Abstract: Silver-modified TiO2 thin films were prepared by the photodeposition method, and their optical characteristics, distribution and size of silver clusters on the surface, and surface states were analyzed by diffuse reflectance ultraviolet-visible spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy, respectively. The photocatalytic activity of the films was tested using phenol degradation as the model reaction under the irradiation with ultraviolet light of different wavelengths in the presence or absence of oxygen. The results showed that when the Ag loading exceeded 0.015?0 mg/cm2, a remarkable blue shift of the absorption band of the Ag-TiO2 thin films was observed. In addition, the minor absorption peak around 346 nm appeared and shifted toward the long wavelength with increasing Ag loading. Silver particles photodeposited on the surface of the films were nonuniform and existed mainly as Ag0 with a little Ag2O. The content of O2 adsorbed on the surface of Ag-TiO2 was increased remarkably in contrast to that of the pure TiO2 thin films. The photocatalytic activity of the Ag-TiO2 thin films was greatly affected by their light absorption character. When irradiation by a low pressure mercury lamp in the presence of oxygen, the Ag-TiO2 thin films reached the maximum activity at a Ag loading of 0.052?3 mg/cm2, and the first-order rate constant was 1.16 times that of the TiO2 thin films. These results indicated that Ag+preferably deposited on silver clusters with a large n value, and the photocatalytic activity of the Ag-TiO2 thin films was mainly affected by their light absorption character, the size of silver clusters, and the adsorption ability of silver clusters to O2.

Key words: silver, titania, thin film, photodeposition, photocatalysis, phenol, degradation