Control of reactive oxygen and nitrogen species production in liquid by nonthermal plasma jet with controlled surrounding gas

Abstract

Abstract We present the development of a low-frequency nonthermal plasma-jet system, where the surrounding-gas condition of the plasma jet is precisely controlled in open air. By restricting the mixing of the ambient air into the plasma jet, the plasma jet can be selectively changed from a N 2 main discharge to an O 2 main discharge even in open air. In the plasma-jet system with the controlled surrounding gas, the production of reactive oxygen and nitrogen species is successfully controlled in deionized water: the concentration ratio of NO 2 − to H 2 O 2 is tuned from 0 to 0.18, and a high NO 2 − concentration ratio is obtained at a N 2 gas ratio of 0.80 relative to the total N 2 /O 2 gas mixture in the main discharge gas. We also find that the NO 2 − concentration is much higher in the plasma-activated medium than in the plasma-activated deionized water, which is mainly explained by the contribution of amino acids to NO 2 − generation in the medium.