The roles of the various plasma agents in the inactivation of bacteria

TLDR

The roles of various plasma agents in bacterial inactivation have been investigated, but the effect of charged particles remains unclear. The study aims to determine the role of charged particles in bacterial inactivation using an atmospheric pressure plasma jet device. The device generates a cold plasma plume with a 300 mA peak current, enabling investigation of charged particle effects. The study found that charged particles play a minor role with He/N₂(3%) but an important role with He/O₂(3%), likely due to O₂⁻ ions, while active species such as O, O₃, and metastable O₂* are crucial, whereas excited He*, N₂ C Π₃ᵤ, N₂⁺ B Σ₂ᵤ⁺, heat, and UV have negligible effects.

Abstract

The roles of various plasma agents in the inactivation of bacteria have recently been investigated. However, up to now, the effect of the charged particles on the inactivation of bacteria is not well understood. In this paper, an atmospheric pressure plasma jet device, which generates a cold plasma plume carrying a peak current of 300 mA, is used to investigate the role of the charged particles in the inactivation process. It is found that the charged particles play a minor role in the inactivation process when He/N2(3%) is used as working gas. On the other hand, when He/O2(3%) is used, the charged particles are expected to play an important role in the inactivation of bacteria. Further analysis shows that the negative ions O2− might be the charged particles that are playing the role. Besides, it is found that the active species, including O, O3, and metastable state O2∗, can play a crucial role in the inactivation of the bacteria. However, the excited He∗, N2 C Π3u, and N2+ B Σ2u+ have no significant direct effect on the inactivation of bacteria. It is also concluded that heat and UV play no or minor role in the inactivation process.