Coating of Transparent Ti-containing Mesoporous Silica Thin Films on Quartz and Aluminum Alloy Substrates for Fabrication of Highly Hydrophilic Surfaces

Abstract

The fabrication of transparent Ti-containing mesoporous silica thin films (Ti-MSTFs) showing highly hydrophilic properties was achieved on quartz and Al alloy substrates by using a sol–gel/spin-coating technique. The presence of the mesoporous structure and titanium oxide species which exist in an isolated and tetrahedrally-coordinated state within the silica framework was observed by XRD and DRUV–vis measurements. The surface wettability on the Ti-MSTFs was also investigated based on the water contact angle measurement. Water contact angles on Ti-MSTFs on quartz and Al alloy substrates were extremely low values of 5° and 8° even under dark conditions, respectively, which were much smaller than those on original substrates. These observations indicate that highly hydrophilic surfaces were formed both on quartz and Al alloy substrates by coating with Ti-MSTFs. It can be interpreted that the capillary condensation due to the mesoporous structure and the presence of isolated titanium oxide species as adsorption sites of water contributed to the appearance of the high hydrophilicity. Furthermore, the irradiation of UV-light led to the decrease in water contact angles on Ti-MSTFs and it was found that Ti-MSTFs exhibited the photoinduced superhydrophilic properties.