C60, Buckminsterfullerene e-w/s
by Dr Jonathan Hare

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Buckminsterfullerene is the name of a beautiful molecule having 60 carbon atoms. It is like a tiny football composed of hexagon and pentagon rings joined together.

An atom is about 1/10th of a billionth of a meter in size and C60 is about 10 times bigger. So the molecule is about a billionth of a meter - a nanometer in diameter. The molecule is as many times smaller than a real football as a football is to the Earth!

You have seen beautiful pictures in astronomy books of swirling dust clouds far out in space. These pictures have been taken using light but since the 1970's scientists have also been looking into these regions in the radio and infra red regions of the spectrum.

During these explorations they found that the space between the stars – the interstellar medium – was choc-a-block full of atoms and molecules. About half of all the different types of molecules are found to be carbon based (e.g. carbon monoxide, carbon dioxide, methane, alcohol …). We believe these molecules and atoms end up in space, exploded out by stars when they become Nova and Super Nova. These catastrophic explosions seed space with the building blocks of new stars, planets and maybe even those molecules needed for the basis of life.

To try and understand these process in more detail in 1985 Harry Kroto at Sussex University (and other colleagues), did an experiment in the lab that has become a scientific classic. They tried to reproduce the conditions in space 'at home' in the laboratory. They fired a laser beam at a piece of carbon (graphite) and heated it until it vaporised: between 3000 to 10,000 ēC. They did this in a laboratory vacuum chamber to re-create the conditions in space but they also had equipment attached to this apparatus so that, most importantly, they could 'look' and investigate what was being produced.

They were looking to see if they could produce the sort of molecules that had been seen in interstellar space and so perhaps understand more about how they form, where they go to and what they might contribute to the chemistry of space. Completely by accident though, they discovered something else very interesting.

In their experiments they saw a strong signal corresponding to a carbon molecule having exactly 60 atoms. They did not observe 59 or 61 atoms, and 58 and 62 were very weak by comparison – they had discovered that there was something special about 60 - C60.

They were vaporising graphite which consists of flat sheets containing many billions of hexagonal arranged carbon atoms. They thought that if somehow a small portion of a graphite sheet could completely curl-up to form a ball it might account for the stability as, closed in on itself, there would no longer be an atomic edge to react (grow) anymore.

It turns out that there is a very beautiful, and elegant, solution to the problem. 60 atoms can come together to form a ball when there are 20 hexagons and 12 pentagons (Note: each pentagon has 5 corners/atoms and 12 x 5 = 60). This is exactly what we see on a real football (take a look).

Euler's Law
There is a simple mathematical law that relates the number of corners, faces and edges in many different 3 dimensional shapes – it's called Euler's law.

Quite simply it is given by:

Number of Corners + Number of Faces - Number of Edges = 2

Or more simply in short hand the formula is: C + F – E = 2

Let us take a cube or die. It has eight corners (C=8), six faces (F=6, there are six numbers on a die) and twelve edges (E=12) putting this data in the formula we get:
8 + 6 – 12 = 2 so it works for a cube!
Try it out for an Egyptian pyramid (remember the base) and other shapes.

Let us now assume it works for the football, can we used it to predict something, something that might be quite hard to do otherwise. Let us see if we can predict the number of edges on the football: We know that the number of Faces is F = 12 + 20 = 32 and the number of corners is of course 60.

So C + F – E = 2, gives us 60 + 12 + 20 – E = 2
So haw many edges does it have?

If you have a look at a football and try and count them up you see clearly why scientists like to use maths!


… Back to the History of Buckminsterfullerene
In a historic week Harry Kroto and his collegues, did the experiments, made the discovery but also worked out how a hexagonal sheet could be made to fold up into a ball. There results were sent to the journal Nature and published. There was some hostility to their announcement, people did not believe that such a simple experiment could 'prove' that C60 was special and that it had the unique structure they claimed.

It was not until 1990 that further developments allowed 'large' (gram rather than micro-gram) quantities of C60 to be made once and for all so that its structure could be proved beyond doubt. We now know there is a family of cage molecules and structures called the fullerenes - C60, buckminsterfullerene, being the head of this new fascinating range of carbon structures. In 1996 the Nobel Prize for chemistry was awarded to Harry Kroto, Rick Smalley and Bob Curl for the discovery of these Fullerenes.

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What you need to do your research
Please go to the following web-sites (link are below) to find out more about C60 and to try to answer as many of the questions below as you can.

Some questions
1) Does Euler's law hold for C60 and the football?

2) How many bonds (edges) are there in C60?

3) C60 is not a 'platonic solid' so what is it?

4) What is the mathematical name of the structure of a football and C60?

5) Buckminsterfullerene was named after which person and what was he famous for?

6) Hexagons on the structure of C60 share edges but do the pentagons ever share edges?

7) are there atoms in the structure that are only in hexagons?

8) C60 was discovered in tiny amounts using a laser technique in 1985. In 1990 another technique was discovered / developed to make C60 in large quantities what was this?

9) What are nanotubes? And why might they be important?

10) Google search of 'space elevator + nanotubes' to see what turns up.


USEFUL URL's
How to draw a football, the SEED web site

Nobel Prize page

The CSC C60 web page

Platonic solids

RB fuller web site

Nanotubes


ONE LAST THING ...
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THE CREATIVE SCIENCE CENTRE

Dr Jonathan Hare, The University of Sussex
Brighton, East Sussex. BN1 9QJ

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