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

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 $He∗$⁠, $N2$ $CΠ3u$⁠, and $N2+$ $BΣ2u+$ 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.