[19] J. Seto, Y. Ma, S.A. Davis, F. Meldrum, A. Gourrier, Y.Y. Kim, U. Schilde, M. Sztucki, M. Burghammer, S. Maltsev, C. Jäger, and H. Cölfen (2012). Structure-property relationships of a biological mesocrystal in the adult sea urchin spine. Proc. Natl. Acad. Sci. USA, 109, 3699-3704.

Abstract: Structuring over many length scales is a design strategy widely used in Nature to create materials with unique functional properties. We here present a comprehensive analysis of an adult sea urchin spine, and in revealing a complex, hierarchical structure, show how Nature fabricates a material which diffracts as a single crystal of calcite and yet fractures as a glassy material. Each spine comprises a highly oriented array of Mg-calcite nanocrystals in which amorphous regions and macromolecules are embedded. It is postulated that this mesocrystalline structure forms via the crystallization of a dense array of amorphous calcium carbonate (ACC) precursor particles. A residual surface layer of ACC and/or macromolecules remains around the nanoparticle units which creates the mesocrystal structure and contributes to the conchoidal fracture behavior. Nature’s demonstration of howcrystallization of an amorphous precursor phase can create a crystalline material with remarkable properties therefore provides inspiration for a novel approach to the design and synthesis of synthetic composite materials. Full text (if subscribed).

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