Evaluation of the antibacterial activity of zinc oxide nanoparticles doped with copper ions and co-doped with copper and silver ions

The current feasibility study deals with the elimination of Escherichia coli (gram-negative) and Staphylococcus aureus (gram-positive) bacterial strains isolated from swimming pools using zinc oxide (ZnO) nanoparticles (NPs) doped with copper (Cu2+) ions (CuX%/ZnO NPs) and co-doped with copper (Cu2+) and silver (Ag+) ions (AgX%/CuY%/ZnO NPs) synthesized by sol-gel method. Antibacterial activity was evaluated by Agar well diffusion assay. As-produced NPs were characterized by X-ray diffraction, Field emission-scanning electron microscopy, Energy Dispersive X-Ray and Transmission electron microscopy techniques. The results showed that the size of the co-doped NPs was smaller than that of mono-doped NPs. Meanwhile, co-doped Ag5%/Cu5%/ZnO NPs had the maximum bactericidal activity, and the destructive effect on Gram-positive bacteria was greater than that on Gram-negative bacteria. The lowest effective nanoparticle concentrations were 0.1 and 0.05 g/mL. The main bactericidal mechanism, in addition to the size of co-doped NPs, was due to the formation of reactive oxygen species, so that the destruction of the bacterial cell wall and finally death occurred through the radicals formed.