Detection of Hydrated Electrons at Liquid-Plasma Interface Using Total Internal Reflection Absorption Spectroscopy*

Polyfluoroalkyl substances (PFAS) are highly stable compounds used in a multitude of commercial applications. Increasing amounts of evidence point to ubiquitous contamination in nature and negative health effects of PFAS bioaccumulation. Removal of PFAS contamination remains difficult due to the strength of the carbon-fluorine bonds. The most promising avenues involve advanced reduction or oxidation pathways, particularly lone electrons dissolved in water (hydrated electrons). Low-temperature plasma is capable of producing hydrated electrons at low power densities, making it a strong candidate for PFAS remediation. Hydrated electrons absorb strongly in the red, so that even very small absorbance can be detected using a helium-neon laser and lock-in detection. This study uses an established total internal reflection absorption spectroscopy (TIRAS) technique to explore whether atmospheric pressure plasma jets can effectively produce hydrated electrons at the liquid surface.