Stable superhydrophobic surface via carbon nanotubes coated with a ZnO thin film

We report the formation of a stable superhydrophobic surface via aligned carbon nanotubes (CNTs) coated with a zinc oxide (ZnO) thin film. The CNT template was synthesized by chemical vapor deposition on an Fe-N catalyst layer. The ZnO film, with a low surface energy, was deposited on the CNT template by the filtered cathodic vacuum arc technique. Contact angle measurement reveals that the surface of the ZnO-coated CNTs is superhydrophobic with water contact angle of 159°. Unlike the uncoated CNTs surface, the ZnO-coated CNTs surface shows no sign of water seepage even after a prolonged period of time. The wettability of the surface can be reversibly changed from superhydrophobicity to hydrophilicity by alternation of ultraviolet (UV) irradiation and dark storage.