The present study applying a plasma jet to activate water in a controllable environment is aimed to investigate the effect of a combination of (working/ chamber gas) on the properties of plasma-activated water. After 10 min of activation, results reveal that a significant decrease in solution pH is observed with the presence of N 2 . Hydrogen peroxide appears to be the major species for most gas mixtures, except [Ar + air/Ar] and [Ar + air/ air], where nitrite and nitrate dominate. A gas mixture of [Ar + air/Ar] produces the maximum concentration of NO 2 − , while the maximum NO 3 − and H 2 O 2 are observed for [Ar + air/air] and (Ar/Ar), respectively. Overall, the antibacterial efficacy correlates well with NO 2 − concentration. K E Y W O R D S plasma jet, plasma-activated water, reactive nitrogen species, reactive oxygen species, sterilization F I G U R E 1 A schematic of the experimental setup 2 of 7 | LAI ET AL.