Highly hydrophilic and superhydrophobic ZnO nanorod array films

The wettability control of solid surfaces is important from the aspects of both science and technology. Herein, we report a surface-modification-induced hydrophilicity to superhydrophobicity transition on well-aligned single-crystalline ZnO nanorod array films (ZnO-NAFs). The ZnO-NAFs were prepared from solution by a hydrothermal method and were characterized by X-ray diffraction and scanning electron microscopy. The surface of transparent ZnO-NAFs was highly hydrophilic with a water contact angle of 9.6 ± 0.8°. However, after being exposed to octadecanethiol solution, the surfaces of the ZnO-NAFs became superhydrophobic with a water contact angle of 156.2 ± 1.8°. The present work offers a technique that has great potentials for preparing two-dimensional micro-patterns with a high wettability contrast for water.