Irish team adds layer to Nobel work

Research on exfoliating graphite to create a very tough material is set to put lead back in many different pencils

USING STICKY tape to peel layers off pencil lead – it doesn’t sound like the kind of experiment that might win you one of science’s top accolades. But it’s what led to two Russian-born scientists scooping the Nobel Prize in Physics this week, when they got the nod from Stockholm for their work on isolating graphene.

As materials go, graphene is something of a wunderkind. An atom-thick layer of carbon, it is likely the strongest material known and it does a good job at conducting too. With those talents, it has plenty of potential and it stands to offer lighter, greener plastics and zippier electronics.

So when the clock counted down to zero on the Nobel website on Tuesday, experts were not surprised the coveted prize went to Andre Geim and Konstantin Novoselov at the University of Manchester “for groundbreaking experiments regarding the two-dimensional material graphene”. But what stopped many in their tracks was the timing, because the duo had only published their findings in 2004.

“I wasn’t very surprised that they had got it, but I was surprised they had got it so soon,” says Jonathan Coleman, associate professor at Trinity College Dublin’s school of physics and a principal investigator at the Centre for Research on Adaptive Nanostructures and Nanodevices (Crann).

“It has been six years, and that is an eyeblink, sometimes people have to wait 40 years to get a Nobel Prize.”

For decades it had been thought that graphene, a two-dimensional layer, could not exist in isolation. So Geim and Novoselov used adhesive tape to peel layers of carbon from a crystal of graphite – yes, that stuff in your pencil – to see how thin they could go before the structure broke down.

When they got down to one layer and the graphene was still happily intact, they knew they were on to something, says Coleman, who describes graphene as “the most exciting material that the 21st century has shown up”.

But shearing off individual layers in large numbers was a laborious process, he notes.

“The people who were making graphene at the start were making one layer at a time, peeling individual layers of graphene off a crystal of graphite.”

Then Coleman’s team at Crann had their breakthrough in 2008, when they discovered a way to exfoliate billions of pure graphene layers from a graphite crystal in a liquid, offering the possibility for industry to scale up and generate graphene in useful amounts.

“It was one of these rare cases where you try this really beyond-the-end-of-the-envelope experiment and it works for the first time,” he recalls of the work, which was funded by Science Foundation Ireland.

“We were rather pleased because once you have the graphene flakes dispersed in a liquid, you can make make thin films of just overlapping graphene sheets very easily.” So what could you use it for? Graphene stands to offer lighter, greener plastics, suggests Coleman.

“One way of doubling the strength of plastic is to add in nanomaterials that are very strong, and normally that’s carbon nanotubes and the results are brilliant. But the problem is that carbon nanotubes cost about a million dollars a kilo,” he says.

“Graphene can potentially do the same role but graphite is virtually free. There’s plastic everywhere and a lot of it is there for strength, so if that strength could be doubled the amount needed could be halved.”

Another application that’s waiting in the wings is electronics, and Cork-based researcher Dr Brenda Long was also excited to hear the Nobel news about graphene, because she is working to physically protect the thin layers so they can be used in transistors.

“It’s only a single atom thick and it interacts with air, oxygen and water molecules, and those interactions have a detrimental effect on the electronic properties of graphene,” explains Long, a post-doctoral researcher at Tyndall National Institute.

“So if you want to use graphene for anything in the future, you are going to have to find a way to control the top, the exposed surface.”

Last year, Long discovered a way to do that: by putting a protective monolayer over the graphene sheet to stop the environment interfering with it.

Dr Aidan Quinn, head of the nanotechnology group at Tyndall, presented the work to the groups of Geim and Novoselov in Manchester on Wednesday after the prize was announced, and the ultimate aim of the Cork project is to make a transistor to support faster and smaller devices, according to Long.

“The electronic properties of graphene are way better than silicon,” she explains.

“If you want to make computers faster and to process even more information, we have to move to a new material and graphene is definitely a runner.”

But we’ll most likely see the strengthened materials before graphene makes its mark on processing power, notes Long.

“It’s 200 times stronger than steel, so we will see mechanical applications sooner than in electronics,” she says. “It took more than 50 years to get to where we are with silicon so it’s just going to take a while to integrate graphene into a viable technology.”

Meanwhile, a patent has been filed on the approach to protecting graphene layers, says Long, whose work is funded by an EU Framework 7 grant. “It’s progressing all the time, and we believe the technology has a lot of potential.”