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The influence of reactive oxygen species on living cells, including various microbes, is discussed. A sterilization experiment with bacterial endospores reveals that an argon–oxygen plasma jet very effectively kills endospores of Bacillus atrophaeus (ATCC 9372), thereby indicating that oxygen radicals are the key element of sterilization. Ozone in acidic water also kills endospores of B . atrophaeus very effectively, demonstrating the capability of cleaning a large surface area contaminated by toxic biological agents. The viable microbe numbers after the contact with acidic ozone water directly correlate with increase in the ozone decay time in water after lowering the pH value of water from pH = 7 to 4 indicating that acidic ozone water is an effective means of sterilizing microbes. However, advanced cells such as fertilized eggs were not greatly influenced by the acidic ozone water. Also, both human and canine cells after treatment with the acidic ozone water prospered without showing signs of stress due to ozone in acidic water. This study suggests that antioxidant enzymes such as superoxide dismutase can be developed in the advanced cells to protect themselves from attacks by reactive oxygen species. Meanwhile, the advanced cells utilize oxygen by certain enzymes, proliferating life on earth.

Presented here is an apparatus consisting of an atmospheric resistive-barrier discharge for the sterilization of medical tools wrapped in typical hospital cloths, for the sterilization of manufactured drugs in typical packaging materials, and for the sterilization of biologically-contaminated articles. The sterilization apparatus consists of layers of the resistive-barrier discharge device operating at room temperature, a sterilization chamber, and an ozone destruction device. An electrical discharge in the resistive-barrier discharge system generates an atmospheric plasma in oxygen gas, generating ozone, which in turn efficiently sterilizes medical tools and biologically contaminated articles at room temperature. A sterilization experiment was carried out at an apparatus volume of 100 liters, with a sterilization chamber volume of 60 liters, and a discharge device volume of 40 liters. The sterilization in this experiment required 60 W of power for 5 hours of residence time. For a given sterilization time, the required electrical power was proportional to the apparatus volume. Ozone in the sterilization chamber was destroyed safely after sterilization.

Sterilization of various microbes was carried out by using several plasma jets. Argon plasma jets penetrate deep into ambient air and create a path for oxygen radicals to sterilize microbes including spores. A sterilization experiment with bacterial endospores indicates that an argon-oxygen plasma jet very effectively kills endospores of Bacillus atrophaeus (ATCC 9372), thereby demonstrating its capability to clean surfaces and its usefulness for reinstating contaminated equipment as free from toxic biological agents. The key element of the sterilization is oxygen radicals. The penciltype configuration produces a long, cold plasma jet capable of reaching 3.5 cm and having various excited plasma species shown through the optical emission spectrum. Operation of an air plasma jet at 2 W in a pencil-type electrode provides an excellent opportunity for sterilization of microbes. An electron microscope was used to observe the effects of the plasma on bacterial cell morphology. Transmission electron micrographs showed morphological changes in E. coli cells treated with an atmospheric plasma at 75 W for 2 min. The treated cells had severe cytoplasmic deformations and leakage of bacterial chromosome. The chromosomal DNA was either attached to the bacterial cells or released freely into the surrounding medium. The results clearly explain the loss of viability of bacterial cells after plasma treatment.

A measurement of the secondary electron-emission coefficient γ from MgO film in a plasma display panel is carried out. The influence of the secondary electron emission on the breakdown voltage in microdischarges on the plasma display panel is investigated by making use of the Townsend sparking criterion. Experimental data agree well with theoretical results, verifying the previous theoretical model.

A theoretical model of the secondary electron emission yield (γ) from a MgO layer is developed based on the Auger neutralization of ions, resulting in an analytical expression of γ in terms of the ionization energy Ei for the density of states in the valence band, being an exponentially decaying function of the energy deviation from the band characteristic energy of 7.88 eV. The analytical expression recovers the previously known empirical formulation of γ∼(Ei−2φ) for the work function φ. Results of the theoretical model agree well with the measured data in terms of the data trend.