Söngen Hagen, Jaques Ygor Morais, Spijker Peter, Marutschke Christoph, Klassen Stefanie, Hermes Ilka, Bechstein Ralf, Zivanovic Lidija, Tracey John, Foster Adam S, Kühnle Angelika
Physical Chemistry I, Faculty of Chemistry, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany.
Institute of Physical Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10 - 14, 55099 Mainz, Germany.
Beilstein J Nanotechnol. 2020 Jun 10;11:891-898. doi: 10.3762/bjnano.11.74. eCollection 2020.
Calcite and magnesite are important mineral constituents of the earth's crust. In aqueous environments, these carbonates typically expose their most stable cleavage plane, the (10.4) surface. It is known that these surfaces interact with a large variety of organic molecules, which can result in surface restructuring. This process is decisive for the formation of biominerals. With the development of 3D atomic force microscopy (AFM) it is now possible to image solid-liquid interfaces with unprecedented molecular resolution. However, the majority of 3D AFM studies have been focused on the arrangement of water at carbonate surfaces. Here, we present an analysis of the assembly of ethanol - an organic molecule with a single hydroxy group - at the calcite and magnesite (10.4) surfaces by using high-resolution 3D AFM and molecular dynamics (MD) simulations. Within a single AFM data set we are able to resolve both the first laterally ordered solvation layer of ethanol on the calcite surface as well as the following solvation layers that show no lateral order. Our experimental results are in excellent agreement with MD simulations. The qualitative difference in the lateral order can be understood by the differing chemical environment: While the first layer adopts specific binding positions on the ionic carbonate surface, the second layer resides on top of the organic ethyl layer. A comparison of calcite and magnesite reveals a qualitatively similar ethanol arrangement on both carbonates, indicating the general nature of this finding.
方解石和菱镁矿是地壳中重要的矿物成分。在水环境中，这些碳酸盐通常会暴露其最稳定的解理面，即(10.4)面。已知这些表面会与多种有机分子相互作用，这可能导致表面重构。这个过程对生物矿物的形成起决定性作用。随着三维原子力显微镜(AFM)的发展，现在能够以前所未有的分子分辨率对固液界面进行成像。然而，大多数三维原子力显微镜研究都集中在碳酸盐表面水的排列上。在这里，我们通过使用高分辨率三维原子力显微镜和分子动力学(MD)模拟，对方解石和菱镁矿(10.4)表面上乙醇（一种带有单个羟基的有机分子）的组装进行了分析。在单个原子力显微镜数据集中，我们能够分辨方解石表面上乙醇的第一个横向有序溶剂化层以及随后没有横向有序的溶剂化层。我们的实验结果与分子动力学模拟结果非常吻合。横向有序的定性差异可以通过不同的化学环境来理解：虽然第一层在离子碳酸盐表面采用特定的结合位置，但第二层位于有机乙基层之上。方解石和菱镁矿的比较表明，两种碳酸盐上乙醇的排列在性质上相似，这表明了这一发现的普遍性。
