Green Synthesis of Silver Nanoparticles Mediated by Cinnamon Extract and Its Potential Insecticidal Effect Against Callosobruchus Maculatus (F.) (Coleoptera: Chrysomelidae)

Abstract

Silver nanoparticles were successfully synthesized using cinnamon extract as a reducing agent. The synthesized nanoparticles, coated with cinnamon extract, were characterized through various optical and spectroscopic techniques. UV-visible spectroscopy confirmed the formation of cinnamon-extract-coated silver nanoparticles (Cinnamon-AgNPs) by optimizing parameters such as precursor salt concentration, pH, temperature and extract volume. The crystalline structure of the nanoparticles was examined using X-ray diffraction (XRD), while size distribution was analyzed through transmission electron microscopy (TEM). It was observed that cinnamon extract effectively stabilized silver nanoparticles and the average particle size was 23.3 nm, with a near-spherical shape. Advances in nanotechnology have recently offered novel approaches in plant protection strategies. The increasing resistance of stored-product pests like Callosobruchus maculatus to conventional insecticides necessitates the exploration of eco-friendly alternatives. In this study, the insecticidal activity of silver nanoparticles coated with cinnamon extract was evaluated against the adult stage of Callosobruchus maculatus. Additionally, the aqueous extract of cinnamon was also evaluated. Toxicity assays were conducted at varying concentrations of the nanoparticles and cinnamon extract, with exposure durations of 24, 48, and 72 hours. The results revealed that cinnamon-extract-coated silver nanoparticles exhibited the highest toxic effect at the highest concentration after 72 hours (60.72%). In contrast, the aqueous extract of cinnamon did not exhibit a significant toxic effect on C. maculatus. This significant difference highlights the synergistic insecticidal effect of the combination of silver nanoparticles and cinnamon extract. Overall, the findings highlight the significant potential of cinnamon-extract-mediated silver nanoparticles as an effective insecticidal agent against Callosobruchus maculatus.