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GRAPHITEDIAMONDBonding: 3 sp2 and 1 piBonding: Four sp3 bonding
crystallizes in the hexagonal system.
crystallizes in the cubic system.
opaque.highly transparent.conductor of electricity.excellent electrical insulator.
very good lubricant.ultimate abrasive.
one of the softest materials known.
Synthetic nanocrystalline diamond is the hardest material known.
Surface of a Graphite Crystal
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High Resolution TEM image of Graphite
Graphite Flake
Three-dimensional Schematic of the Graphite Structure
Edge States of a Graphene Sheet
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Variation of Graphite StructureLecture 3: Fullerenes
Reference:
Nanomaterials Handbook, Edited by Y. Gogotsi, Taylor and Francis, Boca Raton, FL, 2006
Chapter: Fullerenes and their derivatives
From “Nanotech. for dummies”
Schematic of Smalley Apparatus for Generating Carbon-cluster Beams
http://www.chemistry.wustl.edu/~edudev/Fullerene/discovery.html
1985 - Discovery of the fullerenes by Kroto, Curl, Smalley and co-workers.- H.W. Kroto, J.R. Heath, S.C. O’Brien, R.F. Curl, R.E. Smalley, Nature 318 (1985) 167
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a) Low helium density over graphite target at time of laser vaporization. b) High helium density over graphite target at time of laser vaporization.c) Same as b), but with addition of "integration cup" to increase time between vaporization and cluster analysis.
No. of carbon atoms per cluster
Kroto and Smalley’s Experimental Results
Distribution of carbon clusters produced under various experimental conditions.
Carbon Allotropes
Comparison of Size
Fort Worth –Casa MagnanaR. Buckminster Fuller
The molecule was named for Richard Buckminster Fuller, a noted architect who popularized the geodesic dome.
Origin of the Name of Fullerenes
http://en.wikipedia.org/wiki/Fullerene
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R.F. Curl, R.E. Smalley, Fullerenes, Sci. Am., 1991, October issue
Structure of FullerenesA closed 3D carbon structure containing only pentagons and hexagons can form the following structures:•C20: the smallest possible fullerene, containing twelve pentagons and zero hexagons. However, such a structure would possess a great deal of strain, because the local topology at each carbon center would be highly non-planar. •C28, C32, C50. Because the molecular strain tends to be concentrated in the five-member rings that are responsible for closure, structures that avoid contiguous (edge-sharing) pentagons are particularly stable.•C60 and C70 are the smallest carbon clusters avoiding contiguous pentagons.
C32 C70 C78
Stone-Wales Transformation in Fullerenes
Interconversion between fullerene isomers can be achieved by rotation of atom pairs in the molecules about their mutual bond center (Stone-Wales transformation). The activation energy for this process in C60 is very high - about 6.2 eV.
http://newton.ex.ac.uk/research/qsystems/people/latham/papers/1995/C/C.abs.html
Clearly, the proposed structure for C60 is not planar! The angle between the p axis and the C-C bond vector is 101.6° (as compared to 90° in planar graphite). The bowl-shape or concavity at each sp carbon center introduces some strain into the molecule. However, the high symmetry distributes that strain evenly across the entire structure.
Atomic Bonding
Haddon, R.C., Chem. Res., 1992
Physical Properties of C60• Density: 1.65 g cm-3
• Standard heat of formation: 9.08 kcal/mol• Index of refraction: 2.2• Boiling point: Sublimes at 800K• Resistivity: 1014 ohms m-1 (For Si 1000 ohms m-1 )
• Crystal form: FCC
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C60purple/violet
C70brick-red
C84brown
C86olive-green.
Good solvents for extraction of fullerenes from soot are toluene and xylene. Fullerenes are insoluble in water and stable at air. Thin layers of fullerenes are colored from yellow to yellow-green. Fullerene solutions colored because of
Fullerenes in Solvents
http://www.ifw-dresden.de/iff/14/forschg/fulleren/wassindfullerene/index_e.htm
π-π*-electron transitions, solutions of fullerenes are colored.
