FULLERENES Aaron Koga May 1, 2007 Physics 441

OUTLINE Introduction to Fullerenes Some properties A few different fullerenes, applications, interesting things C60 Endoheral fullerenes, bucky onions Fullerite Medicine

INTRODUCTION (History) Discovered 1985, Kroto, Smalley, and Curl Nobel Prize chemistry, 1996: 3 scientists for discovery of Fullerenes Named after Richard Fuller (Architect) Montreal Biosphere by Fuller

INTRODUCTION (What is a Fullerene?) Carbon allotropes Hollow sphere (buckyball), ellipsoid, tube (buckytube, nanotube) Similar structure to graphite: Hexagons Pentagons (curvature) Euler: 12 pentagons to make sphere

INTRODUCTION (Production) Before: vaporization laser 1990 Graphite electrodes Fill chamber with He (inert gas), ~100 torr Run current through graphite Get black soot ~10% C60 Some larger fullerenes

PROPERTIES (Structure) Stable, but not totally unreactive In graphite: sp2 bonding Planar, 120o Fullerenes: [6,6] double bonds, hexagons [6,5] single bonds, pentagons to hexagons [6,6] are shorter than [6,5] Sphere, so not planar  angle strain Estimated that 80% of E-formation due to strain Strain concentrated on pentagons  structures with out touching pentagons are more stable (C60)

PROPERTIES (Other) Slightly soluble in some solvents Toxic? Toluene, carbon disulfide, etc. In water: large clusters (nC60) of 250-350 nm Toxic? 2004: found increase in cellular damage to fish with ~.5ppm in water 2005: computer simulation found deformation of DNA by C60 in water Wave-particle duality with λ=3pm, 1999

C60 Buckminster Fullerene Smallest structure with no pentagons touching ~.7 nm diameter Melting point ~ 550K

Endohedral Fullerenes Have atoms, clusters, molecules inside Endohedral Metallofullerenes: Metals with the fullerene 1985: La@C60 (@ for “inside”) Electrons donated by metal to C60 Different size charge transfers ex. La2@C80 (2 e-) vs. Sc3N@C80 (6 e-) Non-metal doped fullerenes: Ex. He@C60, Ne@C60 Forms when fullerene in ~3 atm of noble gas Noble gas is exactly in center of structure

Bucky Onions One fullerene inside another Up to 70 layers observed Nanotube generation normally produces some onions

Fullerite Bulk solid C60 FCC structure Ultrahard Fullerite: 310±40 GPa hardness Diamond: <240 GPa (sometimes 150 GPa)

Fullerite A3C60, A6C60 Alkali metal cations for each sphere 3 metal holes (grey) per sphere (blue) A3C60: conductor A6C60: insulator at room temp

Fullerite A3C60 becomes super conducting Lattice constant, ao, changes to accommodate the metal cation Different Tc

Fullerenes in Medicine Useful because of size, stability, hydrophobia HIV (Human Immunodeficiency Virus) inhibitor HIVP has cylindrical active site with hydrophobic amino acids C60 is about same size as the cylinder Possible inhibiting of HIVP Drug delivery, attach to outside of cage Improve MRI (Magnetic Resonance Imaging): Gd3+ used to improve imaging, but toxic metal When in fullerene even safer than current method Stabilize other reactive species (not only in medicine)

References “Fullerene.” http://en.wikipedia.org/wiki/Fullerene Unwin, Peter. “Fullerenes (an overview).” http://www.ch.ic.ac.uk/local/projects/unwin/Fullerenes.html Bleeke, John R. and Frey, Regina F. “Fullerene Science Module.” http://www.chemistry.wustl.edu/~edudev/Fullerene/fullerene.html “Bucky Onion.” http://www.3dchem.com/molecules.asp?ID=218 “Diffraction and Interference with Fullerenes.” http://www.quantum.univie.ac.at/research/matterwave/c60/ Dagani, Ron. “Cage Chemistry.” http://pubs.acs.org/cen/coverstory/8024/8024fullerenes.html