1. Physics and Chemistry of Hybrid Organic-Inorganic Materials Lecture 5: Naturally occurring hybrids

2. Biological hybrids: key points
Hybrids made by plants or animals
Strong composites from very weak components
Wet protein and carbohydrates are very soft
calcium carbonate is also weak and soft
Multiple phases, hierarchical structures

3. Hybrid Organic-Inorganic materials are common in nature: composites
Animals
Organic phase is biopolymers
Nacre
Plants
phytolith
Argonite (CaCO3) plates as inorganic
with protein (polyamide) as organic
Teeth, spines in echinderms
Mussel shells, sponges, diatoms and corals are utilize hybrid organic-inorganic materials
Carbohydrates are the template and organic phase

4. Silica (SiO2) & protein radiolaria diatoms
Proteins act as templates for building silica architectures

5. Colloidal silica in diatoms: Hierarchical structure
pH ≈ 5
Silica walls are build up from ca. 5nm particles to give ca. 40nm diameter particles that are organized within the frustule.

6. What is a hierarchical structure?
In materials, a structure with different structures at different length scales: like in tendons (above)

7. More Bio-Hybrids based on CaCO3: Nacre
Argonite (CaCO3) plates as inorganic phase
with protein (polyamide) as organic phase
Fracture strength is 3000 times higher than its mineral constituent CaCO3.
Mother-of-pearl
Opalescence from light diffraction in nacre (argonite blocks height
≈ λ light)

8. The hierarchical structure of nacre
Macromolecular
Growth rings (mesolayers)
Phase
morphology
The shell itself
Inner surface of shell (mother or pearl)
Long range order: stacked crystals
argonite
crystal
structure
Barthelat F Phil. Trans. R. Soc. A 2007;365:

9. Lobster exoskelton
CaCO3
& Carbohydrate & protein

10. Teeth: Enamel, dentin, and cementum
Apatite – hydrated CaPO4
Protein– collagen & others

11. Bones Apatite – hydrated CaPO4 Protein– collagen
200 MPa yield strength
30 MPaM0.5 toughness

12. Echinoderm spine
CaCO3
Protein templating

13. Phytoliths
SiO2 silica
2-3% silicon by weight
Horsetail, banana leaves

14. Silica in Sponges
hierarchical structures
Templated by proteins

15. Metal in Spider Fangs carbohydrate fibers in a protein matrix
with zinc and magnesium ions
Politi, Y., Priewasser, M., Pippel, E., Zaslansky, P., Hartmann, J., Siegel, S., Li, C., Barth, F. G. and Fratzl, P. (2012), A Spider's Fang: How to Design an Injection Needle Using Chitin-Based Composite Material. Adv. Funct. Mater., 22: 2519–2528

16. Bio Hybrid Organic-Inorganic Materials
Sophisticated, highly evolved hybrids
-nominally weak, but bio-accessible minerals (eg. CaCO3)
-hydrophilic, water plasticized biopolymers (eg. protein)
-Integrated at nano-length scales
-Phase separation templating of hierarchical structures
-All water based chemistry!! The ultimate green chemistry
Optimized to give non-additive property (synergistic effects)
Models for many research programs in hybrid materials