Surface phenomena at aqueous interfaces
Ion specific phenomena: Specific ion effects play a key role in a wide range of phenomena, stretching from the systematic variation in the surface tension of simple salt solutions to regulating biological processes crucial for own very existence. Here we specifically target the ion behaviour at different model interfaces. This involves identifying which ions tend to preferentially adsorb to particular interfaces, probing the influence of ions on the surface water structure as well as in the local functional groups.
Ice adhesion and the quasi-liquid layer: In a rather wide temperature range below its bulk freezing point, ice surfaces are covered by a layer of mobile water molecules. Although not moving as quickly and as freely as those in liquid water, their motion earns this phase its name: the quasi-liquid layer (QLL). Here we employ VSFS and TIR Raman to improve our fundamental understanding of this phenomenon by targeting the interface between ice and substrates with varying topographies and surface chemistries.
Molecules under confinement: Measuring forces between surfaces as a function of separation is of utmost importance in the study of interaction energies. Here we combine our spectroscopy techniques in situ with a custom built force measuring device (thin film pressure balance) to study the molecular structural changes in thin wetting films (i.e. a liquid film confined between a solid and a vapour phase) which thickness range from just a few to hundredths of nanometers.
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Properties of biomimetic phospholipid membranes. Lipid membranes lie at the heart of most biological functions, and are increasingly found in a range of novel applications in biotechnology and nanomedicine. One of the key fundamental challenges is controlling asymmetry in lipid bilayers. To this purpose we employ VSFS to measure the intrinsic “flip-flop” rates (trans-membrane transfer of lipids across the bilayer) of model phospholipids in defect free and electrically sealed bilayers. Langmuir and Langmuir-Blodgett films are prepared to model natural cell membranes, and VSFS is used to study their packing, order, orientation, hydration, oxidation, and interactions with drugs.