Comprehensive experimental study on production of vertically aligned ZnO nanorod thin films and their electrical, optical and antimicrobial properties

Abstract

One-dimensional (1D) zinc oxide (ZnO) nanomaterials (e.g. nanorods, nanowires) are the most important due to their electrical and optical properties. As the surface-to-volume ratio in ZnO nanorods (NRs) is very high, the surface states have a crucial role on optical and other properties. So, determination of the production parameters of the ZnO-NRs is important. In this study, a well-aligned ZnO-NRs thin film was produced via the sol–gel and hydrothermal methods. For this purpose, in the first step, a ZnO seed layer was coated onto a cleaned microscope glass slide (sizes of 1.25 × 3.75 cm) by the sol–gel spin coating method. In the second step, ZnO-NRs were grown on the ZnO seed layer by the hydrothermal method. Production parameters for the first step, such as type of the zinc salt; type of the solvent; solution concentration; type of the stabilizer; ageing time process of the solution; spin speed; duration of the spin process; number of repeated coating cycle; heating treatment temperature between coating cycles; duration between coating cycles; final heating treatment temperature and final heating treatment duration of the ZnO seed layer, were obtained. Then similar optimization processes were repeated for the second stage for the ZnO-NRs. The crystal structure, morphological and optical properties of all the produced samples were characterized via X-ray diffraction (XRD) spectroscopy; scanning electron microscopy (SEM); and ultraviolet–visible (UV–Vis) spectroscopy. For comparison, ZnO-NR powders were produced via the mechanochemical solid-state combustion method. The electrical conductivity and optical transparency of the ZnO-NR thin film samples were higher than those of the ZnO-NR powder sample. It was also observed that the well-aligned ZnO-NR thin film sample had a higher bactericidal effect against Bacillus thuringiensis than the ZnO-NR powder sample.