Scientists produce self-cleaning coatings on glass substrate

Iranian researchers succeeded in the production of silica/titania/silica three-layer self-cleaning coating (SiO2/TiO2/SiO2) on glass substrate. The coating has more stable phydrophilic and photocatalytic properties and much more transparency than titania coating. In recent years, self-cleaning properties of titanium dioxide thin films have attracted the attention of many industrialists active in the field of building construction and optical devices. This specification is considered to be the result of combination of superhydrophilicity and photocatalytic properties of the thin film. In this study, a three-layer coating of SiO2 / TiO2 / SiO2 was deposited on glass substrate through vapor physical deposition method by using electron beam (EB-PVD). Next, hydrophilicity, photocatalytic and self-cleaning properties of the produced layer were compared to those of SiO2/TiO2 film. The contact angle between water and the surface of the film exposed to UV light was measured, and the results showed that contact angle in SiO2/TiO2/SiO2 film had a quicker reduction than in SiO2/TiO2 film. In addition, the thin film of SiO2/TiO2/ SiO2 had conserved its hydrophilic properties after being kept in a dark place in comparison with SiO2/TiO2 film. It was also observed that the three-layered film that had a layer of SiO2 deposited on its top had higher photocatalytic activity than the other two films. In general, hydrophilic and photocatalytic properties of the three-layered silica/titania/silica film showed a significant increase in comparison with single-layer coating film of titania and bi-layer film of silica/titania. The three-layered film also had higher optical transparency, which resulted in better self-cleaning properties for the film. Therefore, this film is very desirable to be used in construction industry, automobile manufacturing and optical devices. Results of the research have been published in International Journal of Materials Research, vol. 104, issue 12, December 2013, pp. 1263-1266.