Characteristics modification of TiO2 thin films by doping with silica and alumina for self-cleaning application

Self-cleaning hydrophilic and hydrophobic properties of TiO2-based thin films on glass substrates have been investigated in this study. The addition of SiO2 into TiO2 can increase the wettability of films and maintain the hydrophilic state for a long time even in the dark. The contact angle of water on deposited films containing 15% SiO2 is less than 2 degrees after 2 h of UV illumination. These TiO2-SiO2 films exhibit excellent antifogging characteristics. Meanwhile, TiO2-Al2O3 films possess high water repellent ability and the photo-induced self-cleaning can take place even in visible light. The TiO2 thin film containing 33% of Al2O3 shows a high hydrophobic state with a water contact angle of 73 degrees after being irradiated with sunlight for 2 h. A comparison of hydrophilic TiO2-SiO2 and hydrophobic TiO2-Al2O3 films demonstrates the ability to modify the TiO2 thin film properties for self-cleaning applications.