Effects of Zn and Ag (Co)Doping on the Structural, Optical, and Antibacterial Properties of CuO Nanoparticles

Background: Copper oxide (CuO) nanoparticles exhibit high structural, optical, and antibacterial properties; co-doping with Zn and Ag can further modify these properties but comparative studies of single and co-doped CuO synthesized by sol-gel are limited. This study evaluates the effects of Zn (5 at %), Ag (5 at %), and Zn + Ag (5 at % each) doping on the structure, optical, morphology, and antibacterial activity of CuO nanoparticles. Methods: Pure CuO nanoparticles (NPs) and those doped with Zn (5 at %), Ag (5 at %), and Zn + Ag (5 at % each) were prepared using a sol-gel method and characterized in terms of structural, optical, and antibacterial properties. Results: All samples exhibited the monoclinic tenorite structure. Doping reduced crystallite size and increased defect (e.g., dislocation) density, microstrain, and unit cell volume. The NPs exhibited a homogeneous distribution and featured dopant-dependent morphologies and aggregation extents. Doping increased the absorbance of CuO in the visible region, with the band gaps of pure and Zn/Ag-codoped NPs determined as 1.77 and 1.71 eV, respectively. All NPs inhibited the proliferation of Escherichia coli and Staphylococcus aureus (model Gram-negative and Gram-positive bacteria, respectively). The strongest effect was observed for codoped CuO, which inhibited E. coli more than it did S. aureus. Conclusions: Thus, Zn/Ag-codoped CuO NPs hold promise for different applications, particularly those requiring antibacterial properties.