Photoinduced redox reaction coupled with limited electron mobility at metal oxide surface

Photoinduced oxidation of trimethyl acetate (TMA) was examined on an atomically flat surface of rutile TiO2. The macroscopic rate of reaction (the partial pressure of desorption products) was temporary modulated when a TMA-covered surface was UV-irradiated in oxygen gas. Scanning tunneling microscope imaging revealed spatially modulated distribution of TMA and OH on that surface. The limited surface mobility of electrons photoexcited and trapped at OH-associated Ti sites was proposed to cause the temporal and spatial modulations. The characteristic length of the spatial modulation, i.e., the lateral dimension of electron confinement, was a few lattice constants of the oxide.