Carbon Materials. Prof. Bob Bradley. University of Oxford, Department of Materials Oxford OX1 3PH. MatSURF Technology UK C=O C-OH COOH

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1 Carbon Materials Prof. Bob Bradley University of Oxford, Department of Materials Oxford OX1 3PH MatSUF Technology UK C=O C-OH COOH MatSUF Carbon & Biomaterials Technology

2 Carbon esearch Carbon Materials: nanotubes; porous carbons; fibres; filler particles graphene layers; arrangements of multiple graphene layers; graphene steps Carbon: adsorbents; reinforcement; fillers; electronic devices; biomaterials Surfaces (fluid-solid interactions) - forces, potential energy, non-specific & specific interactions, mechanisms of interaction Thermodynamic studies; first principles calculations & models Control of interfaces bringing two materials together (adsorption; adhesion; wetting); functionalization, composites, coatings

3 Structure of Carbon Materials Graphite J D Bernal; Proc. oy. Soc. 1924, 106A, 749. = nm Turbostratic Structure of Carbons nm Warren; Biscoe & Warren 1934; 1942 Carbon Layers in Coal osalind Franklin Proc. oy. Soc. 1951, 209, 196; Acta. Cryst., , 253 Non-graphitizing carnons Graphitizing

4 Carbon Layers Geim & Novoselov Nobel Laureates Oct. 2010; KsB Dec In 1962 Hanns Peter Boehm used the term graphene to describe single layers of carbon the Basic Structural Unit of carbon materials

5 Carbon Materials Surface Nanostructure Carbon Black MWCNT

6 O Molecular Interactions - Surface Energy φ tot = φ D + φ P + φ Q + φ Involves intermolecular forces (dispersion, polar, quadrupole...) and the corresponding potentials All Surfaces - Mean energy, due to electron density/distribution (polarizability) Non-specific: Dispersion (London) Forces (φ D + φ ) Lennard-Jones 12:6 Potential e Compare: graphite-ar (-10 kj/mol) to Ar-Ar (-1kJ/mol) Enhanced potential due to additive interactions with surface atoms and nearest neighbour effects

10 22 Potential energy, J Interaction Potentials for Kr on Single and Multiple Graphene Layers - y z x 50 0 - x y -50-100 -150-200 - x - y z y x -250 Layer spacing/nm Laurentz-Berthelot

7 10 22 Potential energy, J Interaction Potentials for Kr on Single and Multiple Graphene Layers - y z x x y x - y z y x -250 Layer spacing/nm Laurentz-Berthelot combining rules for each interacting species Pendleton & Bradley 2012 In press Adsorption Science & Technology z, nm Single Lattice Plane Multiple Graphene Planes = nm

8 10 22 Potential energy, J Effect of Layer Spacing ( ) on Interaction Potentials z, nm Graphene layer spacing = nm 0.75 x, nm 1.25 x, nm

9 10 22 Potential energy, J Effect of Layer Width on Interaction Potentials 50 W/2 W/2 0 y = W/2 y y y + = W/2 y z z, nm Graphene layer width, W = 5 nm y = 0 y = y =

10 Molecular Interactions - Surface Energy φ tot = φ D + φ P + φ Q + φ Involves intermolecular forces and the corresponding potentials Specific - Polar (φ P ) Chemically heterogenious surfaces - Interaction a specific sites polar groups, hydrogen bonds... Water molecules hydrogen bonding at functional groups C-OH COOH COOH Hydrophilic (functionalized) Surface System control/pretreatments etc.. Graphene-water -2/3 kj/mol compared to oxidized graphene-water -10/-20 kj/mol) Increased potential due to specific bonds with polar molecules here hydrogen bonding between water and surface oxygen groups

