Rice University and Stanford University Researchers Have Unzipped Carbon Nanotubes into Thin Graphene Strips


Rice University researchers have unzipped carbon nanotubes to make graphene ribbons tens of nanometres wide. This is the cover story from the April 16, 2009 issue of the Journal Nature.

“Ribbon structures are very important structures and they’re not easy to make,” says James Tour, a chemist at Rice University in Houston, Texas. Early techniques used chemicals or ultrasound to chop graphene sheets into ribbons, but could not make ribbons in large amounts or with controlled widths.

As a solution, Tour and his co-workers, and a separate group led by Hongjie Dai of Stanford University in California, decided to try to generate ribbons from carbon nanotubes.

Dai and his colleagues opted to slice the tubes using an etching technique borrowed from the semiconductor industry. They stuck nanotubes onto a polymer film and then used ionized argon gas to etch away a strip of each tube. Once cleaned, the remaining ribbons were just 10–20 nanometres wide.

Tour’s group, by contrast, used a combination of potassium permanganate and sulphuric acid to rip the tubes open along a single axis. The resulting ribbons are wider — around 100–500 nanometres — and not semiconducting, but easier to make in large amounts.

“The techniques complement each other,” says Mauricio Terrones, a physicist at the Institute for Science and Technology Research of San Luis Potosi in Mexico, who was not involved in the work.

UPDATE:
Nanowerk has coverage.

In addition to being fairly straightforward and easy to do, the process can be extremely efficient. “We can open up every carbon nanotube at the same time and convert many nanotubes into ribbons at the same time,” Dai said.
Depending on how large a surface they cover with nanotubes – anything from a chip to a wafer – Dai said his team can create anywhere from one to tens of thousands of graphene nanoribbons at a time. The ribbons can easily be removed from the polymer film and transferred onto any other substrate, making it easy to create items such as graphene transistors, which may hold promise as a way to possibly make high performance electronic devices.

“How much better computer chips using graphene nanoribbons would be than silicon chips is an open question,” Dai said. “But there is definite potential for them to give a very good performance.”

Another advantage of Dai’s method is that the edges of the nanoribbons produced are fairly smooth, which is critical to having them perform well in electronics applications.

The next step in the team’s research is to better characterize the ribbons and try to refine their control of the production process. Dai said it is important to control the width of the ribbon and the edges of the structure of the ribbon, as those things could potentially affect the electrical properties of the ribbons and any device in which they are used. [There is separate recent MIT work in using heat to control the edges of graphite]

MIT Technology Review has coverage as well

Tour’s unzipping method yields graphene in bulk, which is an advantage from a manufacturing perspective. But “[Dai]’s going to have better control,” admits Tour. The width of the Rice group’s nanoribbons is determined by the diameter of the nanotubes that they come from. In contrast, using the Stanford team’s technique, it’s possible to finely control the width of the nanoribbons. In today’s publication, Dai and his colleagues describe nanoribbons six nanometers wide, but he says that they have subsequently made narrower and more semiconducting ones. “There might be an optimum width; that needs to be investigated,” he says.

Tour’s nanoribbons are easy to process because they are graphene oxide, which is soluble in water. “You can use sheer force to align them like logs in a river lining up in parallel,” says Tour. “You can paint them down, and they will align.” Tour adds that the nanoribbons can be made into devices using ink-jet printing. Once the ribbons are in place on a chip, they’re treated with hydrogen at high heat to remove the oxygen at their edges and turn them into semiconductors. Without this step, the ribbons are insulators.

The Stanford research was funded by Intel, and Tour says that he is in talks with companies interested in licensing his manufacturing method as well as devices made with the nanoribbons.

Both techniques are likely to be useful to researchers, and both have a variety of potential applications. Tour believes that his larger ribbons could be used in solar panels and flexible touch displays, where cheap, transparent materials are in demand. They could even be spun into lightweight, conducting fibres that might replace bulky copper wiring on aircraft and spacecraft. Dai’s narrower ribbons, meanwhile, might find uses in electronics because of their semiconducting properties

Dai says that his group has already used the ribbons to make basic transistors, but, he adds, it’s too early to tell whether they will be commercially competitive. “It’s very early in the game,” he says.

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8 comments

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1

I both hope Mills is right AND that his success doesn't kill Bussard on the vine.

