Sustainable fabrication of zinc oxide nanoparticles using Secamone emetica leaf extract: Biological and environmental applications

In recent years, the synthesis of nanoparticles using plant-based protocols has received great attention. The present work concerns the biosynthesis of zinc oxide nanoparticles (ZnO NPs) using aqueous leaf extract of Secamone emetica (Retz.) R. Br. ex Sm. and investigates their biological applications and photocatalytic activity. UV, FTIR (Fourier Transform Infrared Spectroscopy), XRD (X-ray diffraction) and SEM (Scanning Electron Microscopy) with EDX (Energy Dispersive X-ray) analysis were used for characterization of ZnO NPs. In UV analysis, the biosynthesized ZnO NPs demonstrated a peak at 354 nm. FTIR analysis revealed functional groups. The XRD study revealed the presence of hexagonal wurtzite structures consistent with JCPDS (Joint Committee on Powder Diffraction Standards) card no: 89–1397. SEM analysis confirmed the spherical morphology of ZnO NPs, and revealed their size to be 55.38 nm. ZnO NPs efficiently restricted the growth of Gram-negative bacteria (Pseudomonas aureginosa) than Gram-positive bacteria. In DPPH (2,2-Diphenyl-1-picrylhydrazyl) assay, exhibited 48.3 % of inhibition, while in ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) assay, was observed 72.65 % of inhibition. The larvicidal efficacy of ZnO NPs was tested against the 4^th instar larvae of Aedes aegypti and Culex quinquefasciatus. ZnO NPs showed considerable larval mortality against Culex quinquefasciatus (100 %) and Aedes aegypti (93.33 %). The photo-catalytic performance of ZnO NPs was tested for the degradation of methylene blue under direct sunlight exposure. Around 69.76 % of the dye was degraded after 210 min of exposure to sunlight. Therefore, the above results suggest that the biosynthesized ZnO NPs using the eco-friendly method can be applied for a diverse range of biological and environmental applications.