Berlin 2015 – scientific programme

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BP: Fachverband Biologische Physik

BP 38: Electrolytes at Interfaces - Stern Layer (focus session, joint CPP/BP/O)

BP 38.6: Invited Talk

Wednesday, March 18, 2015, 16:45–17:15, C 130

Water flow along a solid interface affects the Stern layer — •Mischa Bonn — Max Planck Institute for polymer research, Mainz, Germany

At the surface or interface of water, the water hydrogen-bonded network is abruptly interrupted, conferring properties on interfacial water different from bulk water. Owing to its importance for disciplines such as electrochemistry, atmospheric chemistry and membrane biophysics, the structure of interfacial water has received much attention.

We elucidate the structure and structural dynamics of interfacial water using ultrafast surface-specific sum-frequency generation (SFG) vibrational spectroscopy. We make use of the fact that the SFG signal depends critically on the interfacial organization of water molecules.

We attempt to bridge continuum models of laminar flow along interfaces, with molecular-level descriptions of the Stern and diffuse layer, which describe the near-surface distribution of ions. For water at two different mineral interfaces, we report a dramatic effect of water flow water along the mineral surface on the organization of water at the interface. Our observations can be explained by considering the coupling between the flow and the dissolution chemistry at the interface. Even for low-soluble quartz at neutral pH, dissolution plays a key role in determining the interfacial water organization through the charge on the surface.