Fast reaction chemistry of plasmas in liquids interacting with surfaces

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Plasmas in direct contact with liquids or plasmas inside liquids allow a high mass transfer of reactive species from the gas phase into the liquid. If these plasmas-in-liquids are interfaced with solids, very fast and efficient reaction rates for surface reactions can be realized. Such systems are relevant for the field of plasma medicine where the plasma interacts with a biological surface inside a liquid, the degradation of toxic organic compounds and plasma enhanced anodization of metal surfaces inside an electrolyte. Dominant reactive species in the liquid at the plasma-liquid-solid interface can be analyzed by gas chromatography, titration or electron spin resonance. However, these methods are either ex-situ or they are only sensitive to long living species. Prominent example is the current debate about plasma-activated media in the field of plasma medicine. However, in many of the above systems, the plasmas are at first directly interacting at the plasma-liquid-solid interface and a more direct insight into the reaction chemistry is desired. In this project, a special setup based on FTIR spectroscopy in the attenuated reflection mode is developed to probe the plasma-liquid-solid interface with high temporal resolution in the microsecond range based on Step-scan FTIR. Two prominent model cases are addressed, the plasma enhanced oxidation of metallic surfaces and the plasma induced modifications or organic and biological surfaces being a model system for the field of plasma medicine.