1 (2004); Angew. Chem. Int. Ed.
43, 3666 (2004); Adv. Mater.
15, 464 (2003); J. Phys. Chem. B
107, 2623 (2003); Nano Lett. 2, 1393 (2002); Chem. Mater.
13, 4395 (2001); Chem. Mater.
13, 233 (2001); J. Phys. Chem. B
105, 3350 (2001); Pure Appl. Chem.
72, 47 (2000)

[2]   F. J. Himpsel et al, J. Electron Spectrosc. Relat. Phenom. 190, 2 (2013); C.X. Kronawitter et al, PhysChemChemPhys
15, 13483 (2013); C. L. Dong et al, Phys. Rev. B
70, 195325 (2004); J.-H. Guo et al, J. Phys.: Condens. Matter
14, 6969 (2002)

[3]   Y. Tachibana, L.Vayssieres, J. R. Durrant, Nat. Photonics
6, 511 (2012)

[4]   C.X. Kronawitter et al, Energy Environ. Sci.
7, 3100 (2014); Energy Environ. Sci.
4, 3889 (2011)

[5]   On Solar Hydrogen & Nanotechnology, L. Vayssieres ed. (Wiley, 2009), Ch. 17, pp. 523-558

[6]   Y.K. Wei et al, Nano Res. (2016) in press

[7]   L. Vayssieres, J. Phys. Chem. C
113, 4733 (2009); Int. J. Nanotechnol. 2, 411 (2005);

[8]   J. Engel et al, Adv. Funct. Mater.
24, 4952 (2014)

[9]   L. Vayssieres et al, Appl. Phys. Lett.
99, 183101 (2011); Adv. Mater.
17, 2320 (2005)

[10] C.X. Kronawitter et al, Nano Lett.
11, 3855 (2011); Phys. Rev. B
85, 125109 (2012); J. Phys. Chem. C
116, 22780 (2012)

[11] J.Z. Su and L.Vayssieres, ACS Energy Lett. Invited review (2016)
(Invited) Electrocatalyst Development for Solar Fuels: H2 Evolution, O2 Evolution, and CO2 Reduction
Authors: Jaramillo Thomas F
Published: February 2020

The development of new, renewable pathways to produce the same kinds of fuels and chemicals that are conventionally derived from fossil resources, namely H2 and C-based products, could play a major role in reaching sustainability goals for the globe. To address technical challenges in this area, this talk will focus on electrocatalyst development for three reactions relevant to the synthesis of solar fuels: the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and the CO2 reduction reaction (CO2RR). Advanced catalysts for each reaction will be described, targeting high activity, stability, and selectivity for these reactions. Challenges and opportunities will be addressed, along with a framework for understanding current limitations and possible solutions for further improvement.
(Invited) Generation of Hot Plasmonic Electrons and Heat in Nanocrystals with Hot Spots
Authors: Govorov Alexander O.
Published: February 2020

The efficiency of generation of energetic plasmonic carriers in metal nanostructures strongly depends on the optical design and material composition.  This study demonstrates the ability to generate large numbers of hot plasmonic carriers in specially-designed hybrid nanostructures [1,2]. The hot-electron generation becomes especially efficient in plasmonic nanostructures with electromagnetic hot spots [1].  The energy distribution of optically-excited plasmonic carriers is very different in metal nanocrystals with large and small sizes [2]. For metal nanocrystals with smaller sizes (less than 10nm) or in nanostructures with hot spots, the excited state gets a large number of carriers with high energies. Nanostructures with a strong plasmonic enhancement generate unusually large numbers of energetic electrons, which can be observed using ultra-fast spectroscopy, photo-currents and photo-chemistry [1,3,4]. Along with the hot-electron generation, which is a quantum effect, the electromagnetic radiation typically causes efficient heating in metal nanostructures, which may also be concentrated in thermal hot spots [5]. The results obtained in this study can be used to design plasmonic hot-electron nanodevices for photo-catalysis, photo-detectors and solar-energy applications.

[1]  H. Harutyunyan, A. B. F. Martinson, D. Rosenmann, L.K. Khorashad, L.V. Besteiro, A.O.Govorov, and G.P. Wiederrecht, Nature Nanotechnology 10, 770–774 (2015).

