Volume 235, 2022

Possible embryos and precursors of crystalline nuclei of calcium carbonate observed by liquid-cell transmission electron microscopy

Abstract

Several different building blocks or precursors play an important role in the early stages of the crystallization of calcium carbonate (CaCO3). Many studies have been conducted over a long period to elucidate the fundamental processes involved in this crystallization. Here, we report the role of an amorphous phase and embryo at the beginning of the nucleation of CaCO3 from solutions of relatively low supersaturation. Prenucleation crystals formed in amorphous calcium carbonate (ACC) at a significantly large formation rate of 2 × 1022 m−3 s−1, suggesting that a low interfacial energy exists between the ACC and crystals. Only one calcite crystal exceeded the size for a critical nucleus (∼104 molecules) in 150 pre-nucleation crystals. Each pre-nucleation crystal might consist of a different polymorph, and ACCs have a similar composition and structure. A particle-detection algorithm, used in conjunction with machine learning, suggested that an embryo with a characteristic structure exists in solution and might play a crucial role in nucleation. No similar embryonic structure could be observed immediately after the dissolution of pre-nucleation particles, implying that their dissolution process is not simply the reverse process of their growth. This method should provide a new approach to understanding nucleation processes.

Graphical abstract: Possible embryos and precursors of crystalline nuclei of calcium carbonate observed by liquid-cell transmission electron microscopy

Associated articles

Supplementary files

Article information

Article type
Paper
Submitted
27 déc. 2021
Accepted
11 févr. 2022
First published
11 févr. 2022

Faraday Discuss., 2022,235, 81-94

Possible embryos and precursors of crystalline nuclei of calcium carbonate observed by liquid-cell transmission electron microscopy

Y. Kimura, H. Katsuno and T. Yamazaki, Faraday Discuss., 2022, 235, 81 DOI: 10.1039/D1FD00125F

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