Graphene Oxide alpha Bi2O3 Composites for Visible Light Photocatalysis, Chemical Catalysis and Solar Energy Conversion

The growing challenges of environmental purification by solar photocatalysis, precious metal free catalysis and photocurrent generation in photovoltaic cells are receiving the utmost global attention. Here we demonstrate the one pot green chemical synthesis of a new stable heterostructured, eco friendly, multifunctional micro composite consisting of amp; 945; Bi2O3 micro needles intercalated with anchored graphene oxide GO micro sheets 1.0 wt for the above mentioned applications in a large economical scale. The bare amp; 945; Bi2O3 micro needles display twice as better photocatalytic activities than commercial TiO2 Degussa P25 while the GO hybridized composite exhibit 4 6 times enhanced photocatalytic activities than neat TiO2 photocatalyst in the degradation of colored aromatic organic dyes crystal violet and rhodamine 6G under visible light irradiation 300 W tungsten lamp . The highly efficient activity is associated with the strong surface adsorption ability of GO for aromatic dye molecules, the high carrier acceptability and efficient electron hole pair separation in Bi2O3 by individual adjoining GO sheets. Introduction of Ag nanoparticles 2.0 wt further enhances the photocatalytic performance of the composite over 8 folds due to a plasmon induced electron transfer process from Ag nanoparticles via GO sheets into the conduction band of Bi2O3. The new composites are also catalytically active. They catalyze the reduction of 4 nitrophenol to 4 aminophenol in presence of borohydride ions. Photoanodes assembled from GO amp; 945; Bi2O3 and Ag GO amp; 945; Bi2O3 composites display an improved photocurrent response power conversion efficiency 20 higher over those prepared without GO in dye sensitized solar cells DSSCs

Phonon-phason coupling in icosahedral quasicrystals

From relaxation simulations of decoration-based quasicrystal structure models using microscopically based interatomic pair potentials, we have calculated the (usually neglected) phonon-phason coupling constant. Its sign is opposite for the two alloys studied, i-AlMn and i-(Al,Cu)Li; a dimensionless measure of its magnitude relative to the phonon and phason elastic constants is of order 1/10, suggesting its effects are small but detectable. We also give a criterion for when phonon-phason effects are noticeable in diffuse tails of Bragg peaks.Comment: 7 pages, LaTeX, uses Europhys Lett macros (included

Mass production of polymer nano wires filled with metal nano particles

Despite the ongoing progress in nanotechnology and its applications, the development of strategies for connecting nano scale systems to micro or macroscale elements is hampered by the lack of structural components that have both, nano and macroscale dimensions. The production of nano scale wires with macroscale length is one of the most interesting challenges here. There are a lot of strategies to fabricate long nanoscopic stripes made of metals, polymers or ceramics but none is suitable for mass production of ordered and dense arrangements of wires at large numbers. In this paper, we report on a technique for producing arrays of ordered, flexible and free standing polymer nano wires filled with different types of nano particles. The process utilizes the strong response of photosensitive polymer brushes to irradiation with UV interference patterns, resulting in a substantial mass redistribution of the polymer material along with local rupturing of polymer chains. The chains can wind up in wires of nano scale thickness and a length of up to several centimeters. When dispersing nano particles within the film, the final arrangement is similar to a core shell geometry with mainly nano particles found in the core region and the polymer forming a dielectric jacket

CO2 electroreduction activity and dynamic structural evolution of in situ reduced nickel indium mixed oxides

In the field of CO2 electroreduction CO2ER , tuning the selectivity among diverse products remains a major challenge. Mixed metal catalysts offer possible synergetic effects which can be exploited for tuning product selectivity. We present a simple wet chemical approach to synthesize a range of nickel indium mixed oxide NiAInBOx thin films with homogeneous metal distribution. CO2 electroreduction results indicate that the NiAInBOx mixed oxide thin films can achieve high CO selectivity gt;70 in contrast with the single metal oxides NiO H2 gt;90 and In2O3 formate gt;80 . The relative composition Ni40In60Ox attained the best CO selectivity of 71 at moderate cathodic bias of amp; 8722;0.8 VRHE, while a higher cathodic bias E lt; amp; 8722;0.9 V promoted a decrease of CO in favor of formate. A detailed investigation of the Ni40In60Ox thin films following progressive stages of reduction during CO2ER revealed dynamic structural transformations strongly dependent on applied bias and electrolysis time. For the CO selective catalyst composition, at moderate cathodic bias E lt; amp; 8722;0.8 V and short electrolysis times 1 h , the catalyst is composed of nickel indium alloy grains embedded in amorphous Ni In mixed oxide as observed by electron microscopy. Extending electrolysis time at amp; 8722;0.8 V for 10 h, or increasing the applied reductive bias to amp; 8722;1.0 V, result in a complete reduction of the residual oxide film into an interconnected array of multicomponent In, Ni, Ni3In7 nanoparticles which display significantly lower CO selectivity lt;50 . Our results indicate that the persistent amorphous NiInOx oxide alloy composite material preserved in the early stages of reduction at amp; 8722;0.8 V plays a key role in CO selectivity. The highly dynamic structure observed in this catalytic system demonstrates the importance of conducting detailed structural characterization at various applied potentials to understand the impact of structural changes on the observed CO2ER selectivity trends; and thus be able to distinguish structural effects from mechanistic effects triggered by increasing the reductive bia

Determining Structure Activity Relationships in Oxide Derived Cu Sn Catalysts During CO2 Electroreduction Using X Ray Spectroscopy

The development of earth abundant catalysts for selective electrochemical CO2 conversion is a central challenge. Cu amp; 63743;Sn bimetallic catalysts can yield selective CO2 reduction toward either CO or formate. This study presents oxide derived Cu amp; 63743;Sn catalysts tunable for either product and seeks to understand the synergetic effects between Cu and Sn causing these selectivity trends. The materials undergo significant transformations under CO2 reduction conditions, and their dynamic bulk and surface structures are revealed by correlating observations from multiple methods X ray absorption spectroscopy for in situ study, and quasi in situ X ray photoelectron spectroscopy for surface sensitivity. For both types of catalysts, Cu transforms to metallic Cu0 under reaction conditions. However, the Sn speciation and content differ significantly between the catalyst types the CO selective catalysts exhibit a surface Sn content of 13 at. predominantly present as oxidized Sn, while the formate selective catalysts display an Sn content of amp; 8776;70 at. consisting of both metallic Sn0 and Sn oxide species. Density functional theory simulations suggest that Sn amp; 948; sites weaken CO adsorption, thereby enhancing CO selectivity, while Sn0 sites hinder H adsorption and promote formate production. This study reveals the complex dependence of catalyst structure, composition, and speciation with electrochemical bias in bimetallic Cu catalyst

Autonomous reconstruction and segmentation of tomographic data

A Bayesian approach to reconstruction and segmentation of tomographic data is outlined and further detailed for the case of absorption tomography. The algorithm allows the quantification of reconstruction errors and segmentation confidence. Calculation results for various experimental settings number of projections, incident dose, different materials are shown and discusse