Organisms use inorganic ions and macromolecules to regulate crystallization from amorphous- precursors, endowing natural biominerals with complex morphologies and enhanced properties.
The mechanisms by which modifiers enable these shape preserving transformations are poorly understood. We used in situ liquid-phase transmission electron microscopy to follow the evolution from amorphous calcium carbonate to calcite in the presence of additives. A combination of contrast analysis and infrared spectroscopy shows that Mg ions, which are widely present in seawater and biological fluids, alter the transformation pathway in a concentration-dependent manner. The ions bring excess (structural) water into the amorphous bulk so that a direct transformation is triggered by dehydration in the absence of morphological changes. Molecular dynamics simulations suggest Mg-incorporated water induces structural fluctuations, allowing transformation without the need to nucleate a separate crystal. Thus, the obtained calcite retains the original morphology of the amorphous state, biomimetically achieving the morphological control of crystals seen in biominerals
Revised: September 2, 2020 |
Published: February 18, 2020
Citation
Liu Z., Z. Zhang, Z. Wang, B. Jin, D. Li, J. Tao, and R. Tang, et al. 2020.Shape-preserving amorphous-to-crystalline transformation of CaCO3 revealed by in situ TEM.Proceedings of the National Academy of Sciences (PNAS) 117, no. 7:3397-3404.PNNL-SA-155767.doi:10.1073/pnas.1914813117