bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystal Structure Refinement of BaCaSiO4:Eu2+/Mn2+ and Its Tunable Luminescence
Authors: Park Jieun , Lee Choong Ki , Kim Young Jin 
Published: February 2020

Color-tunable phosphors have been widely developed to enhance the luminous efficiency of phosphor-conversion white light-emitting diodes using near ultraviolet chips. For this application, the Eu2+ and Mn2+ ions are typically used as sensitizers and activators, respectively. One of suitable host materials is a (Ba,Ca)SiO4 system. For example, the tunable luminescence of Eu2+/Mn2+ co-doped Ba1.55Ca0.45SiO4, Ba1.3Ca0.7SiO4, and Ba1.2Ca0.8SiO4 compounds has been reported. However, the luminescence of BaCaSiO4:Eu2+/Mn2+ has rarely been studied.
In this study, BaCaSiO4:Eu2+/Mn2+ powders were prepared by a solid-state reaction process. And then the phase formation, the crystal structure, and tunable luminescence were investigated. The starting mixtures were fired at 1100−1300 °C for 4 h under a 5% H2 (+ 95% N2) atmosphere. Rietveld refinement was performed to verify the crystal structure. The crystal system of BaCaSiO4 is a hexagonal structure. It was most probable that both of the Eu2+ and Mn2+ ions were incorporated into the Ca2+ sites. The PL spectra exhibited two emission bands: green (A-band) and red (B-band) assigned to the Eu2+ and Mn2+ ions, respectively. The B-band occurred through an energy transfer (ET) from Eu2+ to Mn2+. The intensity ratio of the A- to B-band closely depended on the Eu/Mn ratio, resulting in a change in CIE chromaticity coordinates. Fluorescence lifetimes, multipolar interactions and critical distances between Eu2+ and Mn2+, ET efficiencies, and the evolution of the PL spectra were estimated and discussed.
New Strategy for the Design of Yellow, Red and IR-Emitting LED Phosphors
Authors: Toda Kenji , Kim Sun-Woog , Uematsu Kazuyoshi , Sato Mineo 
Published: February 2020

Typical white LEDs composed of blue light excitable LED phosphors and blue LED chip. Recently, long wavelength (yellow and red)-emitting Eu2+ or Ce3+-activated nitride phosphors have been usually used in the white LEDs as commercial phosphors. The excitation and emission band of Eu2+ or Ce3+-activated phosphors are due to the energy transitions between the 4f ground state and 5d excited state of Eu2+. Strong crystal field splitting of the 5d band in the nitrides lead to decrease the energy gap between the 4f ground state and the lowest level of the 5d excited state. On the other hand, the Eu2+ or Ce3+-activated oxide phosphors are also expected to be obtained the excitation and emission band in the longer wavelength region (yellow, red and IR), if the oxide host materials have small site for substitution of activator ions. Therefore, we focused on oxide materials including a compact octahedral sites in the host lattices.
As a result, we could successfully synthesize the novel long wavelength-emitting Eu2+ or Ce3+-activated phosphors such as NaMgPO4:Eu2+ and (Ba,Sr)3Sc4O9:Ce3+ [1,2]. The NaMgPO4:Eu2+ phosphor can be efficiently excited by blue light irradiation and presents red emission band centered at 628 nm due to the d - f transition of Eu2+. The internal quantum efficiency of NaMgPO4:2.5mol%Eu2+ at the excitation wavelength of 450 nm is estimated to be 81%. (Ba,Sr)3Sc4O9:Ce3+ shows orange to red emission peaking at 583(Ba) and 620(Sr) nm due to the 5d - 4f transition of Ce3+ under blue light excitation. Therefore, this new strategy (octahedrally coordinated sites for the Eu2+ or Ce3+) is a general and powerful tool for searching the long wavelength-emitting phosphors.
This work was supported by a project from NEDO, New Energy and Industrial Technology Development Organization (Rare Metal Substitute Materials Development Project Development of Technology for Reducing Tb and Eu Usage in Phosphors for Fluorescent Lamp by High-speed Material Synthesis and Evaluation).
References
[1] S-W. Kim, T. Hasegawa, T. Ishigaki, K. Uematsu, H. Takaba, K. Toda, M. Sato. “Efficient Red Emission of Blue-Light Excitable New Structure Type NaMgPO4:Eu2+ Phosphor”, ECS Solid State Lett
.
2, (2013). R49-R51.
[2] T. Hasegawa, S-W. Kim, T. Ishigaki, K. Uematsu, H. Takaba, K. Toda, M. Sato. “Novel Ce3+-doped Ba3Sc4O9 Reddish Yellow-emitting Phosphors for Blue-light Based White LEDs”,
Chem
.
Lett
., 40, (2014). 828.
Electrochemiluminescent Molecular Sensor for Point of Care Testing for Homocysteine Measurement
Authors: SHIN Iksoo 
Published: February 2020

