Effect of surface treatment on the photocatalytic activity and hydrophilicproperty 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 treate d in HCl solution. The TiO2 films before and after treatment were character ized by X-ray photoelectron spectroscopy, scanning electron microscopy, and W-visible spectrophotometer. The photocatalytic activity and hydrophilic p roperty of the various TiO2 films were evaluated by the photocatalytic deco lorization of aqueous methyl orange and examining the contact angle for wat er of TiO2 films, respectively. The concentration of sodium and calcium in nascent TiO2 films was effectively reduced and the adsorbed hydroxyl conten t on the surface of TiO2 films was found to increase by soaking the as-prep ared TiO2 films in HCl solution. The deleterious effect of sodium and calci um ions from the soda-lime glass on the photocatalytic activity of the nasc ent TiO2 films was prevented by surface acid treatment. At the same time, h ydrophilic property of the treated TiO2 films was enhanced. (C) 2001 Elsevi er Science Ltd. All rights reserved.