A mechanism for enhanced hydrophilicity of silver nanoparticles modified TiO2 thin films deposited by RF magnetron sputtering

Ag-TiO2 nanostructured thin films with silver volume fraction of 0-40.0% have been deposited on silicon and quartz substrates by RF magnetron sputtering. Their crystal texture, surface topography, and hydrophilicity have been characterized by X-ray diffractometer, transmission electron microscope, and water contact angle apparatus. The relation of hydrophilic property and silver content has been studied in detail. It is shown that silver content influences crystal texture of TiO2 thin films, and silver in the films is simple substance (Ag0). Hydrophilicity of the films increases with increasing silver content up to 5 vol% Ag and then decreases. A suitable amount (around 5.0 vol% Ag) of silver addition can significantly enhance the hydrophilic behavior of TiO2 films. The mechanism can be attributed to the increase of oxygen anion radicals O2- and reactive center of surface Ti3+, and the better separation between electrons and holes on the films surface.