Preparation of Sn-doped TiO2 composite thin films by sol-gel processing and their photocatalytic properties

The uniform, transparent anatase Sn-doped TiO2 composite thin films deposited on glass substrates were prepared by sol-gel processing. The films were composed of TiO2 sphere particles in size of 50-100 nm. The thickness of the films shows some orientation effect in (101) peak. XPS results show that besides Ti, O and Sn in films there are a certain amount of residual carbon from the starting organometallic components and a small amount of Na and Ca diffused from the glass substrates. Photocatalytic degradation of methyl orange aqueous solution indicates that the sol-gel derived Sn-doped TiO2 films show good photocatalytic activity, and its apparent degradation rate constant is larger than that of undoped TiO2 films. These results are explained on the basis of the principle of charge separation in a SnO2/TiO2 composite semiconductor system.