Ag/TiO2 sol prepared by a sol–gel method and its photocatalytic activity Original Research Article

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 90–97 °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 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/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.