Studies on a possible growth mechanism of silver nanoparticles loaded on TiO2 thin films by photoinduced deposition method

The TiO2 thin films loaded with silver nanoparticles were prepared on soda-lime glass substrates by a photoinduced deposition method. The TiO2 films immersed in AgNO3 solution were vertically irradiated by UV light with center wavelength of 365 nm for 60 h. The as-produced films were characterized by X-ray diffraction (XRD), UV–Vis spectroscopy, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The studies show that the film after UV excitation is composed of anatase phase TiO2 and metallic silver with face centered cubic structure. A possible growth mechanism of silver nanoparticles on TiO2 thin films under UV irradiation was proposed. The charge carriers of TiO2 semiconductor are generated by photoexcitation. Owing to the conduction band position of TiO2 which is above the standard potential of Ag+/Ag, the generated electrons could transfer from the conduction band to Ag+ adsorbed on the surface of the TiO2 films. Therefore, the Ag+ was finally reduced into a Ag atom, which could preferentially localize in the grain boundaries of TiO2 particles due to high surface free energy there. With the irradiation time extended, silver nanoparticles were shaped into certain morphologies on the surface of the TiO2 films.