Abstract
Zinc oxide nanoparticles (ZnO NPs) have received wide attention due to their various applications in manufacturing. Extensive research is going on for the development of nanoproducts throughout the world. Due to their unique properties, NPs have gained considerable importance compared to bulk counterparts for their utilisation in gas sensors, biosensors, cosmetics and drug-delivery systems. Sol-gel technology is widely adopted to produce ZnO NPs due to its easy, low-cost and highly controllable features. This review summarises the basic chemical methods for preparing the gel solution of ZnO NPs and focuses on their chemical and physical factors that directly affect their structural properties. ZnO NP synthesis involves four major steps: (1) dissolution, (2) hydrolysis, (3) polymerisation and (4) conversion to ZnO. The sol???gel method effectively controls the homog-enous formation and interaction of materials with minimal effort. The efficacy of these steps and the influence of synthesis parameters on ZnO NPs are also discussed in this review. In the next part of this review, we will evaluate the differences and similarities among ZnO NPs synthesised using different techniques and address the challenges and prospects of this compound.