Fullerene Crystals
Face-Centered Cubic (fcc) Close-packed Structure of Bulk Solid C60
lattice constant a = 14.17 Å
2µm 200 nm
Fullerene Crystals
J. Libera and Y. Gogotsi
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Location of octahedral holes (left) and tetrahedral holes (right) relative to lattice spheres in face-centered cubic unit cell.
Structure of A3C60
Li3C60
The Big Picture of the Nanotechnology Story
Synthesis of Nanostructures
Explore the Properties
Characterization TestingExplore/speculate
Applications
Applications of Fullerenes
Buckyballs as Antioxidants
• The medical field – C Sixty, Inc., is one of the companies developing
medical applications for buckyballs. They are focusing on the ability of buckyballs to act as antioxidants, counteracting free radicals in the human body.
– A free radical is a molecule or atom that has an unpaired electron — which makes it very reactive.
– An antioxidant is a molecule that can supply an electron and neutralize a free radical.
– Merck, Inc., has obtained a licensing option on C Sixty’s antioxidant
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P.R. Birkett, et.al., J. Chem. Soc. Chem. Commun. (1993), 1230 P.R. Birkett, et.al. J. Chem. Soc. Chem. Commun. (1995), 683
Exohedral Fullerene Compounds
C60Cl6 C70Cl10
Improving medical imaging and drug delivery with buckyballs
Another potential use of buckyballs in medicine involves delivering
• elements for medical imaging• drugs directly to infected regions of the body.
One other reason buckyballs are useful for drug delivery is that they are small enough to move around inside the body quite easily.
La Atom in a Fullerene Cage(Metallofullerene)
Endohedral Fullerene Compounds
La@C60
Buckyball ApplicationsDupont and Exxon are using buckyballs to develop stronger polymers.These companies are looking at two ways of doing this: by integrating the buckyballs in the polymer with chemical bonding
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Polymerization of Fullerenes
Polymerized Rb1C60
The A1C60 compound has turned out to be much more interesting than one would have guessed. This picture shows the structure of the polymeric phase of Rb1C60, produced by slow cooling the material from the high temperature rocksalt phase. The fullerenes are now chemically bonded to form long polymer chains. This phase transition is of first order, with a transition temperature around 400K.
(C60)(C60) → C60=C=C=C58Rao, A.M., et.al., Science, 1993.
http://buckminster.physics.sunysb.edu/c60.html
C48N12
When 12 of buckminster-fullerene's 60 carbons are replaced by nitrogens, it can link up with other "buckyballs" to form a strong and springy material.
Buckyball ApplicationsDupont and Exxon are using buckyballs to develop stronger polymers.These companies are looking at two ways of doing this: by integrating the buckyballs in the polymer with chemical bondingSony is developing more efficient fuel cell membranes using buckyballs.Siemens has developed a buckyball-based light detector.Seagate is using buckyballs to develop diamond-hard coatings for computer disk drives.
Fullerene Science
Monument to C60 in Dalian, China
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Ternary “Phase” Diagram of Carbon Allotropes
NEXT
Outline• Introduction – Nanotechnology – definition, application areas…• The Element Carbon – Structure, Chemistry….• Fullerenes: Structure, Physics and Chemistry.
– Article Discussion – Kroto• Carbon Nanotubes: Structure, Synthesis and Properties.
– Article Discussion – Iijima• Carbon Nanotubes: Applications.
– Article Discussion – Wong• Graphene – a new generation of materials.
– Article Discussion – Novoselov
Testing and Characterization on Nanoscale• Part 1. Electron microscopy (SEM, TEM)• Part 2. Raman microspectroscopy….
– Article Discussion – Rao• Part 3. Atomic Force Microscopy (AFM)• Part 4. Nanoindentation• Part 5. Study of properties (optical, electrical)
Introduction to MEMs
Carbon Nanotubes Timetable
ISI Web of Science
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• Carbon nanotubes can be considered as graphene sheets rolled up into seamless cylinders
Rolling Directions of a Graphene Sheet
Arrows are showing two different rolling directions which gives rise to armchair and zigzag nanotube.
Three Archetypal SWNT Nanotubes
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Chiral and Zigzag Nanotubes