Written by Catherine Bolgar
Step aside, silicon. There’s a new substance that promises to revolutionize medicine, industry, water treatment, electronics and much more. That substance is graphene—a single-atom-thick layer of carbon, a millionth of the width of a human hair.
The world’s first two-dimensional material, graphene is potentially plentiful (carbon being the sixth most abundant element in the universe) and cheap. And it possesses amazing qualities and potential uses:
It’s transparent, but conducts…
electricity and heat. Most good conductors are metals such as copper, which is opaque and quick to heat when electricity passes through. But they are prone to hot spots, which form around defects and cause electronic devices to fail. Graphene, by contrast, transfers heat efficiently. “It’s a good alternative to copper,” says Nai-Chang Yeh, professor of physics at California Institute of Technology. Indeed, electronic equipment may in future use graphene-coated copper interconnections to prevent overheating or wear and tear.
It’s light and flexible, but it is…
200 time stronger than steel. The carbon-to-carbon bond is very strong, says Rahul Nair, Royal Society fellow at the University of Manchester. In addition, graphene’s carbon atoms are arranged in a tight, uniform honeycomb structure, which is able to bear loads and resist tearing. A membrane of graphene could withstand strong force without breaking, says Dr. Yeh. It may someday be used in aerospace, transportation, construction and defense.
It’s a superlubricant
“If you take one piece of flawless graphene and put it on top of another, and slide one against the other, there’s almost no friction,” says Dr. Yeh. Coating machines parts with graphene could minimize unwanted friction, providing industry with countless applications.
Graphene’s honeycomb structure is too tight for any molecules to squeeze through. “If you have graphene on metal, it’s perfect protection, because other molecules in the air cannot penetrate that honeycomb hole,” says Dr. Yeh. Indeed, Dr. Nair has dissolved graphene oxide in water to create a paint-like film that can protect any surface from corrosion. This graphene paint could be used by the oil and gas industry to protect equipment against saltwater, or by pharmaceutical and food packaging firms to block out oxygen and moisture, thereby extending their products’ shelf life, says Dr. Nair.
…but can also be permeable. A single-micrometer-thick film containing thousands of layers of graphene oxide has nanosize capillaries between its layers, which expand when exposed to water. However, those capillaries don’t expand when exposed to other substances. This is unusual because a water molecule is bigger than a helium or hydrogen molecule. However, water behaves differently when it’s within the confined space of a nanometer, moving rapidly through the graphene oxide nanocapillary. By contrast, salt that is dissolved in the water is blocked. One use for this, says Dr. Nair, could be water or molecular filtration.
It’s a chemical contradiction
A sheet of graphene is inert, but its edges are chemically reactive, says Dr. Yeh. A little graphene flake has a large perimeter relative to its area, allowing for more reaction. These flakes could be used to remove toxins from water.
It can be magnetic
The zigzag-shaped edges of graphene have magnetic properties.“People imagine that you will be able to use graphene sheets as a magnet that can pick up iron at room temperature,” explains Dr. Yeh. That something all-carbon can be magnetic is “amazing,” she adds. Coupled with its electric conductivity, graphene’s magnetic properties may open up all sorts of applications in spintronics and semiconductors.
Graphene’s potential may be extraordinary, but how easy is it to create? It was first isolated in 2004 at Manchester University by Andre Geim and Konstantin Novoselov who won the 2010 physics Nobel Prize for their work. They arrived at graphene by using adhesive tape to peel off ever-thinner layers from graphite, a process subject to continual improvement. In one common method, copper is heated to 1,000 degrees Celsius, near its melting point. Methane gas, comprising carbon and hydrogen molecules, is then added, and the copper rips off the bond between the two molecules, dissolving the carbon into the copper and letting the carbon “grow” on the surface, Dr. Yeh explains. The result is a sheet of graphene.
David Boyd and Wei-Hsiang Lin, working with Dr. Yeh at Caltech, however, found that what counts most is not heat but clean copper. Copper oxidizes quickly in air and so has a thin layer of carbon oxide on its surface. They use hydrogen plasma, which has “gas radicals that behave like erasers and clean up the surface of the copper,” Dr. Yeh explains. The process allows graphene to grow in five minutes at room temperature.
Most importantly, this method could be scaled up to produce industrial amounts of high-quality graphene—a huge step towards realizing its true potential.
Catherine Bolgar is a former managing editor of The Wall Street Journal Europe.
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