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

在此基础上，我们申请了一种扫描力显微镜来研究高空间分辨率的固液界面。本建议的一个关键方面是基于一种仪器改进，它可以在界面上绘制三维体积，而不是收集传统的（二维）图像。这种方法提供了对垂直于表面的结构变化的见解，这对于研究实际空间和分子尺度上界面的溶剂化结构非常有趣。在界面上成像溶剂化结构的能力是解决基础研究课题的关键。例如，离子在界面上的具体结合情况通常是未知的：离子是直接与表面结合还是完全保持水合状态？离子对界面水化结构的影响是什么？这种效果是否取决于离子和/或表面的特定性质？界面定义了与环境的相互作用，因此，这些问题是广泛领域的基础，包括，例如，地球化学，生物矿化和电化学。我们将特别关注石墨-水界面，因为它们是研究分子自组装的重要模型系统。有趣的是，在这些研究中，溶剂的作用经常被忽视，尽管表面和分子的水合作用预计会对自组装过程产生影响。此外，一些研究报道了石墨-水界面上有序条纹的形成。然而，这些条纹的起源是有争议的。为了阐明这些条纹的本质，精确控制实验条件（如周围的气体气氛和温度）是很重要的，这在提案中应用的仪器中是可能的。虽然平面是高分辨率扫描力显微镜研究的理想选择，但台阶边缘在反应性方面代表了决定性的位置。在台阶边缘实现原子分辨率在实验上是非常具有挑战性的，但对于深入理解分子吸附以及晶体生长和溶解等过程，这无疑是必要的。突破高分辨率扫描力显微镜的极限，现在开启了台阶边缘原子分辨率成像的可能性。利用三维扫描力显微镜，我们的目标是绘制台阶边缘的溶剂化结构并揭示这些位点的反应性。

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.