Graphene: Supermaterial goes superpermeable

Jan 26, 2012
Artistic impression of graphene molecules. Credit: University of Manchester

Graphene is one of the wonders of the science world, with the potential to create foldaway mobile phones, wallpaper-thin lighting panels and the next generation of aircraft. The new finding at the University of Manchester gives graphene's potential a most surprising dimension – graphene can also be used for distilling alcohol.

In a report published in Science, a team led by Professor Sir Andre Geim shows that graphene-based membranes are impermeable to all gases and liquids (vacuum-tight). However, evaporates through them as quickly as if the membranes were not there at all.

This newly-found property can now be added to the already long list of superlatives describing graphene. It is the thinnest known material in the universe and the strongest ever measured. It conducts electricity and heat better than any other material. It is the stiffest one too and, at the same time, it is the most ductile. Demonstrating its remarkable properties won University of Manchester academics the Nobel Prize in Physics in 2010.

Now the University of Manchester scientists have studied membranes from a chemical derivative of graphene called graphene oxide. Graphene oxide is the same graphene sheet but it is randomly covered with other molecules such as hydroxyl groups OH-. Graphene oxide sheets stack on top of each other and form a laminate.

The researchers prepared such laminates that were hundreds times thinner than a human hair but remained strong, flexible and were easy to handle.

When a metal container was sealed with such a film, even the most sensitive equipment was unable to detect air or any other gas, including helium, to leak through.

It came as a complete surprise that, when the researchers tried the same with ordinary water, they found that it evaporates without noticing the graphene seal. Water molecules diffused through the graphene-oxide membranes with such a great speed that the evaporation rate was the same independently whether the container was sealed or completely open.

Dr Rahul Nair, who was leading the experimental work, offers the following explanation: "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.

"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."

"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," comments Professor Geim. "You cannot help wondering what else graphene has in store for us".

"This unique property can be used in situations where one needs to remove water from a mixture or a container, while keeping in all the other ingredients", says Dr Irina Grigorieva who also participated in the research.

"Just for a laugh, we sealed a bottle of vodka with our membranes and found that the distilled solution became stronger and stronger with time. Neither of us drinks vodka but it was great fun to do the experiment", adds Dr Nair.

The Manchester researchers report this experiment in their Science paper, too, but they say they do not envisage use of in distilleries, nor offer any immediate ideas for applications.

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'.

Explore further: Scientists fabricate defect-free graphene, set record reversible capacity for Co3O4 anode in Li-ion batteries

More information: The paper, Unimpeded Permeation of Water Through Helium-Leak–Tight Graphene-Based Membranes, by R. Nair, H. Wu, P. Jayaram, V. Grigorieva and A. Geim, is published in Science on January 26, 2012.

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User comments : 20

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PaulRC
4.8 / 5 (13) Jan 26, 2012
sounds like water desalination/purification just became trivial
RayW
not rated yet Jan 26, 2012
Maxwell's daemon?
h20dr
5 / 5 (4) Jan 26, 2012
Wow, if this is true and I believe it to be, this is huge. These guys deserve another Nobel for this discovery. This will revolutionize and disrupt many industries...
Callippo
1 / 5 (11) Jan 26, 2012
IMO it will not disrupt anything (with compare to cold fusion), but if true, it would be definitely most interesting finding, which I met during last five years in physics. But we should take all things literally in it - for example I don't believe too much the claim, the soaked membrane of graphene-oxide is completely impermeable for helium - it nothing else, it would violate the uncertainty principle, quantum tunneling (and thermodynamics, as RayW noted correctly). From practical perspective exactly the opposite behavior would be more interesting (in applications similar to "super-GoreTex" fabric).
Callippo
1 / 5 (10) Jan 26, 2012
sounds like water desalination/purification just became trivial
Not quite, if it requires the vaporization of water - is such case the water vapor is already pure enough. I cannot understand, why your comment got some upvotes from mindless people - the application of the above finding for water desalination is not straightforward for me at all.
indio007
1 / 5 (1) Jan 26, 2012
Water is one of he strangest molecules because the way in which it's polarization is infleunced brownian motion
jscroft
4.3 / 5 (11) Jan 26, 2012
1. Use a solar concentrator to heat a bucket of dirty water capped with this film.
2. Pipe the resultant low-pressure water vapor through a condensing coil located in the concentrator's own shadow.
3. Wait until your glass dribbles full... and drink.
Lurker2358
1.8 / 5 (4) Jan 26, 2012
Maybe you could use it in some sort of dehydration or vaccuum drying process.

Suck the air out of the container, which would cause the water in the target substance to vaporize, and this would theoretically cross the graphene barrier, resulting in an ultra-dry container, I think.

I dont know, maybe we're thinking backwards.

Maybe its more useful if you need to get water INTO something, without letting air or other materials out.

It could be useful in instrumentation for measuring air samples or something, where you might want to remove the water vapor from the sample without changing anything else about the sample's composition.

Could be useful for removing humidity from sensitive work spaces, such as for electronics or nanotechnology manufacture.

