Ag/TiO 2 sol prepared by a sol–gel method and its photocatalytic activity

Abstract

Ag/TiO 2 sol with narrow particle size distribution was synthesized using TiCl 4 as the starting material. TiCl 4 was converted to Ti(OH) 4 gel. The Ag/TiO 2 sol was prepared by a process where H 2O 2 was added and then heated at 90–97 °C. After condensation reaction and crystallization, a transparent sol with suspended Ag/TiO 2 was formed. Ag/TiO 2 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/TiO 2 film were evaluated by degradation of methylene blue in aqueous solution under UV light irradiation. The suspended Ag/TiO 2 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 TiO 2 and the particle size was only 1–2 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/TiO 2 film showed a significant increase in photocatalytic activity compared to the TiO 2 film. The high amount of surface hydroxyls on Ag/TiO 2 film also played an important role in its photocatalytic activity.