Antioxidant-rich <i>Micromeria imbricata</i> leaf extract as a medium for the eco-friendly preparation of silver-doped zinc oxide nanoparticles with antibacterial properties

Abstract This study explores the versatile features of eco-friendly green synthesized silver-doped zinc oxide nanoparticles (Ag/ZnO NPs) using a fresh leaf extract of Micromeria imbricata as both a reducing and a stabilizing agent. The work primarily evaluates the antibacterial and antioxidant properties of the pre-synthesized Ag/ZnO NPs and the plant extract. Structural and morphological characterization confirmed the hexagonal wurtzite structure of Ag/ZnO NPs via X-ray diffraction (XRD), with absorption peaks at 256 and 374 nm and a band gap of 3.17 eV. Fourier transform infrared analysis confirmed that phytoconstituents in the M. imbricata extract facilitated the synthesis, capping, and stabilization of Ag/ZnO NPs. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and transmission electron microscopy analyses showed spherical NPs with an average size of 28.12 nm. Antibacterial tests demonstrated that both ZnO NPs and Ag/ZnO NPs had strong bactericidal effects against tested strains, with Ag/ZnO NPs exhibiting superior performance. These NPs produced significant zones of inhibition and reduced the bacterial growth and viable cell counts. In comparison, the M. imbricata extract showed moderate antibacterial activity. However, antioxidant assays revealed that the extract had the highest efficacy (IC 50 = 48.72 µg·mL −1 ), surpassing both ZnO NPs (76.41 µg·mL −1 ) and Ag/ZnO NPs (81.51 µg·mL −1 ). Overall, these Ag/ZnO NPs effectively inhibit the growth of various pathogens, underscoring their promise for applications in antimicrobial system design and medical device innovation.