Transport analysis of short-lived reactive species across the plasma-liquid interface

Gas-liquid interfacial plasmas (GLIPs), in which atmospheric pressure plasmas are in contact with liquid, have attracted great interest worldwide, and applied researches are being conducted in a wide range of fields such as material synthesis, cell function control, and plant growth control. In order to obtain the desired results in these applied researches, it is necessary to control the reactive species produced by the GLIPs, and it is especially important to understand the behavior of short-lived reactive species. In this study, we have developed a unique GLIP system with a high-speed liquid column flow to measure the spatio-temporal distribution of short-lived reactive species in the order of msec. Using this system, we have succeeded in experimentally measuring the fast decay of OH radicals and NO₂⁻ precursor species for the first time. The total OH radical flux into the liquid surface was estimated as 4.8 × 10¹⁹ m⁻²s⁻¹ by the experimentally obtained OH radical decay in combination with the numerical modeling based on the reaction-diffusion equation. The gas-phase OH radical dissolution flux, one of the main origins of interfacial OH transfer, was evaluated as 3.6 × 10¹⁹ m⁻²s⁻¹ by the OH-LIF method in the vicinity of the water flow.