Bioinspired Preparation of Ultrathin SiO2 Shell on ZnO Nanowire Array for Ultraviolet-Durable Superhydrophobicity

ZnO nanowire (NW) array was conformally coated with an uitrathin SiO2 shell by a bioinspired layer-by-layer deposition in order to obtain ultraviolet (UV)-durable superhydrophobic property. Uniform SiO2 shell was prepared on ZnO NW by alternative reactive deposition of polyethylenimine and silicic acid. Despite the highly curved morphology of ZnO NW array, the thickness of SiO2 shell increased linearly with the number of deposition cycles, with a thickness increment being of similar to 4.17 nm per deposition cycle. The SiO2 shell only had a slight influence on the superhydrophobic property of ZnO NW array after modification with a monolayer of octadecyltrimethoxysilane (OTS). However, it greatly improved the UV durability of the superhydrophobic property of ZnO NW array due to the confinement effect of insulating SiO2 layer on the photogenerated electron-hole pairs in ZnO NW.