Facile biofabrication of silver nanoparticles using Salvia officinalis leaf extract and its catalytic activity towards Congo red dye degradation

Abstract

A facile, eco-friendly and cost-efficient method has been used for the biofabrication of silver nanoparticles. The aqueous extract of Salvia officinalis was used as a bioreducing agent and as a capping/stabilizing agent in the single-step biosynthesis of silver nanoparticles. Biosynthesized silver nanoparticles were characterized by various instrumental techniques, which included UV–vis spectroscopy, transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) energy-dispersive X-ray spectroscopy (EDS) and thermogravimetric analysis (TGA)-differential thermal analysis (DTA). The colour of the reaction mixture of silver nitrate solution and an aqueous extract of S. officinalis turned dark brown after 10 min of mixing; hence, the reduction of Ag+ to Ag° occurred. UV–vis spectroscopy demonstrated the formation of stable silver nanoparticles with a surface plasmon resonance (SPR) band at λmax of 446 nm. TEM analysis demonstrated that the biosynthesized silver nanoparticles are spherical in shape and approximately 40 nm in size. Based on the observed results, a possible mechanism has been proposed for the formation of the silver nanoparticles. These biosynthesized silver nanoparticles were analysed, and the enhancement of their catalytic properties against toxic dye under various experimental conditions was demonstrated. According to the observed results, the catalytic activity for the degradation of azo dye Congo red (CR) was efficient under optimal experimental conditions. The phytochemical-based synthesis of nanoparticles provides a suitable, inexpensive and ecofriendly alternative for the degradation of highly toxic organic compounds and harmful azo dyes.