The key reactive species in the bactericidal process of plasma activated water

The bactericidal mechanism of plasma activated water (PAW) is an important issue that needs to be addressed in plasma medicine. In this paper, the pH value and the concentrations of RONS (H₂O₂, , , OH·, ONOOH and ¹O₂) in PAW were measured by chemical and optical methods. The bacteria E. coli was used as a microbial model to study the bactericidal effects of PAW. It was found that the concentration of peroxynitrous acid (ONOOH) in PAW was too low to directly realize complete bactericidal effects of PAW. Actually, ONOOH further interacted with H₂O₂ to generate peroxynitric acid (O₂NOOH), which eventually decomposed into superoxide anion radical (·) and singlet oxygen (¹O₂); these two species enhanced the bactericidal effects of PAW substantially. (paper)