By Roland Piquepaille
Carbon nanotubes, which can have useful electrical or optical properties, are typically grown using chemical vapor deposition techniques. During this process, amorphous and useless carbon layers are also produced, meaning that a post-growth purification process is needed. Not anymore. According to this article from Technology Research News (TRN), Japanese researchers have successfully used water to get rid of these impurities. The idea of using water to clean carbon nanotubes is so simple that I'm amazed that nobody thought about it before. Anyway, this method, which eliminates the post-growth purification process, still needs some improvements and will not help to mass produce carbon nanotubes before at least five years. There were several other announcements about nanotechnology achievements in the last two weeks, so read more...Here are the opening paragraphs of the TRN article.
Washing away impurities with water turns out to be as good for growing carbon nanotubes as it is for keeping a clean house.
Carbon nanotubes show great promise as building blocks for molecular machines, high-speed electronics and super-strong materials, but it has proven difficult to reliably grow large amounts of pure carbon nanotubes and to keep the growth process orderly.
And here are the essential details of this new cleaning process.
Researchers from the Japanese National Institute of Advanced Industrial Science and Technology (AIST) have added water to the standard method of manufacturing carbon nanotubes to produce tall, dense, vertically-aligned stands of pure nanotubes.
The purity of the nanotubes makes the usual post-growth purification process unnecessary. This makes the method quicker, less expensive and less likely to damage the nanotubes than existing processes, said Kenji Hata, a senior researcher at the Japan National Institute of Advanced Industrial Science and Technology. Nanotubes produced using the method are orderly and pure enough for use in many fields, including biology, medical implants, chemistry, electronics and magnetics research, he said.
Please read the full article TRN article for other details and keep in mind that this method for growing carbon nanotubes is still a work in progress.
The method could be used to mass produce carbon nanotubes within five years, and for practical applications within ten years, said Hata.
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Here is a photo of a complex nanostructue obtained with this process and evocating a flower (Credit: AIST). |
The research work has been published by Science on November 19, 2004 under the name "Water-Assisted Highly Efficient Synthesis of Impurity-Free Single-Walled Carbon Nanotubes." Here is a link to the abstract.
We demonstrate the efficient chemical vapor deposition synthesis of single-walled carbon nanotubes where the activity and lifetime of the catalysts are enhanced by water. Water-stimulated enhanced catalytic activity results in massive growth of superdense and vertically aligned nanotube forests with heights up to 2.5 millimeters that can be easily separated from the catalysts, providing nanotube material with carbon purity above 99.98%. Moreover, patterned, highly organized intrinsic nanotube structures were successfully fabricated. The water-assisted synthesis method addresses many critical problems that currently plague carbon nanotube synthesis.
This column is getting too long, so you'll find other references in this sidebar, "Nanotech News Roundup #1." Maybe there will be another edition in about a couple of weeks.
Sources: Eric Smalley, Technology Research News, December 1-8, 2004; Science, November 19, 2004
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