Green Synthesis Of Silver Nanoparticles Using Citrullus Lanatus Rind Extract As A Reductant For Selected Antibacterial Applications

ABSTRACT

Silver nanoparticles (AgNPs) are the most studied metal nanoparticles due to their ever

growing range of applications in areas such as chemical sensing, nanomedicine and

electronics which has led to their increased demand. The AgNPs synthesis involves the

use of hazardous reagents and toxic solvents. There is need to develop methods AgNPs

that use environmentally benign reagents and solvents. This research work reports a

green method where AgNPs were synthesized using silver nitrate as a precursor with

aqueous extract of Citrullus lanatus fruit rind as the reductant as well as capping agent.

The optimized conditions for AgNPs synthesis were a temperature of 80 oC, pH 10, 0.001

M AgNO3, 250 g/L watermelon rind extract (WMRE), and a reactant ratio of 4:5

(AgNO3WMRE). The resultant AgNPs were characterized by Ultra violet–Visible

(UV/Vis) Spectroscopy, Cyclic Voltammetry (CV) and Transmission Electron

Microscopy (TEM). UV/Vis results showed a max at 404 nm which is consistent with the

spectra of spherical AgNPs within the wavelength range of 380-450 nm. CV results

showed a distinct oxidation peak at +291 mV while the standard reference AgNPs (20 nm

diameter) oxidation peak occurred at +290 mV and TEM micrographs revealed spherical

shaped AgNPs. The AgNPs were found to have an average diameter of 17.96 nm. Their

antimicrobial activity against clinical isolates of Escherichia coli (E.coli) and Salmonella

typhi (S.typhi) were evaluated using the disc-diffusion method. The Minimum Inhibition

Concentration of the nanoparticles was found to be 45.00 ± 0.01 g/mL for S.typhi and

38.50 ± 0.00 g/ml for E.coli while the Minimum Bactericidal Concentration was found to be 60.00 ± 0.05 g/ml for S.typhi and 50.00 ± 0.00 g/ml for E.coli.