Physics and Chemistry of Hybrid Organic-Inorganic Materials

Lecture 5: Naturally occurring hybrids

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

Hybrid Organic-Inorganic materials are common in nature: composites

Nacre

Argonite (CaCO3) plates as inorganicwith protein (polyamide) as organic

Animals

Plants

phytolith

Teeth, spines in echindermsMussel shells, sponges, diatoms and corals are utilize hybrid organic-inorganic materials

Organic phase is biopolymers

Carbohydrates are the template and organic phase

What is a hierarchical structure?

In materials, a structure with different structures at different length scales: like in tendons (above)

The Building PlanFabrication Conditions in Living Organisms

only few elements: C, H, O, N, P, S, Ca, Si, Mg

mild pH

ambient pressure and temperature

Calcite Crystals Extracted from the Prismatic Layer of Pinna Nobilis Shells

www.cutgana.it/acquario/specie Marin et al., J. Biol. Chem., 2005, 40, 33895

The Building Plan

Hierarchical Design – Morhpology Control on Several Levels

Interaction of an Organic and an Inorganic Component

Fabrication Conditions in Living Organisms

only few elements: C, H, O, N, P, S, Ca, Si, Mg

mild pH

ambient pressure and temperature

Incorporation of biopolymers increased fracture resistence

&

aspartate residue in peptide bond

chitin network

Nudelman et al., Faraday Discuss. 2007, 136, 9

Colloidal silica in diatoms: Hierarchical structure

Silica walls are build up from ca. 5nm particles to give ca. 40nm diameter particles that are organized within the frustule.

pH ≈ 5

Silica (SiO2) & protein

radiolaria diatoms

Proteins act as templates for building silica architectures

Bio-Hybrids based on CaCO3: NacreArgonite (CaCO3) plates as inorganic phasewith protein (polyamide) as organic phase

Mother-of-pearl

Opalescence from light diffraction in nacre (argonite blocks height ≈ λ light)

Fracture strength is 3000 times higher than its mineral constituent CaCO3.

The hierarchical structure of nacre

Barthelat F Phil. Trans. R. Soc. A 2007;365:2907-2919

argonitecrystalstructure

Phasemorphology

Long range order: stacked crystals

Growth rings (mesolayers)

Macromolecular

Inner surface of shell (mother or pearl)

The shell itself

Lobster exoskelton

CaCO3

& Carbohydrate & protein

Teeth: Enamel, dentin, & cementum

Apatite – hydrated CaPO4

Protein– collagen & others

The layered, rod structure of hydroxyapatite (a calcium phopshate) in dental enamel. Very tough for a ceramic.

Hierarchical structure of alligator gar, a primitive fish, scales. Ganoine is mostly mineral, like enamel, with tougher bone beneath.

Enamel and collagen

Regular Fish Scales

Fish scale puncture resistance

fish scales are better than polycarbonate.note how they give, and then reload. This is just one scale.

200 MPa yield strength 30 MPaM0.5 toughness

Apatite – hydrated CaPO4

Protein– collagen

Bones

The Building Plan

Hierarchical Design – Morhpology Control on Several Levels

Interaction of an Organic and an Inorganic Component

structural optimization from the atomic to the macroscopic scale

Fabrication Conditions in Living Organisms

only few elements: C, H, O, N, P, S, Ca, Si, Mg

mild pH

ambient pressure and temperature

&

Bone

Fratzl et al., Progr. Mat. Science, 2007

Peterlik et al., Nat. Mat., 2006

Gupta et al., PNAS, 2006

Echinoderm spine

CaCO3

Protein templating

Phytoliths

Horsetail, banana leaves

2-3% silicon by weight

SiO2 silica

Silica in Sponges

Templated by proteins

hierarchical structures

Euplectella sp.

7 hierarchical levels

Stress-deflection responses of synthetic silica rod and sponge spicule in flexuretesting. (Courtesy of M. Sarikaya and G. Mayer.)

conch shell Almost no protein 3 hierarchical levels of layers made from layers of calcite.

Chiton Teeth

the tips of the teeth are hard magnetite (Fe3O4) with a tough fibrous calcite interior

Metal in Spider Fangscarbohydrate fibers in a protein matrixwith 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

Biomaterial: Toucan Beak

(a) Toucan beak; (b) external shell made of keratin scales. Cellular materials: (a) synthetic aluminium foam; (b) foamfound in the inside of toucan beak.(Courtesy of M. S. Schneider andK. S. Vecchio.)

Bio Hybrid Organic-Inorganic MaterialsSophisticated, 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