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https://www.readbyqxmd.com/read/28230971/multifaceted-gold-palladium-bimetallic-nanorods-and-their-geometric-compositional-and-catalytic-tunabilities
#1
Lichao Sun, Qingfeng Zhang, Guangfang Grace Li, Esteban Villarreal, Xiaoqi Fu, Hui Wang
Kinetically controlled, seed-mediated coreduction provides a robust and versatile synthetic approach to multimetallic nanoparticles with precisely controlled geometries and compositions. Here we demonstrate that single-crystalline cylindrical Au nanorods selectively transform into a series of structurally distinct Au@Au-Pd alloy core-shell bimetallic nanorods with exotic multifaceted geometries enclosed by specific types of facets upon seed-mediated Au-Pd coreduction under diffusion controlled conditions. By adjusting several key synthetic parameters, such as the Pd/Au precursor ratio, the reducing agent concentration, the capping surfactant concentration, and foreign metal ion additives, we have been able to simultaneously fine-tailor the atomic-level surface structures and fine-tune the compositional stoichiometries of the multifaceted Au-Pd bimetallic nanorods...
February 23, 2017: ACS Nano
https://www.readbyqxmd.com/read/28230105/interface-confined-hydrogen-evolution-reaction-in-zero-valent-metal-nanoparticles-intercalated-molybdenum-disulfide
#2
Zhongxin Chen, Kai Leng, Xiaoxu Zhao, Souradip Malkhandi, Wei Tang, Bingbing Tian, Lei Dong, Lirong Zheng, Ming Lin, Boon Siang Yeo, Kian Ping Loh
Interface confined reactions, which can modulate the bonding of reactants with catalytic centres and influence the rate of the mass transport from bulk solution, have emerged as a viable strategy for achieving highly stable and selective catalysis. Here we demonstrate that 1T'-enriched lithiated molybdenum disulfide is a highly powerful reducing agent, which can be exploited for the in-situ reduction of metal ions within the inner planes of lithiated molybdenum disulfide to form a zero valent metal-intercalated molybdenum disulfide...
February 23, 2017: Nature Communications
https://www.readbyqxmd.com/read/28229154/reactions-of-water-and-c1-molecules-on-carbide-and-metal-modified-carbide-surfaces
#3
REVIEW
Weiming Wan, Brian M Tackett, Jingguang G Chen
The formation of carbides can significantly modify the physical and chemical properties of the parent metals. In the current review, we summarize the general trends in the reactions of water and C1 molecules over transition metal carbide (TMC) and metal-modified TMC surfaces and thin films. Although the primary focus of the current review is on the theoretical and experimental studies of reactions of C1 molecules (CO, CO2, CH3OH, etc.), the reactions of water will also be reviewed because water plays an important role in many of the C1 transformation reactions...
February 23, 2017: Chemical Society Reviews
https://www.readbyqxmd.com/read/28229149/recent-advances-in-organocatalytic-enantioselective-transfer-hydrogenation
#4
REVIEW
Ana Maria Faísca Phillips, Armando J L Pombeiro
The organocatalytic reduction of C[double bond, length as m-dash]C and C[double bond, length as m-dash]N double bonds with biomimetic reductants, e.g. Hantzsch 1,4-dihydropyridine esters and benzothiazolines, is reviewed. Very high yields and stereoselectivities have been achieved with a variety of catalysts, including chiral amines, thioureas and phosphoric acids, even with loadings equivalent to those of transition metal-catalyzed reactions in some cases. Reductive amination reactions and the dearomatization of heteroaromatic substrates are the subject of more than one half of the contributions...
February 23, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28229143/metal-free-nitroxyl-radical-mediated-%C3%AE-c-sp-3-h-amination-of-saturated-ketones-with-heteroaryl-halides-multiple-roles-of-tempo
#5
Ping Qian, Yu Deng, Haibo Mei, Jianlin Han, Yi Pan
The first metal-free nitroxyl-radical-mediated β-amination of saturated ketones by using heteroaryl halides as amide precursors has been developed. This reaction proceeds through a cascade α-aminoxylation/Cope-like elimination/aza-Michael addition sequence to afford β-amino ketone derivatives with excellent yields. TEMPO plays multiple roles in the current β-amination process, including those of an oxidant, an α-aminoxylation reagent, a β-hydrogen acceptor, an in situ base, and an oxygen source.
