Synthesis and applications of ZnO nanostructures (ZONSs): a review

Zinc oxide (ZnO) based nanostructures have gained remarkable attention worldwide for their photocatalytic activation behavior as a semi-conductor metal oxide photocatalyst in different industries, i.e. paints, cosmetic, rubber and composites coating. The main motivation of this thematic review is to analyze the mechanism of photocatalytic activity of ZnO nanostructures (ZONSs) in detail, and their application in photovoltaic, biomedical and sensing fields based on photocatalytic performance and other crucial properties that enable nano ZnO as a potential and competitive candidate in commercial markets. ZONSs were characterized with a wide range of analytical tools including X-ray diffraction (XRD), electron microscopies (SEM, FESEM, TEM), dynamic light scattering (DLS) and UV–VIS spectroscopy etc. These characterization tools provide us typical information about the crystal structure, level of crystallinity, shape, size, dimension and the change in physical, optical and chemical properties of ZONSs. Synthesis routes, process variables and their combined effect on the performance characterization of ZONSs have also been discussed in detail. The aim of this review is to provide an up-to-date knowledge to the readers about the applications of nano ZnO in diverse industries either in catalytic or in sensing form.