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Jinlong Gong, Xinhe Bao
Surface and interfacial catalysis plays a vital role in chemical industries, electrochemistry and photochemical reactions. The challenges of modern chemistry are to optimize the chemical reaction processes and understand the detailed mechanism of chemical reactions. Since the early 1960s, the foundation of surface science systems has allowed the study of surface and interfacial phenomena on atomic/molecular level, and thus brought a number of significant developments to fundamental and technological processes, such as catalysis, material science and biochemistry, just to name a few...
March 27, 2017: Chemical Society Reviews
Eric M Hudak, Doe Kumsa, Heidi Martin, J Mortimer
<i>Objective.</i> Neural prostheses employing platinum electrodes are often constrained by a charge/charge-density parameter known as the Shannon limit. In examining the relationship between charge injection and observed tissue damage, the electrochemistry at the electrode-tissue interface should be considered. The charge-storage capacity (CSC) is often used as a predictor of how much charge an electrode can inject during stimulation, but calculating charge from a steady-state i-E curve (cyclic voltammogram) over the water window misrepresents how electrodes operate during stimulation...
March 27, 2017: Journal of Neural Engineering
Xiao Meng, Andrey V Gorbunov, W S Christian Roelofs, Stefan C J Meskers, René A J Janssen, Martijn Kemerink, Rint P Sijbesma
We explore a new approach to organic ferroelectric diodes using a benzene-tricarboxamide (BTA) core connected with C10 alkyl chains to pyrrole groups, which can be polymerized to provide a semiconducting ferroelectric material. The compound possesses a columnar hexagonal liquid crystalline (LC) phase and exhibits ferroelectric switching. At low switching frequencies, an additional process occurs, which leads to a high hysteretic charge density of up to ∼1000 mC/m(2). Based on its slow rate, the formation of gas bubbles, and the emergence of characteristic polypyrrole absorption bands in the UV-Vis-NIR, the additional process is identified as the oxidative polymerization of pyrrole groups, enabled by the presence of amide groups...
April 1, 2017: Journal of Polymer Science. Part B, Polymer Physics
Raphael Chattot, Tristan Asset, Jakub Drnec, Pierre Bordet, Jaysen Nelayah, Laetitia Dubau, Frédéric Maillard
Determining the formation and growth mechanism of bimetallic nanoparticles (NPs) with atomic detail is fundamental to synthesize efficient 'catalysts by design'. However, the understanding of the elementary steps, which take place during their synthesis remains elusive. Herein, we have exploited scanning transmission electron microscopy coupled to energy dispersive X-ray spectroscopy, operando wide angle and small angle X-ray scattering and electrochemistry to unveil the formation and growth mechanism of hollow PtNi/C NPs...
March 24, 2017: Nano Letters
Wesley T E van den Beld, Mathieu Odijk, René H J Vervuurt, Jan-Willem Weber, Ageeth A Bol, Albert van den Berg, Jan C T Eijkel
Electrochemistry on graphene is of particular interest due to graphene's high surface area, high electrical conductivity and low interfacial capacitance. Because the graphene Fermi level can be probed by its strong Raman signal, information on the graphene doping can be obtained which in turn can provide information on adsorbed atoms or molecules. For this paper, the adsorption analysis was successfully performed using three electroactive substances with different electrode interaction mechanisms: hexaammineruthenium(III) chloride (RuHex), ferrocenemethanol (FcMeOH) and potassium ferricyanide/potassium ferrocyanide (Fe(CN)6)...
March 24, 2017: Scientific Reports
Ren-Jei Chung, An-Ni Wang, Shiuan-Ying Peng
In this study, a biosensor, based on a glucose oxidase (GOx) immobilized, carbon-coated tin sulfide (SnS) assembled on a glass carbon electrode (GCE) was developed, and its direct electrochemistry was investigated. The carbon coated SnS (C-SnS) nanoparticle was prepared through a simple two-step process, using hydrothermal and chemical vapor deposition methods. The large reactive surface area and unique electrical potential of C-SnS could offer a favorable microenvironment for facilitating electron transfer between enzymes and the electrode surface...
