The Role of Oxygen in a Large Area of RF-Powered Atmospheric Pressure Dielectric Barrier Glow Discharge Plasma in Sterilization

A nonequilibrium Ar/O₂ plasma at atmospheric pressure was generated between two parallel square electrodes by a 13.56-MHz power supplier. Experimental results demonstrate that the Ar/O₂ plasma more effectively kills Staphylococcus aureus and Escherichia coli than the Ar plasma. When the O₂ flow rate increases from 0 to 100 sccm step by step, the discharge voltage and the radio-frequency (RF) current always show sinusoidal waveforms, and the discharges maintain the α mode as well. In addition, the sterilization efficiency values of the RF-powered atmospheric pressure Ar/O₂ plasma depend on the oxygen fraction in Ar gas. It is found that the sterilization efficiency of the Ar/O₂ plasma is highest with 0.5 vol.% oxygen in argon gas, corresponding to the maximum production of O(³P) radicals. It is considered that the O(³P) radicals produced by the Ar/O₂ plasma play a significant role in atmospheric plasma sterilization.