bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrospun Ni nanofibres as Pt supports for PEMFC electrodes
Authors: Ercolano Giorgio , Cavaliere Sara , Jones Deborah Jacqueline , Rozière Jacques 
Published: February 2020

A thriving market for emerging and established mobile devices, operating on electrical energy is pushing the research and the market demands towards continuous sustainable and clean sources of energy. In particular key operators of the automotive industry are seeking a leading market position introducing hybrid and electric vehicles. Proton exchange membrane fuel cells (PEMFC) provide clean and long lasting electrical energy while being portable and operated at relatively low temperatures and would be the obvious power source for those applications. However a reduction of the fabrication costs and an improved durability are pivotal to a successful market introduction of this technology. A more effective utilisation of the highly priced Pt catalyst and the use of more durable materials for the catalyst supports are the core of the development of novel, market ready PEMFC.
A paradigm shift from Pt nanoparticles supported on carbon to thin layers of platinum deposited on metals, metal oxides or carbon could be achieved adopting electrochemical Pt deposition techniques like the galvanostatic displacement of Ni and Cu ions with Pt 1 , self-terminated Pt electrodeposition 2 or electrochemical atomic layer deposition 1. This novel morphologies could push the boundary of Pt exploitation further and vastly increase the stability of the electrodes, therefore the sought after reduction of fabrication costs and increased stability are within the reach of current researches.
Electrospinning is a proven technique and is reliable and scalable for the production of nanowires made of several metals 3, metal oxides 4 or carbon 5. The capability to finely control the diameter and composition of the nanowires makes this technique appealing in the search of novel catalyst support materials and morphologies. Our research group is actively testing different Pt deposition techniques on electrospun carbon, metal oxide nanowires, pristine and doped, as well as metallic nanowires.
1. Adzic, R. R. et al. Platinum Monolayer Fuel Cell Electrocatalysts. Top. Catal.
46,249–262 (2007).
2. Liu, Y., Gokcen, D., Bertocci, U. & Moffat, T. P. Self-terminating growth of platinum films by electrochemical deposition. Science
338,1327–30 (2012).
3. Wu, H. et al. Electrospun metal nanofiber webs as high-performance transparent electrode. Nano Lett.
10,4242–8 (2010).
4. Cavaliere, S., Subianto, S., Savych, I., Jones, D. J. & Rozière, J. Electrospinning: designed architectures for energy conversion and storage devices. Energy Environ. Sci.(2011).
5. Qiu, Y. et al. Nitrogen-doped ultrathin carbon nanofibers derived from electrospinning: Large-scale production, unique structure, and application as electrocatalysts for oxygen reduction. J. Power Sources
196, 9862–9867 (2011).
Recent Progress in Blue Phosphors: From Non-Thermal Quenching to Highly Efficient Phosphor
Authors: Im Won Bin , Kim Yoon Hwa 
Published: February 2020

In the present era of solid-state lighting, white light-emitting diodes (WLEDs) have received enormous attention as general lighting source due to its energy efficiency and environmental friendly technology. However, the current high power WLED faces serious challenge of luminescence loss of phosphor due to the generation of heat under operation and at elevated temperature known as thermal quenching. Therefore, it is highly desirable to find new phosphors with high efficiency and thermal stability.
Hence, our search for a new and efficient phosphor host, has led to the emergence of oxohalide/oxide host with very high PL and conversion efficiency. In this talk, some works from our laboratory on the recent progress in blue-emitting phosphors are summarized. In particular, new NASICON based blue-emitting phosphor shows negligible thermal quenching for WLED applications, which exhibited broad blue emission under near UV excitation and retains its luminescence at elevated temperature of 473 K. Also, some blue-emitting phosphors with their excellent optical properties are reported.1,2

References
[1] S. J. Gwak, P. Arunkumar, and W. B. Im, J. Phys. Chem. C, Vol.118, pp. 2686-2692, 2014.
[2] Y. H. Kim and W. B. Im, Opt. Lett., Vol.39, pp. 4887-4890, 2014.