11 Effect of Carbon Surface Chemistry Enthalpy of Immersion (- H i /mjm -2 ) carbon-water weak dispersion and relatively strong polar interactions /20 kj mol H i (H 2 O) Jg mjm (-2/3 kj mol -1 ) Bradley H et al., J.Chem. Soc. Faraday Trans, 91, 3201, 1995 Bradley H, Adsorption Science and Technology, 15:477, Bradley H, Daley A and Le Goff F., Carbon, 40, , 2002 Andreu A, Stoeckli HF Bradley H., Carbon, 45, , 2007 [O] T (atom%) Ozone Oxidised Nitric Acid Oxidised Data from ef [9] Data from ref [8] Oxidation of carbon particles in ozone fluidized-bed

12 Enthalpy of Immersion (- hi)/mjm -2 Which parts of molecules interact? Water 1.89 D -10 to -20 kj mol mjm -2 Toluene 0.36 D mjm -2-3 to -5 kj mol -1 Hexane Non-polar Decrease in dispersion Alcohols intermediate: dispersion interaction increases - due with to alkyl loss chain of length sp 2 π electrons to covalent sp 3 bonds with oxygen (surface is less polarizable) Andreu, A, Stoeckli, HF Bradley, H., Carbon, 45, , 2007; Aurik Andreu, Ph.D. Thesis October Functionalized Surface A L-J = α 1 α 2 /(α 1 /x 1 )+(α 2 /x 2 ) QM Calcs. Kirkwood Muller

elative potential energy Enhanced Potentials in Micropores (after Everett) i.e. Between 2 graphene surfaces 2d Model for Slit Lattice Plane(s) Slit Single Lattice Plane f f r ecent Developments in the Physical Adsorption of Vapours by Microporous Carbons,.

13 elative potential energy Enhanced Potentials in Micropores (after Everett) i.e. Between 2 graphene surfaces 2d Model for Slit Lattice Plane(s) Slit Single Lattice Plane f f r ecent Developments in the Physical Adsorption of Vapours by Microporous Carbons,. H. Bradley, Adsorption Science & Technology, 29, 1, 1, d/σ sf s d/ sf Collaboration: Prof Phil Pendleton, Sansom Inst., Uni. of S. Australia, Adelaide; s

14 Enhanced methanol adsorption on CB at 303K by ozone oxidation 1.7 [O]% monolayer capacity 11.2 atomic % 0.7 mmol/g or area of 76.6 m 2 /g 1.7 atomic % ADD OXYGEN - Sub-monolayer adsorption is displaced to higher values due to increases in specific interactions ( H i and H ads increase)

15 Carbon Nanotubes surface functionalization Hydroxylation using Fenton reaction Improves dispersion in polar fluids; promotes specific surface interactions; micro-composites OH OH OH Fenton oxidation OH OH OH Li, NH 3 X Mechanism: OH radical attack and addition across graphene double bond Graphene platelets Collaborators: CAE, Uni. of Kentucky, Lex. US; Oak idge National Laboratory, Materials Group, Tn. US.

Control of Interfaces Understanding and modeling of forces

* A BET - h i I G /I D FWHM % (H 2 O) MWCNT C O (ev) m 2 g -1

64 Hydroxylated 77.7 22.3 0.61 70 71.8 192 1.

16 Control of Interfaces Understanding and modeling of forces (adsorption, bonding, stress transfer) MWCNTs Atomic % C1s π-π * A BET - h i I G /I D FWHM % (H 2 O) MWCNT C O (ev) m 2 g -1 mjm -2 As-produced Hydroxylated aman XPS 60-70% -OH I G /I D π-π * -30% TEM Appl. Surf. Sci., 258, (2012)

17 Theory molecular interactions - prediction Barton (B2 & GB) and D Arcy & Watt equations: the terms a 0 and a s describe the surface polarity, they correlate with [O] t the atom % Oxygen from XPS [O] t polarity parameters Limiting value at. % a ml a 0 a s As-produced Hydroxylated OH Polar surface interactions probed by water vapour a c B2 2 a a 1 exp k a a 0, B2 MC & GCMC simulations of adsorption processes. B2 c, B2 2 P P 0 -COO a c GB n a a 1 k a 0, GB GB P P 0 as-prod Dependence of Water Vapour Adsorption on the Polarity of Graphene Surfaces of MWCNTs,. H. Bradley, K.Cassity,. Andrews, M.Meier, S. Osbeck, A. Andreu and C. Johnston, Adsorption Science and Technology, 28, 10, 69 (2011).

