Self-cleaning cotton fabrics via combination of photocatalytic TiO2 and superhydrophobic SiO2

Fluorine-free superhydrophobic cotton fabrics with photocatalytic self-cleaning property were prepared by the combination of photoactive TiO2 and superhydrophobic SiO2. Organically modified silica (ormosil) aerogel with a high surface area and high porosity was first prepared. TiO2 nanocrystals were then synthesized and simultaneously deposited onto preformed porous ormosil aerogel at low temperature (below 100 °C) to obtain TiO2-SiO2 composite particles. XRD measurements prove that the formed TiO2 is of anatase phase. SEM and TEM images disclose the highly porous structure of the TiO2-SiO2 composite particles and further confirm the existence of highly crystalline TiO2 within the SiO2 matrix. IR spectra indicate the presence of abundant methyl groups on the TiO2-SiO2 composite particle surface. BET measurements show a high surface area of 379.0 m2/g for the TiO2-SiO2 composite particles, which is advantageous to enhance the photocatalysis. The cotton fabrics coated with TiO2-SiO2 composite particles exhibit superhydrophobicity with a water contact angle of 160.5°. However, the superhydrophobic cotton fabrics can be easily wetted by oil dirt and become superhydrophilic. Herein, the TiO2-SiO2 composite particle coated cotton fabric, which was contaminated with oleic acid, can recover its superhydrophobicity after UV irradiation for 4 h.