Science

Graphene reveals yet another extraordinary property

Dr Nair shows his one micron thick graphene oxide film research sample (Photo: University of Manchester)
Dr Nair shows his one micron thick graphene oxide film research sample (Photo: University of Manchester)
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Dr Nair shows his one micron thick graphene oxide film research sample (Photo: University of Manchester)
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Dr Nair shows his one micron thick graphene oxide film research sample (Photo: University of Manchester)

Ever since University of Manchester scientists Andre Geim and Konstantin Novoselov first isolated flakes of graphene in 2004 using that most high-tech pieces of equipment - adhesive tape - the one-atom sheet of carbon has continued to astound researchers with its remarkable properties. Now Professor Sir Andre Geim, (he's now not only a Nobel Prize winner but also a Knight Bachelor), has led a team that has added superpermeability with respect to water to graphene's ever lengthening list of extraordinary characteristics.

Graphene has already proven to be the thinnest known material in the universe, strongest material ever measured, the best-known conductor of heat and electricity, and the stiffest known material, while also the most ductile. But it seems the two-dimensional lattice of carbon atoms just can't stop showing off.

Stacking membranes of a chemical derivative of graphene called graphene oxide, which is a graphene sheet randomly covered with other molecules such as hydroxyl groups OH-, scientists at the University of Manchester created laminates that were hundreds of times thinner than a human hair but remained strong, flexible and were easy to handle.

When the team sealed a metal container using this film, they say that even the most sensitive equipment was unable to detect air or any other gas, including helium, leaking through. The team then tried the same thing with water and, to their surprise, found that it evaporated and diffused through the graphene-oxide membranes as if they weren't even there. The evaporation rate was the same whether the container was sealed or completely open.

"Graphene oxide sheets arrange in such a way that between them there is room for exactly one layer of water molecules. They arrange themselves in one molecule thick sheets of ice which slide along the graphene surface with practically no friction, explains Dr Rahul Nair, who was leading the experimental work. "If another atom or molecule tries the same trick, it finds that graphene capillaries either shrink in low humidity or get clogged with water molecules."

Professor Geim added, "Helium gas is hard to stop. It slowly leaks even through a millimetre -thick window glass but our ultra-thin films completely block it. At the same time, water evaporates through them unimpeded. Materials cannot behave any stranger. You cannot help wondering what else graphene has in store for us."

Although graphene's superpermeability to water makes it suitable for situations where water needs to be removed from a mixture without removing the other ingredients, the researchers don't offer ideas for any immediate applications that could take advantage of this property. However, they did seal a bottle of vodka with the membranes and found that the distilled solution did indeed become stronger over time. But they don't foresee graphene being used in distilleries.

However, Professor Geim adds, "the properties are so unusual that it is hard to imagine that they cannot find some use in the design of filtration, separation or barrier membranes and for selective removal of water."

The University of Manchester team's paper, "Unimpeded Permeation of Water Through Helium-Leak-Tight Graphene-Based Membranes," appears in the journal Science.

22 comments
AdrianV
What about using it as a water purifier?????? Seems like the obvious first-line commercial application to me...
Paul Hutchinson
Graphene oxide straw = straw that only lets water through?
Artisteroi
gills
MzunguMkubwa
So, what about hydrogen? Will it contain that molecule? If so, then this material could have huge advantages when leveraged for use in a hydrogen energy infrastructure as a storage container liner. (This is one of the significant hurdles in using hydrogen as a fuel: its hard to store, since it leaks from almost any container over time...) I also see this being a wonderful water filter membrane... there\'s much talk in this article of removing water from solutions to preserve the other contents, but I see it more as a way to purify the water by containing/separating any impurities.
Chris Helenius
\"don\'t offer ideas for any immediate applications\" Extracting potable water comes first to mind.
TogetherinParis
A superb garment for Denise Richards, perhaps? With other vapor barriers, astronauts might use it to collect & purify water vapor from cometary debris.
Bob Ehresman
Ultralight ultra strong film that is impermeable to helium.... Sounds like a next generation airship or high altitude balloon material to me...
BZD
As other suggest \"water purification\" maybe simply for turning salty sea water into drinking water. If a cheap enough system can be established then this technology may even save the world from wars in the future. Right now we have wars over control of oil, but there are conflicts where water is part of the agenda like how Israel try to take over the occupied areas.
jimbo92107
Purifying water for fuel cells. In a closed H-O system, the recirculated water needs to be as pure as possible to help keep the fuel cell\'s membrane from being polluted by impurities. This material would ensure that the system\'s water was as close to absolutely pure as possible.
Gadgeteer
I don\'t think this would work well for purifying water. The vapor transfer rate is too low. However, if it could be laminated to a durable fabric, it could well be the next generation breathable waterproof membrane. Imagine a rainsuit that could block rainwater but which lets sweat escape as if you weren\'t wearing anything. Look out, Gore-Tex.
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