The generation of hydrogen peroxide and antibacterial effectiveness by copper oxide surface layers

Copper is known as an antibacterial material. Reactive oxygen species (ROS) with antibacterial effectiveness are generated on copper surfaces mainly by the Fenton-type reaction. The antibacterial effectiveness is higher in Cu₂O than in CuO. In this study we discussed the effects of the difference in the amount of generated ROS on the difference in the antibacterial effectiveness between Cu₂O and CuO. Both Cu₂O and CuO produced hydrogen peroxide (H₂O₂）, hydroxyl radical(･OH）, and singlet oxygen (¹O₂）, but not superoxide radical (･O₂^-）. The concentration of H₂O₂ produced was higher in Cu₂O than in CuO. When catalase, a scavenger of H₂O₂, was added, the antibacterial activities of both Cu₂O and CuO reduced to almost the same value. These experimental results indicate that Cu₂O is higher in antibacterial effectiveness than CuO because Cu₂O produced more H₂O₂ than CuO. As ･OH was detected even when H₂O₂ was scavenged by catalase before it reacted with Cu ion, a part of ･OH was generated by chemical reactions different from the Fenton-type reaction when copper oxides were in contact with water.