The Experts below are selected from a list of 282003 Experts worldwide ranked by ideXlab platform
Janet Mary Fisher - One of the best experts on this subject based on the ideXlab platform.
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investigation of hydrothermal routes to mixed Metal cerium titanium oxides and Metal Oxidation state assignment using xanes
Inorganic Chemistry, 2004Co-Authors: Christopher S Wright, Richard I Walton, David Thompsett, Janet Mary FisherAbstract:The reaction between TiF3 or TiO2 and Ce3+ in sodium hydroxide solutions yields highly crystalline NaCeTi2O6 at room temperature and under mild hydrothermal conditions (T ≤ 240 °C). There is no evidence for the formation of ternary Ce−Ti−O materials by this method, and the use of bases other than NaOH always produces poorly crystalline materials. The material NaCeTi2O6 has a distorted perovskite structure with sodium and cerium ions randomly occupying the A sites: Pnma, a = 5.4517(8) A, b = 7.7292(6) A, c =5.4573(3) A. XANES spectroscopy at the Ti K edge and Ce LIII edge, with reference to crystalline model compounds, reveals that cerium is found solely as Ce(III) and titanium as Ti(IV) in NaCeTi2O6. Isomorphous substitution of Ce3+ by Nd3+ or Ti4+ by V4+ is found to be very facile under hydrothermal conditions (at a temperature of 240 °C), by addition of appropriate amounts of Metal salts to the hydrothermal reaction mixtures. The series NaCe1-xNdxTi2O6 (0 ≤ x ≤ 1) and NaCeTi2-xVxO6 (0 ≤ x ≤ 1.8) can be...
Gregory N. Parsons - One of the best experts on this subject based on the ideXlab platform.
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yttrium silicate formation on silicon effect of silicon preOxidation and nitridation on interface reaction kinetics
Applied Physics Letters, 2000Co-Authors: James J Chambers, Gregory N. ParsonsAbstract:The effects of oxygen and nitrogen pretreatments on interface reaction kinetics during yttrium silicate formation on silicon are described. X-ray photoelectron spectroscopy (XPS) and medium energy ion scattering (MEIS) are used to determine chemical bonding and composition of films formed by Oxidation of yttrium deposited on silicon. Capacitance–voltage testing is used to determine the quality of the dielectric and the electrical thickness. The effect of ultrathin silicon oxide, nitrided oxide, and nitrided silicon interfaces on Metal Oxidation kinetics is also described. When yttrium is deposited on clean silicon and oxidized, XPS and MEIS indicate significant mixing of the Metal and the silicon, resulting in a film with Y–O–Si bonding and composition close to yttrium orthosilicate (Y2O3⋅SiO2). A thin (∼10 A) in situ preOxidation step is not sufficient to impede the Metal/silicon reaction, whereas a nitrided silicon interface significantly reduces the silicon consumption rate, and the resulting film is c...
Joann C Williams - One of the best experts on this subject based on the ideXlab platform.
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The evolutionary pathway from anoxygenic to oxygenic photosynthesis examined by comparison of the properties of photosystem II and bacterial reaction centers
Photosynthesis Research, 2011Co-Authors: James P Allen, Joann C WilliamsAbstract:In photosynthetic organisms, such as purple bacteria, cyanobacteria, and plants, light is captured and converted into energy to create energy-rich compounds. The primary process of energy conversion involves the transfer of electrons from an excited donor molecule to a series of electron acceptors in pigment–protein complexes. Two of these complexes, the bacterial reaction center and photosystem II, are evolutionarily related and structurally similar. However, only photosystem II is capable of performing the unique reaction of water Oxidation. An understanding of the evolutionary process that lead to the development of oxygenic photosynthesis can be found by comparison of these two complexes. In this review, we summarize how insight is being gained by examination of the differences in critical functional properties of these complexes and by experimental efforts to alter pigment–protein interactions of the bacterial reaction center in order to enable it to perform reactions, such as amino acid and Metal Oxidation, observable in photosystem II.
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Comparison of bacterial reaction centers and photosystem II.
Photosynthesis research, 2008Co-Authors: László Kálmán, Joann C Williams, James P AllenAbstract:In photosynthetic organisms, the utilization of solar energy to drive electron and proton transfer reactions across membranes is performed by pigment-protein complexes including bacterial reaction centers (BRCs) and photosystem II. The well-characterized BRC has served as a structural and functional model for the evolutionarily-related photosystem II for many years. Even though these complexes transfer electrons and protons across cell membranes in analogous manners, they utilize different secondary electron donors. Photosystem II has the unique ability to abstract electrons from water, while BRCs use molecules with much lower potentials as electron donors. This article compares the two complexes and reviews the factors that give rise to the functional differences. Also discussed are the modifications that have been performed on BRCs so that they perform reactions, such as amino acid and Metal Oxidation, which occur in photosystem II.
Kilian Muñiz - One of the best experts on this subject based on the ideXlab platform.
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high Oxidation state palladium catalysis new reactivity for organic synthesis
Angewandte Chemie, 2009Co-Authors: Kilian MuñizAbstract:Recent years have seen the rapid development of a new field of palladium catalysis in organic synthesis. This chemistry takes place outside the usually encountered Pd 0 /Pd II cycles. It is characterized by the presence of strong oxidants, which prevent further palladium(II)-promoted reactions at a given point of the catalytic cycle by selective Metal Oxidation. The resulting higher-Oxidation-state palladium complexes have been used to develop a series of new synthetic transformations that cannnot be realized within conventional palladium catalysis. This type of catalysis by palladium in a higher Oxidation state is of significant synthetic potential.
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High‐Oxidation‐State Palladium Catalysis: New Reactivity for Organic Synthesis
Angewandte Chemie, 2009Co-Authors: Kilian MuñizAbstract:Recent years have seen the rapid development of a new field of palladium catalysis in organic synthesis. This chemistry takes place outside the usually encountered Pd 0 /Pd II cycles. It is characterized by the presence of strong oxidants, which prevent further palladium(II)-promoted reactions at a given point of the catalytic cycle by selective Metal Oxidation. The resulting higher-Oxidation-state palladium complexes have been used to develop a series of new synthetic transformations that cannnot be realized within conventional palladium catalysis. This type of catalysis by palladium in a higher Oxidation state is of significant synthetic potential.
Peter G Bruce - One of the best experts on this subject based on the ideXlab platform.
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charge compensation in 3d transition Metal oxide intercalation cathodes through the generation of localized electron holes on oxygen
Nature Chemistry, 2016Co-Authors: Matthew R Roberts, Niccolo Guerrini, David M Pickup, Kristina Edstrom, Alan V Chadwick, Laurent Duda, Peter G BruceAbstract:The energy that can be stored in lithium-ion batteries is typically limited by the redox chemistry of the transition Metals within the cathodes. Now it is shown that for Li1.2[Ni2+0.13Co3+0.13Mn4+0.54]O2, a 3d-transition-Metal oxide that breaks this limit, Li-ion extraction is charge compensated not just by transition-Metal Oxidation but also through the generation of localized electron-holes on oxygen.