Homocysteine (Hcy) is a naturally occurring, sulfur-containing amino acid produced from demethylation of methionine, and an essential amino acid found in both animal and plant proteins. The level of plasma Hcy between 5 and 15 μM is generally considered normal. An elevated level of Hcy is, however, strongly linked to cardiovascular disease, Alzheimer’s disease, neural tube defects, and osteoporosis. Therefore a routine, easy-to-usable determination of Hcy is highly desirable. In the talk, an electrochemiluminescent (ECL) molecular sensor for simple Hcy determination will be discussed. Recently, we developed supramolecular probes which recognize Hcy in the solution by producing light emission under ECL process. The synthesized molecular sensor successfully monitors the level of Hcy in 99.9% aqueous media with a linear correlation between 0–40 µM. The method suggests a point-of-care testing of the Hcy level based on ECL analysis, and it is potentially useful for a routine, pre-cautious, and strip-based diagnosis for the cardiovascular diseases.
Morphology-Controllable Ni3Se2 Nanostructures; Synthesis, Characterization and Electrocatalytic Activity Towards Oxygen Evolution Reaction
Authors: Swesi Abdurazag T , Masud Jahangir , Nath Manashi 
Published: February 2020

First raw transition metal-based chalcogenides (FRTMCs) are promising devices for next generation to serve as effective substitutes for the Pt-based electrocatalysts in fuel cell systems. OER and HER are considered to be clean and sustainable energy technology and an alternative for fossil fuels. However, OER involving a complex 4 electron process, has several steps that have large reaction barriers, which lead to large required overpotentials. Identifying more-efficient, stable and earth-abundant catalysts for water splitting has long been investigated. The planar configuration of FRTMCs could lead to robust integration for electronic devices. Nanostructured electroactive materials that are fabricated in-plane FRTMCs have attracted great attentions as a kind of storage energy material due to its electrochemistry properties. Recently we have observed that Ni-chalcogenide (Ni3Se2) is superior to the precious transition metal oxide-based electrocatalysts in terms of onset overpotential for O2 evolution as well as overpotential to reach a current density of 10 mA cm-2. With the onset of decreasing particle size to nanometric scale, electrodeposition techniques have provided an alternative route to obtain a variety of new nanomaterials with improved and well controlled properties. The improvement of properties of the metallic composites is dependent mainly on the morphology of materials. Morphology-controllable Ni3Se2 films were successfully prepared by electrodepositing Ni3Se2 film on Au substrate and following by electrochemical dissolution. In electrochemical dissolution process, Ni3Se2 phase is well-preserved and porous structure formed. This technology is a promising way to fabricate other porous materials. A porous Ni3Se2 film showed an enhanced OER catalytic performance in comparison with the as-deposited Ni3Se2 film. The results proved that the OER catalytic performance of porous Ni3Se2 film delivers the highest activity. Introduction of pores to the catalyst material by the electrochemical dissolution is availability for improve the electrochemical performance of the material for OER electrocatalysts.
The catalytic efficiency of the proposed catalysts was investigated through linear scan voltammetry (LSV), chronoamperommetry and double layer capacitance. Utilizing rotating ring disc electrode (RRDE) assemblies, the kinetics of OER process between various catalysts as well as the Faradaic efficiency were studied. The catalytic activity of the proposed novel compound (Ni3Se2) was also compared to the outstanding electrocatalysts for OER under conditions relevant to an integrated solar water-splitting device which have been reported so far. The synthesis, characterization, catalytic activity and advancement of the field will be presented in details.
(Invited) Enhanced Hydrogen Oxidation Activity at Pt-M Alloy Catalysts in Acid: A DFT Study
Authors: Tryk Donald A. , Shi Guoyu , Yano Hiroshi , Uchida Hiroyuki , Watanabe Masahiro , Iiyama Akihiro 
Published: February 2020

