Control of size and antimicrobial activity of green synthesized silver nanoparticles

A unique way to control the size and antibacterial activities of silver nanoparticles (Ag NPs) using three different leaf conditions (fresh, oven-dried and sun-dried) of Alstonia scholaris has been reported in this paper. The extract of the A. scholaris leaf acts both as a reducing and stabilizing agent in the formation of Ag nanoparticles. The characteristic surface plasmon peak (415 nm), X-ray diffraction (XRD) studies and energy dispersive spectroscopy (EDS) confirmed the formation of crystalline green Ag nanoparticles. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed that there was a difference in size for the Ag NPs synthesized from different leaf conditions. Antibacterial studies with both Gram-positive and Gram-negative bacteria showed that Ag NPs synthesized from the fresh leaves displayed the best antibacterial activity, which can be attributed to the size effect of the nanoparticles. (C) 2016 Elsevier B.V. All rights reserved.