Hierarchical Cu 2 O/CuO/TiO 2 composite films with high superhydrophobicity and strong adhesion

Abstract

Hierarchical Cu₂O/CuO/TiO₂ hollow nanostructured films with petal effect (high superhydrophobicity and high adhesion to water droplets) have been synthesized through a facile solvothermal approach, and the wettability of the product films was studied. The protocol was carefully designed for the preparation of the multi-scaled nanostructures. Cu(OH)₂ nanorod arrays were used as precursors, which decomposed to form CuO and H₂O molecules at high temperature. The produced tiny amount of water molecules was beneficial for both the slow hydrolysis of Ti(OC₄H₉)₄ to formTiO₂ nanostructures and the reduction of CuO to form Cu₂O. The formation of hollow nanostructures is suggested to be based on kirkendall effect. CuO diffuses outward to react with ethanol in the solution, producing Cu₂O/CuO/TiO₂ hollow nanostructured films with rough surfaces. The water contact angle of the product film was estimated to be around 152.8°, and the water droplet remained firmly stuck on the surface when the film was vertically tilted, indicating the superhydrophobicity and strong adhesion of the product films. The Cassie impregnating wetting state was suggested as the wetting state of the product films.