Fabrication of superhydrophobic ZnO surfaces via Zn foil hydrothermal reactions and fluoroalkylsilane modified process

Cake-like, lotus leaf-like, trunk-like, and cactus-like ZnO surfaces grown directly on zinc substrates were fabricated by Zn foil hydrothermal reactions in an ethylenediamine solution at 120, 140, and 160°C. Scanning electron microscopy indicated that the micro-/submicro complex structures were more regular at longer reaction time and higher reaction temperature. The hydrophobicity of typical structured ZnO surfaces modified with a layer of fluoroalkylsilane were measured. Results showed that the structured surfaces prepared at 140°C for 4 h as well as at 160 °C for 5 h exhibited superhydrophobicity with water contact angles of 154.6° and 157.3° as well as sliding angles of about 5° and 3°, respectively. This method may be used to fabricate various microstructured ZnO surfaces showing superhydrophobicity at a low cost.