Polarization-dependent imaging contrast in abalone shells

Metzler, Rebecca A.; Zhou, Dong; Abrecht, Mike; Chiou, J. W.; Guo, Jinghua; Ariosa, D.; Coppersmith, S. N.; Gilbert, Benjamin

doi:10.1103/physrevb.77.064110

Cited by 61 publications

(87 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Ca spectra were acquired by recording 170 images, 0.1 eV apart, and arranging them in stacks in which the energy-dependent intensity of each pixel holds the full spectral information across the Ca L-edge. The pixel size depends on the magnification and is 40-200 nm in this study, while the probing depth is Ϸ3 nm at the Ca L-edge energy range (23). This technique offers the unique opportunity of characterizing the atomic order of the mineral phase (24) along a single larval spicule with sub-micrometer spatial resolution, providing time and space-resolved snapshots of the crystallization pathway through 2 distinct amorphous phases.…”

Section: Resultsmentioning

confidence: 99%

Transformation mechanism of amorphous calcium carbonate into calcite in the sea urchin larval spicule

Politi

Metzler²,

Abrecht³

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

378

423

View full text Add to dashboard Cite

Sea urchin larval spicules transform amorphous calcium carbonate (ACC) into calcite single crystals. The mechanism of transformation is enigmatic: the transforming spicule displays both amorphous and crystalline properties, with no defined crystallization front. Here, we use X-ray photoelectron emission spectromicroscopy with probing size of 40–200 nm. We resolve 3 distinct mineral phases: An initial short-lived, presumably hydrated ACC phase, followed by an intermediate transient form of ACC, and finally the biogenic crystalline calcite phase. The amorphous and crystalline phases are juxtaposed, often appearing in adjacent sites at a scale of tens of nanometers. We propose that the amorphous-crystal transformation propagates in a tortuous path through preexisting 40- to 100-nm amorphous units, via a secondary nucleation mechanism.

show abstract

Section: Resultsmentioning

confidence: 99%

Transformation mechanism of amorphous calcium carbonate into calcite in the sea urchin larval spicule

Politi

Metzler²,

Abrecht³

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

378

423

View full text Add to dashboard Cite

show abstract

“…The carbon and oxygen PIC maps are identical, because XANES spectra are sensitive to specific bonds, and C and O are bonded to each other in carbonates. The different gray levels in the carbon and oxygen PIC maps are thus due to different c axis orientations relative to the polarization vector in the illuminating X-ray beam (16) in alternating regions. Within each of these regions, not only are the tooth plates and needles aligned, but also the high Mg crystals that make up the polycrystalline matrix.…”

Section: Resultsmentioning

confidence: 99%

“…The recently developed polarization-dependent imaging contrast (PIC) displays with varying gray levels, different angles between the c axis of a carbonate crystal and the X-ray polarization vector (15, 16 19). Although the method is not quantitative, it can highlight and spatially resolve regions of cooriented or misaligned crystals (15,16,19,20). Microbeam X-ray diffraction can probe volumes in the micrometer regime (10-m beam size in this work) to obtain local crystal orientation in 3-dimensions.…”

mentioning

confidence: 99%

“…X-ray photoelectron emission spectromicroscopy (X-PEEM), combined with X-ray absorption near-edge structure (XANES) spectroscopy, provide structural (13), compositional (14), and orientational (15,16) information. X-PEEM has a best resolution of 10 nm (17) (20 nm in this work) and a probing depth of a few nanometers (3 nm for carbon, 5 nm for oxygen, 12 nm for magnesium K-edges, and 3 nm for calcium L-edge) (16,18). The recently developed polarization-dependent imaging contrast (PIC) displays with varying gray levels, different angles between the c axis of a carbonate crystal and the X-ray polarization vector (15, 16 19).…”

mentioning

confidence: 99%

See 1 more Smart Citation

The grinding tip of the sea urchin tooth exhibits exquisite control over calcite crystal orientation and Mg distribution

