Preparation and characterization of TiO2–SiO2 nano-composite thin films

TiO2 nanocrystalline particles dispersed in SiO2 have been prepared by the sol-gel method using titanium- and silicon-alkoxides as precursors. Nano-composite thin films were formed on the glass substrates by dip-coating technique and heat treated at temperatures up to 500 °C for 1 h. The size of the TiO2 nanocrystalline particles in the TiO2–SiO2 solution ranged from 5 to 8 nm. The crystalline structure of TiO2 powders was identified as the anatase phase. As the content of SiO2 increased, the anatase phase tended to be stabilized to higher temperature. TEM results revealed the presence of spherical TiO2 particles dispersed in a disk-shaped glassy matrix. Photocatalytic activity of the TiO2–SiO2 (1:1) thin films showed decomposition of ∼95% of methylene blue solution in 2 h and a contact angle of ∼10°. The photocatalytic decomposition of methylene blue increased and the contact angle decreased with the content of TiO2 phase. TiO2–SiO2 with the molar ratio of 1:1 showed a reasonable combination of adhesion, film strength, and the photocatalytic activity.