Aqueous Reactive Species Induced by Dielectric Barrier Discharge Plasma in Pure Water: A Quantitative Study

This study quantitatively examined the generation dynamics of reactive oxygen and nitrogen species (RONS) in low-temperature plasma-activated pure water using a dielectric barrier discharge (DBD) system under different gas atmospheres ($\mathrm{N}_{2}$, air, $\mathrm{O}_{2}$). By systematically adjusting plasma discharge power ($5-15 ~\mathrm{W}$) and treatment duration ($0-60 ~\mathrm{s}$), combined with spectrophotometric and fluorometric assays, we characterized the concentration profiles of nitrate $\left(\text{NO}_{3}{ }^{-}\right)$, nitrite ($\text{NO}_{2}^{-}$), and hydrogen peroxide ($\mathrm{H}_{2} \mathrm{O}_{2}$), while monitoring pH stability. Key findings include: (1) During the plasma treatment process, the $\text{~ p H}$ of PBS remained relatively stable, with a change greater than 2. Such a drastic $\text{p H}$ shift may not be suitable for the treatment of living cells; (2) Nitrogendominated atmospheres ($\approx \text{8 0 \%} \mathrm{N}_{\mathrm{2}}$ content) substantially enhance reactive nitrogen species production. These findings underscore the importance of gas-phase chemistry in tailoring RONS composition and highlight the need for further mechanistic studies on short-lived RONS (e.g., $\cdot \text{OH}, \text{ONOO}^{-}$) generation and their spatiotemporal biological effects.