BiomineralizationBiomineralizationBiomineralization,,, biomimeticbiomimeticbiomimeticandand and nonnonnon--- classicalclassicalclassicalcrystallizationcrystallization crystallization
WaysWaysWaystoto tounderstandunderstand understand thethethe synthesissynthesissynthesisandand and formationformationformation mechanismsmechanismsmechanismsofof of complexcomplexcomplex materialsmaterialsmaterials HelmutHelmut CölfenCölfen
Max-Planck-Institute of Colloids & Interfaces, Colloid Chemistry, Research Campus Golm, D-14424 Potsdam [email protected] CaCOCaCOCaCO333 BiomineralsBiomineralsBiominerals
Coccolith (Calcite) Nacre (Aragonite) Herdmania momus (Vaterite) Characteristics of Biominerals: Complex forms generated from inorganic systems with simple structure Characteristics of inorganic crystals: Simple geometrical form but often complicated crystal structure Default: Rhombohedral Calcite ImportantImportantImportantbiomineralsbiominerals biominerals MineralMineral FormulaFormula FunctionFunction
Calciumcarbonate CaCO3 Calcite Algae / Exoskeleton Birds / Eggshell Aragonite Fishes / Gravity sensor Mussels / Exoskeleton Vaterite Sea urchins / Spikes
Calciumphosphate
Hydroxyapatite Ca10(PO4)6(OH)2 Vertebrates / Skeleton, teeth Octa-Calciumphosphate Ca8H2(PO4)6 Vertebrates / Precursor for bone formation
Silica SiO2 Algae / Exoskeleton
Iron oxide
Magnetite Fe3O4 Salmon, Tuna & bacteria / Magnetic field sensor Chitons / teeth EvolutionEvolutionEvolution ofofof aaa musselmusselmussel shellshellshell
SEM of broken mussel shell SEM of broken mussel SEM of broken mussel shell after protein removal shell after CaCO3 removal
TEM thin cut of SEM of developing SEM mature mussel shell developing mussel mussel shell shell
Biominerals are often formed in confined reaction environments EpitacticalEpitacticalEpitactical matchmatchmatch betweenbetweenbetween crystalcrystalcrystal andandand matrixmatrixmatrix NacreNacre:: Periodicity in protein β-sheets and β-chitin fibers in close geo- metrical match to lattice spacing of aragonite 001 face.
„„SoftSoft EpitaxyEpitaxy““ BoneBoneBone formationformationformation Amino acid sequence Sub-nm - X - Y - GLY - X - Y - GLY - X - Y - GLY - X - Y - regime (primary structure)
left handed α-helix (secondary structure) 0,286 nm 2,86 nm
right handed triple helix (tertiary structure)
nm regime Rod-like tropocollagen 300 nm
Stained collagen fibril as seen in TEM Characteristics: 300 nm 40 nm 27 nm Mineralization Collagen fibril (quatery structure) occurs in organic m regime μ 67 nm Mineralization of oriented plate-like apatite matrix crystals starting in the hole regions of the collagen fibrils. In (A), plate-shaped crystals are arranged in linear coplanar arrays forming Superstructure grooves through the fibrils. In (B) these grooves are shown to be separated by four layers of triple helical collagen molecules. Figure not formation over drawn to scale. several length
mm - m regime scales Here over 9 magnitudes in Sequence of progressive bone development. Osteoblasts (OB) oriented with their backs toward the capillary vasculature (C), secrete osteoid (O) away from the vasculature, causing the formation of a bony strut (B), and length ! eventually forming a second layer of bone (B2). The stacked layer (SC), which provides osteoprogenitor cells for the process, continues to expand in the direction of bone growth. From almost atomic to macroscopic scale ToothToothTooth enamelenamelenamel Enamel
Growth Tomes process direction Tomes process •• Crystallization and assembly of fibers into rods on the μm scale •• Ordered layer structure of rods provides mechanical strength •• Permanent further crystallization and density increase up to 95 wt.-% mineral Crystallization often occurs highly directed MagnetotacticMagnetotacticMagnetotactic bacteriabacteriabacteria
Nucleation on inside wall of vesicle
Linear organization for magnetic compass
10 nm PhasePhasePhasetransitionstransitions transitionsandand andmatrixmatrix matrix assistedassistedassisted nucleationnucleationnucleation Adapted from S.Mann IMPRS lectures, Golm 2003
