Additive-controlled crystallization is of major importance for geochemical, biological, and synthetic material systems [1]. Furthermore, elucidating the mode-of-action of specific additives during surface restructuring and molecular self-assembly processes is of utmost interest within biomineralization [2]. Calcite is one of the most abundant minerals in the earth crust. Consequently, the influence of organic molecules on surface restructuring processes like dissolution and growth of its most stable cleavage plane, the calcite (10.4) surface has been studied intensively [3,4]. Atomic force microscopy (AFM), especially in-situ AFM-measurements allow for directly imaging of surface restructuring and self-assembly of organic molecules on calcite with high-resolution. Here, we study the interaction of the two constitutional isomers Eriochrome Black T (EBT) and Eriochrome Black A (EBA) with the calcite (10.4) cleavage plane using in-situ high-resolution AFM. Despite the difference in their structures, we find that in the presence of each molecule the calcite surface is restructured in a similar way, exclusively exhibiting thermodynamic unfavorable polar step edges. This surface reorganization is independent of the pH. In sharp contrast, we are able to control the structure formation of EBA assemblies by adjusting the pH. This finding indicates that the self-assembly of well-defined molecular structures requires more precise properties of the additive - including specific protonation states - as compared to additive induced surface restructuring processes. References [1] R.-Q. Song, H. Cölfen, CrystEngComm 2011, 13, 1249-1276 [2] F. Nudelmann, N. A. J. M. Sommerdijk, Angew. Chem. Int. Ed. 2012, 51, 6582-6596 [3] R. Momper et al. Langmuir 2015, 31, 7283-7287 [4] M. Ricci et al. Langmuir 2015, 31, 7563-7571

Surface morphology control versus molecular self-assembly: An in situ high-resolution atomic force microscopy study on calcite (10.4)

251st National Meeting (2016)

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