Assessment of the roles of various inactivation agents in an argon-based direct current atmospheric pressure cold plasma jet

Summary form only given. A direct current atmospheric pressure cold plasma jet was used to inactivate Staphylococcus aureus (S. aureus) suspended in a liquid. Three types of gases, pure argon (99.999%), argon with 2% oxygen, and argon with 2% oxygen and 10% nitrogen were used as operating gases respectively. The inactivation efficacies for the plasma jets operating in the three gases decrease from Ar/O₂(2%) to Ar/O₂(2%)/N₂(10%) to pure Ar. Optical emission spectroscopy (OES), electron spin resonance (ESR) spectroscopy, high performance liquid chromatography (HPLC), and atomic absorption spectrophotometry (AAS) were employed to identify and monitor the reactive species in the plasma-liquid system for the three operating gases and revealed the presence of O, ¹O₂, OH, NO, H₂O₂, O₃, and NO₃^-/NO₂^- as well as Cu (Cu⁺/Cu2⁺). The S. aureus inactivation results indicate that atomic oxygen is the key inactivation agent here, while other species play a lesser role in the inactivation progress studied here.