Magnetic and optical properties of ZnO nanoparticles and nanorods synthesized by green chemistry

ZnO nanostructures have attracted considerable attention because of their physicochemical properties and applications as antibacterial agents, photocatalytic reactions for pollutant removal, and electronics. Hence, efficient production and knowledge of their properties under different synthesis conditions are essential. Biosynthesis has emerged as an excellent growth-directing method for synthesizing nanomaterials, representing a soft and cleaner alternative for their production. In this study, we synthesized different ZnO nanostructures using a soft chemistry method at different growth temperatures, from 200 to 800 °C every 200 °C. The crystalline structure was estudied by X-ray Diffraction (XRD) and High-Resolution Transmission Electron Microscopy (HRTEM). The shape and size were studied by Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM), which revealed a ZnO hexagonal phase with two shapes: nanoparticles (NPs) with irregular shapes and nanorods of different sizes. The optical properties were studied by Raman and UV-visible spectroscopy, and optical absorption measurements showed bandgap tuning of the produced nanostructures. Finally, the magnetic characteristics of the samples demonstrated magnetic anisotropy due to the preference for crystalline formation and the size of the nanoparticles. The magnetic interaction between the two types of NPs increased the diamagnetism associated with the nanorods.