Synergistic enhancement of physicochemical and biomedical properties in microwave-synthesized copper-doped zinc oxide nanoparticles

Copper (Cu) doping in zinc oxide (ZnO) nanoparticles (NPs) is known to enhance their functional properties, making them attractive for biomedical applications. In this study, Cu-doped ZnO NPs [Zn_1-xCu_xO with x = 0.0385 (ZCu2), 0.08 (ZCu4), and 0.115 (ZCu6)] were synthesized using a microwave-assisted combustion route and comprehensively characterized. X-ray diffraction confirmed single-phase wurtzite ZnO with Cu incorporation, with crystallite sizes ranging from 54.65 to 71.66 nm and associated variations in strain and dislocation density. SEM analysis revealed particle sizes of 122-197 nm, in agreement with XRD results, while FTIR confirmed Zn-O vibrational shifts due to Cu substitution. UV-vis absorption spectra revealed a blueshift at lower concentrations of Cu doping (ZCu2 and ZCu4) attributed to the Burstein-Moss effect and a redshift at higher concentrations of Cu doping (ZCu6) due to defect-induced band gap narrowing, enhancing visible-light absorption. Photoluminescence analysis revealed band-edge emissions (409-430 nm) with optical band gap widening (3.30-3.47 eV) and defect-related emissions at higher Cu content. Zeta potential measurements indicated improved colloidal stability of the doped samples. Biomedical assays demonstrated notable antibacterial, antifungal, antioxidant, hemocompatible, and anticancer activity against MDA-MB-231 breast cancer cells. These findings establish Cu-doped ZnO NPs as promising candidates for nanomedicine applications.