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Structural and stereochemical relationships between Langmuir monolayers and calcium carbonate nucleation
journal contribution
posted on 2023-05-18, 14:14 authored by Mann, S, Heywood, BR, Rajam, Sundara, Walker, Justin BAThe structural and stereochemical factors involved in the oriented nucleation of CaCO3 under compressed Langmuir monolayers have been studied by optical and electron microscopy, and X-ray and electron diffraction. The effect of headgroup charge, stereochemistry and changes in supersaturation have been investigated. At total (Ca)=9 mM, monolayers with carboxylate headgroups induce the oriented nucleation of calcite with the (11.0) axis perpendicular to the organic surface. At (Ca)=4.5 mM, oriented vaterite with the (00.1) axis normal to the monolayer, is deposited. The common features of these interactions are: Ca accumulation at the stearate headgroups, geometric matching of lattice distances (calcite only) and stereochemical correspondence between carboxylate and carbonate groups at the monolayer/crystal interface. In contrast, nucleation under positively charged octadecylamine monolayers was independent of (Ca) and gave vaterite aligned either along the (00.1) or (11.0) crystallographic axes. Although Ca binding is absent on these films, there is the possibility of stereochemical matching between bidentate binding of bicarbonate and the corresponding anions in the (00.1) and (11.0) crystal surfaces. Crystals (calcite and vaterite) grown under liquid-phase stearate monolayers were of increased size and uniformity in particle size distribution compared with those nucleated under fully compressed films. CaCO3 crystallization under octadecanol monolayers was inhibited and crystals grown in the presence of cholesterol films were the same as in the control experiments.
History
Publication title
Journal of Physics D: Applied PhysicsVolume
24Pagination
154-164ISSN
0022-3727Publisher
Iop Publishing LtdPlace of publication
Dirac House, Temple Back, Bristol, England, Bs1 6BeRepository Status
- Restricted