Liquid method: pure graphene production

May 30, 2010
Graphene

In a development that could lead to novel carbon composites and touch-screen displays, researchers from Rice University and the Technion-Israel Institute of Technology today unveiled a new method for producing bulk quantities of one-atom-thick sheets of carbon called graphene.

The research is available online in the journal Nature Nanotechnology.

When stacked together, sheets make , which has been commonly used as pencil lead for hundreds of years. It wasn't until 2004 that stand-alone sheets of graphene were first characterized with modern nanotechnological instruments. Since then, graphene has come under intense scrutiny from materials scientists, in part because it is both ultrastrong and highly conductive.

"There are high-throughput methods for making graphene oxide, which is not as conductive as graphene, and there are low-throughput methods for making pure graphene," said lead co-author Matteo Pasquali, professor of chemical and biomolecular engineering and chemistry at Rice. "Our method yields very pure material, and it is based on bulk fluid-processing techniques that have long been used by the chemical industry."

Pasquali said the research team found it could dissolve graphite in chlorosulphonic acid, a common industrial solvent. The researchers had to devise new methods to measure the aggregation of the dissolved graphene flakes, but at the end the team was pleasantly surprised to find that the individual graphene layers in the graphite peeled apart spontaneously. The team was able to dissolve as much as two grams of graphene per liter of acid to produce solutions at least 10 times more concentrated than existing methods.

The researchers took advantage of novel cryogenic techniques for that allowed them to directly image the graphene sheets in the chlorosulfonic acid.

"We applied new methods that we had developed to directly image carbon nanotubes in acid," said co-author Yeshayahu "Ishi" Talmon, professor of chemical engineering at the Technion-Israel Institute of Technology. "This was no small feat considering the nature of the acid and the difficulty of specimen preparation and imaging."

Using the concentrated solutions of dissolved graphene, the scientists made transparent films that were electrically conductive. Such films could be useful in making touch screens that are less expensive than those used in today's smart phones. In addition, the researchers also produced liquid crystals.

"If you can make liquid crystals, you can spin fibers," said study co-author James Tour, Rice's T.T. and W.F. Chao Professor of Chemistry. "In liquid crystals, the individual sheets align themselves into domains, and having some measure of alignment allows you to flow the material through narrow openings to create fibers."

If the method proves useful for making graphene fibers in bulk, it could drive down the cost of the ultrastrong carbon composites used in the aerospace, automotive and construction industries.

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User comments : 5

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JoeDuff
not rated yet May 30, 2010
I know about this method, because dissolution of carbon nanotubes in chlorosulphonic acid was described before two years. Therefore a less compact graphite would dissolve even better. In fact, graphite can be dissolved rather easily even in concentrated sulfuric acid, but it degrades during this as a result of sulfonation and oxidation. Chlorosulphonic acid is a stronger acid and it lacks oxidative properties.

http://www.youtub...5If2VU3Q

With respect to electronic industry the properties of resulting product of such method are nothing special, because only tiny graphite flakes similar to particles of soot would remain after such drastical treatment. The chlorosulfonic superacid will ripe them all.
JoeDuff
not rated yet May 30, 2010
Indium is a strategic metal essential to the solar power industry and LCD screen production. Therefore the replacement of indium-tin oxide layers in consumer electronic is a urgent need, because of limited world resources of indium, which are mostly located in China.

http://findarticl...6520720/
Elie
2.3 / 5 (3) May 30, 2010
This technique sounds awesome.

However, just a few days ago I read an article in which researchers used a method similar to that used by the typical cotton candy machine to produce large quantities of carbon nanotubes in a highly controlled and much cheaper fashion.

Here's the link to the article:

http://www.physor...542.html

And here is a short snippet from the article to "whet your appetite".

"Hailed as a "cross between a high-speed centrifuge and a cotton candy machine," bioengineers at Harvard have developed a new, practical technology for fabricating tiny nanofibers."

Enjoy!
daveib6
not rated yet Jun 08, 2010
just a few days ago I read an article

If you had actually read the article, you would have noticed that the machine produced polymer-based threads, not carbon nanotubes. This has nothing to do with producing carbon nanotubes. I suggest that in the future if you claim to have read something that you actually do read it.
Gene_H
not rated yet Jun 08, 2010
My feature is rather the ability to see the things in wider connections & consequences, instead.

The same research group, which developed the method for casting of graphene sheets developed the method for dissolving of nanotubes from simple reason: both materials are composed of graphite sheets, so they're sharing the very same chemistry. Just the nanotube research has become popular earlier. Because you don't know about these connections, it seems for you, my comments are chaotic and mutually inconsistent.

In fact we differ in number of causal dimensions or causal facts, which we are using for consideration of these experiments in wider context. Because my causal structures are larger, they will attract & dissolve those of yours in similar way, like heavier planet attracts the smaller one.

The collision our our stances was a real physical process from certain perspective.