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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 17: Poster Session I

CPP 17.11: Poster

Montag, 1. April 2019, 17:30–19:30, Poster B1

Hydration forces on mica-electrolyte interfaces and their ion specificity — Simone van Lin¹, Igor Siretanu¹, •Kara K. Grotz², Nadine Schwierz², and Frieder Mugele¹ — ¹Physics of Complex Fluids Group and MESA+ Institute, Faculty of Science and Technology, University of Twente, Enschede, The Netherlands — ²Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Frankfurt am Main, Germany

Hydration forces play a fundamental role for a wide range of biological, chemical, and physical phenomena as they control the formation or prevention of direct contact between any kind of dissolved molecules or suspended particles in water. Here, we study the hydration of mica surfaces in contact with pure water as well as with aqueous alkali chloride salt solutions. Using molecular dynamics simulations in combination with atomic force micoscropy experiments, we demonstrate that hydration forces generally consist of both a monotonically decaying and an oscillatory part, each with unique dependence on the specific cation. In measurements, the monotonic hydration force gradually decreases in strength with decreasing ion size, leading to a transition from an overall repulsive (Li⁺) to an overall attractive (Cs⁺) total force. In simulations, the presence of strongly hydrated cations (Li⁺) hardly disturbs the water structure, whereas weakly hydrated cations (Cs⁺) suppress the pronounced layering of water at the interface, as well as the oscillatory part of the measured hydration force.