2-D Bubble Test Cell for the Study of Interactions at the Plasma–Liquid Interface

In plasma-liquid interactions, processes taking place at the gas-liquid interface drive chemical reactions within the bulk liquid. Such reactions and subsequent chemical transport are important to applications, such as plasma medicine and water purification. A 2-D bubble apparatus was investigated as a means to study physical and chemical processes taking place at the plasma-liquid interface. In particular, the approach makes the interfacial and surrounding regions accessible to optical diagnostics. Chemical transport originating at the interface driven by streamer and microdischarges within the bubble was observed, and chemical front propagation velocities were calculated. The propagation of acidification fronts as well as the transport of reactive oxygen species was documented using chemical probes. In addition, plasma-induced convection was observed illustrating the complex coupling of plasma-driven effects to the bulk solution. Time-dependent changes in bubble gas composition presumably driven by gas-phase reactions were also observed.