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Self-assembly of amorphous calcium carbonate microlens arrays.

Lee K, Wagermaier W, Masic A, Kommareddy KP, Bennet M, Manjubala I, Lee SW, Park SB, Cölfen H, Fratzl P - Nat Commun (2012)

Bottom Line: The formation mechanism of the amorphous CaCO(3) microlens arrays was elucidated by confocal Raman spectroscopic imaging to be a two-step growth process mediated by the organic surfactant.CaCO(3) microlens arrays are easy to fabricate, biocompatible and functional in amorphous or more stable crystalline forms.This shows that advanced optical materials can be generated by a simple mineral precipitation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam 14424, Germany.

ABSTRACT
Biological materials are often based on simple constituents and grown by the principle of self-assembly under ambient conditions. In particular, biomineralization approaches exploit efficient pathways of inorganic material synthesis. There is still a large gap between the complexity of natural systems and the practical utilization of bioinspired formation mechanisms. Here we describe a simple self-assembly route leading to a CaCO(3) microlens array, somewhat reminiscent of the brittlestars' microlenses, with uniform size and focal length, by using a minimum number of components and equipment at ambient conditions. The formation mechanism of the amorphous CaCO(3) microlens arrays was elucidated by confocal Raman spectroscopic imaging to be a two-step growth process mediated by the organic surfactant. CaCO(3) microlens arrays are easy to fabricate, biocompatible and functional in amorphous or more stable crystalline forms. This shows that advanced optical materials can be generated by a simple mineral precipitation.

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Confocal Raman spectroscopic imaging of the CaCO3 microlens array.(a) Schematic illustration of the depth scan. (b–d) Depth scanned Raman imaging obtained by integrating over the wavenumber ranges of (b) carbonate (1,040–1,125 cm−1), (c) water (3,000–3,500 cm−1) and (d) organic components (2,800–3,000 cm−1), respectively. The images in the same column indicate the same depth. (e) Raman imaging of carbonate at 0° and 90° polarization of incident laser light. All the scale bars are 5 μm. CCD cts, charge-coupled device counts.
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f4: Confocal Raman spectroscopic imaging of the CaCO3 microlens array.(a) Schematic illustration of the depth scan. (b–d) Depth scanned Raman imaging obtained by integrating over the wavenumber ranges of (b) carbonate (1,040–1,125 cm−1), (c) water (3,000–3,500 cm−1) and (d) organic components (2,800–3,000 cm−1), respectively. The images in the same column indicate the same depth. (e) Raman imaging of carbonate at 0° and 90° polarization of incident laser light. All the scale bars are 5 μm. CCD cts, charge-coupled device counts.

Mentions: The CaCO3 microlenses show structural complexity as found by depth scans with confocal Raman spectroscopic imaging (Fig. 4), revealing the distribution of carbonate, water and organic components. A schematic illustration of a depth scan is shown in Fig. 4a. Figure 4b shows confocal Raman images of carbonate (spectral region 1,040–1,125 cm−1) at different depths. The Raman spectra in this band show the characteristics of ACC (Supplementary Fig. S6). In the ACC, the band slightly shifts to lower wavenumbers and is characterized by a significant broadening (full-width at half-maximum 28 cm−1 in our experimental results), compared with that found in calcite2829. However, the intensity of carbonate varies strongly through different z-section planes. In addition, at the depth positions from 0 to 0.5 μm, the Raman scattering of carbonate is higher at the edge than in the inner parts of the microlenses (Fig. 4b). This could be due to the preferential orientation of the carbonate units in the near-edge region of each microlens, as demonstrated by polarized Raman imaging with different polarization direction (Fig. 4e)30. The direction of the incident laser polarization was found to have no influence on the intensity of spectra in the inner part of the microlenses (Supplementary Fig. S6). However, the upper/lower edges of the microlenses shows higher intensity with 90° polarization with respect to 0° and vice versa for the left/right edges (Fig. 4e and Supplementary Fig. S6).


Self-assembly of amorphous calcium carbonate microlens arrays.