February 23, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28226278/quantitative-methylene-blue-decolourisation-assays-as-rapid-screening-tools-for-assessing-the-efficiency-of-catalytic-reactions
#6
Jan Kruid, Ronen Fogel, Janice Leigh Limson
Identifying the most efficient oxidation process to achieve maximum removal of a target pollutant compound forms the subject of much research. There exists a need to develop rapid screening tools to support research in this area. In this work we report on the development of a quantitative assay as a means for identifying catalysts capable of decolourising methylene blue through the generation of oxidising species from hydrogen peroxide. Here, a previously described methylene blue test strip method was repurposed as a quantitative, aqueous-based spectrophotometric assay...
February 12, 2017: Chemosphere
https://www.readbyqxmd.com/read/28225586/multicolor-electrochromic-devices-based-on-molecular-plasmonics
#7
Grant J Stec, Adam Lauchner, Yao Cui, Peter Nordlander, Naomi J Halas
Polycyclic aromatic hydrocarbon (PAH) molecules, the hydrogen-terminated, subnanometer scale version of graphene, support plasmon resonances with the addition or removal of a single electron. Typically colorless when neutral, they are transformed into vivid optical absorbers in either their positively or negatively charged states. Here we demonstrate a low-voltage, multistate electrochromic device based on PAH plasmon resonances that can be reversibly switched between nearly colorless (0 V), olive (+4 V), and royal blue (-3...
February 22, 2017: ACS Nano
https://www.readbyqxmd.com/read/28225131/modification-of-n-doped-tio2-photocatalysts-using-noble-metals-pt-pd-a-combined-xps-and-dft-study
#8
K Batalović, N Bundaleski, J Radaković, N Abazović, M Mitrić, R A Silva, M Savić, J Belošević-Čavor, Z Rakočević, C M Rangel
Nitrogen-doped TiO2 (N-TiO2) is considered as one of the most promising materials for various photocatalytic applications, while noble metals Pd and Pt are known as good catalysts for hydrogen evolution. This work focuses on the determination of structural and electronic modifications of N-TiO2, achieved by noble metal deposition at the surface, as a starting indicator for potential applications. We focus on the properties of easily synthesized nanocrystalline nitrogen-doped anatase TiO2, modified by depositing small amounts of Pd (0...
February 22, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28225121/the-local-electronic-properties-of-individual-pt-atoms-adsorbed-on-tio2-110-studied-by-kelvin-probe-force-microscopy-and-first-principles-simulations
#9
Ayhan Yurtsever, Delia Fernández-Torre, Jo Onoda, Masayuki Abe, Seizo Morita, Yoshiaki Sugimoto, Rubén Pérez
Noble metal nanostructures dispersed on metal oxide surfaces have applications in diverse areas such as catalysis, chemical sensing, and energy harvesting. Their reactivity, chemical selectivity, stability, and light absorption properties are controlled by the interactions at the metal/oxide interface. Single-atom metal adsorbates on the rutile TiO2(110)-(1 × 1) surface have become a paradigmatic model to characterize those interactions and to understand the unique electronic properties of these supported nanostructures...
February 22, 2017: Nanoscale
https://www.readbyqxmd.com/read/28225110/tuning-the-hydrogen-evolution-activity-of-%C3%AE-mo2c-nanoparticles-via-control-of-their-growth-conditions
#10
Timothy T Yang, Wissam A Saidi
The use of water electrocatalysis for hydrogen production is a promising, sustainable and greenhouse-gas-free process to develop disruptive renewable energy technologies. Transition metal carbides, in particular β-phase Mo2C, are garnering increased attention as hydrogen evolution reaction (HER) catalysts due to their favourable synthesis conditions, stability and high catalytic efficiency. We use a thermodynamic approach in conjunction with density functional theory and a kinetic model of exchange current density to systematically study the HER activity of β-Mo2C under different experimental conditions...