Platinum alloys that include first-row transition metals have been examined extensively as CO-tolerant catalysts for the hydrogen oxidation reaction (HOR) in acidic media. The CO tolerance stems from the decreased CO adsorption strength, so that the surface is not easily poisoned. Recently, we have found experimentally that the intrinsic, area-specific HOR activity is also significantly enhanced for stabilized Pt-Co nanoparticle catalysts in aqueous acid solution.1 This is an aspect of the catalysis that has been little studied. We have found that the enhanced HOR activity is consistent with high-quality density functional theory (DFT) calculations, which show that the adsorption of underpotentially deposited (UPD) hydrogen atoms is weakened by the presence of the alloying metal under the (110) surface, which has been recognized to be the most active (Fig. 1). DFT calculations of Ishikawa and coworkers have explained the high activity of the Pt(110) surface as being due to the ease of H2 dissociation, with the rate-determining step being the desorption of HUPD.2

In addition, we have found recently that Pt-Fe and Pt-Ni catalysts also exhibit enhanced area-specific HOR activities, in addition to their enhanced CO tolerance, as will be presented by G. Shi separately. In particular, we found that the DFT calculated adsorption strength of HUPD on the Pt-Fe nanoparticle (110) surface is greatly weakened, consistent with its high HOR activity. Nevertheless, H2 dissociation remains facile.
Acknowledgements
This work has been supported by the Superlative, Stable, and Scalable Performance Fuel Cell (SPer-FC) project funded by the New Energy and Industrial Development Organization (NEDO) of Japan.
References

G. Shi, H. Yano, D. A. Tryk, M. Watanabe, A. Iiyama, and H. Uchida, A novel Pt-Co alloy hydrogen anode catalyst with superlative activity, CO-tolerance and robustness, Nanoscale, 2016, DOI: 10.1039/C6NR00778C.

J. Santana, J. J. Mateo, and Y. Ishikawa, Electrochemical hydrogen oxidation on Pt(110): a combined direct molecular dynamics/density functional theory study, J. Phys. Chem. C, 114, 4995-5002 (2010).

Figure 1
(Invited) A First-Principles Molecular Dynamics Study on Active Sites on Metal Nano Particles: Application of the Compressed Gas Model
Authors: Sugimoto Manabu 
Published: February 2020

The first-principles Molecular Dynamics (FPMD) is applied to investigate gas adsorption onto surfaces of metal nano particles. Herein we focus on catalytic reactions for ammonia synthesis and decomposition. Some Ru nano clusters are prepared as a model of the catalyst, and gas adrosptions of the H2, N2, and NH3 molecules are investigated.
In order to do a conceptually unbiased mechanistic study, a natural and reasonable strategy would be to make many models to be investigated by “electronic-structure simulations”. In this study, we apply the compressed gas model in which distribution of gas molecule in high pressure simulations are taken into account. The compressed gas cluster is inserted in the simulation box containing a metal nano particle. Because of the compressed nature of the “ball” of the gas molecules, they automatically diffuse into the vacuum region and hit on the nano particle surface with velocity.
By repeating this simulation, we could identify some characteristics of the adsorption sites on the metal nano particle and the gas molecule dependence in the adsorption behavior. It was found that the H2 adsorption should be structure insensitive, while the N2 and NH3 adsorptions should be structure sensitive. In the simulation of the NH3 adsorption, we observed formation of the H2 molecule from NH­
3. It was found that the kink plays an important role as a reaction center of the H2 formation. In the simulation, H2 was yielded in a mechanism similar to the Eley-Rideal mechanism.
Engineering Molybdenum Disulfide Protected Silicon Photocathodes for Corrosion Resistance in Acid
Authors: King Laurie Ann , Hellstern Thomas R , Jaramillo Thomas F 
Published: February 2020

