Influence of Annealing and UV Irradiation on Hydrophilicity of Ag-TiO2 Nanostructured Thin Films

Ag-TiO2 nanostructured thin films with silver content of 5 vol% have been deposited on silicon, glass, and quartz substrates by RF magnetron sputtering and annealed in ambient air at 900 degrees C for 15, 30, 60, 90, and 120 min. Their crystal structure, surface morphology, and hydrophilicity have been characterized by X-ray diffractometer, atomic force microscope, and water contact angle apparatus, respectively. The influence of annealing time and UV irradiation time on hydrophilic property of Ag-TiO2 thin films have been studied in detail. It is shown that annealing time influences crystal structure of Ag-TiO2 thin films. The unannealed film is amorphous and shows poor hydrophilicity. With the increase of annealing time from 15 to 120 min, the grain-size slowly increases and tends to uniformity. A suitable annealing time can significantly enhance the hydrophilic behavior of Ag-TiO2 films. Water contact angle decreases with the increase of irradiation time. The mechanism of hydrophilicity has been proposed and can be attributed to the increase of oxygen anion radicals O-2(-) and reactive center of surface Ti3+.