Plasma-Driven Reactive Species Production and Transport in a 2-D Discharge Cell

A 2-D cell was employed to study the plasma-liquid interface. Chemical probes were used to compare the chemical reactivity induced by both air and argon plasma discharges in bubbles. Methyl orange and potassium iodide-starch solutions were used to visualize the propagation of acidic and oxidative fronts into the bulk liquid beyond the interface. Acidic and oxidative fronts were observed for both air and argon plasmas, indicating that charge exchange and electron impact processes at the interface are crucial to plasma-induced reactivity in liquids. Absorption spectrophotometry of indigo trisulfonate was performed to measure the transport of oxidative species, primarily aqueous ozone, and hydroxyl radicals, from plasma to the liquid region. Chemical reactivity at the interface can be transported far into the bulk liquid region due to plasma-induced fluid flow.