Aqueous-phase chemistry and bactericidal effects from an air discharge plasma in contact with water: evidence for the formation of peroxynitrite through a pseudo-second-order post-discharge reaction of H₂O₂and HNO₂

Formations of transient species and stable chemical products produced at the gas-liquid interface and directly in the liquid by gas discharge plasma in contact with water surface were measured in dependence on the gas atmosphere and solution pH controlled by buffers.The aqueous-phase chemistry and the chemical and biocidal effects of air discharge plasma in the liquid were evaluated using phenol as chemical probe and bacteria E. coli. The nitrated and nitrosylated products of phenol (4-nitrophenol,2-nitrophenol,4-nitrocatechol,4-nitrosophenol) in addition to the hydroxylated products (catechol, hydroquinone, 1,4-benzoquinone, hydroxy-1,4-benzoquinone) evidenced formation of NO2•, NO• and OH• radicals and NO+ ions directly by air plasma at the gas-liquid interface and through post-discharge processes in plasma-activated water (PAW) mediated by peroxynitrite.Kinetic study of post-discharge evolution of H2O2 and NO2- in PAW has demonstrated excellent fit with the pseudo-second-order