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"Water, Ions, Interfaces: Quantum effects, charge and cooperativity in water, aqueous solutions and interfaces"

Final Report Summary - WII (Water, Ions, Interfaces: Quantum effects, charge and cooperativity in water, aqueous solutions and interfaces)

In the WII project Prof. Roke and her team have pioneered new ultrafast nonlinear optical technology that enables trans-disciplinary research linking molecular information to surface physics and soft matter science applied to aqueous systems. The team developed femtosecond elastic second harmonic scattering and a new high throughput wide field second harmonic imaging method together with a multi-level theory package. The frontier of what is possible using femtosecond vibrational sum frequency scattering was also pushed further resulting in the probing of the interfacial structure of water droplets.
Together these developments have resulted in breakthroughs in the molecular level understanding aqueous systems and interfaces: While second harmonic generation has long been used to probe liquids, the method invented by Roke and her team allows to probe long-range (> 1 nm) structure in aqueous solutions. The measurements on electrolyte solutions laid bare an as of yet undiscovered interaction between electrostatic fields and the hydrogen bond network of water. This interaction was also shown to play a central role in unexplained anomalies relating to the interfacial tension and viscosity of aqueous solutions.
The nonlinear light scattering studies of droplets in solution (emulsions) enable many of the known physicochemical properties of soft matter systems to finally be put on a quantified molecular level foundation, which furthers the development of nanotechnology. Molecular spectroscopic surface investigations of nanodroplets and liposomes have demonstrated the deterministic nature of length scale dependent structures of water and surface molecules in steering their macroscopic physical properties.
Finally, high throughput nonlinear imaging studies of aqueous silica and free standing lipid membrane interfaces enabled the creation of electrostatic potential and free energy maps in real time. These maps have shown the presence of (transient) nano- and microscale structure heterogeneities.