Figure 1
Influence of the Starting Solution on the Growth and Morphology of Rare Earth-Doped Yttrium Oxide Spherical Particles By the Urea Precipitation Method
Authors: Silver Jack , Ireland Terry , Fern George Robert 
Published: February 2020

Abstract

Since the start of this millennium, the need for amorphous submicron spherical rare earth element (REE) precursors that after subsequent heat treatment (~1000°C) forms crystalline REE-doped yttrium or gadolinium oxide (Y2O3:REE or Gd2O3:REE) phosphors has generated an active area of research.1 The original impetus was for a variety of display applications such as cathode ray tubes for high definition television and field emission devices.2 Later uses have included X-ray imaging and X–ray computed tomography (after converting these spherical REE phosphor particles to oxysulfide phosphor particles using sulfur and further heat treatment whereby they retained their former size and morphology).3 These spherical REE phosphor particles have the ability to close pack to form a thin emissive layer.2

These REE phosphor particles are produced via a urea homogeneous precipitation method and its modifications. In this work REE nitrate stock solutions which yielded spherical REE-doped hydroxycarbonate precursor particles.1 It was assumed due to the ‘boring’ similarity of the chemical properties of REEs that all the spherical phosphor particles precipitated using different dopants would have identical particle sizes and spherical morphologies. Our observations have found this not to be the case, and that their chemistry is much more interesting. For example precipitated Y2O3:Eu spherical particles are larger than Y2O3:Tb precursor particles, this is also the case after annealing at 980°C where the original morphology is retained (see Figure 1).
Also, it has been found that highly viscous Y2O3:REE and Gd2O3:REE nitrate precursor solutions used for the preparation of three-dimensional photonic structures such as inverse photonic band gap crystals4 and bio-templates5vary in stability (non-precipitation) for each dopant.
The reason behind these findings will be discussed in terms of the pH of the precursor solutions, electron configuration, oxidation state (preferred) and stoichiometry.

Figure 1. Annealed spherical phosphor particles of (a) Y2O3:Eu and (b) Y2O3:Tb.

References

X. Jing, T. Ireland, C. Gibbons, D. Barber, J. Silver, A. Vecht, G. Fern, P. Trogwa, and D. Morton, J. Electrochem. Soc.,
146, 4654 (1999).

M. I. Martinez-Rubio, T. G. Ireland, G. R. Fern, J. Silver, and M. J. Snowden, Langmuir, 17, 7145 (2001).

G.R. Fern, T.G. Ireland, J. Silver, R. Withnall, A. Michette, C. McFaul and S. Pfauntsch, Nucl. Instr. Methods Phys Res.,
A600, 434 (2009).

J. Silver, T.G. Ireland and R. Withnall, J. Mater. Res., 19, 1656 (2004).

J. Silver, R. Withnall, T.G. Ireland, G.R. Fern and S. Zhang, Nanotechnology, 19, 095302 (2008).

Figure 1
Controlling Particle Size and Luminescence in Mn4+ Activated K2SiF6
Authors: Nammalwar Prasanth Kumar , Porob Digamber G , Hanumantha Ravi , Setlur Anant A , Murphy James 
Published: February 2020

Narrow red emitters have attracted large attention within white LED and backlit display world over the past few years. This is partially due to renewed interest in red emitting phosphor, K2SiF6:Mn4+ (PFS). Though, the material is known in literature for more than two decades, its application in white LEDs and display devices can be realized only after some of the key issues in the synthesis of these materials are addressed. In this paper, we discuss synthesis, controlling particle size and luminescence properties of Mn4+ doped K2SiF6. Manganese doped Potassium hexafluorosilicate exists in cubic crystal structure with narrow PL emission with a main peak at 631nm with a FWHM of 2nm. Based on the type of application within display or general lighting, the particle size requirement for PFS varies. We have studied various parameters that can influence particle growth during synthesis in order to obtain PFS of desirable particle size. In the current study we have used variety of anti-solvents (solvents that do not dissolve K2SiF6), including isopropyl alchohol(IPA), acetic acid, Dimethyl sulphoxide (DMSO), acetone, ethanol etc., to initiate crystallization. By controlling quantity of anti-solvents and process of addition, we have shown better control on particle size distribution. Further, in this study we also discuss on influence of anti-solvents on luminescence properties and yield of PFS obtained.
Tuning the Luminescence Properties of Organometal Halide Perovskites for Light-Emitting Applications
Authors: Zhong Haizheng 
Published: February 2020

