Antibacterial Characteristics of Ceramics and Carbon Materials dispersed with Their Powders

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Antibacterial activity for inorganic materials, such as CaO, MgO, ZnO, their solid solutions and activated carbons containing either MgO or ZnO, was studied by measuring the change in electrical conductivity with bacterial growth, and the chemical species contributed in the occurrence of the activity were identified. All samples used in this study showed a strong antibacterial activity without the presence of light, of which activity increased along with increasing powder concentration. The occurrence of antibacterial activity of CaO and MgO was found to be due to the increase of pH value in medium and the generation of super oxide from its surface. In the case of MgO-ZnO and ZnO-CaO solid solutions, the antibacterial activity decreased along with increasing the amount of ZnO and CaO, respectively. On ZnO, the occurrence of activity was found to be due to the generation of hydrogen peroxide from its surface. In this study, however, it was found that the activity by active oxygen such as super oxide and hydrogen peroxide weakened with lengthening the diffusion distance of active oxygen until it reaches the bacteria. Therefore, the activated carbons containing ZnO and MgO were prepared by carbonizing the resins ion-exchanged by Zn and Mg ions. A lot of bacteria adsorbed on the surface of obtained activated carbons, and a strong antibacterial activity showed at low powder concentration. Besides, The activity increased along with increasing the amount of MgO and ZnO in activated carbons.