Content area
This thesis explores the development and application of Photothermal Cantilever Deflection Spectroscopy (PCDS) for the selective and sensitive detection of per- and polyfluoroalkyl substances (PFAS) in the vapor phase. The PCDS technique, which leverages the molecular specificity of mid-infrared (mid-IR) spectroscopy and the exceptional thermal sensitivity of bi-material cantilevers, presents a novel approach for real-time gas sensing with selectivity and sensitivity. This research focuses on detecting key PFAS compounds, such as PFOA and 8:2 FTOH, with a mass sensitivity in the picogram range. The study also introduces a custom-designed open architecture gas sensing setup, which allows experimental modifications for incorporating multi-physics approaches in real-time sensing. The cantilever bending as a function of irradiating mid-IR wavelength shows distinct molecular fingerprints of PFAS compounds, enabling accurate identification and differentiation of structurally similar compounds. Despite its promise, challenges such as targeted analyte adsorption on the ZnSe window of the gas chamber and the continuous heating of the cantilever by the red laser used for monitoring cantilever motion were identified as key obstacles to achieving optimal sensitivity. Proposed solutions include heating the ZnSe window to reduce adsorption and actively cooling the cantilever to improve adsorption conditions. These modifications would enhance the feasibility of real-time vapor detection. These results underscore the transformative potential of PCDS for environmental monitoring, offering a versatile platform for detecting airborne contaminants. This thesis provides a robust foundation for future advancements in PCDS technology, addressing critical environmental challenges and advancing gas sensing methodologies for industrial and public health applications.