Bulk ZnO Produced from Ultrafast Synthesis of ZnO Nanorods by Microwave Plasma for Antimicrobial Elimination of Leptospirosis

Zinc oxide (ZnO) nanorods are successfully synthesized by the microwave plasma and used as a raw material for making a bulk ZnO which can eliminate bacteria without contaminating the environment. Microwave plasma ionizes metallic zinc, while zinc ions are rapidly oxidized and deposited as ZnO nanorods in a confined area. Later on, ZnO nanorods are combined into a ZnO bulk by the sintering method. Although the outer appearance was the same as a ceramics rock, bulk ZnO contains a homogeneous internal submicron structure. The antimicrobial efficiency of sintered bulk ZnO was confirmed with both Gram-positive (Staphylococcus) and Gram-negative (Escherichia coli) bacteria. Unlike ZnO nanorod powder, since bulk ZnO can be placed in the water without dispersing or contaminating water, it was suitable to be used for specific application such as killing the bacteria in still water. One of the bacteria in Southeast Asia which resides in the logged water is Leptospira which is a major cause of leptospirosis in both humans and animals. Therefore, the excellent antimicrobial effect on Leptospira elimination by sintered bulk ZnO was examined. The results show that the bulk ZnO has a potential for biomedical application without being used in the nanostructure form.