Fabrication of Superhydrophobic Surface of ZnO Thin Films by Using Oleic Acid

Zinc oxide (ZnO) nanostructures were successfully prepared by a simple, highly efficient, and low-cost using the hydrothermal method. A superhydrophobic surface with a static water contact angle (CA) >150° has been synthesized by modifying ZnO nanostructures with 100°C at 1 h stable oleic acid (OA) as coupling agents, in order to modify their surface properties and make them more hydrophobic. Surface modification of ZnO nanostructures has been performed, and the effect of the modification on the structure and morphological properties were investigated. The resulting nanostructures were characterized by XRD, FESEM, UV-VIS spectroscopy. XRD pattern revealed that ZnO nanostructures prepared by hydrothermal method (crystallite size ~30 nm) have hexagonal wurtzite structure with a good crystalline quality. FESEM images of ZnO nanostructures prepared by hydrothermal showed hexagonal nanorods assembled in flower-like shape, there was much change in the surface morphology of modified samples after surface modification such as (nanorods, nanoflowers, and nanotube). Results show the water CA of ZnO superhydrophobic surfaces increased steadily from 147±2° to 154±2° when the OA weight percentage increased from 2mg to 10mg. The optical measurements for ZnO nanostructures showed that all samples the absorption band in the ultraviolet region. The band gap of pure ZnO nanostructures 3.5 eV and after modification ZnO surface 3.6 eV. All samples of ZnO were maintained at room temperature for 1 hour to 5 months to test the stability of the surface. The water CAs were measured for each condition, and very little change was observed in the CAs. In addition, the ZnO surface remained superhydrophobic without any contamination observed after water was sprayed on it.