Research ArticleMATERIALS SCIENCE

Extreme biomimetics: Preservation of molecular detail in centimeter-scale samples of biological meshes laid down by sponges

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Science Advances  04 Oct 2019:
Vol. 5, no. 10, eaax2805
DOI: 10.1126/sciadv.aax2805
  • Fig. 1 Overview of the transformation of spongin scaffolds to a carbonized 3D structure at 1200°C.

    (A) Typical cellular and hierarchical morphology of Hippospongia communis demosponge organic skeleton after purification remains unchanged during the process of carbonization in spite of a decrease in volume by up to 70%. (B) Carbonized 3D scaffold can be sawn into 2-mm-thick slices (C). Both stereomicroscopy (D and E) and SEM images (G and H) of carbonized spongin network confirm its structural integrity, typical for sponge-like constructs. However, the surface of carbonized fibers became rough (H) due to the formation of abundant nanopores (I) (see also fig. S9). The EDX analysis of purified carbonized spongin (F) provides strong evidence of its carbonaceous origin. Photo credit: Iaroslav Petrenko and Michael Kraft, TU Bergakademie Freiberg.

  • Fig. 2 Identification of carbonized spongin as turbostratic graphite.

    XRD analysis of spongin carbonized at 1200°C. (A) Circles, measured data; solid line, calculation according to the method described (25) and values given in table S1; bottom line, difference between measured and calculated intensities. Labels are the diffraction indices hkl. (B) HRTEM image with corresponding indexed FFT (C). (D) SAED pattern for carbonized spongin and corresponding 1D intensity distribution (E) as the sum of intensities along the diffraction rings.

  • Fig. 3 TEM images of 80-nm-thin cuts of spongin carbonized at 1200°C.

    (A) Overview image of carbonized spongin consisting mainly of collagen nanofibrils. Arrows indicate pearl necklace structures being parallel to each other. The red frame indicates the enlarged region taken for image (B). In the Fourier transform, diffraction maxima corresponding to the direct-space distances of 8.16 and 25.6 Å are recorded. (B) Enlarged image of the nanostructures. Pearl-like chains appear showing periodicities of 2.86 nm, which is typical for the triple helix periodicity of collagen along the fibril long axis. (C) The enlarged region reveals nanodot-like structures with nanopore inclusions. The Fourier transform shows a regular hexagonal pattern (top left inset) with a 4.5-nm periodicity. (D) Fourier-filtered image of (C). For filtering, the reflections of the Fourier transform corresponding to 0.44 nm−1 were selected corresponding to a spacing of 4.5 nm, as indicated in the inset. In the processed micrograph, hexagonal structures are observed with a pore-to-pore distance of 4.5 nm and pore diameters of about 3 nm (top left).

  • Fig. 4 Spectroscopic characterization of carbonized spongin scaffold.

    (A) Baseline-corrected Raman spectra of spongin carbonized at different temperatures. The intensity of the region between 2400 and 3000 cm−1 is multiplied by a factor of 10 for better visibility. (B) NEXAFS C1s K-edge spectra of native and carbonized spongin heated at different temperatures, HOPG, and nanocomposite MWCNT/Cr2O3 (34).

  • Fig. 5 Structural characterization of CuCSBC.

    SEM images (A and B) of the 3D carbonized scaffold after electroplating with copper and following sonication for 1 hour. The metallized scaffold has been mechanically broken to show the location of carbon microfibers. Well-developed crystals (B) can be well detected on the surface of the microcrystalline phase, which covers the carbon microfibers with a layer of up to 3 μm thick. The XAS fluorescence yield signal for the K-edge of Cu in copper layers deposited on the carbonized spongin surface is shown in comparison with reference spectra of CuO and Cu2O standards (C). STEM bright-field (BF) overview of Cu-carbonized microfiber (D) with corresponding SAED pattern from turbostratic graphite (E), interface layer (F), and reaction layer (G). (H) STEM dark-field (DF) image with the path of the EDX/EELS line scan. (I) Concentration profiles of C, Cu, and O calculated from the EDX scan. Electron energy-loss near-edge structure (ELNES) spectra measured near the K-edge of oxygen and L-edge of copper are shown in (J) and (K), respectively. (L) HRTEM micrograph and indexed FFT of a Cu nanocrystallite. (M) Path of an EDX line scan through the reaction layer and (N) the corresponding intensity profiles of the spectral line Kα of oxygen, Lα of copper, and Kα of carbon.

  • Fig. 6 Catalytic performance of CuCSBC.

    Transformation of 4-NP to 4-AP after addition of 5 mg of the CuCSBC catalyst (A) in simulated sea water, with (C) reaction kinetics, and (B) in deionized water, with (D) reaction kinetics. (E) Proposed mechanism of reduction of 4-NP using CuCSBC.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/10/eaax2805/DC1

    Note S1. Purification of spongin, carbonization procedure, and description of in situ monitoring of carbonization process.

    Note S2. Scanning electron microscopy (SEM).

    Note S3. BET specific surface area measurements.

    Note S4. XRD analysis.

    Note S5. Description of compressive strength measurements.

    Note S6. 13C solid-state NMR measurements.

    Note S7. Raman spectroscopy of carbonized spongin.

    Note S8. XPS measurements.

