Green synthesis of ZnO nanoparticles using loquat seed extract; Biological functions and photocatalytic degradation properties

This research aimed to optimize the loquat (Eriobutria japonica) seed aqueous extract mediated green synthesis of zinc oxide nanoparticles (ZnO NPs) through Response Surface Methodology (RSM). The independent variables including zinc acetate concentration (0.01-0.2 M), the precursor to the extract ratio (1: 2.5 to 1: 10) and pH value (8-12.5) affected the particle size and the absorption content. Microscopic study and spectroscopic examination demonstrated NPs <50 nm diameter in size with good absorption at 349 nm. The optimized ZnO NPs were characterized by XRD (X-ray diffraction), EDX (Energy-dispersive X-ray spectroscopy) and FTIR (Fourier-transform infrared spectroscopy). The results showed that ZnO NPs with a crystalline nature and hexagonal wurtzite structure could be stabilized and capped by the presence of functional groups in the seed extract. Antibacterial study of these NPs against some food pathogens depicted a higher bactericidal activity on Grampositive Staphylococcus aureus in a dose-dependent manner. Concentration-dependent antioxidant activity was also observed for NPs in the FRAP assay. Evaluation of photocatalytic activity revealed that the highest degradation of methylene blue (MB) was achieved with an initial NP concentration of 12 mg/mL under UV light.