Green synthesis of gold nanoparticles using <i>Citrus maxima</i> peel extract and their catalytic/antibacterial activities

Abstract

The peel of <i>Citrus maxima</i> (<i>C. maxima</i>) is the primary byproducts during the process of fruit or juice in food industries, and it was always considered as biomass waste for further treatments. In this study, the authors reported a simple and eco-friendly method to synthesise gold nanoparticles (AuNPs) using <i>C. maxima</i> peel extract as reducing and capping agents. The synthesised AuNPs were characterised by UV-visible spectrum, X-ray diffraction (XRD), transmission electron microscope (TEM) and Fourier-transform infrared spectroscopy (FTIR). The UV-visible spectrum of the AuNPs colloid showed a characteristic peak at 540 nm. The peaks of XRD analysis at (2<i>θ</i>) 38.30°, 44.28°, 64.62°, 77.57° and 81.75° were assigned to (111), (200), (220), (311) and (222) planes of the face-centered cubic (fcc) lattice of gold. The TEM images showed that AuNPs were nearly spherical in shape with the size of 8-25 nm. The FTIR spectrum revealed that some bioactive compounds capped the surface of synthesised AuNPs. The biosynthesised AuNPs performed strong catalytic activity in degradation of 4-nitrophenol to 4-aminophenol and good antibacterial activity against both gram negative (<i>Escherichia coli</i>) and gram positive (<i>Staphylococcus aureus</i>) bacterium. The synthesis procedure was proved simple, cost effective and environment friendly.