Oleic acid-modified superhydrophobic ZnO nanostructures via double hydrothermal method

Superhydrophobic ZnO nanostructures (ZNs) are synthesized via double hydrothermal method without any surface chemical modification. The water contact angle (CA) was approximately similar to 150 +/- 2 degrees. A subsequent chemical treatment with oleic acid (OA) contributed to a superhydrophobic surface with a water CA of 162 +/- 2 degrees. X-ray diffraction pattern revealed high crystalline quality ZNs with hexagonal wurtzite phase. The crystallite size was approximately similar to 23 nm. Field-emission scanning electron microscopy images display nanosheet formations assembled in flower-, cauliflower-, and nanorod-like ZNs. The CA of ZNs surfaces increased steadily from 152 +/- 2 degrees to 162 +/- 2 degrees when the OA weight percentage increased from 2 mg to 10 mg. Furthermore, UV-Vis spectra of ZNs indicated that the absorption band of all samples is distinguished in the ultraviolet region. All ZnO samples were maintained at room temperature for 1 h to 5 months to examine the stability of the structure surface.