18 Biocomposites Carbon Nanotubes Bone (surface functionalization) Hydroxylation using Fenton reaction (also esterification & carboxylation) Improves dispersion in polar fluids; promotes specific surface interactions; micro-composites Fenton oxidation OH OH OH OH OH OH Li, NH 3 X Mechanism: OH radical attack and addition across graphene double bond Graphene platelets Collaborators: CAE, Uni. of Kentucky, Lex. US; Oak idge National Laboratory, Materials Group, Tn. US. AST, 28, 10, 69 (2011); Appl. Surf. Sci., 258, (2012)

alizarin red stain a) b) c) EDX Ca, P SEM

19 Surface Treatments: to promote cell attachment & proliferation Human osteoblast cells: mineralization; new bone HOB idge HDPE hip replacement Calcium spherulites - alizarin red stain a) b) c) EDX Ca, P SEM Poulsson and Bradley, Langmuir, 25, 6, (2009). AFM

20 Human Serum Albumin Adsorbed on Graphite Basal planes STM image of a freshly cleaved HOPG surface ILS nm Orasanu-Gourlay and Bradley Adsorption Science & Technology, 24,2, , 2006.

deconvolution to remove tip-broadening (x-checked against graphite step-heights).

21 AFM - human serum albumin molecules adsorbed on basal plane graphene (1μg/ml). N form (diameter 3-8 nm, height 3 nm) and F Form (11-15x 2-4 nm height 3nm) After deconvolution to remove tip-broadening (x-checked against graphite step-heights). Orasanu-Gourlay A. and Bradley.H. Adsorption Science & Technology, 24,2, , 2006.

Folded dimer structure Top view and cross sections image of an extended

22 AFM images of Fibronectin Molecules Adsorbed on Basal Plane Graphite (1μg/ml) a. b. Folded dimer structure Top view and cross sections image of an extended monomer (length 70nm height from 1 to 1.2 nm) Orasanu-Gourlay A. and Bradley.H. Adsorption Science & Technology, 24,2, , 2006.

23 TM-AFM images of dry nanostructured protein films adsorbed on HOPG surfaces HSA (10 μg/ml) Fn 20 μg/ml) c. Dewetting of aqueous phase from hydrophobic substrate to form network structure (dispersion interactions)

24 Molecular Interactions - Surface Energy φ tot = φ D + φ P + φ Q + φ Involves intermolecular forces and the corresponding potentials lets look at two types: Non-specific Dispersion (φ D + φ ) Specific - Polar (φ P ) All Surfaces - Mean energy, due to electron density/distribution (polarizability) Water molecules hydrogen bonding at functional groups C-OH COOH COOH Hydrophilic (functionalized) Surface e System control/pretreatments etc.. Graphite-Ar: -10 kj/mol (compared to Ar-Ar -1kJ/mol) Enhanced potential due to surface atoms and nearest neighbour effects ---- adsorption, adhesion, wetting, reaction intermediates/catalysis...

PLASMA-POLYMER MODIFICATION OF BASAL PLANE GRAPHITE SURFACES FOR IMPROVED BIOCOMPATIBILITY

PLASMA-POLYMER MODIFICATION OF BASAL PLANE GRAPHITE SURFACES FOR IMPROVED BIOCOMPATIBILITY Anca Orăşanu, Marcus R. Davidson, Robert H. Bradley Advanced Materials & Biomaterials Research Centre, School