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Confinement generates single-crystal aragonite rods at room temperature

DOI: 10.1073/pnas.1718926115 DOI Help

Authors: Muling Zeng (University of Leeds) , Yi-yeoun Kim (University of Leeds) , Clara Anduix-canto (University of Leeds) , Carlos Frontera (Institut de Ciencia de Materials de Barcelona) , David Laundy (Diamond Light Source) , Nikil Kapur (University of Leeds) , Hugo K. Christenson (University of Leeds) , Fiona C. Meldrum (University of Leeds)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Proceedings Of The National Academy Of Sciences , VOL 9

State: Published (Approved)
Published: July 2018
Diamond Proposal Number(s): 14790

Abstract: The topic of calcite and aragonite polymorphism attracts enormous interest from fields including biomineralization and paleogeochemistry. While aragonite is only slightly less thermodynamically stable than calcite under ambient conditions, it typically only forms as a minor product in additive-free solutions at room temperature. However, aragonite is an abundant biomineral, and certain organisms can selectively generate calcite and aragonite. This fascinating behavior has been the focus of decades of research, where this has been driven by a search for specific organic macromolecules that can generate these polymorphs. However, despite these efforts, we still have a poor understanding of how organisms achieve such selectivity. In this work, we consider an alternative possibility and explore whether the confined volumes in which all biomineralization occurs could also influence polymorph. Calcium carbonate was precipitated within the cylindrical pores of track-etched membranes, where these enabled us to systematically investigate the relationship between the membrane pore diameter and polymorph formation. Aragonite was obtained in increasing quantities as the pore size was reduced, such that oriented single crystals of aragonite were the sole product from additive-free solutions in 25-nm pores and significant quantities of aragonite formed in pores as large as 200 nm in the presence of low concentrations of magnesium and sulfate ions. This effect can be attributed to the effect of the pore size on the ion distribution, which becomes of increasing importance in small pores. These intriguing results suggest that organisms may exploit confinement effects to gain control over crystal polymorph.

Journal Keywords: calcium carbonate; biomineralization; bioinspired; biomimetic

Subject Areas: Chemistry, Earth Science

Instruments: B16-Test Beamline

Added On: 10/07/2018 14:55

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