Green Synthesis, Characterization and Antimicrobial Activity of Silver Nanoparticles Using Aqueous Extracts of Allium cepa and Raphanus sativus

Green synthesis of nanoparticles is rapidly evolving because it is cost-effective and eco-friendly, this also contributes to its preference over nanoparticles from other sources. In this study, silver nanoparticles were synthesized from Allium cepa (AC) and Raphanus sativus (RS) aqueous extracts and the biological activities were evaluated. The silver nanoparticles AgNPs@AC and AgNPS@RS were synthesized from AC and RS extracts, respectively, using silver nitrate and characterized using UV-visible spectroscopy (UV-Vis), Fourier transform infrared (FT-IR) spectroscopy, Powder X-ray diffraction (PXRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). The FT-IR spectra of AgNPs@AC and AgNPS@RS showed characteristic groups pertaining to active molecules of the respective extracts indicating their surface functionalization. The XRD pattern of AgNPs@AC revealed diffraction peaks at 38.26, 44.39, 64.65, 77.54 and 81.64 that were indexed to (1 1 1), (2 0 0), (2 2 0), (3 1 1) and (2 2 2) planes of face-centered cubic (FCC) crystalline structure, respectively. The XRD pattern of AgNPs@RS revealed diffraction peaks at 38.24, 44.32, 64.62, 77.46 and 81.65 that was indexed to (1 1 1), (2 0 0), (2 2 0), (3 1 1) and (2 2 2) planes of face-centered cubic (FCC) crystalline structure, respectively. The SEM images indicate that the particles are spherical in shape and have particle size in the range of 25-35 nm. The nanoparticles demonstrated substantial antimicrobial activity against Gram +ve and Gram -ve harmful bacteria species, such as S. aureus, E. coli and fungal species C. albicans. This study shows that A. cepa (Onion) and R. sativus (Radish) aqueous extracts can be used as an effective reducing and capping agent for the green synthesis of silver nanoparticles (AgNP). AgNPS@RS showed acceptable size and shape of nanoparticles and could therefore be a potential source of antimicrobial agents.