February 15, 2017: Nanomaterials
Tamal Chatterjee, Brian Molnar, G G Theophall, Way-Zen Lee, K V Lakshmi, Mangalampalli Ravikanth
The Ru(II) and BF2 complexes of calixsmaragdyrin were prepared under simple reaction conditions and characterized by HR-MS, 1D and 2D NMR spectroscopy, optical spectroscopy, and electrochemistry, and the structure of the Ru(II) complex of calixsmaragdyrin was elucidated by X-ray crystallography. The crystal structure of the Ru(II) complex revealed that the Ru(II) ion is hexacoordinate with the three pyrrole nitrogen ligands from the tripyrrin unit of the calixsmaragdyrin macrocycle, and the remaining coordination sites of Ru(II) ion were occupied by two carbonyl groups and one hydroxyl (-OH) group...
March 23, 2017: Inorganic Chemistry
Olusola Oladele James, Waldemer Sauter, Uwe Schröder
In this study, we demonstrate the electrochemical conversion of xylose to δ-valerolactone via carbonyl intermediates. The conversion was achieved in aqueous media and at ambient conditions. This study also demonstrates that feedstocks for the use of electrochemistry for production of renewable chemicals and biofuels can be extended to primary carbohydrate molecules. This is the first report on a one-pot electrochemical deoxygenation of xylose to δ-valerolactone.
March 22, 2017: ChemSusChem
Ravishankar Sundararaman, William A Goddard, Tomas A Arias
First-principles calculations combining density-functional theory and continuum solvation models enable realistic theoretical modeling and design of electrochemical systems. When a reaction proceeds in such systems, the number of electrons in the portion of the system treated quantum mechanically changes continuously, with a balancing charge appearing in the continuum electrolyte. A grand-canonical ensemble of electrons at a chemical potential set by the electrode potential is therefore the ideal description of such systems that directly mimics the experimental condition...
March 21, 2017: Journal of Chemical Physics
Ellen P Neff
No abstract text is available yet for this article.
March 22, 2017: Lab Animal
Yazhi Liu, Gaoran Li, Jing Fu, Zhongwei Chen, Xinsheng Peng
Rational design of cathode hosts with high electrical conductivity and strong sulfur confinement is a great need for high-performance lithium-sulfur batteries. Herein, we report a self-standing, hybrid-nanostructured cathode host comprised of metal-organic framework (MOF)-derived porous carbon polyhedrons and carbon nanotubes (CNTs) for the significant improvement of both the electrode cyclability and energy density. The strong coupling of the intertwined CNTs and strung porous carbon polyhedrons as a binder-free thin film significantly enhances the long-range electronic conductivity and provides abundant active interfaces as well as robust electrode integrity for sulfur electrochemistry...
March 22, 2017: Angewandte Chemie
Maciej Smiechowski, Joanna Krakowiak, Piotr Bruździak, Janusz Stangret
Infrared (IR) spectroscopy is a widely used and invaluable tool in the studies of solvation phenomena in electrolyte solutions. Using state-of-the-art chemometric analysis of a spectral series measured in a concentration-dependent manner, the spectrum of the solute-affected solvent can be extracted, providing a detailed view of the structural and energetic states of the solvent molecules influenced by the solute. Concurrently, ab initio molecular dynamics (AIMD) simulations provide the solvation shell picture at an atomistic detail level and allow for a consistent decomposition of the theoretical IR spectrum in terms of distance-dependent contributions of the solvent molecules...
March 21, 2017: Physical Chemistry Chemical Physics: PCCP
Alan Francis Williams, Matteo Granelli, Alan M Downward, Robin Huber, Laure Guenée, Céline Besnard, Karl W Krämer, Silvio Decurtins, Shi-Xia Liu, Laurence K Thompson
The synthesis is reported of a series of homo- and hetero-dinuclear octahedral complexes of the ligand 1, 1,2-bis(1-methyl-benzimidazol-2-yl) ethanol, where the two metal centres are linked by hydrogen bonds between coordinated alcohols and coordinated alkoxides. Homonuclear divalent M(II)M(II), mixed valent M(II)M(III) and heteronuclear M(II)M'(III) species are prepared. The complexes have been characterised by X-ray crystallography and show unusually short O…O distances for the hydrogen bonds. Magnetic measurements show the hydrogen bond bridges can lead to ferromagnetic or antiferromagnetic coupling...
