Biosynthesis of silver nanoparticles using plant extracts and their application in water treatment

Abstract

The field of nanoscience cuts across many areas of research and researchers continue to explore this interesting area, with the objective of developing materials or improving the properties of the existing ones. Nanomaterials have promising applications in electronics, agriculture, medicine, photo devices and environment. Phytonanotechnology which involves the use of plants has carved out an interesting niche in the field of nanoscience making most Indian greeneries and spices important substrates for the synthesis of nanoparticles (NPs). Umbrella plant, Welsh onion and Guar plants were used for the synthesis of silver NPs in this work. The aqueous plant extract and different concentrations ( 1 mM, 2 mM and 5 mM) of the precursor compound (AgNO3) were prepared. In the synthesis of the NPs, two volume ratios of I :5 and 1: IO of the substrate to the precursor were made from each of the precursor (AgNO3) concentration (I mM, 2 mM and 5 mM), and the rate of formation of silver NPs was monitored using UV-vis spectroscopy. The biosynthesized NPs which were represented as UmAgNPs, WoAgNPs and GuAgNPs (reflecting the type of plants involved in their synthesis: Umbrella plant, Welsh onion and Guar plants respectively) were further characterized using Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and powder X-ray diffraction (pXRD) techniques. The results of the FTIR analysis revealed the presence of biomolecules such as sugars, amino acids, flavonoids on the surface of the NPs, therefore confirming the role of the plants extracts as passivating/capping agents in addition to their reducing effect. The particle sizes of all the NPs: UmAgNPs. WoAgNPs and GuAgNPs, were below 20 nm. with the NPs synthesized from I mM AgNO3 using Welsh onion plant (WoAgNPs) showing the highest average particle size of 15.72 nm. Averagely, GuAgNPs obtained from 2 mM AgNO3 using I : 10 volume ratio has the lowest particle size among all. However, particles mediated by umbrella plant (UmAgNPs) and prepared from 2 mM AgNO3 using both of I :5 and I: 10 volume ratio gave the most stable NPs with high degree of monodispersity. The potential application of the green synthesized silver NPs in the treatment of water polluted with organic dyes was evaluated by studying their ability to photo-catalytically degrade methyl red, and their antimicrobial potency against some bacteria (majorly the water borne). The U mAgNPs showed the greatest percentage of degradation of about 29. 72%. The antimicrobial properties of the NPs against common microbes: Staphylocucus auerus, Bacillus cerues, Kleb. pneumonia and Echerichia coli displayed interesting results with WoAgNPs having the greatest growth inhibition against the studied microbes.