PUB - Publikationen an der Universität Bielefeld

Solid-liquid interfaces are omnipresent in environmental and technological systems. In this regard, interfacial solvation structures exert a decisive impact on the interface properties and reactivities. The hydration structure of the calcite-water interface has been widely studied due to its relevance in geochemical and industrial processes. However, the influence of dissolved ions on this hydration structure has scarcely been studied. The structure at the calcite-water interface can be investigated with three-dimensional atomic force microscopy (3D AFM), which is a well suited method to directly resolve solvation structures at solid liquid-interfaces.

This thesis focuses on three main subjects, which are the implementation of evaluation methods for dynamic 3D AFM data, the significance of the static deflection in dynamic 3D AFM data acquisition, and the impact of ions on the hydration structure of calcite.
For the evaluation of 3D AFM data, a set of analysis tools is presented. This collection includes new and updated calibration tools for the determination of the deflection sensitivity and physical properties of AFM probes. Moreover, reversible correction tools for *z*-drift, sample tilt and the static deflection are introduced. Also, updated extraction and export methods are presented, as well as a collection of minor implementations.
Regarding the impact of the static deflection on dynamical 3D AFM data, it is shown for the calcite-water system that upon tip-sample approach the increases in static deflection and in the monotonic excitation frequency shift contribution start at different distances to the substrate. Further, data with and without correction for the static deflection are compared, revealing deviations of up to 1 Å for distances between structural features in proximity to the substrate. It is also shown that recorded structures are unaffected from static deflection correction, when the oscillatory contribution of the excitation frequency shift dominates the monotonic contribution.
The influence of dissolved ions on the hydration structure of calcite terraces and step edges is presented using high-resolution 3D AFM data. For aqueous solutions with different concentrations of rubidium chloride, it is shown that similar hydration structures are observed as in pure water experiments. Additionally, the presence of ions at the interface is verified via slice displacements and changes in imaging contrast.
In summary, this thesis adresses three topics regarding hydration layer mapping at solid-liquid interfaces. The obtained results pave the way to a better understanding of hydration structures at interfaces.