GREEN SYNTHESIS OF SILVER NANOPARTICLES FROM NEEM BARK FOR THE REMEDIATION OF WATERBORNE PATHOGENS

Objective: The objective of the study was to develop an eco-friendly method for synthesizing silver nanoparticles (AgNPs) using neem (Azadirachta indica) bark extract as a reducing and stabilizing agent, and to evaluate their antibacterial, antipathogenic, and larvicidal activities for water purification and vector control. Methods: AgNPs were synthesized by green chemistry using neem bark (NB) extract, avoiding hazardous chemicals. Synthesis parameters – pH, temperature, and reaction time – were optimized. Characterization included ultraviolet (UV)-Visible spectroscopy (Shimadzu UV-1800), Fourier transform infrared (Perkin Elmer Spectrum-One, USA), X-ray diffraction (Cu Kα radiation, λ = 1.5406 Å), SEM (Hitachi S-3400N), TEM (JEOL-JEM- 2100F, 200 kV), particle size analysis, and zeta potential measurement. Antibacterial activity against Staphylococcus aureus and Escherichia coli was tested by the well diffusion method. Antipathogenic activity was assessed using pathogenic sewer water, and larvicidal activity was evaluated against mosquito larvae (n=10/concentration). Results: Spherical NB AgNPs (40–150 nm) with a characteristic SPR peak at 425 nm were obtained. X-ray diffraction confirmed a face-centered cubic crystalline structure with an average crystallite size of 7.66 nm. Zeta potential values (–26.7 to –33.2 mV) indicated good colloidal stability. Antibacterial testing showed maximum inhibition zones of 47 mm for S. aureus and 37 mm for E. coli at 25 μg/mL. In pathogenic water, smaller particles exhibited higher inhibition efficiency. Larvicidal assays achieved 100% mortality at 2.5 μg/mL within 3 h (p