Sequence of kinetic inhibitions and phase transformations, resulting in high selectivity degree in crystal structure and composition Direct mechanisms to increase S: Ion pumping + redox Ion complexation/decomplexation Enzymatic regulation Indirect mechanisms to increase S: Ion transport Water extrusion Proton pumping GeneralGeneralGeneralbiomineralizationbiomineralization biomineralization featuresfeaturesfeatures
• Uniform particle size • Well defined structure and composition • High levels of spatial organization • Complex morphologies • Controlled aggregation and texture • Preferential crystallographic orientation • Higher order assembly • Hierarchical structures
Adapted from S.Mann IMPRS lectures, Golm 2003 KnownKnownKnown mechanismsmechanismsmechanismsofof ofBiomineralizationBiomineralization Biomineralization
• Stabilization • Morphology control by selective adsorption • Control of the crystal modification by „Soft Epitaxy“ • Static templates • Confined reaction environments • Adaptive construction and synergistic effects • Structural reconstruction • Higher order assembly PolymerPolymer structuresstructures asas staticstatic templatestemplates
PS-PAA Gel + Fe3O4
Control Fe2+-loaded Magnetic gel Biomimetics Biomineral Zoom
1 μm Mollusc tooth Homogeneous 38 nm Fe3O4 15 - 35 nm in Polysaccharide - Protein Gel Templated 17 nm M. Breulmann, H.P. Hentze DoubleDouble hydrophilichydrophilic blockblock copolymerscopolymers
Molecular tool: = hydrophilic, interacting with mineral Handle Head = hydrophilic, non interacting with mineral
Amphiphilic behaviour induced in presence of mineralic surfaces allows - Size/shape control - Stabilization AdvantageAdvantage ofof DHBCDHBC designdesign forfor CaCOCaCO Advantage of DHBC design for CaCO33 PMAAPMAA PEOPEO--bb--PMAAPMAA
PE block too long, PE block and stab. PE block too short, PE block far too short, stab. block too short block good ratio stab. block too long stab. block too long DoubleDouble hydrophilichydrophilic blockblock copolymerscopolymers Precursor Polymers Functionalities OH COOH PEG-b-PEI (Linear and branched) SO3H PEG-b-PMAA PO3H2 PO4H2
CH3SCN PEG-b-PB
NR3, HNR2, H2NR Modular Synthesis Hydrophobic M = 3000 – 10000 g/mol M. Sedlak, M. Breulmann, J. Rudloff, P. Kasparova, S. Wohlrab, T.X. Wang BaSO Morphogenesis at pH 5 BaSOBaSO44 MorphogenesisMorphogenesisat atpH pH 55 2μm
0.5μm
PEG-b-PEI-SO3H PEG-b-PMAA-Asp
2μm 0.5μm
No additive
2μm PEG-b-PEI-COOH PEG-b-PMAA-PO H L.M.L.M. QiQi PEG-b-PMAA-PO3H2 CdS + PEO-b-PEI CdSCdS+ + PEOPEO--bb--PEIPEIbranchedbranched L.M.L.M. QiQi • Particle size adjustable 2 - 4 nm • Monodisperse stable particles • No photooxidation • Branched PEI more effective than
linear or dendrimer 2.0 0.05 g/l 1.8 0.10 g/l 1.6 0.25 g/l 0.50 g/l 1.4 1.00 g/l 1.2
1.0
0.8
Absorbance 0.6 0.05 g/l
PL Intensity (a.u.) Intensity PL 0.10 g/l 0.4 0.25 g/l 0.2 0.50 g/l 1.00 g/l 0.0 250 300 350 400 450 500 550 400 450 500 550 600 650 Wavelength (nm) Wavelength (nm) SelectiveSelectiveSelectiveAdsorptionAdsorption Adsorption Gold crystallized in presence of PEG-b-1,4,7,10,13,16-Hexaazacycloocatadecan (Hexacyclen) EI macrocycle
Interference patterns due to deformations in sub-Angström range
Very thin platelets
200 nm
Very thin platelets with Au (111) surface and exposed 111 surface, adsorbed hexacyclen Well developed plasmon molecule in vacuum band in UV/Vis S.H.S.H. YuYu SurfacesSurfaces asas staticstatic templatetemplate
CaCO3 +
O
m n
OPO(OH)2 PEG(m)-b-PHEE(n)-(PG rad%)
J.J. RudloffRudloff 2+ - CaCO3(s) + CO2(g) + H2O(l) Ca (aq) + 2 HCO3 (aq)
50 μm 50 μm
50 μm StructuralStructuralStructural reconstructionreconstructionreconstruction pH = 5
BaSO4 with PEG-b-PMAA-PO3H2
Parallel cut to to fiber axis Perpendicular cut to fiber axis Fiber axis is [210] Diameter 20 - 30 nm Bundles of single crystalline fibers
L.M.L.M. QiQi StructuralStructuralStructural reconstructionreconstructionreconstruction pH = 5 BaSO4 fibers obtained in the presence of PEG-b-PMAA-PO3H2 on carbon films with an aging time of 5d.