Aichmayer

Paris

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

158

157

View full text Add to dashboard Cite

The sea urchin tooth is a remarkable grinding tool. Even though the tooth is composed almost entirely of calcite, it is used to grind holes into a rocky substrate itself often composed of calcite. Here, we use 3 complementary high-resolution tools to probe aspects of the structure of the grinding tip: X-ray photoelectron emission spectromicroscopy (X-PEEM), X-ray microdiffraction, and NanoSIMS. We confirm that the needles and plates are aligned and show here that even the high Mg polycrystalline matrix constituents are aligned with the other 2 structural elements when imaged at 20-nm resolution. Furthermore, we show that the entire tooth is composed of 2 cooriented polycrystalline blocks that differ in their orientations by only a few degrees. A unique feature of the grinding tip is that the structural elements from each coaligned block interdigitate. This interdigitation may influence the fracture process by creating a corrugated grinding surface. We also show that the overall Mg content of the tooth structural elements increases toward the grinding tip. This probably contributes to the increasing hardness of the tooth from the periphery to the tip. Clearly the formation of the tooth, and the tooth tip in particular, is amazingly well controlled. The improved understanding of these structural features could lead to the design of better mechanical grinding and cutting tools. echinoderms ͉ grinding tool ͉ self-sharpening ͉ spectromicroscopy ͉ X-ray microdiffraction

show abstract

“…9 High-resolution X-ray diffraction (XRD) and neutron diffraction indicate structural and microstructural differences between biogenic and geologic aragonite; there are differences in atomic positions as well as in the lattice parameters. [13][14][15] Specifically, biogenic aragonite is slightly distorted with respect to geologic aragonite.…”

Section: Introductionmentioning

confidence: 99%

Assignment of Polarization-Dependent Peaks in Carbon K-Edge Spectra from Biogenic and Geologic Aragonite

et al. 2008

Self Cite

View full text Add to dashboard Cite

Many biominerals, including mollusk and echinoderm shells, avian eggshells, modern and fossil bacterial sediments, planktonic coccolithophores, and foraminifera, contain carbonates in the form of biogenic aragonite or calcite. Here we analyze biogenic and geologic aragonite using different kinds of surface-and bulksensitive X-ray absorption near-edge structure (XANES) spectroscopy at the carbon K-edge, as well as highresolution scanning transmission X-ray microscopy (STXM). Besides the well-known main π* and σ* carbonate peaks, we observed and fully characterized four minor peaks, at energies between the main π* and σ* peaks. As expected, the main peaks are similar in geologic and biogenic aragonite, while the minor peaks differ in relative intensity. In this and previous work, the minor peaks appear to be the ones most affected in biomineralization processes, hence the interest in characterizing them. Peak assignment was achieved by correlation of polarization-dependent behavior of the minor peaks with that of the main π* and σ* peaks. The present characterization provides the background for future studies of aragonitic biominerals. IntroductionThe calcium carbonates (CaCO 3 ) aragonite and calcite constitute the majority of biominerals, including the outer shells of mollusks: bivalves, gastropods and cephalopods; the endoskeletons of echinoderms, avian eggshells, corals, planktonic coccolithophores and foraminifera, and bacterial biominerals, comprising extant and fossil bacterial biofilms. 1,2 It is therefore of great interest to characterize all spectral components in X-ray absorption near-edge structure (XANES) spectra from aragonite, which is done here.One of the most interesting and studied aragonitic biominerals is mother-of-pearl, or nacre: a composite of 95% aragonite and 5% organic molecules. 1,2 Its remarkable toughnesssmany thousands of times more resistant to fracture than aragonite 3 shas stimulated many studies of nacre's mechanical performance, structure, proteins and glycoproteins, and the role that these might play in nacre formation. [4][5][6][7][8] We recently discovered that nacre exhibits X-ray linear dichroism, a phenomenon widely studied in man-made materials but never before reported in a biomineral. 8,9 Dichroism in carbonates generates a polarizationdependent imaging contrast (PIC), which is particularly useful to investigate the meso-scale architecture of nacre using X-ray photoelectron emission spectromicroscopy (X-PEEM) 10 and scanning transmission X-ray spectromicroscopy (STXM). 11,12 With X-PEEM we revealed that the 400-nm high, 5-µm wide aragonite tablets that form the layered abalone nacre structure are arranged in stacks of co-oriented tablets, staggered with respect to each other.We have previously extensively characterized the origin of PIC and X-ray linear dichroism with a series of pure-

show abstract

Polarization-dependent imaging contrast in abalone shells

Cited by 61 publications

References 34 publications

Transformation mechanism of amorphous calcium carbonate into calcite in the sea urchin larval spicule

Transformation mechanism of amorphous calcium carbonate into calcite in the sea urchin larval spicule

The grinding tip of the sea urchin tooth exhibits exquisite control over calcite crystal orientation and Mg distribution

Assignment of Polarization-Dependent Peaks in Carbon K-Edge Spectra from Biogenic and Geologic Aragonite

Contact Info

Product

Resources

About