μ-XAFS of a single particle of a practical NiO(x)/Ce2Zr2O(y) catalyst

μ-XAFS analysis using an X-ray μ-beam (1000 nm (h) × 800 nm (v)) was successfully carried out on a single particle of a practical catalyst NiO(x)/Ce(2)Zr(2)O(y) (0 ≤x≤ 1, 7 ≤y≤ 8). The oxidation state and local coordination structure of the NiO(x)/Ce(2)Zr(2)O(y) particle were characterized by Ni K-edge μ-XANES and μ-EXAFS, which showed the catalytically active and inactive phases of a single catalyst particle.     

Adsorption properties and behavior of the platinum group metals onto a silica-based (Crea + TOA)/SiO2–P adsorbent from simulated high level liquid waste of PUREX reprocessing

To separate platinum group metals (PGMs) from high level liquid waste (HLLW), a novel silica-based (Crea + TOA)/SiO₂–P adsorbent was synthesized by impregnating Crea (N′,N′-di-n-hexyl-thiodiglycolamide) and TOA (trioctylamine) two extractants into the macroporous SiO₂–P support with a mean diameter of 60 μm. Adsorption properties and behavior of PGMs from simulated HLLW onto the novel silica-based (Crea + TOA)/SiO₂–P adsorbent were investigated by batch method. It was found that (Crea + TOA)/SiO₂–P adsorbent exhibited good adsorption selectivity for PGMs over the other tested fission product element in a wide HNO₃ concentration. This adsorbent showed strong affinity to Pd(II) but almost no adsorption for rare earth elements. Adsorption process of PGMs could be expressed by Langmuir monomolecular layer adsorption mode and be governed by the chemisorption process. In addition, the adsorption isotherms and thermodynamic parameters of tested elements were calculated by Langmuir equation, Freundlich equation and van’t Hoff equation, respectively.     

Visible-light-driven copper acetylacetonate decomposition by BiVO4

Visible-light irradiation to monoclinic scheelite BiVO(4) (m-BiVO(4)) in a solution of copper acetylacetonate (Cu(acac)(2)) has led to its decomposition and Cu recovery. The photonic efficiency at λ = 440 ± 15 nm reaches 3.4%, exceeding the value for the TiO(2)-photocatalyzed reaction at λ = 355 ± 23 nm (2.0%). The adsorption isotherm and the light intensity-dependence of the decomposition rate indicate high adsorptivity of m-BiVO(4) for Cu(acac)(2) or its sufficient supply to the surface reaction sites, which mainly contributes to the high photocatalytic activity. Electrochemical measurements using cyclic voltammetry suggest that the reaction proceeds via the oxidative degradation of the ligand followed by the reduction of the resulting Cu(2+) ions. Under aerobic conditions, the Cu(2+) ions mediate the electron transfer from the conduction band of m-BiVO(4) to O(2) to complete the catalytic cycle.     

Electron-transporting oligothiophenes containing dicyanomethylene-substituted cyclopenta[b]thiophene: chemical tuning for air stability in OFETs

We have synthesized new electron-transporting oligothiophenes containing dicyanomethylene-substituted cyclopenta[b]thiophene as an active material for the fabrication of solution-processable n-type organic field-effect transistors (OFETs). The influence of the number of dicyanomethylene groups as well as the position of hexyl groups was investigated in detail by performing photophysical and electrochemical measurements. Results revealed that the optical energy gaps and the lowest unoccupied molecular orbital (LUMO) energy levels can be controlled by changing the number of dicyanomethylene groups. In contrast, the position of hexyl groups has little influence on molecular electronic properties. X-ray diffraction and atomic force microscopy measurements revealed that spin-coated thin films of the new compounds had a crystalline structure. OFETs based on these compounds were evaluated in vacuum and air-exposed conditions, and the electron mobility of up to 0.016 cm(2) V(-1) s(-1) was achieved. Furthermore, we demonstrated that the air stability of the OFETs depends on the LUMO energy level of the compounds.     

Direct measurement of the binding energy and bohr radius of a single hydrogenic defect in a semiconductor quantum well

Low-temperature scanning tunneling spectroscopy under ultrahigh vacuum was used to study donor point defects located at the epitaxial surface of an In(0.53)Ga(0.47)As quantum well. The electronic local density of states was measured with nanoscale resolution in the vicinity of single defects. In this way, both the binding energy and the Bohr radius of the defects could be determined. The binding energy and the Bohr radius were found to be functions of the quantum well thickness, in quantitative agreement with variational calculations of hydrogenic impurity states.