Graphene: a Nobel Prize experiment in your own home

Carbon has been known to humankind since before recorded history, so it’s not surprising that discovering a new form of it – especially a form as remarkable as graphene, the wonder material of the 21st century – nets one a Nobel Prize. What is surprising is that it was discovered using everyday office supplies.

(Before you get alarmed about this unashamed and unfashionable pro-carbon stance, let’s be clear: too much carbon dioxide in the atmosphere leading to climate change = bad, carbon the versatile element that’s the basis for all life on Earth = good.)

Apart from the fact that there are more known compounds containing carbon than all the other elements combined (except for hydrogen of course, but we won’t mention that) pure carbon itself comes in many forms.

Diagram showing eight different forms or allotropes of pure carbon: diamond, graphite, lonsdaleite, buckminsterfullerene or buckyball, C540 fullerene, C70 fullerene, amorphous carbon and a single-walled carbon nanotube (click to embiggen)
Diagram showing eight different forms or allotropes of pure carbon: a. diamond, b. graphite (with its layers of graphene), c. lonsdaleite, d. buckminsterfullerene or buckyball, e. C540 fullerene, f. C70 fullerene, g. amorphous carbon and h. a single-walled carbon nanotube (image by Michael Ströck, via Wikimedia Commons)

There’s non-crystalline amorphous carbon, found in coal and charcoal and soot and such. And of course if you subject it to high temperatures and pressures, like in Superman’s fist, it forms the crystals we call diamonds.

Then there are the more complicated structures. The year 1985 saw the arrival of buckyballs, or to give them their proper name, buckminsterfullerene (named after Richard Buckminster Fuller, inventor of the geodesic dome), which are spherical molecules of 60 carbon atoms arranged in the shape of a soccer ball.

But the most recent and perhaps the most amazing form of carbon comes from one of the most common.

Graphite is best known for being the raw material of pencil leads, but it has many other uses including being a dry lubricant. This is because it’s made out of millions of tiny flakes of 2-dimensional crystals with carbon atoms arranged in a hexagonal pattern (see allotrope b in the diagram above). These flat crystals can slip and slide against each other, or flake off to make marks on paper.

Individually, these 2-dimensional crystals are called graphene. And of course, they’re not really new – we’ve known they exist for a long time – but it wasn’t until 2004 that anyone figured out how to extract graphene from graphite and do experiments on it.

The secret is amazingly simple. Starting with graphite extracted from, say, a HB pencil, it’s possible to peel off individual layers using common sticky tape. And because the tape is transparent, you can put it under a microscope and find the pieces of graphene crystal.

Sticky tape being used to peel off powdered graphite, leaving a single layer of graphene (click to embiggen)
Sticky tape can be used to peel off powdered graphite, leaving a single layer of graphene

It sounds nothing special, but because no one had thought of it before it won Andre Geim and Konstantin Novoselov the 2010 Nobel Prize in Physics.

But why the big deal? Well, graphene has a lot of interesting properties:

  • Clearly, it’s very thin: just one atom thin. Which means it’s nearly transparent, letting through 97.7% of visible light.
  • And yet it’s practically impermeable. The carbon atoms in graphene are only 0.142 nanometres apart, so not even the smallest gas atoms (i.e., helium) can get through.
  • It’s also incredibly strong, more than 100 times stronger than steel of the same thickness.
  • It’s a great heat conductor, about 10 times better than copper.
  • It’s easily turned into a better electrical conductor than copper. In fact, electrons move through graphene as if they had zero mass, a fact that was the subject of that episode of The Big Bang Theory where Sheldon Cooper had to get a job at the Cheesecake Factory so that he could figure out why.
  • Being both transparent and such a good conductor, graphene has great potential for use in the next generation of touch screens – that would be strong, flexible touch screens – as well as in lighting panels and solar cells.

Newer, more sophisticated techniques are needed to make sheets large enough for industrial purposes – now up to 70 cm wide – but it’s amazing that it all started with two physicists mucking around with sticky tape.

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