Photocatalytic degradation of 4-nitrophenol pollutant and in vitro antioxidant assay of gold nanoparticles synthesized from Apium graveolens leaf and stem extracts

Abstract

This investigation represents green, fast, facile and cost-effective approaches for production of stable gold nanoparticles from leaf and stem extracts of Apium graveolens without using any chemical reducing or capping agent. The UV–Vis absorption spectra displayed surface plasmon resonance bands at 567 and 577 nm after 30 min for leaf extract-synthesized gold nanoparticles (L-AuNPs) and stem extract-synthesized gold nanoparticles (S-AuNPs), respectively, confirming gold nanoparticles formation. Furthermore, very high yields of L-AuNPs and S-AuNPs were acquired (approximately 99.99%). Transmission electron microscopy pictures displayed that the synthesized L-AuNPs and S-AuNPs had different shapes (e.g., triangular, rhombic, pentagonal, hexagonal and spherical). X-ray diffraction analysis confirmed the formation of metallic gold. Fourier transform infrared spectroscopy indicated that the surfaces of biosynthesized gold nanoparticles were capped with different bioactive compounds which were responsible for gold nanoparticles formation and stabilization. In vitro antioxidant activity studies proved that the inhibitions of 2,2-diphenyl-1-picrylhydrazyl and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) free radicals were done by gold nanoparticles due to the existence of A. graveolens biomolecules capped on nanoparticles. In addition, these gold nanoparticles could be used as an eco-friendly catalyst for reduction of toxic organic pollutant 4-nitrophenol.