Multitalented graphene is wowing scientists the world over. Lisa Clausen reports on those at the forefront of game-changing Australian research.
Three clear bottles stand like trophies on an otherwise empty shelf in Professor Dan Li's office at Melbourne's Monash University. Two are filled with powder the colour of midnight, while the third contains a lump of silver-grey rock. They're all forms of graphite, a type of coal we all rely on somehow, whether it's in brake lining, batteries or pencils. But that's not why Li has the bottles displayed behind his desk. Among scientists like Li, graphite is now celebrated as the source of graphene, the phenomenal new material researchers, governments and corporations the world over are betting could transform a multitude of industries, from electronics to renewable energy.
Scientists had long suspected graphite contained something interesting. But while they knew this smudgy, light rock was composed of stacks of graphene sheets, none of the brilliant minds working on it could figure out how to isolate a single sheet, let alone manipulate it. Then in 2004, University of Manchester physicists Andre Geim and Konstantin Novoselov had an inspired idea. Taking a block of graphite, the pair simply began stripping off flakes with sticky tape. They ended up with micro flakes of a completely new material, each too thin to be seen by the naked eye, its carbon atoms arranged in a dazzlingly perfect honeycomb pattern. Their playfulness won them, just six years later, the Nobel Prize in Physics. "No one really thought [releasing graphene] was possible," said the Royal Swedish Academy of Sciences. "Carbon, the basis of all known life on earth, has surprised us once again."
Since then, the surprises have kept coming, as graphene continues to show just how much it may be capable of. For starters, it's the world's thinnest material - with a sheet of graphene just an atom thick, it's a two-dimensional material. You'd need 3 million sheets to make a stack one millimetre high. It's very flexible, yet harder than diamond and 200 times stronger than steel; it is so strong, Columbia University researchers once calculated it would take an elephant balanced on a pencil to break through a layer of graphene as thick as plastic food wrap. It is practically transparent, so dense that not even the smallest gas atoms can penetrate it, and it conducts electricity and heat beautifully. While other commonly used materials such as silicon can match graphene in maybe one or two ways, what makes graphene so special is that it brings so many desirable qualities together in one package. In short, it seems to have it all.
So what might this marvellous material give us?
With such prizes on offer, scrutiny of graphene is intense. In 2004, the year Geim and Novoselov had their Eureka moment, fewer than 500 scientific papers on graphene were published. In 2012, there were almost 9000. Thousands of patents have been issued, and while few graphene-based devices are yet a reality, corporations such as Samsung are racing to control the market. The European Union last year committed €1 billion ($1.5 billion) to its multi-nation research efforts.
In such a busy crowd, Australia's researchers must find ways to stand out. "Our funding pool in Australia is much more limited," says Dan Li, who leads a team of 10, "but that doesn't mean we can't do something unique." A cheerful man with the rapid-fire speech of the very bright, Li is one of Australia's leading researchers in graphene, a field he entered after arriving in Australia on a fellowship from the US in 2006. "I wasn't that optimistic about graphene at first," he admits. "A lot of promising materials never make it to market."
While most researchers have focused on individual graphene sheets, Li is on a quest to use these sheets as molecular "bricks", assembling them in different ways to create new materials and devices infused with graphene's talents. He likens graphene to a world-beating athlete - extraordinary on its own and capable of as yet unimagined feats when teamed up with other materials. But as an engineer he knows that architecture is everything. "You could have the strongest bricks, but that doesn't necessarily mean you'll end up with the strongest building - it depends on how all the components interact."
Having already come up with a ground-breaking technique for separating graphene sheets, Li's team's latest success has been in the area of supercapacitors, specialised batteries already used in, for example, digital camera flashes, laptops and hybrid electric vehicles. Their flaw has always been their bulky size and regular need for recharging; using a graphene-based gel they invented at Monash, Li and his team have been able to produce supercapacitors in the lab that can store triple the amount of energy in a much smaller, and hence cheaper, package. "It's a kind of an impossible thing to do, but now we can do it," says Li. Since publishing results in August last year, they've been swamped with inquiries from around the world.
