bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microwave-Assisted Hydrothermal Synthesis of Co Doped ZnO Nanocrystals
Authors: Nishiumi Nobuyuki , Sun He , Yasuhara Taichi , Mastushima Yuta , Furis Madalina , White Matthew Schuette , Stadler Philipp , Shiroishi Hidenobu , Khosla Ajit , Yoshida Tsukasa 
Published: February 2020

Spintronic devices employing both semiconducting and ferromagnetic properties of materials are to be realized by doping of high spin transition metal ions to semiconductors such as ZnO. Transition metal oxides are also interesting as electrocatalysts for electrochemical conversion of renewable electricity to chemical energy for its storage. In this study, we have attempted microwave (MW)-assisted hydrothermal synthesis of Co, Mn-doped ZnO nanoparticles.

Aqueous precursor solutions containing ZnCl2 and CoCl2 or MnCl2 at various ratios in a total concentration of 0.2 M were basified with NaOH to ca. pH 13, and subjected to a 2.45 GHz MW[1,2] to promote reaction at 160°C for 30 min. The products were characterized by FE-SEM, XRD and UV-Vis. Mesoporous electrodes of ZnO and Zn0.92Co0.08O were fabricated by doctor blading method.
The green-colored Co-doped samples exhibit characteristic absorption peaks at around 560, 610 and 650 nm due to d-d transition of Co(II) and a red shift of the bandgap absorption onset. Phase separation of Co(OH)2 has also been suggested by XRD and FE-SEM images for x > 0.1, so that doping up to about 10% was apparently possible. Systematic shift of the three major XRD peaks of Wurtzite ZnO towards low angles was recognized upon increasing x, suggesting substitution of the lattice Zn2+ ions with Co2+. Lattice constants were calculated as a = b = 3.252 Å, c = 5.204 Å for ZnO, whereas they were enlarged to 3.277, 5.244 Å, respectively, for x = 0.20.
CVs of ZnO and Zn0.92Co0.08O electrodes in a neutral electrolyte are compared in Fig. 1. Besides the clear decrease of cathodic charging and discharging currents, Co-doping results in an anodic wave at around + 1 V due to Co2+ → Co3+, followed by a large increase of irreversible anodic current, as compared to the non-doped sample. Chronoamperograms for a few minutes confirmed this current enhancement and gas bubble evolution from the anode due to catalytic oxidation of water (2H2O → O2 + 4H+ + 4e-).

[1] Y. Hirai, K. Furukawa, H. Sun, Y. Matsushima, K. Shito, A. Masuhara, R. Ono, Y. Shimbori, H. Shiroishi, M. S. White & T. Yoshida, “Microwave-assisted hydrothermal synthesis of ZnO and Zn-terephthalate hybrid nanoparticles employing benzene dicarboxylic acids” Microsyst Technol (2017). doi: 10.1007/s00542-017-3392-y
[2] H. Sun, L. Sun, T. Sugiura, M. S. White, P. Stadler, N. S. Sariciftci, A. Masuhara & T. Yoshida, “Microwave-assisted hydrothermal synthesis of struture-controlled ZnO nanocrystals and their properties in dye-sensitized solar cells” Electrochemistry, in press.

Figure 1
Fabrication of Cu3BiS3 Photocathode for Photoelectrochemical Hydrogen Evolution
Authors: Kamimura Sunao 
Published: February 2020

Hydrogen production from water using abundant solar light is now an important research subject from viewpoints of usage of renewable energy and environmental issues. Photoelectrochemical (PEC) water splitting utilizing semiconductor electrodes has been studied extensively as a potential means of converting solar energy into chemical energy in the form of H2.
Chalcogenide compounds have emerged as a leading class of thin films for photocathodes due to their suitable band gap for solar energy absorption, high photo-absorption coefficients, and usability in the polycrystalline state. Although Cu-chalcogenide photocathodes such as CuInS2,CuGaSe2, CuGa3Se5,(Ag,Cu)GaSe2,

and Cu(In,Ga)Se2, show excellent solar-to-hydrogen conversion efficiency, there are many difficulties in largescale production from the viewpoints of low throughput and material utilization because of the limited availably of elements (i.e., In, Ga and Se). It is therefore evident that more research is required to search for alternative inexpensive and earth-abundant materials.
Cu3BiS3 is one of the promising chalcogenide compounds for a photovoltaic device due to its ability to absorb visible light (Eg
≈ 1.4–1.7 eV), a high absorption coefficient (>105 cm-1) compared to that of CuInSe2 and Cu2ZnSnS4, and p-type conductivity with a carrier concentration of ~ 2×1016 cm-3

