Ag/TiO₂ sol prepared by a solgel method and its photocatalytic activity

Ag/TiO₂ sol with narrow particle size distribution was synthesized using TiCl₄ as the starting material. TiCl₄ was converted to Ti(OH)₄ gel. The Ag/TiO₂ sol was prepared by a process where H₂O₂ was added and then heated at 9097 °C. After condensation reaction and crystallization, a transparent sol with suspended Ag/TiO₂ was formed. Ag/TiO₂ was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, contact angle analysis, and X-ray photoelectron spectroscopy. The photocatalytic properties of Ag/TiO₂ film were evaluated by degradation of methylene blue in aqueous solution under UV light irradiation. The suspended Ag/TiO₂ particles were rhombus primary particles with the major axis ca. 40 nm and the minor axis ca. 10 nm. Ag nanoparticles were well dispersed on TiO₂ and the particle size was only 12 nm. Ag could restrain the recombination of photo-generated electrons and holes effectively. Transparent thin films could be obtained through dip-coating glass substrate in the sol. The thin film had strong hydrophilicity after being illuminated by UV light. Ag/TiO₂ film showed a significant increase in photocatalytic activity compared to the TiO₂ film. The high amount of surface hydroxyls on Ag/TiO₂ film also played an important role in its photocatalytic activity.