Synthesis and Characterization of Self-cleaning and Anti-reflective SiO_2-TiO_2 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 the 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.