Superior Electron Transport and Photocatalytic Abilities of Metal-Nanoparticle-Loaded TiO2 Superstructures

Metal-semiconductor nanocomposites have been widely employed for designing efficient optoelectronic devices and catalysts. The performance of such nanocomposites is significantly influenced by both the method of preparation and the electronic and morphological structures of metals and semiconductors. Here, we have synthesized novel nanocomposites containing plate-like anatase TiO2 mesocrystal superstructures and noble metal (Au, Pt) nanoparticles. These metal nanoparticles were preferentially photodeposited on the edge of TiO2, mesocrystals. The electron transport and photocatalytic properties of the novel nanocomposites were subsequently studied. Single-molecule fluorescence spectroscopy measurements on a single particle directly revealed that most of the photogenerated electrons could migrate from the dominant surface to the edge of the TiO2 mesocrystal with the reduction reactions mainly occurring at its lateral surfaces containing {101} facets. The loading of metal nanoparticles on the superstructure of TiO2 was found to greatly improve the photogenerated charge separation efficiency allowing significant (more than 1 order of magnitude) enhancement of the photocatalytic reaction rate in organic degradation reactions. These outstanding features allowed significantly reduced consumption (ca. 10% of that of typical TiO2 nanocrystal samples) of the Au or Pt loading on the TiO2 mesocrystal while maintaining the same photocatalytic activity.