. Moreover, it is made of cheap, non-toxic, earth-abundant elements and can be easily produced on a large scale.
We fabricated a Cu3BiS3 thin film by a simple electrodeposition technique on a molybdenum-coated glass substrate to utilize it as a photocathode for PEC hydrogen evolution. The Cu3BiS3 film was composed of dense crystallites with thicknesses of ca. 0.65 μm, and the optical bandgap was estimated to be ca. 1.6 eV. Photoelectrochemical characterization revealed that the Cu3BiS3 film was a p-type semiconductor with a flat band potential of ca. +0.1 V (vs Ag/AgCl at pH 6), which is suitable for water reduction but cannot be used for water oxidation. Deposition of an In2S3 buffer layer, by which effective contact between p-type Cu3BiS3 and n-type In2S3 was formed, resulted in a significant increase in the photocurrent and a large shift of the photocurrent onset to the positive region. H2 evolution under AM 1.5G simulated solar light was demonstrated using the Pt-In2S3/Cu3BiS3 electrode combined with a Pt electrode under an applied bias (0 V vs. RHE).
(Invited) Redox Reaction of Proteins in Hydrated Cholinium Dihydrogen Phosphate
Authors: Fujita Kyoko 
Published: February 2020

Ionic liquids (ILs) have attracted attention as solvents because of their fascinating features, such as negligible vapor pressure and high thermal, chemical, and electrochemical activity. ILs have been widely studied as green, multi-use media for electrochemistry and chemisry even in bio-applications. Generally, however, most proteins are not soluble in ILs. Surface modification on the proteins, e.g. poly(ethylene oxide) (PEO) modification is one of the way to dissolve biomolecules in ILs [1]. PEO modified cytchrome c dissolved and showed the redox activity in ILs.
As another way, hydrated IL have been studied to realize the dissolution of proteins without chemical modification. Hydrated ILs maintain the basic properties of ILs, but a small amount of water was added. However, it is difficult to dissolve proteins in most hydrated ILs. Selection of component ion is essential to realize the dissolution and maintaining the higher ordered structure of proteins in hydrated IL. Hydration state of ILs which could be estimated on kosmotropicity was suggested one of the key factor to control the protein compatibility [2]. Hydrated cholinium dihydrogen phosphate ([ch][dhp]) acts as an excellent solvent to dissolve and preserve proteins for long term [3]. Furthermore, the original reactions such as enzymatic reactions and electron transfer reactions were observed in hydrated ILs, when the higher ordered structures were remained [4]. However, when the biocatalytic reaction was detected as an electrochemical response, the observed redox current was smaller than that in buffer solution. The redox reaction rate between a fixed protein and electrode was investigated to clarify the reason for the depression of the redox response of biocatalytic reactions in hydrated [ch][dhp] [5]. It was revealed that the electron transfer rate between protein and electrode was fast in hydrated [ch][dhp] as same that in buffer. Fast electron transfer reaction in hydrated ILs is expected to be more stable over a wider temperature range and longer period of time than general aqueous system.

References

[1] H. Ohno, C. Suzuki, K. Fukumoto, M. Yoshizawa, K. Fujita, Electron Transfer Process of Poly(ethylene oxide)-Modified Cytochrome c in Imidazolium Type Ionic Liquid, Chem. Lett., 32 (2003) 450-451.
[2] Y. Nikawa, K. Fujita, H. Ohno, Quantitative Assessment of Kosmotropicity of Hydrated Ionic Liquids by Nuclear Magnetic Resonance, Phys. Chem. Chem. Phys., 19 (2017) 8148-8151.
[3] K. Fujita, D. R. MacFarlene, M. Forsyth, Protein solubilising and stabilising ionic liquids, Chem. Commun. (2005) 4804-4806.
[4] K. Fujita, N. Nakamura, K. Igarashi, M. Samejima, H. Ohno, Biocatalytic oxidation of cellobiose in an hydrated ionic liquid, Green Chem., 11 (2009) 351-354.
[5] K. Fujita, J. Kuwahara, N. Nakamura, H. Ohno, Fast Electron Transfer Reaction of Azurin Fixed on the Modified Electrode in Hydrated Ionic Liquids, J. Electrochem. Soc., 163 (2016) G79-G81.
Ab Initio Studies of Ultrathin Ionic Liquid Films on Au (111) Surface
Authors: Liu Mingjie , Sitaputra Wattaka , Stacchiola Dario J , Wishart James F. , Wang Feng , Sadowski Jerzy T. , Wu Qin 
Published: February 2020