[2] A.O. Govorov, H. Zhang, V. Demir, and Y. K. Gun’ko, NanoToday 9, 85 (2014).

[3] ] W. Li, Z. J. Coppens, L. Vázquez, W. Wang, A. O. Govorov, and J. Valentine, Nature Communications 6, 8379 (2015).

[4] L. Weng, H. Zhang, A. O. Govorov, and M. Ouyang, Nature Communications 5, 4792 (2014).

[5] A. Govorov and H.H. Richardson, NanoToday 2, 20 (2007).
(Invited) Development of Wide Bandgap Copper Chalcopyrite Materials for Economical Photoelectrochemical Hydrogen Production
Authors: Gaillard Nicolas , DeAngelis Alexander , Horsley Kimberly
Published: February 2020

Photoelectrochemistry (PEC) is theoretically one of the most efficient methods to produce alternative fuels, although the efficiency, cost, and durability of lab-scale systems are currently not at the level required to make this technology economically feasible. The chalcopyrite material class provides exceptional candidates to meet the requirements for cheap, sustainable solar fuels production. As we have previously reported, co-evaporated 1.7 eV CuGaSe2 offers very high-saturated photocurrent densities (>15 mA.cm-­2) and high Faradaic efficiency (>85%). However, CuGaSe2 photocathodes suffer from non-ideal surface energetics, requiring additional PV cells to drive the water splitting process. The hybrid photo-electrode (HPE) device, in which a PEC electrode is placed on top of a solar cell, is by far the most efficient approach for unbiased solar water splitting. Unfortunately, CuGaSe2’s narrow bandgap prohibits this integration scheme.

In the present communication, we report on our efforts to synthesize 1.8-2.2 eV band-gap chalcopyrite materials for PEC water splitting. Specifically, we investigated the effect of sulfur on the optical and photoelectrochemical characteristics of the copper chalcopyrite material class. Using co-evaporated 1 μm-thick CuGaSe2 as a baseline system, we demonstrate that the substitution of selenium with sulfur can be accomplished through a simple annealing step. As a result, a dramatic change in optical properties was observed, with a bandgap increase from 1.6 eV (CuGaSe2) to 2.4 eV (CuGaS2). Then, by simply adjusting the indium content during the initial growth process, the bandgap of sulfurized copper chalcopyrite was decreased from 2.4 eV to 2.0 eV. X-ray diffraction data indicated successful bulk sulfurization by the shift of the prominent (112), (220), and (312) reflections to higher angles. Saturated photocurrent densities of 5 mA/cm2 were achieved with 2.0 eV red CuIn0.3Ga0.7S2 photocathodes in 0.5M H2SO4 under AM1.5G simulated illumination. From this proof of concept experiment, we have further developed new synthesis approaches and innovative characterization protocols to achieve PV-grade wide bandgap sulfide-based chalcopyrites capable of generating photocurrent densities over 10 mA.cm-2.
(Invited) Computational Design of Chalcopyrite Photoabsorber for Photoelectrochemical H2 Production Cell
Authors: Ogitsu Tadashi , Varley Joel , Zhou Fei , Lordi Vincenzo , Gaillard Nicolas
Published: February 2020

The chalcopyrite material class presents excellent candidates for PEC water splitting due to the high tunability of band gaps. An optimal band gap for the front absorber (~1.8eV) is larger than that for a PV cell and is unattainable with conventional selenide-based chalcopyrites (e.g. CuInGaSe2). We have investigated the stability and electronic structure of related alloys within a broader group I-III-VI2 system (I=Ag,Cu ; III=In,Ga,Al ; VI=S,Se) to identify desirable compositions for optimal absorbers, using hybrid density functional theory for reliable predictions. In this presentation, we will assess the suitability of such alloys in a comprehensive manner, considering properties, in addition to band gap, that include the thermodynamic stability, the propensity for incorporation of various types of defects under given synthesis conditions, the impact of defects on the electronic properties, and the availability of appropriate buffer materials.