March 20, 2017: Chemistry: a European Journal
Menglu Chen, Philippe Guyot-Sionnest
The absolute positions of the energy levels of colloidal quantum dots of Hg(S, Se, Te), which are of interest as mid-infrared materials, are determined by electrochemistry. The bulk valence bands are at -5.85, -5.50, and -4.77 eV (±0.05 eV) for zinc-blend HgS, HgSe, HgTe, respectively, in the same order as the anions p-orbital energies. The conduction bands are conversely at -5.20, -5.50, and -4.77 eV. The stable ambient n-doping of Hg(S, Se) quantum dots compared to HgTe arises because the conduction band is sufficiently lower than the measured environment Fermi level of ∼ -4...
March 21, 2017: ACS Nano
Laurent Bouffier, Neso Sojic, Alexander Kuhn
A bipolar electrode is quite unconventional as it behaves simultaneously as an anode and a cathode in contrast to a classic electrochemical setup where the electron-transfer reactions are promoted on two different electrodes. The driving force is the polarization potential established between the solution and the bipolar electrode which allows a wireless electrochemical addressing. In the past decade or so, bipolar electrochemistry (BPE) has encountered a remarkable renewal of interest with extraordinary potentialities ranging from materials science to analytical chemistry...
March 17, 2017: Electrophoresis
Xiang Li, Long Luo, Richard M Crooks
We describe the design and characteristics of a paper-based analytical device for analyte concentration enrichment. The device, called a hybrid paper-based analytical device (hyPAD), uses faradaic electrochemistry to create an ion depletion zone (IDZ), and hence a local electric field, within a nitrocellulose flow channel. Charged analytes are concentrated near the IDZ when their electrophoretic and electroosmotic velocities balance. This process is called faradaic ion concentration polarization. The hyPAD is simple to construct and uses only low-cost materials...
March 17, 2017: Analytical Chemistry
Courtney E Wise, Thomas M Makris
The β-hydroxylation of l-histidine is the first step in the biosynthesis of the imidazolone base of the antifungal drug nikkomycin. The cytochrome P450 (NikQ) hydroxylates the amino acid while it is appended via a phosphopantetheine linker to the non-ribosomal peptide synthetase (NRPS) NikP1. The latter enzyme is comprised of an MbtH and single adenylation and thiolation domains, a minimal composition that allows for detailed binding and kinetics studies using an intact and homogeneous NRPS substrate. Electron paramagnetic resonance studies confirm that a stable complex is formed with NikQ and NikP1 when the amino acid is tethered...
March 28, 2017: ACS Chemical Biology
Yujin Tong, François Lapointe, Martin Thämer, Martin Wolf, R Kramer Campen
Quantitative description of reaction mechanisms in aqueous phase electrochemistry requires experimental characterization of local water structure at the electrode/aqueous interface and its evolution with changing potential. Gaining such insight experimentally under electrochemical conditions is a formidable task. The potential-dependent structure of a subpopulation of interfacial water with one OH group pointing towards a gold working electrode is characterized using interface specific vibrational spectroscopy in a thin film electrochemical cell...
March 16, 2017: Angewandte Chemie
Jiefu Yin, Alexander B Brady, Esther S Takeuchi, Amy C Marschilok, Kenneth J Takeuchi
MgMn2O4 nanoparticles with crystallite sizes of 11 (MMO-1) and 31 nm (MMO-2) were synthesized and their magnesium-ion battery-relevant electrochemistry was investigated. MMO-1 delivered an initial capacity of 220 mA h g(-1) (678 mW h g(-1)). Electrolyte water content had a profound effect on cycle retention.
March 15, 2017: Chemical Communications: Chem Comm
David Ibañez, Aranzazu Heras, Alvaro Colina
Bipolar electrochemistry is receiving growing attention in the last years, not only because it is an important tool for studying electron transfer processes, but also because it is really fruitful in the development of new analytical sensors. Bipolar electrodes show promising applications as a direct analytical tool since oxidation and reduction reactions take place simultaneously on different parts of a single conductor. There are several electrochemical devices that provide information about electron transfer between two immiscible electrolyte solutions, but to the best of our knowledge, this is the first time that a bipolar device is able to record two spectroelectrochemical responses concomitantly at two different compartments...
March 24, 2017: Analytical Chemistry
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