Photoelectrochemical (PEC) water splitting devices offer a promising path to sustainable production of hydrogen.1 Silicon shows great promise as a small band gap photocathode in tandem photoelectrochemical (PEC) water splitting due to its appropriate band structure, energetic alignment for driving hydrogen evolution, and its band gap of 1.1 eV.2 However, some challenges remain to ensure that silicon photoelectrodes possess the required catalytic activity and stability for use in highly effect PEC water splitting devices.
Molybdenum disulfide (MoS2) is a low permeability material known for its excellent stability and HER activity in acid. We have previously demonstrated MoS2 protected silicon photocathodes which operate for 100 hrs without significant loss of activity.3 Here, we further this study to design strategies, such as the utilization of a molybdenum silicide interface layer, for improved activity and over 600 hour stability with unchanged photoelectrochemical performance (onset potential, fill factor and light limited photocurrent density), which is among the best performance of any precious metal free photocathode.
Critical to developing future electrodes with enhanced stability, we probe the failure mechanism of the MoS2 protected photocathodes. By XPS we observe that the MoS2 is fully absent post stability testing. Detailed failure mechanisms of the photocathodes and electrolyte are uncovered by electrochemical methods, SEM, Raman microscopy and ICP. Furthermore, we implement increased light intensity (10 suns), as well as light and dark cycling to probe accelerated durability testing protocols utilizing MoS2 protected photocathodes. From such analyses we uncover a feedback loop that enables insightful design of future corrosion resistant protection schemes.
(1) Walter, M. G.; Warren, E. L.; McKone, J. R.; Boettcher, S. W.; Mi, Q. X.; Santori, E. A.; Lewis, N. S. Solar Water Splitting Cells. Chem. Rev.
2010, 110, 6446–6473.
(2) Seitz, L. C.; Chen, Z.; Forman, A. J.; Pinaud, B. A.; Benck, J. D.; Jaramillo, T. F. Modeling Practical Performance Limits of Photoelectrochemical Water Splitting Based on the Current State of Materials Research. ChemSusChem
2014, 7 (5), 1372–1385.
(3) Benck, J. D.; Lee, S. C.; Fong, K. D.; Kibsgaard, J.; Sinclair, R.; Jaramillo, T. F. Designing Active and Stable Silicon Photocathodes for Solar Hydrogen Production Using Molybdenum Sulfide Nanomaterials. Adv. Energy Mater.
2014, 4 (18), 1400739.
Maskless Generation of Highly Periodic 3D Semiconductor Nanostructures in Response to Defined Illumination Inputs
Authors: Carim Azhar I , Batara Nicolas A. , Premkumar Anjali , Atwater Harry A , Lewis Nathan S. 
Published: February 2020

Template-free photoelectrodeposition of semiconducting chalcogen alloys resulted in the spontaneous generation of highly periodic nanostructured films over macroscopic length scales. The exact nature of the optical excitation was encoded in the deposit morphology in terms of the feature sizes, periodicities, anisotropies, and orientations of the nanoscale pattern. The use of unpolarized light generated isotropic morphologies consisting of ordered arrays of nanopores whereas linearly polarized light resulted in a highly-anisotropic lamellar morphologies with the long axes of the patterns aligned along the E-field vector. Utilization of two non-orthogonal polarized sources simultaneously generated patterns oriented along the average E-field vector and with degrees of anisotropy related to the difference in orientation between the two input E-field vectors and the phase correlation between the sources. The illumination spectral profile encoded the pattern periodicity and feature width. A single periodicity in single in-plane direction was consistently observed even with the use of broadband and multimodal spectral profiles and the periodicity was found to be sensitive to all investigated tuning of such profiles. The incidence of the illumination set the direction the material grew from the substrate, mimicking natural phototropism: grazing illumination resulted in growth at significant angle to the surface normal. Modeling of the growth using a combination of full-wave electromagnetic simulations of light absorption and scattering coupled with Monte Carlo simulations of mass addition successfully reproduced the experimentally observed morphologies and indicated that the encoding process was a consequence of the fundamental light-matter interactions during growth.
This photoelectrochemical deposition process is unique from other methods of generating ordered mesostructures with electrochemical means as no photomask, no photoactive substrate, no lithographic processing, nor any chemical templating agents (ligands, surfactants) were utilized. Moreover, films were deposited from aqueous solution using oxide precursors at room temperature with low-intensity illumination (~10 mW cm-2). Thus, this process displays significant potential to possibly enable the generation of complex morphologies for functional materials without some of the limitations imposed by traditional fabrication techniques.
Modified Electrodes with Nanocomposite Films Based on Conducting Polymers and Functionalized Carbon Nanotubes
Authors: Branzoi Florina , Branzoi Viorel , Pahom Zoia 
Published: February 2020

