Chemical state

About: Chemical state is a research topic. Over the lifetime, 2378 publications have been published within this topic receiving 78183 citations.

Vanadium-Tin Oxide Nanoparticles with Gas-Sensing and Catalytic Activity

Abstract: Nanopowders of vanadium-tin oxides were prepared by a co-precipitation process and characterized for their bulk structures, chemical state, sensing capability, and surface reactivity The solid solutions (cassiterite) were evaluated as sensing elements in a carbon monoxide gas sensor and as catalysts for methanol oxidation in a fixed-bed reactor Sensing and catalytic properties were observed dependent upon doping concentration and oxidation state of vanadia species The sensor response was favored for lower vanadium loadings (V/Sn = 005−01), related to the reduced vanadium sites The catalytic activity for methanol conversion was favored for higher vanadium loadings (V/Sn = 015−02), related to the oxidized vanadium sites Results demonstrate that the V–O–Sn structure provides redox activity to facilitate oxygen activation for CO gas-sensing response and promote methanol partial oxidation to formaldehyde Mechanistic aspects that elucidate the redox pathways are discussed These oxide nanostructures are promising ceramic materials for use in sensing and catalysis fields involving electron transfer

Influence of the chemical state on the stopping of protons and He-ions in some oxides

Abstract: We present stopping cross section data of Al2O3 and SiO2 for hydrogen- and helium-ions in the energy range 2–1000 keV, measured in transmission and in backscattering geometry. To interpret the data, we discuss the high velocity and the low velocity limit of so-called chemical effects commonly defined as the difference in stopping of the compound and of a mixture of its constituents, as calculated by applying Bragg's rule. At high velocities, the projectiles are point charges and only changes in the target electron states contribute to the chemical effect. In addition, at low velocities the charge states of the projectiles and the screening by the target valence electrons may differ in the compound and in the mixture, due to different electron densities.

Synthesis of M-doped (M = Ag, Cu, In) Bi2Te3 nanoplates via a solvothermal method and cation exchange reaction

Abstract: Highly quality 2D Bi2Te3 nanoplates are obtained via solvothermal synthesis and cations with different chemical valences (Ag+/Cu2+/In3+) are doped into Bi2Te3 by a cation exchange reaction in ethanol solution at room temperature. By combining precise XRD, SEM, HRTEM and XPS characterization, the cations are shown to be doped into the lattice of Bi2Te3 bringing lattice defects and distortion, and cation-doping caused a change in chemical state but without obvious changes in the hexagonal morphology. This research provides a possible general strategy for obtaining cation-doped bismuth telluride.