Green Fabrication of Psidium guajava-assisted Silver Nanoparticles for Efficient Photocatalytic Degradation, Broad-spectrum Antimicrobial Activity and Biomedical Applications
Abstract
Green synthesis of silver nanoparticles (Ag-NPs) has emerged as a sustainable alternative to conventional chemical methods owing to its environmental compatibility and low toxicity. In this study, Ag-NPs were successfully synthesized using Psidium guajava leaf extract (PG) and comprehensively characterized for their structural, optical, morphological, thermal, photocatalytic, antimicrobial, and antioxidant properties. X-ray diffraction confirmed the formation of crystalline face-centered cubic silver nanoparticles with an average crystallite size of approximately 16 nm. UV–Visible spectroscopy exhibited a characteristic surface plasmon resonance band at 430 nm, while the optical band gap determined from the Tauc plot was 2.98 eV. The FTIR analysis confirmed the involvement of phytochemicals in nanoparticle reduction and stabilization. Characterization revealed quasi-spherical nanoparticles with good colloidal stability (−35.0 mV), an average hydrodynamic diameter of 85 ± 5 nm, excellent thermal stability, and a mesoporous structure with a specific surface area of approximately 96 m2 g-1. The biosynthesized Ag-NPs–PG exhibited remarkable photocatalytic activity toward Rhodamine B degradation, achieving 94.2% removal within 90 minutes under UV irradiation and maintaining 81.7% degradation efficiency after five reuse cycles. Furthermore, the nanoparticles demonstrated significant antibacterial activity against Bacillus cereus (20.8 mm) and Pseudomonas aeruginosa (18.3 mm), as well as strong antifungal activity against Candida albicans (22.0 mm) and Aspergillus flavus (19.8 mm) at 1000 μg/mL. The DPPH assay further revealed concentration-dependent antioxidant activity with a maximum radical scavenging efficiency of 91.2%. The findings demonstrate that Psidium guajava-mediated Ag-NPs possess photocatalytic, antioxidant, and antimicrobial properties, showing potential as eco-friendly multifunctional nanomaterials for wastewater treatment and biomedical applications.