•• Heterogeneous nucleation on carbon films •• Perfectly flat surface of growth edge due to surface minimization L.M.L.M. QiQi CrystallographicallyCrystallographically orientedoriented nanoparticlenanoparticle attachmentattachment
Single crystalline anatase TiO2 particles hydrothermally synthesized in 0.001 M HCl Topotactic particle attachment at high energy surfaces (112) a) Single primary crystal, b) four primary crystals forming a single crystal via oriented attachment, c) Single crystalline anatase particle
R.L. Penn, J.F. Banfield; Geochim. Cosmochim. Acta. 63 (1999) 1549 - 1557 1) 2) 3) L.M.L.M. QiQi
Nucleation of amorphous nanoparticles, polymer stabilization
4) 5) 6) 7)
-
Crystallization of amorphous particles, directed particle fusion Perfect Single Crystals Fiber Bundles: Elongation along [210]
[2 1 0 ]
500nm <001> 4 -20 400 4-10 420 410 2-20 200 2-10 220 210
0-20
020 -2-10 -2-20 -200 -220 -210 XY -4-10 -4 -20 projection -400 S.H.S.H. YuYu BaSO4, 2 mM, polyacrylate ( Mn = 5100) StructuralStructuralStructural reconstructionreconstructionreconstruction 0.11mM, pH = 5.5, 25 °C
10 μm 1 μm Cuttlefish bone β-Chitin + aragonite
100 μm 2 μm S.H.S.H. YuYu HigherHigher orderorder assemblyassembly [PEG-b-PMAA] = 1 g/l, 30 min 60 min [CaCO3] = 8 mM, pH = 10 •• Chains of aggregated amorphous nanoparticles •• Dumbbell 100 nm 100 nm shaped and spherical 90 min 120 min aggregates •• Nanoparticle crystallization Primary crystals 40 nm
10 μm 10 μm Zoom L.M.L.M. QiQi LightLight microscopymicroscopy onon CaCOCaCO 3 withwith PEOPEO--bb--PMAAPMAA 8 5.6 8-15 min 7 3.8 19-30 min 45-90 min 6 3.2 Images not 5 drawn to scale
2.7 l/r 4 pH 6.5 1.8 3 1.4 2
1 0246810121416 r/µm A. Reinecke, H.G. Döbereiner HigherHigher orderorder assemblyassembly
Aggregate structures are also observed if the crystals are dissoved with HCl A. Reinecke, H.G. Döbereiner HigherHigherHigherorderorder orderassemblyassembly assembly pH 11 L.M.L.M. QiQi
10
9
[Polymer] / [CaCO3]
••• SupersaturationSupersaturationand andstrength strengthof of polymer polymer-mineral-mineral interaction interaction ( (pH)pH) and and [Polymer] / [CaCO ] play important role for morphogenesis [Polymer] / [CaCO33] play important role for morphogenesis HigherHigher orderorder assemblyassembly
CaCO in oyster marrow matrix CaCO3 + CaCO3 in oyster marrow matrix P. Harting 1873 PEG-b-PEDTA-C17H35 Composed of nanoparticles M.M. SedlakSedlak HigherHigherHigherorderorder orderassemblyassembly assembly L.M.L.M. QiQi
pH 11 pH 9
pH 7 pH 5 pH 3
BaSO4 with PEG-b-PMAA additive; pH variation BaCOBaCO3 MorphogenesisMorphogenesis BaCO + PEG-b-PMAA (1g/L), Ba2+ = 10 mM, Default 3 gas-diffusion reaction, 2 days Different growth stages from rods (1), growth at the ends (2), via dumbbells (3) to spheres (4). 2 μm Apparently no directed 50 μm nanoparticle assembly but dendritic radial outgrowth.
3 3 3 1 4 1
2 2 4
3 μm 1 μm S.H. Yu ChiralityChirality introductionintroduction byby aa racemicracemic polymerpolymer S.H. Yu, K. Tauer
-1 1 g L , pH = 4, [BaCl2] = 10 mM, on glass slip, gas diffusion reaction 14 d
Amorphous precursor after PEG-b-[(2-[4-Dihydroxy phosphoryl)-2-oxabutyl) acrylate 14 d 5h ethyl ester, Mw = 120000 g/mol, PEO = 2000 g/mol BaCO orthorhombic crystal structure BaCO3 orthorhombic crystal structure 4000 011 & 022 broadened Restricted growth 3000 111
2000 With polymer 102 Intensity (a.u.) Intensity
Vacuum equilibrium 1000 122 211 213 013 311 020 104 220 011 morphology 200 022 202 002 201 004 Default 0 011 15 20 25 30 35 40 45 50 2θ (degree)
020
110 favourable for 111 polymer interaction S.H. Yu, K. Tauer GenerationGeneration ofof unidirectionalunidirectional aggregationaggregation
Particles aggregate and AggregationAggregation // fuse predominately at 011 growthgrowth directiondirection
Favourable for polymer adsorption
Unfavourable for polymer adsorption
Polymer is sterically demanding Possible Possible Impossible
S.H. Yu, K. Tauer Polymer adsorption on the timescale of aggregation ChiralityChirality introductionintroduction byby aa racemicracemic polymerpolymer Overlay of directed aggregation and turn
Alteration between 020 and 011 aggregation creates turn S.H. Yu, K. Tauer ControlControl experimentsexperiments onon mechanismmechanism
IncreaseIncrease laterallateral growthgrowth DecreaseDecrease laterallateral growthgrowth
Particle attachment prevails Polymer adsorption prevails over polymer adsorption. over particle attachment.
