Janus Nanostructures Based on Au−TiO2 Heterodimers and Their Photocatalytic Activity in the Oxidation of Methanol

Au−TiO2 snowman-like heterodimer nanoparticles were prepared by a surface sol−gel process based on gold Janus nanoparticles whose surface-protecting monolayers consisted of a hemisphere of hydrophobic 1-hexanethiolates and the other of hydrophilic 2-(2-mercaptoethoxy)ethanol. Transmission electron microscopic measurements showed that the resulting TiO2 nanoparticles (diameter 6 nm) exhibited well-defined lattice fringes that were consistent with the (101) diffraction planes of anatase TiO2. The heterodimer nanoparticles displayed apparent photoluminescence that was ascribed to electronic transitions involving trap states of TiO2 particles, and the photocatalytic activity was manifested by the oxidative conversion of methanol into formaldehyde, which was detected quantitatively by the Nash method. The enhanced photocatalytic performance, as compared to that of the TiO2 nanoparticles alone, was ascribed to the charge separation of photogenerated electrons and holes at the Au−TiO2 interface that was facilita...