Green Synthesis of Platinum@Silver (Pt@Ag) Bimetallic Nanoparticles Using Carica papaya Aqueous Leaf Extract for Catalytic Reduction of Dyes and their Antimicrobial Activity

This study presents a green, plant-mediated synthesis of platinum@silver (Pt@Ag) bimetallic nanoparticles using aqueous extracts of Carica papaya leaves as a bio-reducing and capping agent. The synthesized nanoparticles were characterized via UV-Vis spectroscopy, FTIR, XRD, SEM and HRTEM, confirming their crystalline nature, face-centered cubic structure and nanoscale core-shell morphology. FTIR analysis revealed functional groups such as hydroxyl and amide, supporting the biomolecular involvement in nanoparticle stabilization. The Pt@Ag nanoparticles exhibited a significant catalytic activity in the reduction of methylene blue and Congo red dyes, with a pseudo-first-order rate constant of 0.00512 min-1 for methylene blue. Furthermore, the antimicrobial studies demonstrated significant inhibition zones against both Gram-positive and Gram-negative bacteria, outperforming standard antibiotics in some cases. The observed synergistic effects of platinum and silver enhance both redox and ion-release mechanisms, making these nanoparticles promising candidates for environmental remediation and biomedical applications.