Room-temperature ionic liquids (RTILs) as alternative electrolytes are of great interest to electrochemical energy storage devices, such as supercapacitors. A key to understanding the performance of these systems is to know the ion arrangement near the electrode surface and the ion-electrode interaction. In this work, we will present our ab initio studies of a few layers of 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide (EMMIM TFSI) ionic liquid on gold (111) surface, a system that was recently studied in a novel experiment using low-energy electron and photoemission electron microscopy (LEEM/PEEM). [1] Our work probes different ion arrangements on Au (111) and the corresponding work function change. We further investigate the most stable ion arrangement at different electrode charge densities and identify their out-of-plane layering structure. The dynamics of the ions with reordering and drifting under electric field can be inferred as well. We then use our findings to explain the observed changes in electron reflectivity/photoemission yield in LEEM/PEEM. Together, our results provide important understanding towards the structures and responses of ionic liquids on an electrified metal surface.
This research was carried out at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under contract DE-SC0012704.
[1] Wattaka Sitaputra, Dario Stacchiola, James F. Wishart, Feng Wang, and Jerzy T. Sadowsk, In situ Probing of Ion Ordering at Electrified Ionic Liquid/Au Interface, Adv. Mater. DOI:10.1002/adma.201606357
Influence of Mesoscale Organization on Charge Transport and Dynamics in Ionic Liquids
Authors: Cosby James Tyler , Tsunashima Katsuhiko , Liu Hongjun , Paddison Stephen J. , Sangoro Joshua R 
Published: February 2020

Mesoscale aggregates arising from the separation of ionic and alkyl groups into polar and nonpolar regions have been observed for a variety of ionic liquids (ILs). The existence of these distinct regions provides ILs with the ability to solvate both polar and nonpolar molecules and has important implications for applications such as energy storage, nanoparticle growth, biomass processing, and organic synthesis. It has been found by computational studies and x-ray scattering that the morphology of the mesoscopic structure is highly sensitive to the alkyl chain length, however, the influence of aggregate formation and morphology on physicochemical properties, such as ionic conductivity and dynamics, is not yet well understood. In this study, a homologous series of imidazolium, quaternary ammonium and phosphonium-based ionic liquids are investigated by broadband dielectric and shear-mechanical spectroscopy as well as molecular dynamics simulations to elucidate the impact of alkyl chain length and hydrophobic aggregation on charge transport and dynamics. It is observed that systematic ordering of ionic liquids into complex polar and nonpolar domains results in the emergence of slow, sub-α dynamics in both the dielectric and shear-mechanical spectra. These findings confirm the existence of long-lived nanoscale aggregates in neat ionic liquids and provide a new avenue to elucidate the interplay of morphology, ion transport and dynamics in these nanostructured fluids.
(Invited) Electrochemical Studies of Zinc/Cysteine Interactions in Aqueous Buffers
Authors: Cheek Graham T. , Worosz Matthew A. , Doan Michelle Y 
Published: February 2020

Introduction
The naturally occurring amino acid L-cysteine is involved in many important biochemical processes, including the formation of “zinc finger” proteins (1). The electroactive thiol group in cysteine allows electrochemical investigation of its properties and interactions with other substances. The present contribution deals with the complexation of L-cysteine with zinc(II) ions in various buffered aqueous media and is a continuation of work previously presented (2).
Experimental
L-Cysteine was obtained from Sigma-Aldrich Corporation. Electrochemical experiments were carried out under nitrogen using a Gamry Instruments Interface 1000 potentiostat and Framework software. Working electrodes were obtained from BASi (Glassy carbon, 3.0 mm diameter; platinum 1.6 mm) and eDAQ (gold, 1.0 mm diameter). Potentials were measured with respect to a silver/silver chloride saturated KCl reference electrode (BASi).
Results and Discussion
Recent work from this laboratory has shown that the interaction of zinc(II) ions, added as ZnSO4 heptahydrate, with L-cysteine can be followed by cyclic voltammetry (Figure 1). This work is intended as a model for the formation of “zinc finger” proteins, which involve interactions between zinc(II) and cysteine and histidine units in the protein structure (1). Figure 1 (a) shows the voltammogram for 8.6 mM L-cysteine in 0.1 M pH 7.4 phosphate buffer at glassy carbon. Upon addition of ZnSO4 to L-cysteine in a 1:2 Zn2+: Cysteine mole ratio [Figure 1(b)], the broad oxidation process underwent a significant shift to a more positive potential. This observation is consistent with the complexation of Zn(II) by L-cysteine. Upon sweeping to more negative potentials, reduction of the complex was found to occur near the solvent reduction limit, followed by zinc stripping at approximately -1.0 V vs Ag/AgCl. Interesting comparisons with results at gold electrodes (2) can also be made. Further details for the complexation process are also planned for presentation. Other investigations have involved electrochemical impedance spectroscopy (EIS) to determine the extent to which L-cysteine interacts with various electrode surfaces.
References

C.K. Mathews, K.E. Van Holde, D.R. Appling, and S. J. Anthony-Cahill, Biochemistry, 4th Edition, Pearson Canada, Toronto, 2013.

