Hydrophobic effect evolution dependent manipulation of ZnO nanostructures morphology

The morphologies of different ZnO nanostructures (ZNSs) films (deposited on glass substrates) are investigated using simple and low-cost techniques. Two synthesis techniques, i.e., direct hydrothermal technique and a combination of pulsed-laser ablation under liquid and hydrothermal (PLAL-H) technique, are employed. The first technique (direct hydrothermal technique) is used to fabricate three-dimensional (3D) flower-like ZNSs and one-dimensional (1D) solid rod- along with enclosed tube-like ZNSs under different pH conditions/values. Moreover, a zero-dimensional (0D) ZnO nanoparticles (ZNPs)-based film is prepared by PLAL-H technique. The influence of tuning morphology of ZNSs films on the hydrophobic effect is examined by XRD, FE-SEM, and photoluminescence (PL). XRD patterns confirmed the polycrystalline structures of ZNSs films. FE-SEM explored the morphology transformation from 3D flower-like to 1D solid rod- and enclosed tube-like ZNSs films by varying the pH values from 10.5 to 5.7. The PL spectra revealed a higher surface area and deep-level defect density related to the ZnO morphology. Depending on the surface contact angle measurements, the hydrophobic performance of flower-like ZNSs is much superior than 1D solid rod-like, enclosed tube-like, and 0D ZNPs films. The super-hydrophobic effect of flower-like ZnO is attributed to the synergism of regular formed and higher density of ZNSs. Therefore, it is inferred that the successful controllable morphology of ZNSs film under mild deposition conditions could play a crucial role to get a superior hydrophobic behavior of ZNSs film.