nanotechnology from natural porous tissues metal micro coating of spongy bone tissue to realize...

A. Agazzi, C. Margaroli, S. Reiser, M. Salazar; Liceo Lugano 2. Lavoro di maturità in chimica 2008-2009 1

Nanotechnology from natural porous tissues

Metal micro coating of spongy bone tissue to realize catalytic systems

with high active surface


AbstractBy applying Physical Vapor and Chemical Vapor Deposition methods it has been possible to coat with thin metal layers the macro-, micro- and nano-porous surface of degreased and deproteinized horse humerus spongy bone. The obtained coated surface shows high heterogeneous catalytic activity for fuel cell hydrogen combustion and for organic oxidation reactions.


Anatomy of the bone tissue


Cutting the bone (butcher)

To the butchers Gianocca and Migros has been cut slices of spongy bone with sides of about 50x50 mm and thickness of 20 mm


Washing the bone

The bone is washed with hot water in order to remove muscle and blood present after cutting.


Degreasing of the spongy bone

Fats and fluids are extracted from washed pieces through Supercritical CO2 (300 bar, 45°C, 2 kg/h, 48 h).(Extraction by soxhlet / petroleum ether : 1 week!)


SCCO2 Extraction curve of the spongy boneSpongious bone extraction

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

mass of circulated CO2 (kg)

The fat recovering ends after about 50 hours (100 kg circulated SCCO2)


The degreased spongy tissue

The fat and liquid free collagen/hydroxyapatite structure by stereoscope


Working

• Mechanical action after cryogenicembrittlement

• (lathing)• Cutting with

hacksaw• smoothing


Deproteinization of the degreased spongy tissue

- Removing the protein matrix by digesting with 30% hydrogen peroxide during 24 h- Combustion of the residual organic matter at 700 ° C. A heat resistant “mineral sponge” is obtained.


The deproteinized spongy tissue (mineral sponge)

The collagen free hydroxyapatite structure by stereoscope


Macro and Micro pores (stereoscope)


Macro, micro and nanopores (SEM)


Specific surface and porosity

Material Specific surface (m2*g-1)

Porosity

Ni-Raney 60-100 20%

MCM-41* 750-1200 80%

SBA-15* 800 50%

Spongious tissue 50-85 60%


CVD coating by using organometallic complexes

These are synthesized from chlorides and carbonates salts: Copper Bis-acetylacetonate (bis-ACAC-Cu) Iron Bis-acetylacetonate (bis-ACAC-Fe) Chromium Tris-acetylacetone (tris-ACAC-Cr) Cobalt Tris-acetylacetonate (tris-ACAC-Co) Cobalt Di-aquo-bis-acetylacetonate (di-aq-ACAC-Co)

O

O

M

CH3

CH3

O

O

CH3

CH3

M

O

O

O

O

O

O

Target Molecules


Synthesis of acetylacetonates

bis-ACAC-Cu

bis-ACAC-Fe tris-ACAC-Crtris-ACAC-Co


CVD coating

Heating under vacuum of acetylacetonates allows the reduction of the metal ion to metal and the production of thin metal layers


Coating methods

The organometallic compound is heated under vacuum in contact with the mineral sponge :a thin metal layer is deposited on thehydroxyapatite and on the glass surface.


CVD coating methods

A copper layer on the glass surface from bis-ACAC-Cu


CVD results

The obtained metal layer is often very thin. To obtain a homogeneous coating we will probably need several deposition

steps


CVD results

Amorphous (?) and/or crystalline growth is observedAn excessive deposit may block the pores!


PVD coating

Coating with Cu and Ni-Cr alloy:the metal is sublimed from a electrically heated filament; under vacuum and at hightemperatures the metal sublimes and deposits by frosting.


PVD coating on salt surfaces

Test of adherence on NaCl


Test of the coating degree: conductivity

• To obtain anelectrical conducting depositiona long-time process is needed. The deposition must beuniform over all the surface.


Test of the coating degree by PVD

Insufficient deposition on the internal porous surface is normally observed: the metal vapor frosts on the outer surface


Test of the catalytic activity• Test for methane combustion • Catalysis of the synthesis of

acetaldehyde from ethanol

• Using as electrode in a fuel cell


Coating by sputteringPrinciples of the sputtering process

Avantages: • no heating: the cold vapor can diffuse into the pores!• rapid process but easily controllable


Coating by sputtering

Copper sputtering: 700 V, Ar



Copper sputtering: 700 V, Ar



click the image to start the video


Coating by sputtering on the mineral sponge: Copper


Coating by sputtering on the mineral sponge: Cobalt


Demineralisation of the degreased spongy tissue: proteic sponge

Soft and flexible protein sponge, sensitive to temperature is obtained: covering only possible through sputtering!

• Decalcification with HCl• Washing and neutralisation with water• Drying with ethanol


Conclusions• Preparation of the support (mineral and/or protein sponge):

• Degreasing: OK • Decalcification: OK • Deproteinizing : OK

• CVD coating *: - Cu, Co: applicable - Fe, Mn in verification - Cr: dangerous (explosion!) - Rh, Ir, Pd, Pt, Ag: unverified (high costs!) - Ni: not checked (protocol of the acac synthesis not found)

* In any case:• applicable only to the heat-resistant mineral sponge. • great difficulty of layer’s growth control!


Conclusions

• PVD by sublimation and frosting: – Applicable to mineral sponge for the outer surface but with

fatigue to penetrate the cavities– Not applicable to sponge with protein (no heat-resistant)

• PVD by sputtering : – Good applicable to mineral sponge with Cu, Co and probably

with every others interesting metal– Well controllable for layer thickness – Capillary deposition on the porous system– Optimization of the process conditions needed (pAr, U) – To be verified on the protein sponge


Questions

• How to control the growth of the coating and the thickness achieved?

• How to check the catalytic efficiency and duration its duration?

• Other applications of spongy covered? • Other non-metallic coating of interest?

nanotechnology from natural porous tissues metal micro coating of spongy bone tissue to realize...

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