Green synthesis of colloidal silver nanoparticles through electrochemical method and their antibacterial activity

This paper presents a facile, and ecofriendly method to prepare colloidal silver nanoparticles (AgNPs) at room temperature using bulk silver bars, bi-distilled water, trisodium citrate, and a direct-current voltage source. AgNP formation was confirmed and characterized by ultraviolet-visible spectroscopy, transmission electron microscopy and X-ray diffraction. Their antibacterial activity was examined by disc diffusion and minimum inhibitory concentration (MIC) techniques against three bacterial strains, including the Gram-positive bacteria Staphylococcus aureus and the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa. Results showed that the size of AgNPs formed was about 19.7 +/- 4.3 nm with nearly spherical shape and high purity. The antibacterial activity of as-prepared AgNPs was determined through zones of inhibition against the growth of three bacterial strains on agar. MIC analysis showed that S. aureus had resistance to AgNPs that was about 2-3 times higher than those of E. coli and P. aeruginosa, and that resistance ability depended on the bacterial concentrations inoculated. This work revealed the effective method of synthesizing a large quantity of colloidal AgNPs with high antibacterial effectiveness and potential application in different fields. (C) 2016 Elsevier B.V. All rights reserved.