Regensburg 2022 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 15: Solid-Liquid Interfaces 2: Structure and Spectroscopy

O 15.1: Topical Talk

Montag, 5. September 2022, 15:00–15:30, S054

Hydration Layer Mapping at Solid-Liquid Interfaces — •Angelika Kühnle — Physical Chemistry I, Department of Chemistry, University Bielefeld, Universitätsstraße 25, 33615 Bielefeld, Germany

Solid-liquid interfaces are omnipresent in nature and technology. Under ambient conditions, the properties of many materials are governed by a thin layer of water at the interface. Understanding processes occurring at the solid-liquid interface thus almost always requires a detailed knowledge of the hydration structure at the interface. Recent improvements in atomic force microscopy (AFM) instrumentation now enable molecular-level insights into the three-dimensional (3D) solvation structure at the interface.

In this talk, the capability of 3D AFM will be presented by discussing the hydration structure at the gypsum-water interface. Gypsum, the dihydrate of calcium sulfate, is an abundant rock-forming mineral in the Earth's crust. It is composed of alternating bilayers of calcium sulfate and water. Upon cleavage, the crystal water is exposed. What is the fate of this crystal water at the aqueous interface? Comparing 3D AFM data with water density maps derived from molecular dynamics simulations allows for elucidating molecular-level details of the gypsum-water interface. Our findings indicate that the crystal water at the interface remains tightly bound, even when in contact with bulk water. Thus, the interfacial chemistry of gypsum is governed by the crystal water rather than the calcium or sulfate ions.