Wetting behavior of triethoxyoctylsilane modified ZnO nanowire films

ZnO nanowire films have been prepared by chemical process at 90 °C for different growth time varied from 4 h to 12 h. The effect of growth time on the structure, morphology, and the hydrophobicity of ZnO nanowire films were investigated. The results indicate that all of the films exhibit the hexagonal wurtzite phase with growth direction perpendicular to the substrate surface. The scanning election microscopy images of ZnO nanowire films show that prolonging the growth time results in longer nanowires with uneven diameter. The influence of the diameter of nanowires on the wettability of the film was analyzed. Typically, the film prepared for 4 h exhibits a high water contact angle of about 161.7 ± 0.3° with the advancing contact angle of 157.2 ± 0.5° and receding contact angle of 163.2 ± 0.5° and a small sliding angle of 6° after hydrophobic treatment. Based on the Cassie theory, the analysis results reveal that only about 6% of the water surface contacts with the ZnO films and the remaining 94% contacts with the air cushion, which is reasonable for the hydrophobicity of a ZnO nanowire films.