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 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