Abstract

• The biosynthesis of silver nanoparticles from extracts of neem leaves was studied. In this research, silver nitrate was used as a metal precursor and nee1m leaves extract was taken as a reducing agent for synthesis of silver nanoparticles, AgNPs. The characteristics of silver nanoparticles were mainly confirmed by UV-Visible spectroscopy, Energy Dispersive X-ray Fluorescence (EDXRF) spectroscopy, X-ray Diffraction (XRD) analysis, Fourier Transform Infra-red (FT IR) spectroscopy and Scanning Electron Microscopy (SEM). In the biosynthesis process, effect of neem leaves extract and effect of stirring time on synthesized AgNPs were also studied. It was observed that the maximum wavelength of synthesized AgNPs was 410 nm that agreed with the literature value of the wavelength range of 400-500 nm for silver nanoparticles. The EDXRF data showed a percent relative abundance of Ag (50.108%) that confirmed the presence of silver in the suspension. From XRD data, the average crystallite size was calculated by Scherrer equation and found to be 37.14 nm. FT IR analysis showed the presence of the protein or amino acid group in neem extract which reduced Ag+ ion into metallic Ag nanoparticles. In SEM analysis, it was found that the sample was likely to be well dispersed agglomerates of grains with narrow size distribution. As other evidence, the characteristic of AgNPs was observed by Tyndall effect. The antimicrobial activity of prepared AgNPs was also studied by the six microorganisms - Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus pumilus, Candida albicans and Escherichia coli. It was observed the AgNPs suspension was more potent than neem extract only especially in Bacillus pumilus and Escherichia coli with the zone diameters of 15 mm.