February 22, 2017: Nanoscale
https://www.readbyqxmd.com/read/28223966/geological-and-geochemical-controls-on-subsurface-microbial-life-in-the-samail-ophiolite-oman
#11
Kaitlin R Rempfert, Hannah M Miller, Nicolas Bompard, Daniel Nothaft, Juerg M Matter, Peter Kelemen, Noah Fierer, Alexis S Templeton
Microbial abundance and diversity in deep subsurface environments is dependent upon the availability of energy and carbon. However, supplies of oxidants and reductants capable of sustaining life within mafic and ultramafic continental aquifers undergoing low-temperature water-rock reaction are relatively unknown. We conducted an extensive analysis of the geochemistry and microbial communities recovered from fluids sampled from boreholes hosted in peridotite and gabbro in the Tayin block of the Samail Ophiolite in the Sultanate of Oman...
2017: Frontiers in Microbiology
https://www.readbyqxmd.com/read/28223704/material-witness-metallic-hydrogen-in-the-spotlight
#12
Philip Ball
No abstract text is available yet for this article.
February 22, 2017: Nature Materials
https://www.readbyqxmd.com/read/28223030/heterologous-expression-of-a-rice-metallothionein-isoform-osmti-1b-in-saccharomyces-cerevisiae-enhances-cadmium-hydrogen-peroxide-and-ethanol-tolerance
#13
Zahra Ansarypour, Azar Shahpiri
Metallothioneins are a superfamily of low-molecular-weight, cysteine (Cys)-rich proteins that are believed to play important roles in protection against metal toxicity and oxidative stress. The main purpose of this study was to investigate the effect of heterologous expression of a rice metallothionein isoform (OsMTI-1b) on the tolerance of Saccharomyces cerevisiae to Cd(2+), H2O2 and ethanol stress. The gene encoding OsMTI-1b was cloned into p426GPD as a yeast expression vector. The new construct was transformed to competent cells of S...
February 4, 2017: Brazilian Journal of Microbiology: [publication of the Brazilian Society for Microbiology]
https://www.readbyqxmd.com/read/28220917/ditopic-receptors-containing-urea-groups-for-solvent-extraction-of-cu-ii-salts
#14
Israel Carreira-Barral, Marta Mato-Iglesias, Andrés de Blas, Carlos Platas-Iglesias, Peter A Tasker, David Esteban-Gómez
The ditopic receptor L3 [1-(2-((7-(4-(tert-butyl)benzyl)-1,4,7,10-tetraazacyclododecan-1-yl)methyl)phenyl)-3-(3-nitrophenyl)urea] containing a macrocyclic cyclen unit for Cu(ii)-coordination and a urea moiety for anion binding was designed for recognition of metal salts. The X-ray structure of [CuL3(SO4)] shows that the sulfate anion is involved in cooperative binding via coordination to the metal ion and hydrogen-bonding to the urea unit. This behaviour is similar to that observed for the related receptor L1 [1-(2-((bis(pyridin-2-ylmethyl)amino)methyl)phenyl)-3-(3-nitrophenyl)urea], which forms a dimeric [CuL1(μ-SO4)]2 structure in the solid state...
February 21, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28220172/mechanistic-insights-into-biomimetic-carbonic-anhydrase-action-catalyzed-by-doped-carbon-nanotubes-and-graphene
#15
Manju Verma, Parag A Deshpande
Electronic structural analyses of hydrogen terminated metal doped carbon nanotube/graphene (M-CNT/Gr, MN3-CNT/Gr, M = Ru/Rh) and ruthenium cluster decorated carbon nanotube/graphene (Ru4-CNT/Gr) were carried out for examining the biomimetic catalytic activity towards CO2 hydration reaction. The carbonic anhydrase action was followed for the reaction of CO2 with H2O resulting in a bicarbonate ion and a proton. All the catalysts were found to be active for CO2 hydration and the mechanism proved them to be biomimetic...
