Preparation of zinc oxide ceramics with a sustainable antibacterial activity under dark conditions

Fabrication of ZnO ceramics with a sustainable antibacterial activity even in the dark has been conducted. Fine ZnO powders were hydrothermally treated in 0.5-3 mol ml(-1) Zn(NO(3))(2) aqueous solutions at 110-180 degrees C for 3-20 h. After an uniaxial pressing of the ZnO powders thus prepared, they were sintered at 400-600 degrees C for I h in air. Sustainability in antibacterial activity was evaluated using a colony count method with Escherichia coli bacteria on nutrient agar medium (36 degrees C/24 h) in a Na-P-buffer solution. The best data was attained for the ZnO ceramics prepared from the following conditions: a 3 mol ml(-1) zinc nitrate solution for the hydrothermal treatment at 120 degrees C for 7 h and sintering in air with a step-by-step pattern (470 degrees C/1 h-485 degrees C/1 h-500 degrees C/1 h). ESR and chemical photoluminescence analyses have cleared that radical oxygen of super-oxide ((center dot)O(2)(-)) originated from the surface of ZnO might exhibit an antibacterial activity even under the dark condition. (C) 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved.