Biological Evaluation of Silver Nanoparticles Obtained from T. arjuna Bark Extract as Both Reducing and Capping Agent

Abstract

A simple, environmentally benign and cost effective method is reported to obtain silver nanoparticles (AgNPs) using aqueous solution of AgNO₃ and T. Arjuna (Terminalia Arjuna) bark extract, which act as both reducing and capping agent, under microwave irradiation. The formation of AgNPs was monitored by recording optical absorption spectra for surface plasmon resonance observed at ~425 nm. The bioactive polyphenols extracted from the plant extract are responsible for reduction of Ag⁺ → Ag⁰. During the formation of AgNPs, the reaction mixture showed gradual decrease in pH and an increase in reduction potential. The powder XRD pattern of AgNPs confirmed their fcc structure. An FTIR spectrum showed the presence of plant-residues adsorbed on the surface of AgNPs, which indicates the in situ bio-capping. The TG curve of AgNPs showed ~30 % weight loss due to thermal degradation of these plant-residues. The FE-SEM images showed spherical shape of AgNPs with an average particle size of 10–15 nm. The EDX analysis confirmed the presence of Ag as a major element. The biological evaluation of AgNPs showed higher inhibitory action for both bacteria and yeast when compared to that of fungus. A very good antioxidant property was also observed for these bio-capped AgNPs.