Green Synthesis and Characterization of Silver Nanoparticles Using Citrullus lanatus Fruit Rind Extract

The wide-scale application of silver nanoparticles (AgNPs) in areas such as chemical sensing, nanomedicine, and electronics has led to their increased demand. Current methods of AgNPs synthesis involve the use of hazardous reagents and toxic solvents. There is a need for the development of new methods of synthesizing AgNPs that use environmentally safe reagents and solvents. This work reports a green method where silver nanoparticles (AgNPs) were synthesized using silver nitrate and the aqueous extract of Citrullus lanatus fruit rind as the reductant and the capping agent. The optimized conditions for the AgNPs synthesis were a temperature of 80°C, pH 10, 0.001 M AgNO₃, 250 g/L watermelon rind extract (WMRE), and a reactant ratio of 4 : 5 (AgNO₃ to WMRE). The AgNPs were characterized by Ultraviolet-Visible (UV-Vis) spectroscopy exhibiting a λ_max at 404 nm which was consistent with the spectra of spherical AgNPs within the wavelength range of 380-450 nm, and Cyclic Voltammetry (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 Transmission Electron Microscopy (TEM) revealed spherical shaped AgNPs. The AgNPs were found to have an average diameter of 17.96 ± 0.16 nm.