Eco-friendly synthesis of silver nanoparticles via Cassava starch: structural analysis and biocidal applications against aedes aegypti and pathogenic bacteria

Abstract

This study presents the eco-friendly synthesis of silver nanoparticles (AgNPs) using cassava starch via the sol-gel method, offering a sustainable approach with significant biocidal properties. Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) confirmed the formation of spherical AgNPs ranging in size from 18 to 75 nm. After calcination at 200 °C, the nanoparticles displayed a cubic crystalline structure, as indicated by crystallographic planes (111), (200), (220), (311), and (222) in the XRD analysis. Morphological analysis via field-emission scanning electron microscopy (FESEM) revealed predominant particle sizes of 25 nm and 64 nm. Energy-dispersive X-ray spectroscopy (EDS) confirmed silver as the main constituent (48.5%), along with smaller amounts of carbon and oxygen (45.6% and 5.9%, respectively). Antimicrobial tests revealed significant inhibition zones against Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli, with maximum inhibition of 12.08 mm for S. aureus at a concentration of 100 µg/mL. These results highlight the potent antibacterial activity of the synthesized AgNPs against both Gram-positive and Gram-negative bacteria. The AgNPs also demonstrated strong larvicidal and pupicidal activity against Aedes aegypti mosquitoes. Larval mortality exceeded 90% after 72 h, with LC50 and LC90 values of 0.06 mg/mL and 0.07 mg/mL, respectively. Pupal mortality similarly surpassed 90%, with LC50 values of 0.03 mg/mL and LC90 values of 0.06 mg/mL after 72 h. These findings emphasize the efficacy of the nanoparticles in mosquito control, even at low concentrations. This study is the first to use cassava starch as both a reducing and stabilizing agent in the synthesis of AgNPs, underscoring its potential as an environmentally safe and cost-effective alternative for controlling vector-borne diseases and bacterial infections.

Graphical Abstract