Tailored order: the mesocrystalline nature of sea urchin teeth.

We investigated the pattern of crystal co-orientation at different length scales, together with variations in chemical composition and nanomechanical properties in the teeth of the modern sea urchin Paracentrotus lividus with electron backscatter diffraction (EBSD), electron probe microanalysis, energy-dispersive X-ray spectroscopy and nanoindentation testing. Modern sea urchin teeth are Mg-dominated calcite composite materials. They are distinctly harder than inorganically precipitated calcite.

Synthesis of well-ordered COF monolayers: surface growth of nanocrystalline precursors versus direct on-surface polycondensation.

Two different straightforward synthetic approaches are presented to fabricate long-range-ordered monolayers of a covalent organic framework (COF) on an inert, catalytically inactive graphite surface. Boronic acid condensation (dehydration) is employed as the polymerization reaction. In the first approach, the monomer is prepolymerized by a mere thermal treatment into nanocrystalline precursor COFs.

Interdigitating biocalcite dendrites form a 3-D jigsaw structure in brachiopod shells.

We report a newly discovered dense microstructure of dendrite-like biocalcite that is formed by marine organisms. High spatial resolution electron backscatter diffraction (EBSD) was carried out under specific analytical conditions (15 and 10 kV) on the primary layer of the modern brachiopod Gryphus vitreus. The primary layer of modern brachiopods, previously termed nanocrystalline, is formed by an array of concave/convex calcite grains with interdigitated recesses and protrusions of abutting crystals without any cavities in or between the dendrites.