Characterization and antimicrobial activity of gold and silver nanoparticles synthesized using saponin isolated from Trianthema decandra L.

Synthetic methods based on naturally occurring biomaterials provide an alternative, environmental-friendly means of obtaining nanoparticles. We describe, one step green synthesis of gold (AuNPs) and silver nanoparticles (AgNPs) using a benign solvent, i.e., water and a surfactant isolated from Trianthema decandra, i.e., saponin without any special reducing or capping agents. On treatment of aqueous solutions containing chloroauric acid or silver nitrate with a solution of saponin isolated from T. decandra, stable gold or silver nanoparticles were rapidly formed. The reduction of gold and silver ions during the reaction was analyzed by ultraviolet-visible spectroscopy. Field emission-scanning electron microscopy showed formation of gold nanoparticles in various shapes, including spherical, cubical and hexagonal, while silver nanoparticles were spherical. The size of the gold nanoparticles was 37.7-79.9 nm and that of the silver nanoparticles was 17.9-59.6 nm. Energy dispersive X-ray and Fourier transform infrared spectroscopy confirmed the presence of metallic gold and metallic silver in the respective nanoparticles. The antimicrobial activity of the synthesized nanoparticles was analyzed using the Kirby-Bauer method, indicated varied susceptibility of microorganisms to the gold and silver nanoparticles. (C) 2013 Elsevier B.V. All rights reserved.