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and funded by the Department of Energy office of Energy Efficiency & Renewable Energy (EERE).
Simultaneous Decomposition and Energy Production from Industrial and Bio- Waste Using Flexible Photocatalytic Fuel Cell
Authors: Lui Gregory , Jiang Gaopeng , Lenos Jared , Lin Edric , Fowler Michael , Yu Aiping , Chen Zhongwei
Published: February 2020

Herein, we design a flexible, photocatalytic fuel cell (fPFC) that utilizes light irradiation to provide electrical power via the decomposition of organic compounds (lactic acid, ethanol, methanol, urea, glycerol, and glucose). Photocurrent measurements, polarization curves, and electrochemical impedance spectroscopy are used to characterize the fPFCs and analyze their performance. The fPFC is shown to provide power under both flat and bending (r = 3 cm) conditions. Lastly, the fPFC is employed as a power generation device in two applications: in wastewater treatment and in a sweat band using methylene blue and human sweat as fuel sources, respectively.
Three-Dimensional ZnO-BiVO4 Core-Shell Nanosturctured Array for Photoelectrochemical Water Oxidation
Authors: Yang Jih-Sheng , Wu Jih-Jen
Published: February 2020

In this work, three-dimensional (3D) ZnO-BiVO4 core-shell nanostructured arrays were constructed on fluorine-doped tin oxide (FTO) substrates for use in photoelectrochemical (PEC) water splitting. The ZnO nanodendrite (ND) arrays were grown on FTO substrates using a wet chemical route. A photocurrent density of 0.6 mA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE) under AM 1.5 at 100 mW cm-2 is monitored in the ZnO ND array photoanode with a thickness of 3 mm. To construct the 3D ZnO-BiVO4 core-shell nanostructured arrays, the BiVO4 nanoparticle (NP) layers were subsequently formed on the surface of ND arrays using metal organic decomposition method. The absorption spectrum of the 3D ZnO-BiVO4 core-shell nanostructured array shows an absorption edge at the wavelength of ~510 nm. An optimized photocurrent density of 2.5 mA/cm2 at 1.23 V vs. RHE is obtained in the 3D ZnO-BiVO4 core-shell nanostructured array photoanode. The 3D ZnO ND array provides a large surface area for the deposition of the thin BiVO4 layer. Moreover, due to the formation of type II heterojunction in the ZnO-BiVO4 core-shell nanostructured array, the photocarriers generated in the ZnO ND core and BiVO4 shell can be effectively separated. Therefore, photoholes generated and collected in the thin BiVO4 layer can transport to the surface for water oxidation. On the other hand, the photoelectron generated and collected in the ZnO ND core can transport to the FTO substrate due to the quasi-single crystal structure of the ZnO ND array. To further improve the PEC performance, Co–Pi was further electrodeposited on the surface of the 3D ZnO-BiVO4 core-shell nanostructured array photoanode. With the Co-Pi deposition, the onset potential in the J-V curve of the 3D ZnO-BiVO4 core-shell nanostructured array photoanode shows a cathodic shift from 0.7 V to 0.2 V vs. RHE. Moreover, the photocurrent density of the 3D ZnO-BiVO4 core-shell nanostructured array photoanode is significantly improved. An optimized photocurrent density of 3.5 mAcm-2 are monitored in the Co-Pi deposited photoanode at 1.23 V vs. RHE.
Conjugated Organic Polymers As Photocathodes for Hydrogen Evolution
Authors: Fortin Patrick , Holdcroft Steven
Published: February 2020

Currently, there is a global effort being made to reduce greenhouse gas emissions through the implementation of renewable energies. An attractive alternative to fossil fuels is hydrogen, as it can be stored, transported and used as on demand as a liquid fuel while producing only water vapour as a by-product. The production of hydrogen can be attained through the photoelectrochemical splitting of water into hydrogen and oxygen, representing a sustainable, carbon neutral method of hydrogen generation. Here we have explored the use of poly(3-hexylthiophene) (P3HT) films as photocathodes for hydrogen evolution. Our research has been mainly focused on the investigation of the origin of photocurrent at the polymer/electrolyte surface. We show that the photocurrents observed at the P3HT/electrolyte interface are dominated by the oxygen reduction reaction (ORR), contrary to what was previously reported in the literature as the hydrogen evolution reaction (HER). Although sluggish kinetics prevent H2 evolution at the polymer interface, we have shown that the addition of an inorganic hydrogen evolution catalyst, such as Pt, on top of the polymer active layer allows for measurable amounts of H2 gas to be produced photoelectrochemically.
(Invited) Bioinspired Water Oxidation and CO2 Reduction Electrocatalysts
Authors: Nam Ki Tae
Published: February 2020

