Superhydrophilic porous TiO2 film prepared by phase separation through two stabilizers

A novel method was developed to produce a TiO2 film with circular pores on its surface. The pores aroused from the precursor solution using both acetylacetone (AcAc) and diethanolamine (DEA) as stabilizers. 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 Acac and DEA. Macropore size, together with connectivity of pores and gel skeleton, can be controlled by selecting an appropriate composition for preparation at DEA amount or regulating a time scale of the sol-gel transition. Finally, wetting behavior of the resulting films was characterized by using contact angle measurements. The TiO2 films with interconnected or relatively isolated pores exhibit superhydrophilic characteristic, although it is not exposed to ultraviolet irradiation. Deducing from the Wenzel-Cassie regimes' transition criterion, the existence of Cassie impregnating wetting regime rather than Wenzel one upon these porosity-driven superhydrophilic surfaces can be obtained.

Research highlights▶ This manuscript presented the novel fabrication of porous TiO2 thin film with only two stabilizers without any templates. ▶ 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 Acac and DEA. ▶ The TiO2 films with interconnected or relatively isolated pores exhibit superhydrophilic characteristic. Deducing from the Wenzel-Cassie regimes' transition criterion, we can find out that the existence of Cassie impregnating wetting regime can be used to explain the decrease of water contact angles upon these porosity-driven superhydrophilic surfaces.