Control of Polymorph Selection in Amorphous Calcium Carbonate Crystallization by Poly(Aspartic Acid): Two Different Mechanisms

Poly(aspartic acid) (pAsp) is known to stabilize amorphous calcium carbonate (ACC) and affect its crystallization pathways. However, little is known about the mechanisms behind these phenomena. Here it is shown that ACC is stabilized by pAsp molecules in the solution rather than by the amount of pAs...

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Bibliographic Details
Published in:Small (Weinheim an der Bergstrasse, Germany) Germany), 2017-06, Vol.13 (21), p.n/a
Main Authors: Zou, Zhaoyong, Bertinetti, Luca, Politi, Yael, Fratzl, Peter, Habraken, Wouter J. E. M.
Format: Article
Language:English
Subjects:
amorphous
Aspartic acid
Calcite
Calcium carbonate
Crystallization
Low concentrations
Nanospheres
Nanotechnology
Nucleation
Phase transitions
pseudomorphic transformation
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Summary:Poly(aspartic acid) (pAsp) is known to stabilize amorphous calcium carbonate (ACC) and affect its crystallization pathways. However, little is known about the mechanisms behind these phenomena. Here it is shown that ACC is stabilized by pAsp molecules in the solution rather than by the amount of pAsp incorporated into the ACC bulk, and that the effect of pAsp on the polymorph selection is entirely different at low and high concentration of pAsp. At low concentrations, pAsp is more effective in inhibiting the nucleation and growth of vaterite than calcite. At high concentrations, when calcite formation is prevented, the crystallization of vaterite proceeds via a pseudomorphic transformation of ACC nanospheres, where vaterite nucleates on the surface of ACC nanospheres and grows by a local transformation of the bulk ACC phase. These results shed some light on the function of pAsp during an ACC‐mediated biomineralization process and provide an explanation for the presence of metastable vaterite at conditions where calcite is thermodynamically favored. Poly(aspartic acid) at low and high concentration shows opposite effects on polymorph selection from amorphous calcium carbonate (ACC). At low concentrations, ACC transforms into calcite and vaterite via a dissolution and reprecipitation mechanism. At high concentrations, ACC nanospheres transform into vaterite via a pseudomorphic transformation mechanism, where vaterite nucleates on ACC surface and propagates by consuming the bulk ACC.
ISSN:1613-6810
1613-6829
DOI:10.1002/smll.201603100