Organometal halide perovskites are inexpensive materials with desirable characteristics of color-tunable and narrow-band emissions for lighting and display technology, but suffering from the low photoluminescence quantum yields at low excitation fluencies.2 We developed a ligand-assisted reprecipitation (LARP) strategy to fabricate CH3NH3PbX3 (X=Br, I, Cl) nanocrystals.3 By controlling their size and shape, we demonstrated the size- and shape- dependent photoluminescence properties. Especially, we obtain brightly-luminescent and color-tunable colloidal quantum dots with absolute quantum yield up to 70% at room temperature and low excitation fluencies. The comparisons between small sized CH3NH3PbBr3 quantum dots (average diameter 3.3 nm) and corresponding micrometer-sized bulk particles (2-8 μm) suggest that the intense increased photoluminescence quantum yield originates from the increase of exciton binding energy due to size reduction as well as proper chemical passivations of the Br rich surface. We further demonstrated the fabrication of prototype light-emitting devices, providing enhanced color quality for display technology.
[1] Shirasaki, Y.; Supran, G. J.; Bawendi, M. G.; Bulovic, V. Nat. Photon.
2013, 7, 13-23
[2] Stranks, S. D.; Burlakov, V. M.; Leijtens, T.; Ball, J. M.; Goriely, A.; Snaith, H. J. Phys. Rev. Appl.
2014, 2, 034007.
[3] Zhang, F.; Zhong, H. Z.; Chen, C.; Wu, X. G.; Hu, X. M.; Huang, H. L.; Han, J. B.; Zou, B. S.; Dong, Y. P. ACS Nano
2015, DOI: 10.1021/acsnano.5b01154
Upconversion Luminescence of HfO2 Phosphors Embedded into Polyester FILMS
Authors: Carmona S. , Mariscal B. L. , Hérnandez J. M. , Alarcón-Flores Gilberto , Murrieta H. , Falcony Ciro 
Published: February 2020

Upconversion (UC) luminescence in powder hafnia (HfO2) doped with Er3+, Yb3+ and Li+ was studied under continuous wave excitation at 980 nm. Powder samples were prepared by the simple evaporation technique. The simple evaporation technique is an inexpensive and scalable technique to obtain powders with excellent properties. The technique works heating a chemical solution until its evaporation point to achieve a powder. A thermal treatment is practiced in this powder in order to eliminate any kind of remnant from precursor materials and/or achieve an appropriate crystalline structure if it is necessary. This powders were attached into polyester films by spin coating technique; spin coating process consists in supplying a small puddle of a liquid resin onto the center of a substrate and then spinning the substrate at high speed (between 3000 and 6500 rpm), centripetal acceleration will cause the resin to spread and eventually it covers the substrate leaving a thin film of resin on the substrate surface.
This powders and films were optical, structural and luminescent characterized using x-ray diffraction, electron microscopy, IR spectroscopy and UV-Vis. A study of the infrared to green and infrared to red UC processes was performed including the analysis of the spectral and the temporal behavior. The mechanisms contributing to the UC luminescence were identified as excited state absorption and energy transfer among rare earth ions. (x, y) coordinates of CIE diagrams are reported also.
Finally, it is important to sight, that this kind of phosphors attached at polymeric films could be eventually incorporated to solar cells in order to increase its nominal efficiency.
1. François Auzel, Upconversion and Anti-Stokes Processes with f and d Ions in Solids, Chemical Reviews 2004 104 (1), 139-174
2. S. Carmona-Téllez, G. Alarcón-Flores, A. Meza-Rocha, E. Zaleta-Alejandre, M. Aguilar-Futis, H. Murrieta S and C. Falcony, Polyethylene terephthalate thin films; a luminescence study, Optical Materials, 42, 2015, 99–105.
Optical and Thermal Management of Phosphor-Converted LEDs
Authors: Raukas Madis , Kelso John , Lenef Alan , Linkov Alexander , Tchoul Maxim 
Published: February 2020

