Controlled Synthesis and Surface Hydrophilic Properties of Ti-Containing Mesoporous Silica Thin Films Using Various Structure-Directing Agents

Transparent Ti-containing mesoporous silica thin films (Ti-MSTFs) have been successfully prepared on quartz substrates by a sol–gel/spin-coating method using various structure-directing agents (SDAs) with different chain lengths. Characterizations of their porous structures and local environments of Ti-oxide moieties in the silica framework were performed by XRD, XAFS, and FT-IR measurements, which revealed that all Ti-MSTFs had mesoporous structures and tetrahedrally coordinated Ti-oxide moieties. Their surface wetting properties were investigated by water contact angle measurements. Interestingly, water contact angles of Ti-MSTFs change depending on the length of the hydrophilic domains of the employed SDA, indicating that the surface wettability can be precisely controlled by varying the types of the SDA. Moreover, Ti-MSTFs act as a photocatalyst for the degradation of organics, such as methylene blue dyes and oleic acid, in which photocatalytic activities were influenced by the porous structure and surface wettability.