ZnO nanowires grown directly on zinc foils by thermal oxidation in air: Wetting and water adhesion properties

• ZnO nanowire arrays were grown directly on zinc foils by thermal oxidation in air.
• ZnO nanowires show a hexagonal wurtzite structure and Eg values of 3.2-3.3 eV.
• Density and dimensions of ZnO nanowires are modified with oxidation temperature.
• Zn foils reveal a hydrophilic behavior with high water droplet adhesion.
• ZnO nanowires exhibit a superhydrophobic behavior with low water droplet adhesion.

Large scale ZnO nanowire arrays were grown directly on zinc foils using the thermal oxidation in air method. The X-ray diffraction and reflectance investigations confirm that the as-grown nanowires properties are typical for ZnO having a hexagonal wurtzite crystalline structure and band-gap values between 3.2 and 3.3 eV. The scanning electron microscopy images prove that the density and the dimensions (diameter and length) of the ZnO nanowires can be tuned by controlling the oxidation temperature. Wettability studies reveal in the case of Zn foils a hydrophilic behavior with high water droplet adhesion which is transformed into a superhydrophobic one with low water droplet adhesion after the foils' surfaces are covered with ZnO nanowires. Obtaining functional surfaces with such interesting wetting properties using a simple, inexpensive and highly reproducible thermal oxidation in air technique is very attractive for anticorrosion coatings and self-cleaning applications.