    Note S9. NEXAFS measurements.

    Note S10. Raman spectroscopy of electroplated carbonized spongin.

    Note S11. XPS of electroplated carbonized spongin.

    Note S12. For Fig. 5.

    Note S13. Catalytic activity of CuCSBC.

    Note S14. Calculation of thermodynamic parameters.

    Note S15. Resistance to poisoning.

    Note S16. Influence of the chemical composition of the catalyst on its catalytic properties.

    Fig. S1. Cultivated H. communis bath sponges can be unique sources for 3D spongin scaffolds with diameters of up to 70 cm.

    Fig. S2. Monitoring of the selected spongin scaffold carbonization in the temperature range between 25° and 1200°C in an argon atmosphere.

    Fig. S3. Parameters of the porous structure of native and carbonized spongin.

    Fig. S4. Mechanical properties of native and carbonized spongin.

    Fig. S5. TEM micrographs of ultramicrotomy of nonstained, naturally occurring collagen-based spongin fiber.

    Fig. S6. 13C solid-state NMR analysis of carbonized spongin.

    Fig. S7. Impact of carbonization temperature on the carbonized spongin scaffold visualized by Raman spectroscopy.

    Fig. S8. Impact of carbonization temperature on carbonized spongin scaffold visualized by XPS.

    Fig. S9. SEM images of the 3D carbonized scaffold with nanoporous surface after electroplating with copper and following sonication for 1 hour.

    Fig. S10. Raman spectrum of copper layers deposited on spongin carbonized at 1200°C.

    Fig. S11. XPS analysis of carbonized spongin before and after metallization.

    Fig. S12. Reduction of 4-NP without heterogenic catalyst.

    Fig. S13. Catalytic performance of CuCSBC.

    Fig. S14. Thermodynamics of the 4-NP to 4-AP transformation reaction in the presence of CuCSBC.

    Fig. S15. Catalytic behavior of nonmodified carbonized spongin.

    Table S1. Microstructure parameters of turbostratic graphite as used in the model reported by Dopita et al. (22).

    Table S2. Position, intensity ratio of D and G Raman bands, and calculated nanocrystallite size La of spongin carbonized at different temperatures.

    Table S3. Comparison of catalytic activity using non-noble metal catalysts.

    Table S4. Calculated thermodynamic parameters of 4-NP reduction using CuCSBC.

    References (4476)

  • Supplementary Materials

    This PDF file includes:

    • Note S1. Purification of spongin, carbonization procedure, and description of in situ monitoring of carbonization process.
    • Note S2. Scanning electron microscopy (SEM).
    • Note S3. BET specific surface area measurements.
    • Note S4. XRD analysis.
    • Note S5. Description of compressive strength measurements.
    • Note S6. 13C solid-state NMR measurements.
    • Note S7. Raman spectroscopy of carbonized spongin.
    • Note S8. XPS measurements.
    • Note S9. NEXAFS measurements.
    • Note S10. Raman spectroscopy of electroplated carbonized spongin.
    • Note S11. XPS of electroplated carbonized spongin.
    • Note S12. For Fig. 5.
    • Note S13. Catalytic activity of CuCSBC.
    • Note S14. Calculation of thermodynamic parameters.
    • Note S15. Resistance to poisoning.
    • Note S16. Influence of the chemical composition of the catalyst on its catalytic properties.
    • Fig. S1. Cultivated H. communis bath sponges can be unique sources for 3D spongin scaffolds with diameters of up to 70 cm.
    • Fig. S2. Monitoring of the selected spongin scaffold carbonization in the temperature range between 25° and 1200°C in an argon atmosphere.
    • Fig. S3. Parameters of the porous structure of native and carbonized spongin.
    • Fig. S4. Mechanical properties of native and carbonized spongin.
    • Fig. S5. TEM micrographs of ultramicrotomy of nonstained, naturally occurring collagen-based spongin fiber.
    • Fig. S6. 13C solid-state NMR analysis of carbonized spongin.
    • Fig. S7. Impact of carbonization temperature on the carbonized spongin scaffold visualized by Raman spectroscopy.
    • Fig. S8. Impact of carbonization temperature on carbonized spongin scaffold visualized by XPS.
    • Fig. S9. SEM images of the 3D carbonized scaffold with nanoporous surface after electroplating with copper and following sonication for 1 hour.
    • Fig. S10. Raman spectrum of copper layers deposited on spongin carbonized at 1200°C.
    • Fig. S11. XPS analysis of carbonized spongin before and after metallization.
    • Fig. S12. Reduction of 4-NP without heterogenic catalyst.
    • Fig. S13. Catalytic performance of CuCSBC.
    • Fig. S14. Thermodynamics of the 4-NP to 4-AP transformation reaction in the presence of CuCSBC.
    • Fig. S15. Catalytic behavior of nonmodified carbonized spongin.
    • Table S1. Microstructure parameters of turbostratic graphite as used in the model reported by Dopita et al. (22).
    • Table S2. Position, intensity ratio of D and G Raman bands, and calculated nanocrystallite size La of spongin carbonized at different temperatures.
    • Table S3. Comparison of catalytic activity using non-noble metal catalysts.
    • Table S4. Calculated thermodynamic parameters of 4-NP reduction using CuCSBC.
    • References (4476)

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