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Pina, Carlos M.; Merkel, Casjen; Jordan, Guntram (2009): On the Bimodal Effects of Silicic Acids on Calcite Growth. In: Crystal Growth and Design, Vol. 9, No. 9: pp. 4084-4090
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The effects of silicic acids on calcite growth area model for theeffects of partially polymerized additives on crystal growth. Atalkaline pH, silicic acid polymers coexist with small mono- andoligomers, Atomic force microscopy (AFM) showed that large polymerspromote two-dimensional nucleation, while mono- and oligomers have abimodal promoter/inhibitor effect on step propagation. This bimodalitycan be interpreted as the result of attachment of mono- and oligomersalong the steps along with a modification of the kinetics of kinkgeneration and/or propagation. The bimodal step kinematic effect isaccompanied by a single morphologic effect: growth islands transformfrom a rhombus into an ellipse. This effect has been reported for otheradditives, indicating that many additives generate few morphologies.Such a convergence limits the versatility of chemical control onbiomorphogenesis. Contrarily, the strong kinetic effect of silicic acidsmay make them very efficient controllers of biomorphogenesis, if coupledwith a physical shape control, for example, by templates. Thus, silicicacids show a unique bimodality as a controller of calcitebiomineralisation and its an abundant biomineral.