A comparative study of optical, reversible wettability and UV light sensitivity of ZnO nano-structures via chemical methods

Usage of cost effective synthesis methods are inevitable due to increasing economic conditions worldwide. In this study, zinc oxide nano-structures were synthesized by low cost chemical methods. Outcomes of X-ray diffraction analysis revealed dominating plane was c-axis for ZnO seed layer and nano-rods deposited by sol–gel spin coating and chemical bath deposition method (CBD), respectively. However, a-axis plane dominance was observed for ZnO nano-rods prepared by hydrothermal method. Scanning electron microscopy offered the surface morphology of granular structure and well aligned compact ZnO nano-rods by sol–gel and CBD, respectively. Conversely, randomly oriented ZnO nano-rods were found by hydrothermal method. Presence of zinc and oxygen in the samples was confirmed by EDS results. Optical band gap of 3.29 eV, 3.25 eV and 3.21 eV were obtained by sol–gel, CBD and hydrothermal method, respectively. Likewise, photoluminescence results were also analyzed for all the samples. The super-hydrophobic state with water contact angle (WCA) of 150° was observed for ZnO nano-rods by CBD. However, hydrophilic and hydrophobic state was detected for ZnO seed layer and nano-rods with WCA of 70° and 118°, respectively. The super-hydrophilic state was also noticed after the induction of Ultra-Violet (UV) light. The WCA reduction rate of the values 0.067 and 0.17 were estimated for ZnO nano-rods. Furthermore, CA recovery time was also measured. The UV sensing photo-response was evaluated among seed layer and nano-rods, and better result was produced by ZnO nano-rods by CBD.