부산대학교 도서관

This study highlights an eco-friendly microwave-assisted synthesis of colloidal silver (Ag°) and gold (Au°) nanoparticles, prepared using plant extract of Oroxylum indicum (Oi). Flavonoids present in the plant extracts act as stabilizing and reducing agents for synthesis of silver (Oi-AgNPs) and gold nanoparticles (Oi-AuNPs). The presence of flavonoids in plant extracts of Oi was confirmed by NMR and mass spectroscopy. The synthesized nanoparticles were analyzed by different characterization techniques. Surface plasmon (SPR) peaks appear at 403 nm (AgNPs) and 546 nm (AuNPs) in the UV-spectrum, revealing the formation of Oi-Ag and Oi-AuNPs. The size of the particles, as indicated by HRTEM analysis, was found to be 15 nm ± 3 nm (AgNPs) and 5.25 nm ± 1.00 nm (AuNPs). The resulting Oi-Ag and Oi-AuNPs exhibit face-centered cubic structures (FCC). Using Debye-Scherrer’s equation, the average particles were 21 nm and 8 nm in diameter, respectively. The synthesized Oi-Ag and Oi-AuNPs are found to be extremely toxic against Staphylococcus aureus (S. aureus) and Escherichia coli (E. Coli) bacteria. Furthermore, the catalytic efficiency of the prepared Oi-Ag and Oi-AuNPs were studied by the reduction of 4-nitrophenol. The obtained kobs values were 0.12 s-1 for AgNPs and 0.22 s-1 for AuNPs, and these results reveal that the AuNPs are 2-fold more active than AgNPs. The obtained results illustrate that the prepared microwave-assisted green synthesis of Ag and AuNPs is non-toxic and can be utilized for dual applications, including the reduction of 4-NP and serving as an efficient antibacterial agent. The reaction kinetics and recycling efficiency of the catalysts for the reduction of 4-NP were also examined. In conclusion, the Ag and AuNPs synthesized using the microwave-assisted biosynthesis method exhibit promising potential as catalysts for hydrogenation reactions and highly effective antimicrobial agents.