The superhydrophilicity and photocatalytic property of Zn-doped TiO2 thin films

In this paper, Zn-doped TiO2 thin films were prepared by sol-gel method and spin coating technology. The chemical combination states of various elements in both reference TiO2 and Zn-doped TiO2 thin films was characterized by X-ray photoelectron spectroscopy. The results showed that Zn2+ occupied TiO2 lattice in the form of substitutional ions, and caused some lattice distortion. However, the grain size and morphology of the film do not have a great effect on doping, since the doping content is very low. In addition, the surface oxygen vacancies and the content of hydroxyl groups increase significantly caused by Zn-doping. We used the contact angle meter to characterize the surface wettability of the films, the results showed that the increase of hydroxyl groups on the films surface have effectively promoted the formation of superhydrophilic surface. The optical absorption spectra of the films were collected by UV-Vis spectrophotometer, which illustrated a phenomenon of blue-shift in absorption edge caused by Zn-doping. Finally, the photocatalytic activity of the films was measured by self-assembled test system, and the results indicated that Zn-doping could greatly improve the photocatalytic activity and 2.0at% Zn-doped TiO2 thin films had the best photocatalytic efficiency among these samples.