Stable Au25(SR)18/TiO2 Composite Nanostructure with Enhanced Visible Light Photocatalytic Activity

We report the visible light photocatalytic properties of a composite material consisting of Au-25(SR)(18) nanoclusters (R:CH2CH2Ph) and TiO2 nanocrystals. The effects of Au-25(SR)(18) nanoclusters on the photocatalytic activity of TiO2 nanocrystals were evaluated in the reaction of photocatalytic degradation of methyl orange. The loading of Au-25(SR)(18) nanoclusters onto TiO2 results in strong visible light absorption by the composite and, more importantly, a 1.6 times increase in visible light photocatalytic activity. Furthermore, the Au-25(SR)(18)/TiO2 composite nanostructure exhibits high stability in recycling tests. The Au-25(SR)(18) nanolusters dispersed on the TiO2 surface can act as a small-band-gap semiconductor to absorb visible light, giving rise to electron-hole separation and producing singlet oxygen (O-1(2)). Both the generated hydroxyl radicals (HO center dot) and O-1(2) are rationalized to be responsible for the decomposition of the dye.