Colloidal pathways of amorphous calcium carbonate formation lead to distinct water environments and conductivity

authored by: Maxim B. Gindele, Sanjay Vinod-Kumar, Johannes Rochau, Daniel Boemke, Eduard Groß, Venkata Subba Rao Redrouthu, Denis Gebauer, Guinevere Mathies
Abstract: CaCO₃ is the most abundant biomineral and a major constituent of incrustations arising from water hardness. Polycarboxylates play key roles in controlling mineralization. Herein, we present an analytical and spectroscopic study of polycarboxylate-stabilized amorphous CaCO₃ (ACC) and its formation via a dense liquid precursor phase (DLP). Polycarboxylates facilitate pronounced, kinetic bicarbonate entrapment in the DLP. Since bicarbonate is destabilized in the solid state, DLP dehydration towards solid ACC necessitates the formation of locally calcium deficient sites, thereby inhibiting nucleation. Magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy of poly-aspartate-stabilized ACC reveals the presence of two distinct environments. The first contains immobile calcium and carbonate ions and structural water molecules, undergoing restricted, anisotropic motion. In the second environment, water molecules undergo slow, but isotropic motion. Indeed, conductive atomic force microscopy (C-AFM) reveals that ACC conducts electrical current, strongly suggesting that the mobile environment pervades the bulk of ACC, with dissolved hydroxide ions constituting the charge carriers. We propose that the distinct environments arise from colloidally stabilized interfaces of DLP nanodroplets, consistent with the pre-nucleation cluster (PNC) pathway.
Organisation(s): Institute of Inorganic Chemistry
External Organisation(s): University of Konstanz
Type: Article
Journal: Nature Communications
Volume: 15
No. of pages: 14
ISSN: 2041-1723
Publication date: 02.01.2024
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: General Chemistry, General Biochemistry,Genetics and Molecular Biology, General Physics and Astronomy
Electronic version(s): https://doi.org/10.1038/s41467-023-44381-x (Access: Open)

BibTeX

@article{29b8d3534e63427782f50d8be537867b,
title = "Colloidal pathways of amorphous calcium carbonate formation lead to distinct water environments and conductivity",
abstract = "CaCO3 is the most abundant biomineral and a major constituent of incrustations arising from water hardness. Polycarboxylates play key roles in controlling mineralization. Herein, we present an analytical and spectroscopic study of polycarboxylate-stabilized amorphous CaCO3 (ACC) and its formation via a dense liquid precursor phase (DLP). Polycarboxylates facilitate pronounced, kinetic bicarbonate entrapment in the DLP. Since bicarbonate is destabilized in the solid state, DLP dehydration towards solid ACC necessitates the formation of locally calcium deficient sites, thereby inhibiting nucleation. Magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy of poly-aspartate-stabilized ACC reveals the presence of two distinct environments. The first contains immobile calcium and carbonate ions and structural water molecules, undergoing restricted, anisotropic motion. In the second environment, water molecules undergo slow, but isotropic motion. Indeed, conductive atomic force microscopy (C-AFM) reveals that ACC conducts electrical current, strongly suggesting that the mobile environment pervades the bulk of ACC, with dissolved hydroxide ions constituting the charge carriers. We propose that the distinct environments arise from colloidally stabilized interfaces of DLP nanodroplets, consistent with the pre-nucleation cluster (PNC) pathway.",
author = "Gindele, {Maxim B.} and Sanjay Vinod-Kumar and Johannes Rochau and Daniel Boemke and Eduard Gro{\ss} and Redrouthu, {Venkata Subba Rao} and Denis Gebauer and Guinevere Mathies",
note = "Funding Information: This research was supported by the Deutsche Forschungsgemeinschaft through the Emmy Noether Program awarded to GM (project number 321027114). The authors thank Sarah Busse for providing gold nanoparticles, Thomas Herzog for help with AFM measurements, Stella Kittel for help with ICP-OES measurements, Katharina Nolte for support during TGA-MS-IR experiments, and David McDonogh for help with XRD measurements, and Ilya Kuprov and Albert A. Smith-Penzel for advice and stimulating discussions. ",
year = "2024",
month = jan,
day = "2",
doi = "10.1038/s41467-023-44381-x",
language = "English",
volume = "15",
journal = "Nature Communications",
issn = "2041-1723",
publisher = "Nature Publishing Group",
}