Mills' process (if it works) produces heat, which is then run into a dynamo for electricity. There are conversion losses there. Polywell produces electricity directly.

An efficient economy would use Polywell for main, baseline electric power and BLP for heat (HVAC, etc.) and "smaller than 100MW" devices.

Joel: BLP's Business Applications slideshow used to talk about putting these things in cars a few years ago, but since they've actually made a prototype they've taken that part out. Now they talk about distributed power in the 1 to 10MW range to be placed at "refilling stations" for charging electric cars or for distributed H2 fuel generation. My guess is that the generator they have made is too hot to put under a hood.

2

There is a very simple way to determine the authenticity of the Blacklight Power system.

Get a copy of their electric bill.

3

You know how to tell if Blacklight is for real? Look at the board of directors.

Lets see...

1 Asst Sec of Energy
1 Asst Sec of the Navy
1 Air Force Joint Chief of Staff
1 CINCLATFLT (Commander in Chief Altantic Forces)
1 Director of Naval Nuclear Propulsion.

Others in the list are a little bit more murky.

That list is filled with a lot of people that have never failed.

K

4

I just read the CNN Money article. It is quite good. Even though I am a serious skeptic of Blacklight Power, I thought the article was quite balanced and objective. I especially like how the article discussed the corruption and self-serving nature of academic and government-funded research. This is spot on and needs to be said far more often.

Randell Mills may be right. He may be wrong. We all get to find out in fall of next year. Certainly the people backing him are of a caliber that are not easily fooled. Their comments with regards to performance being the acid test of a new idea indicate to me that they are level-headed.

One thing you can say to Randall's credit is that he has financed all of this with his own money and the money from private investors. He does not live off of the public treasury, unlike his scientific detractors.

This fact alone speaks kudos to me.

5

I have to say I get tired of seeing scientists "debunk" anything they didn't invent and use theory alone without ever considering the idea that the theorems they worship are in error. Look at Einstein when presented with quantum physics he "debunked" it and ignored it. Today however quantum physics has been validated and is achieving real results.

I'm with Kurt a bit. This seems far fetched, but the investors that backed him must have seen something to convince them to invest millions in his work. Even the wildest actually look before throwing that kind of money at something.

That said lets take the optimists approach... Assume it works as stated. It would be interesting to see if this could be scaled down as well as up. A 10-15KW version would power a vehicle reasonably well, and would also make a dandy backup generator.

If it doesn't science is littered with failed experiments. That's how the vast majority of the science we use today came to be. Though if it fails I'm sure he'll regret the publicity then.

6

Barba, wait til the end of 2009 and see.
CNN covered them, so why is this coverage invalid/wrong ?

4 articles on blackwater out of 2300. Ignore the 0.3% on that topic. Many other people are interested in it.

I would not mind a $60+ million humiliation.

How much as been spent on tokomaks and how many kwh have been supplied from it ?

7

GW, you seem to have a spam filter malfunction. Whenever I open up your web page, ludicrous claims of old junk and already humiliated and debunked thesis such as Mill's, which has 17 years old already and hasn't produced really anything worth of value since then (despite the red herring of his own page showing up the inevitable "revolutionary" theory that solves Quantum Mechanics with Relativity, what does this fellow not solve by himself, really?) open up and fill your web page.

I don't know, but if I would guess, I would probably say that some hacker who is lacking googling abilities is posting when you aren't looking.

/irony

Seriously, GW. You should check your filters before posting outright cons. I have no pity for those venture idiots, though.

8

Yes, we will see in fall of next year. Even though I think he is wrong, I wish Randall Mills the best of luck. I would love to see Randal Mill's process achieve success. It will be really entertaining to watch Robert Park's reaction if this is successful.

Robert Parks and much of the physics establishment appears to be quite defensive these days. They should be.

Big physics (and government-funded science in general) really has not resulting in any new products in the past 35 years. We were supposed to have L-5 space colonies and we got NASA, the shuttle, and the ISS. We were supposed to have commercial fusion. Yet, despite spending billions of dollar over the past 40 years, it is still "40 years in the future". Finally, private funding of effective anti-aging biomedical reseach (SENS) is starting to occur, when 40 years of government funded biomedical research (NIH, etc.) has failed to do anything about the aging process.

If Randall Mill's ideas are for real, more power to him. At least he is not mooching off the public treasury for his ideas.