Zinc oxide nanostructures: review of eco-friendly synthesis and technological applications

The global community faces significant challenges with regard to energy and the environment. Scientists and engineers have developed innovative techniques in nanotechnology and materials science, particularly in eco-friendly synthesis of metal oxides, to address these challenges. This review discusses current trends in eco-friendly synthesis and technological applications of zinc oxide (ZnO) nanostructures beyond the biomedical field mostly presented in the literature. Green methods of zinc oxide synthesis have attracted researchers due to their low toxicity, versatility and environmentally friendly nature. Zinc oxide nanoparticles (NPs) possess unique optical and thermal characteristics, a wide band gap, high excitation binding energy and are generally recognized as safe and effective, contributing to their broad range of applications. Conventional synthesis methods have been reported to have potential toxicity effects, while green synthesis offers recognized advantages. This review also explores the mechanism of zinc oxide NP formation. Moreover, this review provides an overview of diverse applications of zinc oxide NPs, including energy devices (solar cells), cement concrete, sensors, water and environmental remediation, enhanced oil recovery, coolants and biomedicine. Further studies are recommended to explore additional properties and applications of zinc oxide NPs using the latest environmentally friendly approaches.