Synthesis and Characterization of Self―cleaning and Anti―reflective SiO2―TiO2 Nanometric Films

A series of bi―layer TiO2/SiO2 (ST) and SiO2/TiO2 (TS) films were fabricated respectively by changing the coating sequences and rates, via a Sol―Gel dip―coating method. The morphology, light transmittance, photocatalytic activitiy and hydrophilicity of t he obtained products were characterized by FESEM, spectrophotometer, photo―degradation of methyl orange (MO), etc. The experimental results show that SiO2 layer can enhance the light transmittances of ST and TS films due to its lower refractive index. As to the self―cleaning function, the photocatalytic activity and hydrophilicity of TS bi―layer film are both weakened while increasing the dip―coating speed of the overlayer SiO2 film, owing to that more TiO2 is covered by SiO2. However, it is the opposite for ST bi―layer film. When the dip―coating speed of the overlayer TiO2 film reaches 6mm/min, the obtained film exhibits the best photocatalytic activity and hydrophilicity even without UV illumination, which favors greatly the self―cleaning function of the films.