Green synthesis of silver nanoparticles (Ag NPs) using Gomphrena globosa (Globe amaranth) leaf extract and their characterization

Among the various methods explored for the synthesis of silver nanoparticles (Ag NPs), the green synthesis method has received great attention as a cost effective and environmental friendly method as it avoids toxicity. In the present work, silver nanoparticles were synthesized using silver nitrate as the precursor and an aqueous extract of fresh leaves of Gomphrena globosa (Globe amaranth) as the reducing and stabilizing agent. The active phytochemicals present in the leaves cause quick reduction of silver ions (Ag+) to metallic silver nanoparticles (Ag-0). The formation of Ag nanoparticles was initially confirmed by visual observation through the color change of the mixture. The silver nanoparticles obtained were characterized using UV-visible absorption spectroscopy, X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDAX), High-resolution transmission electron microscopy (HR-TEM), and Selected area electron diffraction (SAED) analysis. The synthesized silver nanoparticles show excellent antibacterial activity against three gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus) and three gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae). (C) 2019 Elsevier Ltd. All rights reserved.