GREEN SYNTHESIS OF SILVER NANOPARTICLES FROM AZADIRACHTA INDICA AND STUDY OF THEIR ANTIBACTERIAL AND CATALYTIC PROPERTIES

Abstract

Background: Nanotechnology has become a pivotal discipline in material science due to its potential for developing highly reactive and functional materials at the nanoscale. Among various nanomaterials, silver nanoparticles (AgNPs) are particularly significant because of their unique optical, chemical, and biological properties. Conventional synthesis methods involve toxic chemicals and energy-intensive processes, often resulting in hazardous by-products. Green synthesis offers an eco-friendly, cost-effective, and sustainable alternative using biological resources such as plant extracts, which act as both reducing and stabilizing agents.

Objective: This study aimed to synthesize and characterize silver nanoparticles using aqueous leaf extract of Azadirachta indica through a green synthesis protocol and evaluate their catalytic and antimicrobial properties.

Methods: Aqueous extract of Azadirachta indica leaves was mixed with 1 mM silver nitrate (AgNO₃) solution and incubated at room temperature for four hours. The reaction mixture exhibited a visual color change indicating nanoparticle formation. Characterization was conducted using UV–Visible spectrophotometry, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The surface plasmon resonance (SPR) peak was recorded at 443 nm. FTIR analysis revealed the presence of hydroxyl, amine, and carbonyl functional groups responsible for reduction and stabilization. Antibacterial efficacy was assessed using the disc diffusion method against E. coli and S. aureus, with inhibition zones measuring 17 mm and 20 mm, respectively. Catalytic activity was evaluated by methylene blue reduction, demonstrating 86% dye degradation within 15 minutes.

Conclusion: The synthesis method was confirmed to be a rapid, one-step, non-toxic, and eco-friendly approach for producing stable and monodispersed AgNPs. The biological activity of these nanoparticles highlights their promising application in biomedical and environmental fields.