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Tin oxide powders were prepared by a homogeneous precipitation method using an aqueous solution of SnCl 4 with urea and followed by a calcination process for the crystalline phase. The calcination method affects the crystalline properties of the tin oxide powders in terms of crystallinity and crystalline size. The degree of crystallinity strongly increases as the calcination temperature increases. In comparison with other calcination methods, the rapid thermal annealing (RTA) method yields a high specific surface area and a smaller crystalline size of the tin oxide powder than that achieved by the conventional furnace annealing method. In the RTA process, crystallinity increases as the calcination temperature increases and the ramp-up speed to reach a designated temperature decreases.

Torch-type atmospheric pressure plasma with two ring-type copper electrodes has been analyzed to investigate the characteristics of plasma plume and local sterilizing effect on microorganisms. The concentration of ozone as an active oxygen species in plasma plume was varied with the level of applied voltage and the proportion of gasses in a mixture composed of helium and oxygen. The temperature of the plasma flume could be increased to 38 C as a maximum temperature under an exposure time of 10 min, which suggests that the plasma plume can be directed manually by a user to come in contact with delicate objects and materials without causing any heating or painful feeling. An advantage of the plasma is that it is controllable at low temperatures with high stability. Sterilization for E. coli was strongly affected by the applied voltage, the oxygen ratio in the gas mixture of He/O 2 , and the treatment time. Reactive oxygen species, including atomic oxygen and ozone, which are generated by the plasma plume, play an important role in the bacteria inactivation processes. Our plasma can be used successfully to sterilize E. coli for biomedical applications.

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