Ecofriendly Synthesis of Zinc Oxide Nanoparticles by Carica papaya Leaf Extract and Their Applications

Zinc oxide nanoparticles (ZnO NPs) were synthesized by Carica papaya leaf extract. The nanoparticles were characterized by UV-Vis spectrum, Fourier Transform Infrared spectroscopy (FTIR), X-ray Diffraction (XRD), Dynamic light scattering (DLS) analyser and Energy-dispersive X-ray spectroscopy analysis with a scanning electron microscope (SEM-EDX). The ZnO NPs were assessed using 2,2 '-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay with varying ZnO NP concentration, showed scavenging activity with the half maximal inhibitory concentration (IC50) = 130.1 and 104.9 mu g/mL(-1) respectively. Antifungal studies were conducted for ZnO NPs against S. sclerotiorum, R. necatrix and Fusarium species, which demonstrated a higher inhibition rate for S. sclerotiorum (59.7%). Seeds of chickpea were separately treated with various concentrations of ZnO NPs. An exposure to ZnO NPs (25%, 50%, 75% and 100%) and control caused significant changes in seed germination, root length, shoot length and antioxidant enzyme were studied. Compared with control the maximum seed germination, root and plant growth was observed with the treatment of ZnO NPs. Superoxide dismutase and catalase activity increased due to ZnO NPs treatment. This suggest that ZnO NPs may significantly alter antioxidant metabolism during seed germination.