Controlled crystallization of CaCO3 under stearic acid monolayers

A fundamental concept in the study of biomineralization concerns the molecular recognition of inorganic materials at organized organic macromolecular substrates. Here we investigate this concept through the use of stearic acid monolayers in the controlled crystallization of CaCO₃ from supersaturated solutions. Whereas crystallization in the absence of a monolayer results in rhombohedral calcite crystals, the presence of an organized monolayer gives rise to oriented vaterite formation. The vaterite nuclei are aligned with their (0001) face parallel to the plane of the organic substrate and develop initially in the form of disk-shaped single crystals. The degree of compression of the monolayer dictates the homogeneity of vaterite nucleation. In particular, partially compressed films are optimal for controlled crystallization, suggesting that the mobility of organic surfaces may be of general importance. Our results can be explained by electrostatic and stereochemical interactions at the inorganic–organic interface and these observations support current theories of biomineralization, as well as being of potential significance in the crystal engineering of microscopic inorganic assemblies.