Water splitting is regarded as a promising step towards environmentally sustainable energy schemes because electrolysis produces only hydrogen and oxygen, without any by-products. Within the overall water splitting process, the oxygen evolution reaction (OER), an anodic half-cell reaction that generates an oxygen molecule from two water molecules, requires extremely high overpotential due to its slow reaction kinetics. In this regard, development of cost-effective and robust catalyst has been demanding challenge to solve the modern energy crisis. In nature, there exists a water oxidation complex (WOC) in photosystem II (PSII) comprised of the earth-abundant elements Mn and Ca. The WOC in PSII, in the form of a cubical Mn4CaO5 cluster, efficiently catalyzes water oxidation under neutral conditions with extremely low overpotential value (~160 mV) and a high turnover frequency (TOF) number (~25,000 mmolO2 mol-1
Mn s-1). Inspired from the asymmetric geometry and flexible ligation of the biological CaMn4O5 cluster, we designed new manganese based water oxidation catalysts, Mn3(PO4)2-3H2O and Li2MnP2O7.

We first identified a new crystal structure, Mn3(PO4)2-3H2O, and demonstrated its superior catalytic performance at neutral pH. From the combined ex-situ spectroscopic analysis and DFT calculations, we revealed that structural flexibility can stabilize Jahn-Teller distorted Mn(III), and thus facilitate Mn(II) oxidation during catalytic cycle. We also studied a new pyrophosphate based Mn compound, Li2MnP2O7 for water oxidation catalysis. We verified the influence of oxidation state of Mn and asymmetric Mn geometry on water oxidation catalysis using Li2MnP2O7 and its derivatives. We believe higher Mn(III) portion and asymmetric arrangement of Mn atoms which can be seen in the WOC, enhance catalytic water oxidation reaction.

Specific questions that our group intensively focus for the further applications include 1) how we can translate the underlying principles in Manganese Calcium Clusters into the synthetic heterogeneous catalysts and 2) how we can mimic the redox molecule involved biological dark reaction for the CO2 reduction. Toward this vision, we have been developing a new catalytic platform based on sub-10 nm uniform nanoparticles to bridge the gap between atomically defined biological catalysts or their metalloenzyme counterparts and the scalable, electrode depositable heterogeneous catalysts. In this approach, the local atomic geometry is controlled by the nitrogen containing graphitic carbon and the heterogeneous atom doping, that enhance the catalytic activity and selectivity. Additional surface modification by the specific ligand allow for the atomic scale tunability to realize the unique electronic hybridization.
(Invited) Photocatalytic CO2 Conversion to Selective Hydrocarbons Using Graphene Oxides and Related 2D Hybrids
Authors: Chen Li-Chyong , Lien Hsiang-Ting , Shown Indrajit , Chen Kuei-Hsien
Published: February 2020

Photocatalytic conversion of carbon dioxide (CO2) to hydrocarbons makes possible simultaneously harvesting solar energy for production of fuels or useful chemicals, as well as reducing CO2 for a greener society, two birds with one stone for the pressing global energy and environmental problems of our time. Here, we describe a highly efficient photocatalytic conversion of CO2 to selective hydrocarbons using graphene oxides (GOs) and their related 2D hybrids as photo-catalysts. Several approaches have been employed to synthesize GOs and reduced GOs (rGOs) with tunable bandgap and band alignment with respect to the CO2 reduction level. The functionalities of the GOs/rGOs were investigated by UV-Vis, cyclic voltammetry, and x-ray photoemission spectroscopy.

Under visible light, the photocatalytic conversion of CO2 to methanol of GOs/rGOs is several-fold higher than that of TiO2 (e.g., commercial P-25). Further, metal and metal sulfides, especially the 2D materials such as MoS2, as well as optically active polymers, were deposited onto GO as co-catalysts or sensitizers, to enhance the photocatalysis reaction. Besides methanol, other selective hydrocarbons including acetaldehyde were also detected. Total solar to fuel yield of ~200 times enhancement over that of P-25 has been achieved. In all these GOs-2D hybrids, the photo-catalytic performance is always much better than that of constituent component when used alone. Detailed preparation and characterization of the catalysts will be presented. The role and interplay of the constituent components will also be discussed.