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 center dot, ONOOH and O-1(2)) 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 (center dot) and singlet oxygen (O-1(2)); these two species enhanced the bactericidal effects of PAW substantially.