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Five new uses for miracle material graphene


Graphene – a single-layer lattice of carbon atoms – is yet to make the jump from laboratory to day-to-day life, but that's not stopped researchers coming up with new ways to exploit its marvellous properties. Belinda Smith reports on five of the latest.


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Graphene – a single-layer carbon lattice – is yet to make the jump from laboratory to day-to-day life, but that's not stopped researchers coming up with new ways to exploit its marvellous properties.
Laguna Design / Getty Images

Graphene has been described as a revolutionary material, and when you know what it can do, it's not hard to see why.

A single-atom-thick layer of carbon atoms arranged in a honeycomb lattice, graphene efficiently conducts heat and electricity while being almost completely transparent. Perhaps its most extraordinary quality is its super strength – around 100 times stronger than the equivalent thickness of the strongest steel.

But despite netting Andre Geim and Konstantin Novoselov the 2010 physics Nobel prize, and various applications such as touchscreens and bullet-proof vests bandied around, graphene is yet to make the jump from the laboratory to our day-to-day life.

Still, scientists probe the limits of graphene. Here are five recent studies into the material, with applications ranging from medicine to machinery.

Microscope images (20x) of S. aureus bacteria (red) trapped in graphene oxide aggregates (green) formed after incubation in saline solution. – Valentina Palmieri

Antibiotics

Graphene oxide, a form of graphene with molecular oxygen incorporated into it, wraps around bacteria, puncturing its membrane. With a burst membrane, bacteria die or are unable to reproduce.

Coating surgical tools with this carbon-based compound could kill bacteria, reducing the need for antibiotics, decreasing the rates of post-operative infections and speeding recovery times.

In work presented at the annual meeting of the Biophysical Society in Los Angeles today, scientists from the Università Cattolica del Sacro Cuore in Rome found graphene specifically attacks bacterial cells, while sparing human cells, but the mechanism behind this specificity is still unclear.

The compound is most effective when paired with just the right amount of salt. Too little salt and the graphene oxide won't wrap around the bacteria. Too much, and the graphene clumps.

The next step is to test graphene oxide's effectiveness against fungi. Fungi can also cause significant problems if they infect an open wound. At the moment, though, fungi cells are too big for graphene oxide to wrap all the way around.

Biotechnologist Valentina Palmieri says she wants to alter the salt content to see if she can solve this issue.

An ultra-light graphene-based lens will reduce satellite launch costs. – Swinburne University

Camera lenses

A flat optical lens just a billionth of a metre thick will let us see living creatures as small as a single bacterium better than ever before, and dramatically decrease the costs of launching satellites into orbit, say researchers at Melbourne's Swinburne University of Technology.

In a paper published in Nature Communications, they report a new lens that breaks the "diffraction limit" – the wavelength of light – allowing focus to narrow down to half the wavelength of light.

The researchers developed a 3-D printer that could spray graphene oxide solution onto a surface to create a lens 300 times thinner than a sheet of paper.

They then used lasers to etch three concentric rings on the graphene oxide lens to bounce light to an exceptionally narrow focus. It allows a detailed view of objects as small as 200 nanometres long at wavelengths ranging from visible to near infrared.

While we're probably not going to see the lenses in smartphones any time soon, the team is working with the Australian Defence Science and Technology Organisation to integrate them into nanosatellites – tiny satellites weighing a few kilograms.

At the moment, nanosatellite optical lenses weigh a couple of hundred grams. The new lenses developed by the Swinburne group weigh just a microgram. Integrating the lighter lenses with nanosatellites will mean significant launch cost savings as well as better pictures of Earth and space.

The device consists of a solar cell containing graphene stacked on top of a semiconductor, which in turn is stacked on an industrial substrate (either soda-lime glass, SLG, or sodium-free borosilicate glass, BSG). The research revealed that the SLG substrate serves as a source of sodium doping, and improved device performance in a way not seen in the sodium-free substrate. On the right is a scanning electron micrograph of the device as seen from above. – Brookhaven National Laboratory

Glass-based electronics

Scientists have layered graphene on top of common glass – a scalable and inexpensive process to get graphene into microelectronic and optoelectronic devices.

What's more, they found the sodium in common soda-lime glass, which is used in windows and bottles, "dope" the graphene, boosting the density of electrons, and in turn increased its electronic properties.

"We actually discovered this efficient and robust solution during the pursuit of something a bit more complex, says study co-author Nanditha Dissanayake.

"Such surprises are part of the beauty of science."

The team initial set out to increase the efficiency of a solar cell containing graphene stacked on a semi-conductor, which was itself stacked on soda-lime glass.

Then they proceeded with baseline testing before they added anything to their basic mix. But their tests revealed the graphene was already performing well. They eventually found why: the glass.

Scaling up technology quickly and cheaply is key to getting graphene into touchscreens and flat panel displays. A glass-graphene system, the researchers say, could rise to that challenge.

The work was published in Scientific Reports.

Solar cells operate by absorbing light first, then converting it into electricity. The most efficient cells needs to do this absorption within a very narrow region of the solar cell material. The narrower this region, the better the cell efficiency. – University of Surrey

Solar cells

Who knew moths could inspired scientists to create new solar cells? That's exactly what researchers from the University of Surrey did, nano-patterning the otherwise poorly-absorbant graphene to let it soak up more light.

Because graphene is so thin, it tends to allow loads of light through. This is great for applications that need transparency, such as touchscreens, but not so great for solar cells, which need to absorb as many photons as possible.

In work published in Scientific Advances, the researchers too inspiration from moths. "Moths' eyes have microscopic patterning that allows them to see in the dimmest conditions," says senior study author Ravi Silva.

"These work by channelling light towards the middle of the eye, with the added benefit of eliminating reflections, which would otherwise alert predators of their location."

Etching these patterns onto a few layers of graphene boosted absorption from 2-3% to 95% from ultraviolet to the infrared.

A graphene nanoribbon, anchored at the tip of an atomic force microscope, was dragged over a gold surface. The observed friction was extremely low. – University of Basel, Department of Physics

Lubricant

Rounding out our list is lubricity. While much research into graphene explores its conductive qualities, a team in at the University of Basel in Switzerland has been exploring its lubricating prowess on a nanometre scale.

In a paper published in Science, they anchored strips of graphene, called nanoribbons, to a sharp tip, and dragged them across a gold surface.

They found almost perfectly frictionless movement.

In future, they write, graphene could be used as a coating on machinery, resulting in almost zero energy loss between moving parts. This would not only inprove energy efficiency, it would extend the life of the equipment.

Related reading:
Enter the graphene era

Explore #graphene
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Belinda Smith is a science and technology journalist in Melbourne, Australia.
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