Superhydrophilicity of TiO2/SiO2 thin films: Synergistic effect of SiO2 and phase-separation-induced porous structure

Porous TiO2/SiO2 (TS) composite thin films with superhydrophilic performance were successfully prepared by a sol–gel process under template-free conditions. The appearance of interconnected or isolated pores for the films was discussed in relation to the phase separation in the sol–gel process with the presence of acetylacetone (AcAc) and diethanolamine (DEA). The surface topography, crystal morphology and surface chemical composition of TS films, resulting in the changes of surface wetting property, were significantly affected by the molar content of SiO2. When the SiO2 content was 20%, the as-prepared TS composite thin films exhibited the optimum superhydrophilicity with a water contact angle (WCA) 2.5° without UV irradiation, and the spreading time was less than 1 s. The natural superhydrophilicity was attributed to the synergistic effect of SiO2 and phase-separation-induced porous structure.