Physicochemical properties of ZnONPs synthesized by chemical, sonochemical, and green methods: comparative study

Zinc oxide nanoparticles (ZnONPs) have gained wide interest owing to their distinct characteristics. ZnONPs are commonly synthesized by chemical methods that have the challenges of using reductants and stabilizing agents, thus inducing harmful effect on human health. Green synthesis of ZnONPs using plants provides a safe and non-toxic category of nanoparticles that have a positive impact on human health. In the present study, ZnONPs have been fabricated by green method using curcumin, in addition to their fabrication by traditional chemical and sonochemical methods for comparison. The effects of different synthesis methods on photoluminescence, structure, morphology, and surface charge of ZnONPs were analyzed using different techniques such as fluorescence spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and zeta potential. Fluorescence spectroscopy results showed variation in zinc oxide emission bands depending on synthesis method. XRD pattern of green-synthesized ZnONPs confirmed the formation of pure hexagonal wurtzite structure similar to that prepared using traditional chemical and sonochemical methods. In TEM images, ZnONPs appeared morphologically different in accordance with the synthesis method. SEM image of green-synthesized ZnONPs revealed the formation of uniform and well-distributed crystals in comparison with those synthesized chemically. The zeta potential magnitudes of the three nanoformulations showed variation, but they all have negative surface charge. The comparative analysis indicated the successful preparation of ZnONPs using curcumin as an alternative for chemicals. No distinctive changes were observed in the measured physicochemical properties of ZnONPs synthesized either greenly or chemically, except for the safety and ecofriendly of the former.