I don't know, talk to somebody in food preservation and processing. I'm sure some industry chef or chemist could find a use for this in foods preperation.
h20dr
5 / 5 (3) Jan 26, 2012
@jscroft: thank you for boiling it down for the less enlightened.
skajam66
5 / 5 (3) Jan 26, 2012
@h20dr @jscroft: thank you for boiling it down for the less enlightened
I think you mean 'condensing it down for the less enlightened'
NOM
5 / 5 (2) Jan 26, 2012
The researchers obviously don't drink much, or they would see that distilleries would find this product of great value.
Brandy is currently produced by heating wine, this causes many changes to the flavours in the wine. However, if the wine could be concentrated by removing most of the water, the flavour of the concentrated wine would be enhanced rather than changed.
Graeme
5 / 5 (1) Jan 26, 2012
Iscroft's invention does not actually need the graphene oxide film. But this does sound to be a great way to concentrate alcohol or water containing substances. It would be interesting to see if this c an work in very dry conditions, or does the water film disappear from the G-O surface when humidity is very low.

For food it sounds good to dehydrate food without losing flavour.
antialias_physorg
5 / 5 (3) Jan 27, 2012
Is graphene impermeable with regard to hydrogen?
Hydrogen storage is still somewhat of a problem as it tends to leak and/or make substances brittle.

If this form of graphene could block hydrogen then that would be great.
Eikka
5 / 5 (3) Jan 27, 2012

Brandy is currently produced by heating wine, this causes many changes to the flavours in the wine. However, if the wine could be concentrated by removing most of the water, the flavour of the concentrated wine would be enhanced rather than changed.


It is done so for traditional reasons, if at all. Vacuum distillation works just as well by lowering the boiling point of water to room temperature.

The real difficulty in the process is that you remove the alcohol with the water, so the resulting vapors have to be distilled a second time and the alcohol returned to the wine. It's a costly process, and would work much better if they could just leave the wine in an aging vat covered with graphene, and then wait for the water to come out.

It also means that home distilling can now be accomplished with a glass bottle and a hand pump. You take two bottles, connect them with a hose, put a graphene film in between and pump the air out of the other. Water moves in to fill the void.
rawa1
1 / 5 (2) Jan 27, 2012
Is graphene impermeable with regard to hydrogen?
Hydrogen is less permeable than helium despite of its lower molecular weight because the elongated hydrogen molecule share a lot of energy during their impacts in their momentum of rotation - so they're travelling through tiny channels a way slower, than the single-atomic helium.
ab3a
not rated yet Jan 27, 2012
@NOM: One might not want to do that. Typically the yeast in beer or wine will produce small amounts of non-ethanol alcohols that are not recommended for consumption in concentration. When making Whiskey, distilleries will typically discard the first stuff out of the still for exactly this reason.

Concentrating all that non-water stuff to a brew is not a good idea. A still enables the lighter alcohols to be removed, and the heavier alcohols to stay behind.
stun-dexim
4.5 / 5 (2) Jan 27, 2012
Question that I don't seem to see addressed any anyone's comments (that I've read)... or in the article: This graphene membrane allows water molecules through it as if it's not there.... but it doesn't necessarily only allow it through in one direction....right? Is likely 2 way (based on what they describe they aren't taking pains to place the membrane right side up, etc). So in any application.... success would totally depend on difference in atmospheric pressure (or a similar delta). Correct? Passive processes like what they describe w/ vodka would also have the possibility to reverse depending on environment. Not a deal breaker of course... but important to note.
Callippo
1 / 5 (2) Jan 28, 2012
Preprint of this work is here. IMO the excellent permeability of these membranes for water is connected with ballistic transport of watter molecules in thin film, where the water is behaving like sorta superfluid (similar to electrons at the surface of graphene). This anomalous behavior of water (which is close to supersolidity mechanism of solid helium) manifests itself with crunching of fresh snow under pressure. But what is still complete mystery for me is the low permeability of helium - which is even lower, than then permeability of much larger molecules.
DKBOND
not rated yet Jan 28, 2012
Does anyone now the best method for making graphene for commercial applications ? Scotch-tape, chemical exfoliation, chemical vapor deposition, induced growth, graphite oxide reduction or another I'm unaware of? Which one is most likely to become the standard for graphene production and why?
Kafpauzo
not rated yet Jan 31, 2012
1. Use a solar concentrator to heat a bucket of dirty water capped with this film.
2. Pipe the resultant low-pressure water vapor through a condensing coil located in the concentrator's own shadow.
3. Wait until your glass dribbles full... and drink.


The way the scouting movement does this is: Take a bucket. If possible, put it in sunshine. Pour an inch or two of dirty water at the bottom. Place an upright, empty drinking glass at the center of the bottom. Cover the bucket's opening with a plastic sheet or film, fixed around the bucket's opening, not stretched too taut. Put a pebble on the plastic sheet, just above the glass.

The water inside evaporates and condenses on all inner surfaces. The water that condenses on the plastic sheet runs downward to the sheet's lowest spot, the pebble spot, and drips into the glass.

If you ever get lost in the wilderness and this saves your life, please remember to send me a reward of $100,000, or whatever you think your life is worth.