Effect of surface treatment on the photocatalytic activity and hydrophilic property of the sol-gel derived TiO2 thin films

Transparent anatase TiO2 nanometer thin films were prepared via the sol-gel method on soda-lime glass, and then the as-prepared TiO2 films were treated in HCl solution. The TiO2 films before and after treatment were characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, and UV-visible spectrophotometer. The photocatalytic activity and hydrophilic property of the various TiO2 films were evaluated by the photocatalytic decolorization of aqueous methyl orange and examining the contact angle for water of TiO2 films, respectively. The concentration of sodium and calcium in nascent TiO2 films was effectively reduced and the adsorbed hydroxyl content on the surface of TiO2 films was found to increase by soaking the as-prepared TiO2 films in HCl solution. The deleterious effect of sodium and calcium ions from the soda-lime glass on the photocatalytic activity of the nascent TiO2 films was prevented by surface acid treatment. At the same time, hydrophilic property of the treated TiO2 films was enhanced.