Effects of oxygen radicals in low-pressure surface-wave plasma on sterilization

Abstract

The effects of oxygen radicals on sterilization were studied using a $2.45\mathrm{GHz}$ surface-wave oxygen plasma. A population of $1.5\times {10}^6$ Bacillus stearothermophilus spores was irradiated for $3\min$ or more with oxygen plasma, generated at pressures between 6 and $14\mathrm{Pa}$ . The decimal reduction value ($D$ value), a measure of the effectiveness of sterilization, was determined to be about $15–25\mathrm{s}$ . Using only oxygen radicals, excluding all charged particles, the $1.5\times {10}^6$ spores were sterilized with a $D$ value of $30–45\mathrm{s}$ after $5\min$ or more of irradiation. On scanning electron microscopy, the length and width of the spores changed significantly due to chemical etching by oxygen radicals.