Phosphor conversion generates over 95% of the light source lumens and affects efficacy, spectral tuning and quality of Solid State Lighting (SSL) devices as much as the efficient generation of suitable primary light from the pumping semiconductor chips. In SSL, a large number of applications such as low/mid-power distributed area illumination may not need the highest luminance sources that typically bring along most stringent requirements on materials, for example, as with high-brightness spotlights or automotive headlights. The cumulative efficiency of handling generated photons matters everywhere. Basic properties of phosphors like refractive index and temperature-dependent quantum efficiency, in a series of physical processes and according to conditions surrounding the converter (for example optical scattering and reflection off of various interfaces, transmission and heat conductivity through materials), determine the overall amount of light being extracted and in use. Modifying the light scattering, reflectance and transmission in different conversion media types and adding to it options for reducing the converter temperature has the cumulative effect that allows for optimizing the light generation process. Crucial to the overall efficiency are losses both from light recycled back into the LED, from various reflective surfaces, and weak volume absorption, including self-absorption of the phosphor emission. The influence of these factors will be demonstrated through examples of thermal-optical modeling and actual measurements on specific packaging configurations for a range of forward currents If. For example, advantages gained through controlling the scattering in ceramics versus powder-in-silicone and using thermally conductive materials will be elaborated. The gains can be realized in either efficacy or luminous flux.
Reversibility of Ferri-Ferrocyanide Redox during in-Situ Soft X-Ray Spectroscopy
Authors: Risch Marcel , Stoerzinger Kelsey A. , Regier Tom Z. , Peak Derek , Nagy Sayed , Shao-Horn Yang 
Published: February 2020

Ferri-ferrocyanide is a common facile redox couple in electrochemistry and related fields; select applications include charge storage in flow batteries, prevention of electrolyte decomposition in batteries, redox shuttling in dye-sensitized solar cells and photoanodes, as well as measuring charge transfer on catalytic surfaces. Ferri-ferrocyanide is also frequently employed as a standard to establish new steady-state and time-resolved in-situ spectroscopy methods. Despite the ubiquity of the ferri-ferrocyanide redox couple in diverse fields, discussion exists as to whether its kinetics may depend on the composition of both the electrode and electrolyte. Furthermore, ferri-ferrocyanide decomposes when exposed to ionizing radiation such as soft X-rays at a synchrotron, which may lead to electrodeposition on the electrode.
We studied the photochemical response of ferri-ferrocyanide to intense synchrotron radiation by in-situ X-ray absorption spectroscopy at the iron L edge. For photon flux densities above a defined threshold, precipitation of ferric (hydr)oxide from both ferricyanide and ferrocyanide solutions was clearly detectable. The formation of the precipitate was accelerated during cyclic voltammetry, which we probed by time-resolved in-operando X-ray absorption spectroscopy. The iron redox was completely inhibited in the probed volume after only two electrochemical cycles (70 min). Our study highlights the importance of considering both electrochemical and spectroscopic conditions when designing in-situ experiments that can shed light on charge transfer and chemistry of active sites in energy and health research.
Enrichment of Novel Electroactive Bacteria from Equatorial Climate Sediments Via Potentiostatic Growth and Subsequent Characterisation Via Metagenomics, Metatranscriptomics, Voltammetry and Electrochemical Impedance Spectroscopy
Authors: Doyle Lucinda Elizabeth , Yung Pui Yi , Wuertz Stefan , Williams Rohan Benjamin Hugh , Marsili Enrico 
Published: February 2020

