Professor in Physical Chemistry.
Teacher of the Year 2020 - Chemistry Chapter (award given by the Educational Board at KTH)
I am a surface and colloidal chemist with a background in chemical engineering. My research interests are in general focused on understanding from a molecular perspective, surface phenomena in aqueous interfaces, primarily by making use of spectroscopic techniques that target molecular vibrations (vibrational sum frequency spectroscopy and TIR Raman). My current research areas can be summarized as follows:
- 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. Despite being studied for over a century, starting with the pioneering work of Hofmeister who ranked the relative efficiency of different salts depending on their ability to precipitate proteins from solution, a comprehensive molecular explanation remains elusive. A key element to further our comprehension and endorse, disprove, or extend the new theories and simulations of Hofmeister phenomena, is obtaining direct molecular information from ions and water at interfaces. 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). The actual thickness and molecular structure of this layer remains a source of debate but it is generally agreed that it extends from just a few to tens of nanometers, that is less than 1/10 000 the thickness of a human hair. It is believed that the properties of this quasi-liquid layer will have important implications on how firmly ice adheres to a surface. 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. Nonetheless, the link between the measured forces and their molecular origin remains ambiguous, as force measurements provide no direct chemical, structural and conformational information, which is expected to change significantly in confined geometries. 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.
- 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. Such self-assembled amphiphilic interfaces can adopt an astonishing range of complex shapes. Gaining molecular understanding of how these interfaces structure, their order, as well as their dynamic behavior upon changes in the chemical structure and temperature, is the key to learning how we can manipulate such self-assembled soft interfaces to create novel and useful structures. 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.