Nanoporous composite films of functionalized single–walled carbon nanotubes (SWCNTs), 3-methylthiophene and 2-aminophenol were grown electrochemically from aqueous solutions such that constituents were deposited simultaneously onto substrate electrodes. Scanning electron microscopy (SEM) revealed that the composite films consisted of nanoporous networks of SWCNTs (SWANTs- with carboxylic acids functionalized - CNT-COOH and with octadecylamina) coated with polymeric film.
Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) demonstrated that these composite films had similar electrochemical response rates to pure polymeric films but a lower resistance and much improved mechanical integrity. The negatively charged functionalized carbon nanotubes (CNTsF) served as anionic dopant during the electropolymerization to synthesize polymer/CNTsF composite films. The synthetic, morphological and electrical properties of the obtained nanocomposite films were compared. The specific electrochemical capacitance of the composite films is a significantly greater value than that for pure polymer films prepared similarly. Using these composite films, the modified electrodes with improved properties were obtained. These nanoporous composites showed improved mechanical integrity, higher electronic and ionic conductivity and exhibited larger electrode specific capacitance than the polymer alone.
All of the composite films were a very promising electrode material for application in supercapacitor
Mechanism of Ethanol Oxidation on Unsupported Noble Metal Nanoalloys Studied By Differential Electrochemical Mass Spectrometry
Authors: Piwowar Justyna , Lewera Adam 
Published: February 2020

Electrooxidation of ethanol on noble metals is of particular interest due to its potential application in low temperature direct ethanol fuel cells (DEFCs). However there is no known ethanol electrooxidation reaction (EOR) catalyst, allowing for complete electrooxidation of ethanol to CO2. Even for the most active systems, incomplete and slow EOR renders the DEFCs not economically viable. As a result significant effort has been devoted to understand the reasons of low activity of known catalysts and to finding better, more active and selective systems. It is widely accepted that systems consisting of platinum, and platinum alloyed with other metals are most active towards ethanol electrooxidation. Pt-Ru and Pt-Sn systems are often reported as those with the highest current density in acidic media. However, despite the higher current, addition of Ru or Sn to Pt further decrease the already small amount of CO2, produced in EOR on pure Pt. Selectivity of a given catalyst towards CO2 in EOR is especially important, due to the facts, that CO2 is the product of complete, 12-electron oxidation of ethanol molecule, where acetaldehyde and acetic acid (other possible products) yields respectively 2- or 4-electrons. Additionally acetic acid cannot be further oxidized in a working fuel cell, thus it is effectively a dead-end of EOR in a working low temperature DEFC. As a result other catalysts, more active and selective toward ethanol electrooxidation to CO2 are needed for a commercially viable DEFC.
In this report we used unsupported ultra-pure platinum-containing nanoalloys as a catalyst for EOR, to determine the possible changes in mechanism of EOR (based on product distribution determined by DEMS) as a function of nanoalloy composition. We focused on possible changes in surface morphology and changes in electronic properties due to alloying and how those factor impact electrode reaction mechanisms.
Using DEMS experiments we determined how the amounts of products like carbon dioxide, acetaldehyde and acetic acid per active surface area changed as a function of nanoparticle composition and how it impacted the onset potential for particular products. As a result we were able to comment on the selectivity and activity of unsupported Pt-containing nanoalloys in EOR as well as on the activity of this material in C-C bond scission.