Effects of Atmospheric-Pressure Nonthermal Nitrogen and Air Plasma on Bacteria Inactivation

An atmospheric-pressure nonthermal plasma jet operated with nitrogen and air is used to investigate the inactivation of bacterium P. aeruginosa. To better understand the bactericidal efficiency of the reactive species (RS) with a different lifetime, direct and indirect treatments are used to inactivate the bacteria with different initial bacteria numbers and Petri dishes. No obvious difference is observed between the nitrogen and air plasmas in the direct treatment, but the air plasma is more efficient in the indirect treatment due to more O₃ and NO. The direct treatment is much more efficient than the indirect one because of the participation of charged particles and RS, such as N₂(A), N (⁴S), O(¹S), and O(³P). However, the indirect treatment covers a larger area on account of the more diffusion of the long-lived RS O₃ and NO. Our results show that the plasma jet is more suitable for wound therapy although the treated area is small.