Polymer 1 g L-1, pH = 5.6, Less particle Polymer 2 g L-1, pH = 4,
charge as IEP = 10.0 – 10.5 [BaCl2] = 10 mM
S.H. Yu, K. Tauer OrganicOrganic MesocrystalsMesocrystals,, thethe D,LD,L--AlaninAlanin exampleexample
41 % functionalization Default PEG-PEI n O cPolymer = 1 g/l Supersaturated solution HO at 65 °C cooled to 20 °C PEG-b-PEI-s-But-COOH
200 μm
100 μm
S. Wohlrab OrganicOrganic MesocrystalsMesocrystals,, thethe D,LD,L--AlaninAlanin exampleexample
2 μm 2 μm
Crystalline appearance but: Partial polymer dissolution • Rough and even surfaces after boiling in MeOH • Nonplanar surfaces indicates hybrid structure • Cracks indicate swollen structure
S. Wohlrab D,LAlanin+ 1 g/l PEG-b-PEI-s-But-COOH OrganicOrganic MesocrystalsMesocrystals,, thethe D,LD,L--AlaninAlanin exampleexample Overview Rough face
100 μm 2 μm
Fracture structure Single crystal Powder Mesocrystal
X-ray single crystal analysis 2 μm D,L Alanin + 10 g/l PEG-b-PEI-s-But-COOH S. Wohlrab DifferentDifferent modesmodes ofof cyrstalcyrstal growthgrowth
Nucleation clusters
Crystal growth Temporary Primary Stabilization Mesoscale nanoparticles assembly > 3 nm Mesocrystal Amplification Mesoscale assembly
Single crystal Iso-oriented crystal OrganicOrganic MesocrystalsMesocrystals,, thethe D,LD,L--AlaninAlanin exampleexample D,LAlanin+ 1 g/l PEG-b-PEI-s-But-COOH + NaCl 0 N 0.1 N 1.0 N 2.0 N
3.0 N 4.0 N 5.0 N saturated
Salt addition dramatically changes the mesocrystal morphology • Counterplay between electrostatic & vdW forces • Polymers attach to different surfaces • D,L Alanin molecule is already a dipole ! S. Wohlrab ConclusionsConclusionsConclusions •• Bio-inspired mineralization can transfer biomineralization principles towards the synthesis of advanced organic-inorganic hybrid materials at ambient temperature in water. •• Self-assembled superstructures can be generated by tuneable interacting organic block copolymer additives. But: Self assembly only possible up to the micron scale (Need for macroscopic templates) •• Up to now, synergistic effects as often present in biomineralization processes cannot yet be applied in bio- inspired mineralization. Bio-inspired mineralization has still the character of a model system. •• Structure formation mechanisms are still often unknown due to demanding analytics. •• Principles can be extended to organic crystals exploiting new variables like chirality or inherent molecular dipoles. Bio-inspired mineralization offers a large playground for future materials ConclusionsConclusionsConclusions •• Bio- and biomimetic mineralization offer many indications for non-classical crystallization routes e.g. a crystal is not always built up from ions or molecules but by precursor particles via mesoscopic transformations •• Mesocrystals can be isolated for organic crystals with low lattice energy, for the inorganic counterparts, the lattice energy is too high and forces crystallite fusion with resulting defect structures •• Often, amorphous precursors are observed and mesoscopic transformation generally plays an important role in the final alignment of the crystallites. •• Coding of crystal surfaces by additives can alter the mesocrystal structure and thus the structure of the final single crystal (additive inclusions) RecommendedRecommendedRecommended readingreadingreading
•• S. Mann, Biomineralization, Oxford University Press, Oxford, 2001 •• S. Mann, J. Webb, R. J. P. Williams, Biomineralization: Chemical and biochemical perspectives, VCH Weinheim, 1989 •• S. Weiner, CRC Critical Reviews in Biochemistry, 1986, 20, 365 - 408 •• H. Cölfen, S. Mann, Angew. Chem. Int. Edit. 2003, 42, 2350-2365 •• S.H. Yu, H. Cölfen, J. Mater. Chem. 2004 in press