The effect of air on solvated electron chemistry at a plasma/liquid interface

Plasmas in contact with liquids initiate complex chemistry that leads to the generation of a wide range of reactive species. For example, in an electrolytic configuration with a cathodic plasma electrode, electrons from the plasma are injected into the solution, leading to solvation and ensuing reactions. If the gas contains oxygen, electronegative oxygen molecules may react with the plasma electrons via attachment to reduce the electron flux to the solution reducing the production of solvated electrons or produce reactive oxygen species that quickly scavenge solvated electrons in solution. Here, we applied a total internal reflection absorption spectroscopy technique to compare the concentration of solvated electrons produced in solution by an argon plasma containing various amounts of oxygen, nitrogen, and air. Our measurements indicate that in oxygen or air ambients, electron attachment in the plasma phase greatly attenuates the electron flux incident on the liquid surface. The remaining electrons then solvate but are quickly scavenged by reactive oxygen species in the liquid phase.