Li and his team are also working with Australian and Chinese researchers to use graphene in bone and tissue regeneration, harnessing its super-conductivity to deliver electrical stimulation for cell growth. They've also patented a graphene-based foam which, by mimicking the natural structure of cork, is super elastic and lighter than air but able to support objects up to 50,000 times its own weight. Blended with other materials, such as plastics, it could vastly improve toughness and heat resistance. Li, who has received several fellowships for his work and is now looking to the private sector for commercialisation partners, has a preference for graphene projects with a social dividend. "I want to get something useful out there into the real world. I'm grateful to Australia for giving me these opportunities and I'd like to make sure Australia gets something in return."
University of Wollongong researchers also have high hopes.
By placing two sheets of graphene - 25,000 times thinner than a human hair - on a biopolymer (a naturally-produced molecule such as a protein), they hope to create a device to implant in the brains of people with epilepsy. The plan is that its graphene electrodes could detect an impending seizure and trigger the release of anti-seizure medication. Researchers last year also devised a way of using textile techniques to spin nano-fibres of graphene, designed to give super-strength to materials used in bullet-proof vests and aircraft fuselages. They're working, too, in collaboration with Australian colleagues on applying graphene in nerve regeneration for damaged limbs.
Professor Gordon Wallace, executive research director of the Australian Research Council Centre of Excellence for Electromaterials Science, says while the scientific community is taking a wait-and-see approach, the excitement around graphene is more than hype. "The question is whether we, as scientists, technologists and engineers, can take its amazing properties from the nanomaterial world to the level of macroscopic devices," he says. "And that's not graphene's challenge - it's ours."
Graphene is not giving up all its secrets easily. Its amazing properties, for instance, mean that electrons surge through it at a constant speed of a million metres per second - yet it's not fully understood how they can be guided. Moving from the nanoscale to the commercial scale remains hugely complex. Making enough of it is still tricky. "We want to be able to press a button and have kilometres of the stuff come out," says CSIRO's Cathy Foley. At the moment, complex chemical and thermal processes are used to obtain graphene, but most take hours or days, involve toxic ingredients or only produce small amounts, not the mass quantities consumer products would need.
One group of CSIRO researchers thinks they've solved that conundrum, in part thanks to a bad cold. In 2011, PhD student Donghan Seo was at home in Sydney nursing a cold with lemon and honey tea and reading the Bible. When he came to Exodus, which talks of "a land flowing with milk and honey", he had his own epiphany. "I suddenly thought, why wouldn't honey work in making graphene? I had a strong religious feeling that it would work, and from a scientific point of view it made sense." The next day, he took some honey to the lab, where he subjected less than a gram to plasma testing, pelting it with highly charged ions to purify it down to its basic carbon structure. The CSIRO Plasma Nanoscience team he's part of can now create a 1cm x 1cm sheet of graphene in nine minutes - "while I go and get a coffee," he says. While not everyone is convinced, Seo says they have already used honey-derived graphene in a gas sensor and butter-derived graphene in a battery. "We know it works in the lab."
In the meantime, Australia has graphite deposits, and several companies keen to begin mining. Adelaide-based Archer Exploration Ltd hopes to fire up its new mine on South Australia's remote Eyre Peninsula within two years. With world graphite prices rising, high-quality deposits "are ripe for development", says Archer managing director Gerard Anderson. Back at the University of Wollongong, Gordon Wallace says he'd love to use local graphite. It's one way, he says, in which Australia has the chance to help shape the era of graphene. "But the window of opportunity for that is not going to be there forever," he says. "We need to get that alignment of the mining opportunities with the technical expertise, from graphite to graphene to graphene-based devices, as quickly as possible. We won't be the only people thinking of doing that - but we have to be nimble enough to be the first."