Design of mesoporous silica thin films containing single-site photocatalysts and their applications to superhydrophilic materials

Abstract

This review article deals with the superhydrophilic modification on surfaces of various materials by coating with transparent mesoporous silica thin films containing single-site photocatalysts (isolated Ti-, V-, Cr-, Mo-, or W-oxide moieties). Mesoporous structures have been formed via evaporation-induced self-assembly (EISA) methods including two different surfactant removal processes. One is conventional calcination. The other is photocatalytic decomposition by photocatalysis of Ti-oxide moieties within the mesoporous silica matrix, which enables one to coat the surface with low thermal resistance effectively. After coating, the materials exhibit very high hydrophilic properties under dark conditions and photoinduced superhydrophilicity under UV-light irradiation. Among them, the W-containing mesoporous silica thin film shows the highest hydrophilic properties. These unique surface wetting properties are attributed to water adsorption properties of isolated transition metal oxide moieties and mesoporous structures having a large number of surface hydroxyl groups. Furthermore, the Ti-containing mesoporous silica thin film acts as a photocatalyst for the decomposition of oleic acid on the surface; therefore, the highly hydrophilic surface easily recovers under UV-light irradiation. These fascinating surface functionalities would contribute to practical applications.