Synthesis and characterization of ZnO and Ca-ZnO nanoparticles for potential antibacterial activity and plant micronutrients

Abstract Zinc oxide nanoparticles (ZnO NPs) and calcium-doped zinc oxide (Ca-ZnO) NPs were produced via co-precipitation assay. Physicochemical properties of synthesized NPs have been studied by X-ray powder diffraction (XRD), Ultraviolet-visible (UV-vis), Photoluminescence (PL), scanning electron microscopy (SEM), Energy Dispersive X-ray (EDAX) with fluorescent elemental mapping, High-Resolution Transmission Electron Microscopy (HR-TEM) analyses. UV-vis analysis shows the presence of the incorporation of Ca doping in the Zn lattice, which reduces the bandgap. The XRD patterns of the NPs has a hexagonal wurtzite structure. SEM and HR-TEM images exhibited spherical morphology. The PL spectral measurements indicated six bands embedded due to zinc and oxygen vacancies. The crystallization temperature of the as-prepared samples was measured by a thermogravimetric (TG) analysis. Moreover, the antibacterial activity of the NPs was tested against Staphylococcus aureus and Escherichia coli bacteria using a disk diffusion method. The antibacterial activity of ZnO NPs was advanced compare to Ca-ZnO NPs. By contrast, Ca-ZnO NPs reduced antibacterial efficacy. Additionally, Sphaeranthus indicus shootlets were tested in different concentrations (0-5 mg/L) of ZnO NPs and Ca- ZnO NPs in Murashige and Skoog media. An impact of Ca-ZnO NPs significantly induced the development of shootlets, leaves and node initiation on S. indicus, compared to pure ZnO NPs. Plant development was increased by increasing the concentrations of NPs. Therefore, these biocompatible Ca-ZnO NPs can be used for target-drug delivery in biomedicine and as a micro-nutrient for in vitro plant growth and development.