Effect of Plasma Modification of Copper Nanoparticles on their Antibacterial Properties

Surface modification of copper nanoparticles (CuNPs) was performed in a radiofrequency plasma reactor using acrylic acid, acrylonitrile, and methyl methacrylate monomers. Treated and untreated CuNPs were analyzed by thermogravimetrical analysis, X-ray diffraction (XRD), transmission electronic microscopy, energy dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. The oxidation of CuNPs was assessed by XRD as a function of the plasma treatment. The antibacterial properties of plasma treated CuNPs were evaluated using Pseudomonas aeruginosa and Staphylococcus aureus. It was found that the plasma modification did not affect significantly the antibacterial properties of CuNPs, since the plasma films deposited on their surfaces were in the order of few nanometers and copper ions traveled easily through the plasma polymer to interact with the bacteria. Further, the nanocoating deposited by plasma on the CuNPs protects them against the oxidation even in solution dispersions. CuNPs coated with acrylonitrile presented a slightly lower antibacterial activity than pristine CuNPs.