Tuning hydrophobicity of TiO2 layers with silanization and self-assembled nanopatterning.

The wettability of TiO2 layers is controlled by forming highly ordered arrays of nanocones using nanopatterning, based on self-assembly and dry etching. Nanopatterning of TiO2 layers is achieved via formation of self-assembled monolayers of SiO2 spheres fabricated using the Langmuir-Blodgett technique, followed by dry etching. Three I types of TiO2 layers were fabricated using the sol-gel technique, sputtering, and thermal process in order to address the relationship between the wettability and the structure of TiO2 nanostructures. Compared to a thin film TiO2 layer, the nanopatterned TiO2 samples show a smaller static water contact angle (i.e., where the water contact angle etching time increases), which is attributed to the Wenzel equation. When TiO2 layers are coated by 1H,1H,2H,2H-perfluorooctyltrichlorosilane, we observed the opposite behavior, exhibiting superhydrophobicity (up to contact angle of 155) on the nanopatterned TiO2 layers. Self-assembled nanopatterning of the TiO2 layer may provide an advanced method for producing multifunctional transparent layers with self-cleaning properties.