Characterization and antibacterial activity of silver nanoparticles biosynthesized by using aquatic weeds extracts

Abstract

The physical and chemical properties of Silver Nano Particles (SNPs) are of great concern to research and industry. Recently, aquatic weeds attain increasing economic and environmental concerns worldwide and in Iraq particularly. In this article, the work aims at 3 goals: SNPs were synthesized by the biological method (1st goal), using two different aquatic weeds’ extracts named: water hyacinth (Eichhornia crassipes) and coontail (Ceratophyllum demersum) (2nd goal). The SNPs synthesis were studied with two treatment conditions; 37 °C in dark overnight incubation and boiling for 15 min. No SNPs were formed by using the incubation method. The UV–vis spectrum analysis revealed a very low intensity broad absorbance peek between 400−550 nm with no clear maxima for the Nano Silver synthesized when using water hyacinth extract (wSNPs). While a clear peak between 377−445 nm was detected with maxima at 414 nm for SNPs synthesized when using coontail (cSNPs) extract. The later blue shifting indicated the existence of a considerable quantity of small sized cSNPs (about 10 nm) which agree with other characterization tests FESEM, EDAX, FEI-TEM, and XRD results. These results confirmed that the SNPs were amorphous with the presence of few crystalline shape particles with average size of about 20 nm for wSNPs and 10 nm for cSNPs. Antibacterial activity of the two SNPs was examined against two different food and water spoiling bacteria. A 100 micro-litter of wSNPs inhibited the growth of Escherichia coli (G–ve) and Staphylococcus aureus (G + ve) with about 15 mm diameter zone of inhibition. Nearly, the same was observed with cSNPs towards E. coli, but no inhibition was detected by cSNPs for the growth of Staph. aureus. These results suppose the possibility to use these SNPs as water disinfectors, especially for food factories wastewater which may contain many microorganisms and some nutrients encouraging their growth increasing the environmental contamination, and that is the 3rd goal of this study.