9.08.4 Graphene and Fullerenes

Syllabus

Graphene is a single layer of Graphite and has properties that make it useful in electronics and composites.
- Students should be able to explain the properties of Graphene in terms of its structure and bonding.
- Fullerenes are molecules of Carbon atoms with hollow shapes.
- The structure of Fullerenes are based on hexagonal rings of Carbon atoms but they may also contain rings with five or seven Carbon atoms.
- The first Fullerene to be discovered was Buckminsterfullerene (C60) which has a spherical shape.
- Carbon nanotubes are cylindrical fullerenes with very high length to diameter ratios.
- Their properties make them useful for nanotechnology, electronics and materials.
- Students should be able to:

1. recognise graphene and fullerenes from diagrams and descriptions of their bonding and structure
2. give examples of the uses of fullerenes, including Carbon nanotubes.

What does this mean?

Fullerenes

Until recently we believe that there were only two allotropes of Carbon -ways Carbon atoms could be arranged in a pure solid.

These were Graphite and Diamond.

Actually, a third exists in almost all soot from fires but no one had really looked.

Football shaped moles containing 60 Carbon atoms (C60)are actually very common.

This is not a Giant Covalent Lattice of millions of atoms - its a simple molecule, although quite a big one.

It's made up of hexagons and pentagons.

This hollow shaped reminded its discoverers of buildings designed by an architect called Buckminster-Fuller.

So they called it Buckminsterfullerene - though most people call them Bucky-Balls.

Since then we've discovered that other Fullerenes are quite common.

All Fullerenes are made of hexagons, pentagons.

Althoug some may contain heptagons.

And all of them share a feature with Graphite - three covalent bonds per atom.

Meaning that they have one delocalised electron per atom.

So, electrons can move from one atom to another but can't go outside the molecule.

As a result, these ball shaped structures aren't really useful for their electrical properties

But that's not true of Nanotubes.

A lot of work has been put into trying to build Carbon Nanotubes - essentially Fullerenes that are very long compared to their width.

They also have one delocalised electron per atom but their shape and size (many thousands of atoms rather than dozens) means that electricity can move much further - suggesting future uses.

They could make electrical wires one day - though we're not good at making them yet.

They're also very strong for their weight so could make very strong ropes if we could make long enough ones.

At the moment we're only able to make shorter ones - some of which go into Tennis Racquets and Gold clubs.