G. T. Cheek and M. A. Worosz, ECS Transactions, 2016, 72(27), 1-8.

Figure 1. Cyclic voltammograms at glassy carbon in aqueous pH 7.4 phosphate buffer, 100 mV/s scan rate.

Solid black line : L-Cysteine 8.6 mM, initial positive-going sweep

Dashed red line : ZnSO4 . 7 H2O 4.3 mM addition, to previous solution, initial positive-going sweep

Figure 1
(Invited) Tunable CNT Fiber and Yarn Microelectrodes for Measurements of Different Neurochemicals
Authors: Yang Cheng , Venton B. Jill 
Published: February 2020

Traditionally, in vivo analysis of neurotransmitters has concentrated on the molecule dopamine and much of the surface characterization of new electrodes has been focused on the kinetics of dopamine detection. However, the field of in vivo electrochemistry is expanding to many new molecules and electrode design should follow suit to examine the extent to which it is possible to design new electrodes that have surface chemistry that is advantageous for different neurochemicals. Beyond dopamine, other small neurotransmitters that are often targeted include serotonin, norepinephrine and epinephrine. Serotonin and it’s metabolite 5-HIAA are known to foul the electrode surface of carbon fibers, but recently developed carbon nanotube-polyethyleneimine (PEI/CNT) fiber microelectrodes show reduced susceptibility for fouling. PEI/CNT fiber microelectrodes are more selective to DOPAC, and CNT yarn microelectrodes show significantly higher selectivity to serotonin than other fibers. Chlorosulfonice acid (CA)/CNT fiber microelectrodes have the highest selectivity of dopamine to ascorbic acid and uric acid, because of the negative charge carried by CA. Our lab has also investigated CNT yarn microelectrodes for adenosine detection and found that CNT yarns may be advantageous for detecting all three oxidation peaks for adenosine. In addition, we have explored surface treatments of microelectrodes, including laser treatment, oxygen plasma treatment, and antistatic gun treatment. These treatments increase the sensitivity and change the selectivity of the sensors, allowing the properties to be tuned. Thus, electrode materials, design, and surface materials are important considerations for designing in vivo microelectrodes that are sensitive to a variety of different analytes.
(Invited) Enhancing Electron Transfer Rates on Ultra-Thin Graphene Electrodes Using a Sub-Surface Patterning Approach
Authors: Rodriguez-Lopez Joaquin 
Published: February 2020

We will discuss the potential of mono- and few-layer graphene electrodes as versatile platforms for the exploration of new electrocatalyst design principles. By transferring cm2 layers of CVD-grown graphene over metal deposits patterned on insulating substrates, and following passivation of pinholes and grain boundaries, we have measured enhanced rates of outer-sphere and inner-sphere electron transfer on sites modified with the sub-surface metal. Reactive imaging of these electrodes using scanning electrochemical microscopy was used to confirm our modification strategy and to highlight the possibility of using this strategy to spatially encode reactivity on surfaces. These electrodes enable a unique opportunity to modify the reactivity and mechanism of electrochemical reactions by means of electronic interactions that operate at scales coincident with their limiting thickness.
In a first study,[1] we deposited bi-layer graphene on SiO2 chips modified with thin deposits of Au and Pt. SECM imaging using reversible outer-sphere mediators (ferri/ferrocyanide and ferrocenemethanol) showed a five-fold increase in the heterogeneous electron transfer constant on sub-surface modified sites. These enhancements are likely a consequence of increased electronic density of states due to a donating effect from the substrate. Following this principle, we explored the impact on an inner-sphere process, the oxygen reduction reaction. Our results indicate that both the kinetics and mechanism of the reaction are sensitive to sub-surface modification, with the kinetics largely driven by the identity of the metal and the reaction mechanism dominated by graphene or adsorbed molecular catalysts.[2] SECM imaging in the redox competition mode and in the H2O2 collection mode confirmed observations done on macro-electrode interfaces. The design principles derived from these experiments open new opportunities in the coupling of materials with different electrocatalytic properties using graphene as a mediating surface. We will discuss our recent progress expanding this toolbox for mitigating problems associated with several electrocatalytic reactions and exploring other reactions of interest, including the electrochemical reduction of CO2.
[1] Hui, J.; Zhou, X.; Bhargava, R.; Chinderle, A.; Zhang, J.; Rodríguez-López, J. Electrochim. Acta 2016, 211, 1016-1023.
[2] Hui, J., et al., Rodríguez-López, J. In Preparation.