February 21, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28220171/towards-highly-active-pd-ceo2-for-alkene-hydrogenation-by-tuning-pd-dispersion-and-surface-properties-of-the-catalysts
#16
Sai Zhang, Jing Li, Zhaoming Xia, Chao Wu, Zhiyun Zhang, Yuanyuan Ma, Yongquan Qu
Extensive applications of noble metals as heterogeneous catalysts are limited by their global reserve scarcity and exorbitant price. Identifying the intrinsic active nature of a catalyst benefits the designing of catalysts with trace amounts of noble metals; these catalysts display better or comparable overall catalytic efficiency than their heavily loaded counterparts. Herein, systematic studies on Pd dispersion and surface properties of a series of Pd/CeO2 catalysts for styrene hydrogenation showed that high Pd dispersion and surface abundant defects of the catalysts are essential to realize superior activity...
February 21, 2017: Nanoscale
https://www.readbyqxmd.com/read/28220164/an-efficient-noble-metal-free-supported-copper-catalyst-for-selective-nitrocyclohexane-hydrogenation-to-cyclohexanone-oxime
#17
Qian-Qian Zhang, Jing Dong, Yong-Mei Liu, Yong Cao, He-Yong He, Yang-Dong Wang
It was shown for the first time that cyclohexanone oxime (CHO) can be selectively produced by heterogeneous copper-catalyzed hydrogenative transformation of nitrocyclohexane (NC). The combination of Cu(0) and Cu(+) and their cooperative interaction with weakly acidic SiO2 supports elicited a significantly unique and selective catalysis in the hydrogenation of NC to CHO.
February 21, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28218822/single-molecular-junction-study-on-h2o-c60-h2o-is-electrostatically-isolated
#18
Satoshi Kaneko, Yoshifumi Hashikawa, Shintaro Fujii, Yasujiro Murata, Manabu Kiguchi
A water molecule exhibits characteristic properties on the basis of hydrogen-bondings. In the past decade, a single water molecule placed in the non-hydrogen-bonding environment has attracted growing attention. To reveal fundamental properties of a single water molecule, endohedral fullerene H2O@C60 becomes an ideal and suitable model. We examined the electronic properties of H2O@C60 by applying the single-molecule measurement. The conductance of a single molecular junction based on H2O@C60 was found to be comparable with that of empty C60...
February 20, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28218800/hydrogen-atom-transfer-hat-initiated-by-intramolecular-ligand-metal-electron-transfer
#19
Hendrik Herrmann, Elisabeth Kaifer, Hans-Jörg Himmel
Hydrogen-atom transfer (HAT) is of key importance for several catalytic and biological processes, and provides an elegant access to C-H activation. In synthetic chemistry, a photoactivated metal complex is often employed to abstract an oxygen- or nitrogen-bound hydrogen, and the as generated oxygen- or nitrogen-centered radical is the hydrogen atom acceptor for HAT. Herein we report the first examples for HAT processes initiated by one-electron oxidation of urea azines. A further novelty is that the HAT-initiating oxidation can be realized by intramolecular ligand-metal electron transfer in copper(II)-urea azine complexes...
February 20, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28218318/metal-borohydrides-and-derivatives-synthesis-structure-and-properties
#20
REVIEW
Mark Paskevicius, Lars H Jepsen, Pascal Schouwink, Radovan Černý, Dorthe B Ravnsbæk, Yaroslav Filinchuk, Martin Dornheim, Flemming Besenbacher, Torben R Jensen
A wide variety of metal borohydrides, MBH4, have been discovered and characterized during the past decade, revealing an extremely rich chemistry including fascinating structural flexibility and a wide range of compositions and physical properties. Metal borohydrides receive increasing interest within the energy storage field due to their extremely high hydrogen density and possible uses in batteries as solid state ion conductors. Recently, new types of physical properties have been explored in lanthanide-bearing borohydrides related to solid state phosphors and magnetic refrigeration...
February 20, 2017: Chemical Society Reviews
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