Green synthesis of Ag@Au bimetallic composite nanoparticles using a polysaccharide extracted from Ramaria botrytis mushroom and performance in catalytic reduction of 4-nitrophenol and antioxidant, antibacterial activity

Abstract

An eco-friendly synthetic procedure was used to prepare silver-gold bimetallic composite nanoparticles (Ag@AuCNPs)by using a mixture of aqueous solutions of silver nitrate, chloroauric acid and Ramaria botrytis mushroom polysaccharide (RBPS) at 80−85 °C in water medium. The synthesized Ag@AuCNPs were characterised by using UV–vis spectroscopy, X-ray diffraction (XRD) analysis, high resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDAX) and X-ray photoelectron spectroscopy (XPS). The synthesized Ag@AuCNPs showed potential antioxidant activities towards DPPH radical, NO radical, hydrogen peroxide scavenging assays and ferric ion reducing assay. Besides that Ag@AuCNPs showed powerful antibacterial activity towards a gram negative bacterium Pseudo monasaeruginosa (MTCC No.-424). Catalytic activity of Ag@AuCNPs was tested by considering, 4-nitrophenol reduction as a model reaction in aqueous medium at room temperature using UV–vis spectroscopy. The catalyst concentration was varied to find out the optimum conditions. The rate constant was evaluated by using pseudo first order kinetic model. The prepared nanoparticles showed a good catalyst towards p-nitrophenol reduction, a good antioxidant and a moderate antibacterial agent towards Pseudomonas aeruginosa. These observations signify that such green method opens up new avenues in nano biotechnology for the synthesis of nanoparticles with intensive industrial and biomedical applications.