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