Green synthesis of silver nanoparticles using tea leaf extract and evaluation of their stability and antibacterial activity

A simple, environmentally friendly and cost-effective method has been developed to synthesize silver nanoparticles (AgNPs) using tea leaf extract. We have studied the effects of the tea extract dosage, reaction time and reaction temperature on the formation of AgNPs. The AgNPs were synthesized using silver nitrate and tea extract, and the reaction was carried out for 2 h at room temperature. The synthesized AgNPs were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analyzer, and zeta potential analyzer. The synthesized AgNPs were nearly spherical, with the sizes ranging from 20 to 90 nm. FT-IR spectral analysis indicated the tea extract acted as the reducing and capping agents on the surface of AgNPs. Furthermore, the study of silver ion release from the tea extract synthesized AgNPs showed a good stability in terms of time-dependent release of silver ions. In addition, the antibacterial activity of AgNPs was determined by monitoring the growth curve and also by the Kirby-Bauer disk diffusion method. Due to the larger size and less silver ion release, the AgNPs synthesized by tea extract showed low antibacterial activity against Escherichia coli. (C) 2014 Elsevier B.V. All rights reserved.