Vibrational Dynamics of Water at Interfaces : Study of vibrational dynamics of water with interface specific time resolved vibrational spectroscopy

Abstract

Although not proven, it is generally excepted that life without water is not possible. From cloud formation to protein folding, water holds an irreplaceable position in its importance for life. This thesis investigates the structure and the vibrational dynamics of the interfacial water hydrogen bond network at various charged interfaces. The hydrogen bond network is studied by specifically exciting the stretch vibration and probed with interface-specific sum-frequency spectroscopy. Moreover, phase-resolved and pump-probe spectroscopy are used to obtain molecular orientational and temporal information, respectively. At first the muscovite mica mineral-water interface, important for the heterogeneous ice nucleation, is investigated. A correlation between the interfacial water orientation and the ice nucleation temperature on mica is found, establishing water orientation as a possible inducer for ice nucleation. Then the effect of Na 2 SO 4 and Na 2 CO 3 on the water-air interface is compared. Despite significant differences in the static vibrational spectrum, due to the electrolytes, the same is not found for the vibrational dynamics, hinting towards ion independent water dynamics, even for the here tested large ion concentrations. Last, the influence of charged induced water orientation on the vibrational dynamics of lipid bound interfacial water is studied. The water orientation is hereby controlled using lipids with either a zwitterionic phospho- choline, or a reversed choline-phospho headgroup. The vibrational dynamics, as well as the energy transfer are found to be identical, suggesting orientation independent vibrational dynamics for lipid-bound water.