Phytochemical-Assisted Synthesis of Silver Nanoparticles Using Eucalyptus Leaf Extract: Structural Characterization and Antimicrobial Evaluation

Abstract

The search for safer and environmentally friendly nanoparticle-synthesis methods is becoming more prominent in sustainable nanotechnology. In this study, phytochemical-assisted green synthesis of silver nanoparticles (AgNPs) was achieved using Eucalyptus globulus leaf extract (ELE), a rich source of phenolics, flavonoids, and tannins. The ELE concentrations ranging from 1–6% w/v provided differential phytochemical availability, directly influencing nanoparticle nucleation, growth, and stabilization. UV–Vis spectroscopy confirmed surface plasmon resonance bands at 420-422 nm responsible for AgNPs. FTIR analysis confirmed the presence of O–H, C=O, and C=C functional groups responsible for both reduction and capping of the AgNPs. TEM imaging demonstrated a concentration-dependent decrease in particle agglomeration, with 6% w/v ELE producing predominantly spherical nanoparticles averaging 12.90 nm. XRD analysis indicated crystalline face-centred cubic structures of AgNPs. Antibacterial assays showed significant inhibitory activity against Staphylococcus aureus and Klebsiella pneumoniae, with MIC values surpassing those of Neomycin. These findings established that phytochemical-assisted green synthesis of AgNPs has a promising antimicrobial potential against the pneumonia-causing pathogens with controlled morphology and bioactivity.