Electrochemically-active microorganisms couple the degradation of organic matter to the production of electricity via extracellular electron transfer. They are usually enriched from sediments via growth at certain potentials, either in microbial fuel cells or in potentiostat-controlled electrochemical cells. Despite the great microbial diversity of sediments from natural and man-made environments, most electrochemical enrichments select a small group of dissimilatory metal-reducing microorganisms.
In this study, we aim to enrich novel electrochemically-active strains in sediments from various equatorial environments. Sediment inocula from urban waterways and mangroves were tested in long-term enrichment experiments at controlled anodic potentials. In addition to the conventional voltamperometric characterisation, the biofilm formed at the working electrode was subjected to electrochemical impedance spectroscopy (EIS) over a wide range of potentials. EIS of the biofilms revealed several charge transfer routes at different potentials and with different characteristic times. Furthermore, EIS enabled monitoring of the long-term changes of the electroactive biofilm and quantification of the effect of biofilm accumulation on the conductivity of the biofilm/electrode interface.
Electrochemical analysis was coupled to metagenomics and metatranscriptomics to reveal novel electrochemically-active microorganisms and to understand their charge-transfer mechanism. The understanding of the microbe/electrode interaction in the sediments will assist in controlling the dynamic of metal cycling in urban sediments. Furthermore, novel electrochemically-active microorganisms will find application in bioremediation and environmental sensing applications.
Naphthoquinone Derivatives As Low-Potential Electron Mediators of Fad-Dependent Glucose Dehydrogenase
Authors: Hickey David P , Milton Ross D , Abdellaoui Sofiene , Lim Koun , Tan Boxuan , Minteer Shelley D. 
Published: February 2020

Flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) is rapidly emerging as an alternative glucose-oxidizing enzyme in enzymatic fuel cells (EFCs). FAD-GDH has the benefit over its commonly used counterpart, glucose oxidase (GOx), of not undergoing the parasitic reduction of O2 to H2O2, which can be troublesome in EFC applications. Additionally, the FAD cofactor has a relatively low redox potential in comparison to heme-based and PQQ-dependent enzymes, which can allow for a much higher theoretical cell potential. However, FAD-GDH is unable to facilitate rapid rates of direct electron transfer, and therefore requires a low-overpotential redox mediator to take full advantage of the low oxidation potential of its FAD cofactor.
We have prepared a range of naphthoquinone analogues that are capable of mediating electron transfer between FAD-GDH and carbon electrodes, with onset potentials ranging between -0.425 to -0.150 V (vs. SCE), at pH 7.4. Several naphthoquinone derivatives were immobilized either onto a poly(ethylenimine) backbone or directly onto the outer shell of FAD-GDH to yield a naphthoquinone redox hydrogel and a naphthoquinone-labeled FAD-GDH. Both methods demonstrated large catalytic current densities at low onset potentials. When coupled with an O2-reducing biocathode (bilirubin oxidase, direct electron transfer-type) the glucose/O2 EFC possessed a large open-circuit potential (OCP) of 0.864 V and was able to deliver a maximum current density of 5.4 mA cm-2. The EFC reached its maximum power density (2.3 mW cm-2) at 0.55 V.
Liquid Catholyte Investigations for Safer Storage of a Li Primary Battery
Authors: Patrissi Charles J. , Schumacher Christian R. 
Published: February 2020

The close proximity of the electrode materials is a design risk for commercial off the shelf (COTS) Li batteries. COTS Li batteries can off gas and ignite if the electroactive materials are inadvertently mixed by events such as thermal abuse, crush, penetration, and shock. Crew safety on US Navy ships and submarines critically depends on minimizing the probability of exposure to toxic gases and fire. The Naval Undersea Warfare Center (NUWC) is investigating a primary Li battery design for undersea applications that is, in principle, safer to store and transport than COTS batteries. In this approach a liquid catholyte is stored separately from a Li metal anode. The catholyte is added to the anode housing immediately prior to off board deployment of the energy section. With this configuration the electroactive materials can be stored separately and more safely than in COTS batteries. NUWC has recently begun investigating slurry catholytes1 comprised of solid redox active cathode materials and electronically conductive carbon powders dispersed in a nonaqueous electrolyte. Our goals are high volumetric charge capacity, high voltage, good power density and a “pumpable” rheology. These properties are significantly affected by the formulation of the slurry such as the choice of redox active material, the volumetric solids concentration of the redox active and carbon materials, the interaction between the particles, and the particle size distributions. This talk will discuss NUWC’s separated anode / catholyte battery concept, the tradeoffs of various electroactive cathode materials, and the results of catholyte investigations and their expected impact on the performance of a Li-slurry catholyte primary battery.

1) M.Duduta., B.Ho, V.C. Wood, P. Limthongkul, V. E. Brunini, W. C. Carter, and Y-M Chiang,
Semi-Solid Lithium Rechargeable Flow Battery
, Adv. Energy Mater. 2011, 1, 511–516