Oxygen Spectroscopy and Polarization-Dependent Imaging Contrast (PIC)-Mapping of Calcium Carbonate Minerals and Biominerals
MetadataShow full item record
X-ray absorption near-edge structure (XANES) spectroscopy and spectromicroscopy have been extensively used to characterize biominerals. Using either Ca or C spectra, unique information has been obtained regarding amorphous biominerals and nanocrystal orientations. Building on these results, we demonstrate that recording XANES spectra of calcium carbonate at the oxygen K-edge enables polarization-dependent imaging contrast (PIC) mapping with unprecedented contrast, signal-to-noise ratio, and magnification. O and Ca spectra are presented for six calcium carbonate minerals: aragonite, calcite, vaterite, monohydrocalcite, and both hydrated and anhydrous amorphous calcium carbonate. The crystalline minerals reveal excellent agreement of the extent and direction of polarization dependences in simulated and experimental XANES spectra due to X-ray linear dichroism. This effect is particularly strong for aragonite, calcite, and vaterite. In natural biominerals, oxygen PIC-mapping generated high-magnification maps of unprecedented clarity from nacre and prismatic structures and their interface in Mytilus californianus shells. These maps revealed blocky aragonite crystals at the nacre-prismatic boundary and the narrowest calcite needle-prisms. In the tunic spicules of Herdmania momus, O PIC-mapping revealed the size and arrangement of some of the largest vaterite single crystals known. O spectroscopy therefore enables the simultaneous measurement of chemical and orientational information in CaCO3 biominerals and is thus a powerful means for analyzing these and other complex materials. As described here, PIC-mapping and spectroscopy at the O K-edge are methods for gathering valuable data that can be carried out using spectromicroscopy beamlines at most synchrotrons without the expense of additional equipment.
Showing items related by title, author, creator and subject.
Goh, Ching Yong (2012)A selection of amino acid functionalised calixarenes was studied. Acidic amino acid functionalised calixarenes were investigated as crystal growth modifiers. The self-assembly behaviour of proline functionalised ...
Bewernitz, M.; Gebauer, Denis; Long, J.; Cölfen, H.; Gower, L. (2012)Invertebrate organisms that use calcium carbonate extensively in the formation of their hard tissues have the ability to deposit biominerals with control over crystal size, shape, orientation, phase, texture, and location. ...
Brooker, L.; Lee, Alasdair; Macey, D.; Webb, J.; Van Bronswijk, Wilhelm (2006)The major lateral radula teeth of chitons (Mollusca: Polyplacophora) are composite materials, incorporating a variety of biominerals within an organic scaffold. While magnetite is ubiquitous to these teeth in all ...