Design and investigation of photo-induced super-hydrophilic materials for car mirrors

During the past decades, interests in various properties in titanium dioxide thin films have been growing rapidly. There have been several reports for TiO2 thin films prepared on various media with photocatalytic and hydrophilic properties, in order to function as self-cleaning and/or anti-fogging materials. An obvious application is usually found in side-view car mirrors in the automobile industries. In this study, a number of photocatalytic TiO2 films are prepared on soda-lime glasses for car mirrors by an electron-beam evaporation. The designs and development of the photocatalytic TiO2 films, based on crystallinity, deposition rate, film thickness, film structure, and surface roughness are discussed. In comparison to the commercialized products, a systematic investigation procedure for the super-hydrophilic properties of the light-induced TiO2 films for car mirrors has been developed, based on super-hydrophilicity, sustainability, self-cleaning property, and degradation of the samples. In addition, physical characterization by X-ray diffraction and surface roughness are also discussed. It has been found that most commercial products attain super-hydrophilicity only after exposed to ultraviolet and solar irradiation in less than 1 h. They can also maintain hydrophilicity after rigorous cleaning process. On the other hand, our prepared TiO2 thin films demonstrate super-hydrophilic and photocatalytic properties after exposed to ultraviolet light for more than 2 h. According to the study, their anatase crystallinity, small grain size, and surface conditions all contributes to the excellent results. However, the prepared samples do not attain sufficient retention property to maintain their hydrophilicity. Conclusively, the designs of the TiO2 films on car mirrors prove adequate to produce super-hydrophilic materials, which still degrade over normal usage. Nevertheless, our proposed investigation methods prove useful in quality evaluation in order to differentiate the results of super-hydrophilic materials of interests.