Scanning force microscope for investigating solid-liquid interfaces

采用扫描力显微镜对固液界面进行高分辨率成像。应用仪器的一个重要方面是可以精确地控制测量条件，如大气、湿度和温度在一个可能的范围内。这些仪器将用于需要明确定义的测量条件的研究项目。这尤其适用于在方解石-水界面研究pH依赖过程的研究项目，因为溶液的pH值取决于周围大气中的二氧化碳分压。溶液的组成由给定pH值下的碳酸盐平衡来确定。在这种情况下，我们的目的是研究硼在方解石中的掺入。利用海洋方解石样品中的硼浓度和同位素组成作为气候指标，重建了过去的大气二氧化碳分压。与冰芯记录相比，硼的掺入在原则上提供了了解80多万年前古代大气的可能性。然而，合并机制的细节仍在讨论中。在这个项目中，我们希望在良好控制的条件下直接成像方解石中的硼缺陷，以阐明硼的结合方式。在这里，我们将受益于这样一个事实，即缺陷可以用原子分辨率成像，缺陷部位上方的三维水化结构的变化是离子特异性的。应用扫描力显微镜的另一个研究领域是矿物表面的冰成核。众所周知，大气中的矿物粉尘可以高效地作为冰核粒子。为了了解云中冰的形成和发展可靠的气候模式，对冰成核粒子进行了广泛的研究。然而，气溶胶颗粒冰成核过程中的分子水平机制仍然知之甚少。特别是，人们在很大程度上仍然不清楚为什么有些矿物质高度活跃，而另一些却不是。在此背景下，我们希望研究活性和非活性冰核矿物在矿物-水界面的水化结构。对于上述项目，我们将利用扫描力显微镜不仅可以提供二维图像，还可以在界面处研究三维体积。这将有助于直接绘制和比较不同冰成核矿物的水化结构，并确定活性冰成核颗粒的特征性质。

A scanning force microscope is applied for, which shall be used for high-resolution imaging of solid-liquid interfaces. An important aspect of the applied instrument is the possibility to precisely control the measurement conditions such as atmosphere, humidity and temperature in a wide range of possible values. The instruments will be used for research projects that require well-defined measurement conditions. This particularly applies for research projects in which pH-dependent processes are studied at the calcite-water interface, as the pH value of the solution depends on the carbon dioxide partial pressure in the surrounding atmosphere. The composition of the solution is then defined by the carbonate equilibrium at the given pH value.In this context, we aim at studying the incorporation of boron into calcite. The boron concentration and isotope composition in maritime calcite samples is used as a climate proxy to reconstruct the atmospheric carbon dioxide partial pressure in the past. As compared to ice core records, the boron incorporation in principle provides the possibility to obtain insights into the ancient atmosphere more than 800,000 years ago. However, the details of the incorporation mechanism are still under debate. In this project, we want to directly image boron defects in calcite under well-controlled conditions to shed light on the way boron is incorporated. Here we will benefit from the fact that defects can be imaged with atomic resolution and changes in the three-dimensional hydration structure above a defect site are ion specific.A further research area in which the applied scanning force microscope will be used is ice nucleation on mineral surfaces. It is known that mineral dust in the atmosphere can be highly efficient as ice nucleating particles. For understanding ice formation in clouds and developing reliable climate models, ice nucleating particles are extensively studied. The molecular-level mechanisms during ice nucleation at aerosol particles are, however, still poorly understood. In particular, it remains largely unclear why some minerals are highly active while others are not. In this context, we want to study the hydration structure at the mineral-water interface of active and less active ice nucleating minerals. As for the above project, we will make use of the fact that the scanning force microscope not only provides two-dimensional images but also allows for investigating a three-dimensional volume at the interface. This will enable to directly map and compare the hydration structure of different ice nucleating minerals and to identify characteristic properties of active ice nucleating particles.