Evaluation of the Photocatalytic and Antimicrobial Properties of Cu-Doped ZnO Nanoparticles Synthesized by Phytochemical Methods

In this study, zinc oxide (ZnO) and copper-doped zinc oxide nanoparticles (Cu-ZnO NPs) were synthesized using a green method that employed Rosmarinus officinalis leaf extract as a reducing agent. Copper was incorporated as a dopant at concentrations of 3% and 5%. Zinc acetate dihydrate and copper acetate served as the precursors and dopants, respectively. The synthesized samples were characterized utilizing a range of techniques, including XRD, SEM, EDX, Raman spectroscopy, UV-visible spectroscopy, and PL spectroscopy. XRD and Raman spectroscopy analyses validated the effective incorporation of Cu²⁺ ions into the ZnO wurtzite structure. SEM analysis indicated that the nanoparticles displayed a spherical morphology, while EDX analysis confirmed the presence of zinc (Zn), copper (Cu), and oxygen (O), thereby validating the sample's purity. UV-visible spectra revealed a reduction in the optical band gap with increasing Cu concentration. Photoluminescence peaks observed at 383 nm and 565 nm were ascribed to electron transitions from deep donor levels, particularly from Zn interstitials to Zn and oxygen vacancies. The 5% Cu-doped ZnO NPs demonstrated the highest photocatalytic activity, achieving 90% degradation of Rhodamine B (RhB) dye under UV irradiation in 135 minutes. They also exhibited significant antibacterial activity, particularly against Gram-positive bacteria ( Staphylococcus aureus ) compared to Gram-negative bacteria ( Escherichia coli ).