Stable ZnO@TiO2 core/shell nanorod arrays with exposed high energy facets for self-cleaning coatings with anti-reflective properties

Nanostructured metal oxides such as ZnO and TiO2 have been extensively employed as self-cleaning coatings due to their large band gaps as well as their hydrophilic and photocatalytic properties. We have developed a simple hydrothermal method to coat thin TiO2 nanosheets with exposed (001) facets onto a ZnO nanorod array. The chemical stability of the ZnO nanorods was great improved due to the existence of the TiO2 layer. Owing to the porous structure of the ZnO@TiO2 nanorod arrays, this thin coating layer possesses anti-reflective properties. A transmittance improvement of ∼5% was observed for one-side coated FTO glass. This coating also exhibits good hydrophilic properties, after addition of the TiO2 nanosheets. More importantly, these ZnO@TiO2 nanorod arrays display excellent photocatalytic properties for the degradation of dye molecules, due to the heterojunction between the ZnO nanorods and TiO2 nanosheets. This heterojunction facilitates the charge separation of photo generated carriers. Based on the above features, the ZnO@TiO2 core/shell nanorod array film has many advantages as a self-cleaning coating.

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