Green Synthesis of Silver Nanoparticles from Melissa officinalis Flower: Evaluation of Antimicrobial, Antioxidant, and Photocatalytic Activity

Silver nanoparticles (AgNPs) synthesized via green approaches have attracted considerable attention because of their eco-friendly production and versatile biological and photocatalytic properties. In this study, Melissa officinalis flower extract was employed as a natural reducing, capping, and stabilizing agent for the green synthesis of AgNPs. HPLC-DAD analysis revealed that the flower extract exhibited a diverse phytochemical profile, including phenolic acids and flavonoids, which may contribute to the reduction of Ag+ ions and the stabilization of the synthesized AgNPs. The synthesized nanoparticles were characterized using UV–Vis spectroscopy, ATR-FTIR, SEM, DLS, zeta potential analysis, and XRD. The AgNPs exhibited predominantly spherical to hemispherical morphology with an average particle size of 40 nm and a characteristic surface plasmon resonance peak at 414 nm. DLS analysis revealed a particle size of 111.2 nm and a Z-average hydrodynamic diameter of 296.0 nm, while the zeta potential of −73.2 mV suggested high colloidal stability. XRD analysis confirmed the formation of a face-centered cubic (fcc) crystalline structure. The synthesized AgNPs exhibited photocatalytic activity, achieving degradation efficiencies of 93.6 ± 0.3% for methylene blue and 44.8 ± 0.6% for Coomassie Brilliant Blue R-250 after 180 min. In addition, the nanoparticles exhibited considerable antioxidant activity in the DPPH assay and antimicrobial activity against Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, and Candida albicans. Overall, the findings indicate that AgNPs synthesized from M. officinalis flowers via the green synthesis method exhibited photocatalytic, antioxidant, and antimicrobial activities under the experimental conditions studied. These findings suggest that the synthesized AgNPs could be considered a potential material, particularly for dye removal and antimicrobial applications.