Scanning force microscopy for high-resolution imaging of solid-liquid interfaces

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With this proposal, we apply for a scanning force microscope to study solid-liquid interfaces with high spatial resolution. A key aspect of the present proposal is based on an instrumental improvement that enables mapping of a three-dimensional volume at the interface rather than collecting conventional (two-dimensional) images. This method provides insights into structural changes vertical to the surface, which is highly interesting for studying the solvation structure at an interface in real space and at the molecular scale.The ability to image the solvation structure at an interface is pivotal to address fundamental research topics. As an example, the specific binding situation of ions at the interface is usually unknown: Do ions bind directly to the surface or do they remain entirely hydrated? What is the impact of ions on the hydration structure at the interface? Does this effect depend on the specific nature of the ions and / or the surface? The interface defines the interaction with the environment, thus, these questions are fundamental to a wide range of fields including, e.g., geochemistry, biomineralization and electrochemistry.A special focus will be put on graphite-water interfaces as they are important model systems for studying molecular self-assembly. Interestingly, the role of the solvent is often neglected in these studies, although the hydration of both the surface and the molecules is expected to have an impact on the self-assembly process. Moreover, several studies have reported the formation of ordered stripes at the graphite-water interface. The origin of these stripes is, however, discussed controversially. To shed light on the nature of these stripes, it is important to precisely control experimental conditions such as the surrounding gas atmosphere and temperature, which is possible with the instrument applied for in the proposal.While flat surfaces are ideal for high-resolution scanning force microscopy investigations, step edges represent decisive sites in terms of reactivity. Achieving atomic resolution at step edges is experimentally very challenging, but surely required for arriving at an in-depth understanding of processes such as molecule adsorption as well as crystal growth and dissolution. Pushing the limits of high-resolution scanning force microscopy has now opened up the possibility of atomic resolution imaging of step edges. Using three-dimensional scanning force microscopy, we aim for mapping the solvation structure at step edges and unraveling the reactivity of these sites.