The bactericidal effects of plasma-activated saline prepared by the combination of surface discharge plasma and plasma jet

Plasma-activated water (PAW), as a derivative of cold atmospheric pressure plasma, can inactivate bacteria and greatly expand the application of plasma technology. Commonly used PAW is activated by a plasma device, plasma jet, or surface discharge plasma. PAW prepared by some methods, such as a plasma jet with low frequency, exhibits little bactericidal effect and cannot be applied for use in disinfection or sterilization. Therefore, developing strategies to improve the bactericidal effects of PAW is necessary. Here, the air was first activated by a surface discharge device with a ceramic dielectric under two modes—the ozone mode and nitrogen oxide mode—and then incorporated with helium as the working gas for the plasma jet, which was used to prepare the plasma-activated saline (PAS). The concentrations of long-lived NO2− and NO3− and the short-lived 1O2 in the PAS activated by the nitrogen oxide mode and plasma jet were highest. The amount of ONOO− in the PAS activated by the combination was lower than the amount in the PAS activated only by the plasma jet. The PAS activated by the combination of nitrogen oxide mode and plasma jet exhibited the strongest bactericidal effect, which was consistent with the intracellular reactive oxygen species levels. The scavenger analysis demonstrated that 1O2 and ONOO− play essential roles in bacterial inactivation. These results indicate a new strategy for the preparation of PAW with strong bactericidal ability for application in environmental disinfection.