Design of mixed metal oxide nanostructured superhydrophilic surfaces with self-cleaning properties

The present paper describes the design of a superhydrophilic self-cleaning surface using mixed metal oxides. SiO₂/ZnO/TiO₂ layers were deposited on a cleaned glass surface by a dip coating method. The silica layer imparts stability and adhesion to the coating of the glass surface. ZnO was deposited in the form of nanoflowers over silica which was further coated by titania nanoparticles in a multilayer. This renders the exposed titania layer to be superhydrophilic having a contact angle of eight. High surface area combined with superhydrophilicity helps impart enhanced photocatalytic activity of the coating due to increased wetting characteristics of the surface. The surface, therefore, acts as a self-cleaning surface by effectively degrading pollutants. Moreover, the formation of a heterojunction between ZnO/TiO₂ layers reduces the band gap to 2.98 eV from 3.59 eV in TiO₂ thus enabling the degradation of pollutants in the visible range (416.25 nm).