Xiaoke Tan

Central South University, Ch’ang-sha-shih, Hunan, China

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Publications (6)6.65 Total impact

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    ABSTRACT: Sm(3+)-doped TiO(2) nanocrystalline has been prepared by sol-gel auto-combustion technique and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, and also UV-vis diffuse reflectance spectroscopy (DRS). These Sm(3+)-doped TiO(2) samples were tested for methylene blue (MB) decomposition and *OH radical formation. The analysis of *OH radical formation on the sample surface under UV irradiation was performed by fluorescence technique with using terephthalic acid, which readily reacted with *OH radical to produce highly fluorescent product, 2-hydroxyterephthalic acid. It was observed that the presence of Sm(3+) ion as a dopant significantly enhanced the photocatalytic activity for MB degradation under UV light irradiation because both the larger specific surface area and the greater the formation rate of *OH radical were simultaneously obtained for Sm(3+)-doped TiO(2) nanocrystalline. The adsorption experimental demonstrated that Sm(3+)-TiO(2) had a higher MB adsorption capacity than undoped TiO(2) and the adsorption capacity of MB increased with the increase of samarium ion content. The results also indicated that the greater the formation rate of *OH radical was, the higher photocatalytic activity was achieved. In this study, the optimum amount of Sm(3+) doping was 0.5 mol%, at which the recombination of photo-induced electrons and holes could be effectively inhibited, the highest formation rate of *OH radicals was, and thereby the highest photocatalytic activity was achieved.
    Journal of Hazardous Materials 02/2008; 150(1):62-7. · 3.93 Impact Factor
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    ABSTRACT: Bi2WO6 powders are synthesized through hydrothermal process and Co3O4/Bi2WO6 composites with p–n heterojunction structure are prepared by the impregnation method. Co3O4/Bi2WO6 composites are characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), UV–Vis absorption spectrum, and photoluminescence spectrum. After Co3O4 is loaded, the ability of visible light absorption of Co3O4/Bi2WO6 composite is enhanced greatly. The PL intensity of Co3O4/Bi2WO6 composite is lower than that of pure Bi2WO6, which clearly indicates that the recombination of photogenerated charge carrier between the hybrid orbital of Bi6s and O2p (VB) to the empty W5d orbital is inhibited greatly in the composite semiconductors. The presence of Co3O4 leads to an increase in photocatalytic activity. The highest efficiency is observed when calcined at 300°C with 0.2wt% cobalt content. On the basis of the calculated energy band positions and PL spectra, the mechanism of enhanced photocatalytic activity has been discussed. In addition, the effects of H2O2 concentration and pH value on photocatalytic activity were also presented.
    Catalysis Communications - CATAL COMMUN. 01/2008; 9(6):1247-1253.
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    ABSTRACT: ZnO nanosheets have been successfully synthesized by a sonochemical method under ambient air without any template. The prepared ZnO particles were characterized by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that both high pH value and zinc salt counter-ion played critical roles for the formation of ZnO nanosheets. A plausible formation mechanism of ZnO nanosheets was discussed in detail.
    Journal of Alloys and Compounds 01/2008; 459(1). · 2.73 Impact Factor
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    ABSTRACT: Carbon-doped TiO2 nanoparticles were prepared by sol–gel auto-combustion method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Brunauer–Emmett–Teller method (BET), UV–vis diffuses reflectance spectroscopy (DRS). UV–vis diffuse reflectance spectra showed that carbon-doped TiO2 exhibited obvious absorption in the visible light range. The visible light photocatalytic activity of carbon-doped TiO2 was ascribed to the presence of oxygen vacancy state between the valence and the conduction bands because of the formation of Ti3+ species in the as-synthesized carbon-doped TiO2. The sample calcined at 873K showed the highest photocatalytic activity under solar irradiation. The effects of photocatalyst concentration, initial concentration of methylene blue, and pH value in aqueous solution were also presented.
    Solar Energy - SOLAR ENERG. 01/2008; 82(8):706-713.
  • Qi Xiao, Xiaoke Tan, Lingling Ji, Jing Xue
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    ABSTRACT: Polyaniline/nano-Fe3O4 composites were prepared by a novel solids-stabilized emulsion (Pickering emulsion) route for the first time. The products were characterized by SEM, XRD, FTIR spectra and particle size analyzer. Sphere-like morphology and sub-micrometer fibers of polyaniline/nano-Fe3O4 composites were synthesized in a toluene/water emulsion stabilized by Fe3O4 nanoparticles. It was found that the morphology of the resulting PANI/nano-Fe3O4 composites depended not only on the volume ratio of toluene to water (R), but also the amount of Fe3O4 in the reaction system. A possible mechanism for the formation of the different morphologic composites has been proposed. The room-temperature conductivity of PANI/nano-Fe3O4 composites also depended not only on the volume ratio of toluene to water (R), but also the amount of Fe3O4 in the reaction system. In addition, it was found that the magnetization under applied magnetic field for the as prepared the PANI/nano-Fe3O4 composites exhibited a clear hysteretic behavior, and both MS and HC for the PANI/nano-Fe3O4 composites exhibited a decrease with decreasing the nano-Fe3O4 content.
    Synthetic Metals - SYNTHET METAL. 01/2007; 157(18):784-791.
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    ABSTRACT: Co-doped ZnO photocatalysts were prepared by hydrothermal method. The obtained Co-doped ZnO powders were characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy and photoluminescence (PL) spectra. The prepared Co-doped ZnO photocatalysts showed high photocatalytic activities for methylene blue decolorization at pH 10.5 under visible light irradiation. It was found that there were certain relationships between PL spectra and photocatalytic activity, namely, the stronger the PL intensity, the larger the content of oxygen vacancies and defects, the higher the photocatalytic activity. Therefore, in this study 3.0 mol% was the most suitable content of Co2+ in ZnO, at which the recombination of photoinduced electrons and holes could be effectively inhibited and thereby the highest photocatalytic activity was formed.
    Materials Science and Engineering: B. 01/2007; 142:121-125.