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 facecentred 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.