Effect of plasma treatment on chemical bonding states of porous TiO2 thin films prepared from polymer-blended solution

Dense TiO2 (D-TiO2) thin films and porous TiO2 (P-TiO2) thin films were prepared by using a polymer-blended solution. The film porosity decreased gradually or disappeared with an increase in the polyethylene glycol (PEG) or TiO2 content of the solution. To modify their surface properties, the thin films were treated with atmospheric pressure (AP) plasma by using a reactive gas. The surface morphologies of the O2-plasma-treated TiO2 (O-TiO2) thin films were smooth and did not change significantly. The decolorization efficiency of the P-TiO2 thin films was found to be enhanced when compared to that of the D-TiO2 thin films. The enhancement was due to an increase in the specific surface area and the number of hydroxyl groups, and a decrease of Ti2O3 states.