Figure 1
Electrochemical Investigation of CO2 Conversion Utilizing Nanoporous Polystyrene-Polyvinylpyridine Catalyst
Authors: Ghebremichael Habte , Sidorenko Alexander 
Published: February 2020

The threat of climate change proves to be one of mankind’s most daunting challenges. Carbon dioxide emissions are believed to be a leading contributor to climate change. The development of nontoxic and abundant catalysts for the reduction of CO2 is critical in enabling this much needed technology. A method of reverse combustion would be prove to be advantageous in mitigating climate change and providing for a carbon neutral fuel source. Pyridine has shown to be electrocatalytically active at reducing carbon dioxide at low overpotentials to hydrocarbons.The development of nanoporous polymer thin films have exhibited many useful properties that have yet to be exploited. Taking advantage of the microphase separation phenomenon of poly(styrene)poly(4vinylpyridine), PSP4VP, block copolymers allows for pyridine moieties to assemble onto the cylindrical interior of these nanoporous surfaces. These moieties we've shown to be both electrocatalytically active in conjunction with conductive cocatalyst via a radical mechanism.
Grain Boundary Effect in Electroreduction Catalysis for Renewable Energy Conversion
Authors: Feng Xiaofeng 
Published: February 2020

Electrocatalysis plays a key role in the energy conversion processes that are central to renewable energy technologies such as fuel cells and artificial photosynthesis. A rational design of catalyst relies on our understanding of structure-activity relationships and identification of catalytically active sites. So far, numerous efforts have been made to optimize nanostructured catalysts by tuning their size, composition, and shape, while new design principles are essential for electroreduction catalysis such as CO2 recycling using renewable electricity. Here we show that grain boundaries (GBs) in metal nanoparticles create new active sites for electroreduction catalysis. Through a careful design of metal nanoparticle catalysts with different GB densities, extensive TEM characterization, and electrochemical measurements, we found that the catalytic activity for CO2 reduction on Au and CO reduction on Cu is directly correlated with GB density in the catalysts [1, 2]. The quantitative GB-activity relationships indicate that GBs in metal nanoparticles create new active sites for electroreduction catalysis and lead to highly active and stable catalysts for a two-step electrochemical conversion of CO2 to liquid fuels such as ethanol and acetate. In addition, we found that GBs in Au enhance its activity for oxygen reduction reaction, which suggests that GB engineering is a general strategy for improving electrocatalytic activity for renewable energy conversion.

References:

(1) Feng, X.; Jiang, K.; Fan, S.; Kanan, M. W. J. Am. Chem. Soc.
2015, 137, 4606–4609.
(2) Feng, X.; Jiang, K.; Fan, S.; Kanan, M. W. ACS Cent. Sci.
2016, 2, 169−174.
Resistance Values of Aluminum Oxide Film in Situ during Anodization of Aluminum By Fabry-PéRot Interferometry
Authors: Habib Khaled 
Published: February 2020

A combination of Fabry-Pérot interferometry and the DC electrochemical method have been used for the first time, in situ, to measure the resistance of aluminium oxide films in 2% sulfuric acid solution. Values of the corresponding resistance of the obtained Al2O3 film thickness were determined during anodization of aluminium (Al) in 2% H2SO4. The obtained resistance values were verified by electrochemical impedance spectroscopy (EIS) and holographic interferometry. The corresponding resistance (2.4 x109 Ohms) to the final thickness of the aluminum oxide film was found in an agreement with the resistance value that was measured by holographic interferometry, 2.54x109 Ohms, in 2% H2SO4. On the contrary, the corresponding resistance (2.4 x109 Ohms) to the final thickness of the aluminum oxide film was found twice the value of the resistance that was measured by the electrochemical impedance spectroscopy (EIS), 1.25x109 Ohms, in 2% H2SO4.

Keywords
. Aluminium, Thickness of Oxide Film, Fabry-Pérot interferometry, Holographic Interferometry, Electrochemical Impedance Spectroscopy (EIS), Resistance, and Sulfuric Acid.