Antibacterial persistence of hydrophobically glazed ceramic tiles

The antibacterial properties and durability of copper-glazed ceramic tiles were systematically investigated in detail in terms of the hydrophobicity change with glaze thickness. The water contact angle of the standard glaze without copper was 25.2° ± 0.2°, whereas the copper glaze showed hydrophobicity which was dependent on the glaze thickness. A maximum contact angle of 109.6° ± 0.4° was measured from the copper-glazed surface with thickness of 150–200 μm. As the contact angle and hydrophobicity of the copper glaze increased, the antibacterial efficiency against Staphylococcus aureus and Escherichia coli also increased. An antibacterial efficiency of 99.9% was demonstrated from the copper-glazed sample with the thickness of 150–200 μm. In addition, it was confirmed that 99.9% of the antibacterial efficiency of the copper-glazed ceramic tiles could be maintained for at least 2 years. In ion dissolution measurements of the standard and copper glazes, Ca, Na, Si, and K ions were observed, and Cu ion dissolution was only observed from the copper glaze. These results suggests that the hydrophobicity and strongly negative surface charge, which were contributed from Cu addition into the glaze composition, could block the access of bacteria to the glaze surface, and bacterial killing via Cu ion dissolution occurs.