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Self-assembled three-dimensional (3D) hierarchical umbilicate Bi 2 WO 6 microspheres from nanoplates have been synthesized by a new controllable hydrothermal route on a large scale. It was found that citrate played multifold roles in the formation process of Bi 2 WO 6 hierarchical microspheres in our reaction system. In order to obtain well-assembled Bi 2 WO 6 microspheres, NaHCO 3 was used to adjust pH values of the reaction solution and establish a buffer system by the equilibrium of the formation and dissociation of carbonic acid. On the basis of XRD analysis and TEM observation of the products at the different reaction time periods, the formation mechanism of Bi 2 WO 6 hierarchical microspheres was proposed. UV-vis diffuse reflectance spectra indicated that as-synthesized Bi 2 WO 6 hierarchical microspheres had absorption in both UV and visible light areas. The BET surface area of the sample was ca. 24.1 m 2 /g, which was 35 times higher than that of the Bi 2 WO 6 powder prepared by the solid-state reaction method. The hierarchical umbilicate Bi 2 WO 6 microspheres exhibited good photocatalytic activity in degradation of Rhodamine-B (RhB) under 150 W Xe lamp light irradiation. In addition, the wettability of Bi 2 WO 6 films fabricated by as-obtained Bi 2 WO 6 microspheres was also studied.

Due to its intrinsic structure and characteristics, small size and monodispersity, control of singlecrystalline Cu 2 O polyhedra in aqueous media is a challenge, which is important to overcome to achieve enhanced photocatalytic activity. Here, we use heterogeneous nucleation, rather than homogeneous nucleation, of Cu 2 O with gold nanorods as seeds to realize subsequent uniform crystal growth. We obtained nearly monodisperse octahedral Au@Cu 2 O nanocrystals with single-crystalline shells, which are distinct from the pentagonal column-shaped structures previously described. Due to the fact that one Au@Cu 2 O holds only one Au nanorod, two formulas were deduced for convenient size control of the Cu 2 O shell. The formulas were calculated by adjusting the amount of Au rods that are relatively quantified. The formula also allows the size of the final product to be predicted when a given amount of gold seeds are employed. The experimental results agree well with the calculated data. The result of larger surface area and improved charge separation from core-shell interaction, made five samples of different sizes exhibit excellent photocatalytic activity toward MO degradation. The synthetic strategy reported here provides a clue to monodispersity and size control of core-shell nanocrystals, which is useful in developing new catalysts with better performance that are urgently needed in the fields of both science and technology.

In this study, hollow olive-shaped BiVO(4) and n-p core-shell BiVO(4)@Bi(2)O(3) microspheres were synthesized by a novel sodium bis(2-ethylhexyl)sulfosuccinate (AOT)-assisted mixed solvothermal route and a thermal solution of NaOH etching process under hydrothermal conditions for the first time, respectively. The as-obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy, Brunauer-Emmett-Teller surface area, and UV-vis diffuse-reflectance spectroscopy in detail. The influence of AOT and solvent ratios on the final products was studied. On the basis of SEM observations and XRD analyses of the samples synthesized at different reaction stages, the formation mechanism of hollow olive-shaped BiVO(4) microspheres was proposed. The photocatalytic activities of hollow olive-shaped BiVO(4) and core-shell BiVO(4)@Bi(2)O(3) microspheres were evaluated on the degradation of rhodamine B under visible-light irradiation (λ > 400 nm). The results indicated that core-shell BiVO(4)@Bi(2)O(3) exhibited much higher photocatalytic activities than pure olive-shaped BiVO(4). The mechanism of enhanced photocatalytic activity of core-shell BiVO(4)@Bi(2)O(3) microspheres was discussed on the basis of the calculated energy band positions as well. The present study provides a new strategy to enhancing the photocatalytic activity of visible-light-responsive Bi-based photocatalysts by p-n heterojunction.