Antibacterial behavior of copper glazes: effect of copper(II) oxide concentrations and sintering atmospheres

This study reports the antibacterial activity of copper glaze, prepared with varying amounts of copper(II) oxide (CuO) and sintering atmospheres, against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). When sintered in an oxidizing atmosphere, samples with 3 wt% or more CuO showed antibacterial activity against S. aureus , killing 99.9% of the initial bacterial population. However, only the sample with 3 wt% CuO exhibited antibacterial activity against E. coli . When sintered in a reducing atmosphere, all the samples with CuO showed antibacterial activity against S. aureus and E. coli . The glazes showed antibacterial activity against S. aureus , regardless of the sintering atmosphere, when the concentration of Cu ions dissolved with alkali and alkaline metal ions was greater than 0.01 ppm. However, only the glazes with a water contact angle of 43° or higher, along with Cu ion dissolution, showed antibacterial activity against E. coli . This suggests that bacterial adhesion occurs on the glaze surface, and antibacterial activity is exhibited by contact-mediated killing that destroys bacterial cell walls through the dissolution of Cu ions. These results provide a complementary strategy for generating an antibacterial active surface that can prevent the infection or colonization of bacteria.