GREEN SYNTHESIS AND CHARACTERIZATION OF SILVER NANOPARTICLES USING BACTERIAL CULTURE AND ITS ANTIMICROBIAL ACTIVITY

Abstract

Microorganisms are being used since a very long time as a reducing agent of metal ions due to the growing concern of environment-friendly and sustainable method. Metallic nanoparticles can be synthesized either by isolating metals inside the cell else exuding them into the extracellular media. Plenty of the microorganisms have already been used to synthesize nanoparticles of numerous metals such as gold, silver, titanium, palladium, platinum etc. The thesis includes the nanoparticle synthesis by two bacterial species Shewanella putrefaciens and Shewanella algae using the supernatant as well as the pellet of the cells to synthesize silver nanoparticles. Variants of the silver nitrates have been used to analyse the nanoparticle formation on the basis of concentration. The microbes are being used as both reducing as well as the capping agents. The synthesis was done at different temperatures and the pH was monitored. UV-VIS spectroscopy was used to monitor the formation of silver nanoparticles quantitatively. UVVIS peaks were obtained in the range of 380-460nm. After the silver nanoparticles are obtained Fourier Transform Infrared Spectroscopy is done to obtain the functional groups responsible for reduction of the silver nitrate. Scanning Electron Microscopy and Transmission Electron Microscopy results were obtained to confirm the size of the silver nanoparticles which was obtained to be 14-20nm. Lastly the antimicrobial activity was checked by the disc diffusion and well diffusion method against Escherichia coli DH 5α.