Graphene oxide grafted gold nanoparticles and silver/silver chloride nanoparticles green-synthesized by a Portulaca oleracea extract: Assessment of catalytic activity

Abstract

A Portulaca oleracea (or purslane) extract was used as a green reductant for synthesizing both gold nanoparticles and silver/optical chloride nanoparticles without the use of any other external reductants, surfactants, stabilizing agents, or halide ions. Both nanoparticles demonstrated their surface plasmon resonance at 543 nm for the gold nanoparticles and 423 nm for the silver/silver chloride nanoparticles. The X-ray diffraction pattern exhibited a face-centered cubic nanoparticle structure. Mainly spherical-shaped nanoparticles were observed in field emission transmission electron microscopy images with an average size of 11.34 ± 4.23 nm for the gold nanoparticles and 15.01 ± 4.49 nm for the silver/silver chloride nanoparticles. Graphene oxide-grafted gold nanoparticles and silver/silver chloride nanoparticles using the P. oleracea extract were synthesized by either in situ or ex situ methods. X-ray photoelectron spectra confirmed that gold and silver/silver chloride nanoparticles were successfully grafted onto the graphene oxide sheet. The catalytic activity of these graphene oxide nanocomposites was assessed with the 4-nitrophenol reduction reaction. Among the tested nanocomposites, graphene oxide-grafted silver/silver chloride nanoparticles synthesized by the ex situ method exhibited an excellent capacity as a nanoscale catalyst with reasonable recyclability. The straightforward method offers new insight into grafting metallic nanoparticles onto graphene sheets via an entirely green strategy using plant extracts.