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This cumulative thesis is based on five peer-reviewed publications and one conference contribution/proceedings. Three of the manuscripts discuss in-situ infrared spectroscopic studies on gas hydrates, while two additional publications address IR-ATR sensing of dissolved ions and ion pairs in synthetic salt solutions and in real seawater. Finally, one publication covers the infrared spectroscopic detection of perfluorinated tracer molecules for potential usage during subsurface storage of carbon dioxide. Therefore, various attenuated total reflection mid-infrared spectroscopic (IR-ATR spectroscopy) sensing methods were developed to enable measurements at extreme conditions in aqueous environments, i.e. at high-pressure conditions or at high saline concentrations. IR-ATR spectroscopy is a powerful tool for the detection of molecular changes that occur in materials and molecules (i.e. phase transitions, adsorption, etc.). Each molecule shows individual infrared absorption patterns, which – next to its molecular identity - also give information on its physical condition. Fiber optic MIR ATR spectroscopy is a robust and reliable spectroscopic sensing technique that may not only be miniaturized but enables in-situ measurements even at conditions that are occurring, e.g. in the deep sea and in other geologically relevant environments. |