Lee K, Wagermaier W, Masic A, Kommareddy KP, Bennet M, Manjubala I, Lee SW, Park SB, Cölfen H, Fratzl P - Nat Commun (2012)

Confocal Raman spectroscopic imaging of the CaCO3 microlens array.(a) Schematic illustration of the depth scan. (b–d) Depth scanned Raman imaging obtained by integrating over the wavenumber ranges of (b) carbonate (1,040–1,125 cm−1), (c) water (3,000–3,500 cm−1) and (d) organic components (2,800–3,000 cm−1), respectively. The images in the same column indicate the same depth. (e) Raman imaging of carbonate at 0° and 90° polarization of incident laser light. All the scale bars are 5 μm. CCD cts, charge-coupled device counts.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3316890&req=5

f4: Confocal Raman spectroscopic imaging of the CaCO3 microlens array.(a) Schematic illustration of the depth scan. (b–d) Depth scanned Raman imaging obtained by integrating over the wavenumber ranges of (b) carbonate (1,040–1,125 cm−1), (c) water (3,000–3,500 cm−1) and (d) organic components (2,800–3,000 cm−1), respectively. The images in the same column indicate the same depth. (e) Raman imaging of carbonate at 0° and 90° polarization of incident laser light. All the scale bars are 5 μm. CCD cts, charge-coupled device counts.
Mentions: The CaCO3 microlenses show structural complexity as found by depth scans with confocal Raman spectroscopic imaging (Fig. 4), revealing the distribution of carbonate, water and organic components. A schematic illustration of a depth scan is shown in Fig. 4a. Figure 4b shows confocal Raman images of carbonate (spectral region 1,040–1,125 cm−1) at different depths. The Raman spectra in this band show the characteristics of ACC (Supplementary Fig. S6). In the ACC, the band slightly shifts to lower wavenumbers and is characterized by a significant broadening (full-width at half-maximum 28 cm−1 in our experimental results), compared with that found in calcite2829. However, the intensity of carbonate varies strongly through different z-section planes. In addition, at the depth positions from 0 to 0.5 μm, the Raman scattering of carbonate is higher at the edge than in the inner parts of the microlenses (Fig. 4b). This could be due to the preferential orientation of the carbonate units in the near-edge region of each microlens, as demonstrated by polarized Raman imaging with different polarization direction (Fig. 4e)30. The direction of the incident laser polarization was found to have no influence on the intensity of spectra in the inner part of the microlenses (Supplementary Fig. S6). However, the upper/lower edges of the microlenses shows higher intensity with 90° polarization with respect to 0° and vice versa for the left/right edges (Fig. 4e and Supplementary Fig. S6).

Bottom Line: The formation mechanism of the amorphous CaCO(3) microlens arrays was elucidated by confocal Raman spectroscopic imaging to be a two-step growth process mediated by the organic surfactant.CaCO(3) microlens arrays are easy to fabricate, biocompatible and functional in amorphous or more stable crystalline forms.This shows that advanced optical materials can be generated by a simple mineral precipitation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Potsdam 14424, Germany.

ABSTRACT
Biological materials are often based on simple constituents and grown by the principle of self-assembly under ambient conditions. In particular, biomineralization approaches exploit efficient pathways of inorganic material synthesis. There is still a large gap between the complexity of natural systems and the practical utilization of bioinspired formation mechanisms. Here we describe a simple self-assembly route leading to a CaCO(3) microlens array, somewhat reminiscent of the brittlestars' microlenses, with uniform size and focal length, by using a minimum number of components and equipment at ambient conditions. The formation mechanism of the amorphous CaCO(3) microlens arrays was elucidated by confocal Raman spectroscopic imaging to be a two-step growth process mediated by the organic surfactant. CaCO(3) microlens arrays are easy to fabricate, biocompatible and functional in amorphous or more stable crystalline forms. This shows that advanced optical materials can be generated by a simple mineral precipitation.

Show MeSH
Related in: MedlinePlus