Tracking Water Molecules and Carboxylate Ions in Confinement Using Advanced Vibrational Spectroscopy

This thesis delves into the properties of small molecular species in various confined environments in condensed phase using non-linear infrared spectroscopy. Chapter 1 provides an overview of the relevant confined systems and methodologies applied, while Chapters 2 and 3 provide the description of theoretical background and experimental techniques. In Chapter 4, we explore the ultrafast dynamics of water molecules enclosed in small clusters formed by 2,6-lutidine near the lower solution critical temperature (LSCT) using mid-infrared pump-probe spectroscopy. Chapter 5 reports on the vibrational coupling in aqueous acetate and terephthalate ions using two-dimensional infrared spectroscopy (2D-IR). In Chapter 6, we introduce a novel synthetic approach for preparing polycrystalline UiO-66 metal-organic framework membranes superimposed on flat c-sapphire substrates and investigate the vibrational interactions of terephthalate linkers in this material using information from Chapter 5. Finally, in Chapters 7 and 8, we use vibrational sum-frequency generation (VSFG) spectroscopy to investigate the absorption and orientation of carboxylate ions with different substituents at the water-air interface.