Harnessing nature for dual action: silver nanoparticles synthesized from guava leaf extract for photocatalytic degradation of methyl red and antibacterial applications†

This study revealed novel insights into key parameters affecting the biogenic synthesis of silver nanoparticles (AgNPs) with a dual-faceted application via a green route utilizing aqueous guava (Psidium guajava L.) leaf extract as both a reducing and stabilizing agent. The formation of AgNPs was visually confirmed by a color change of the reaction mixture from pale yellow to reddish-brown. Characterization of the synthesized AgNPs revealed a surface plasmon resonance band at 415–420 nm in the Ultraviolet-Visible (UV-Vis) spectra, confirming the presence of AgNPs. Dynamic light scattering (DLS) analysis indicated an average particle size of approximately 29 nm, while X-ray diffraction (XRD) analysis confirmed the crystalline nature and high purity of the synthesized AgNPs. Transmission electron microscopy (TEM) images displayed a primarily spherical morphology with an average size of about 12 nm. Fourier transform infrared (FTIR) spectroscopic analysis further supported the role of phytochemicals, such as phenolic acids and flavonoids, in the bioreduction and stabilization of the AgNPs. The synthesized AgNPs exhibited significant antibacterial activity against Gram-positive (S. aureus, E. faecalis) and Gram-negative (P. aeruginosa) bacterial strains, as demonstrated by the disc diffusion method. Furthermore, the AgNPs demonstrated promising photocatalytic activity, achieving approximately 95–96% degradation of methyl red (MR) within 72 hours under sunlight exposure. The dual functionality of the as-synthesized AgNPs opens up exciting avenues in both environmental remediation and biomedical fields.