Scientists Cut Nanotubes into Pipes a Usable Form

first_imgFacebookTwitterPrintEmailAddThis Share CONTACT: Lia Unrau PHONE: (713)831-4793E-MAIL: [email protected] CUT NANOTUBES INTO PIPES: A USABLEFORMNearly endless tangles of fullerenenanotubes, tiny tubular fibers of carbon, have been converted into short,open-ended pipes, a form which allows scientists to manipulate the nanotubeschemically for the first time. This is a vital step in developing usefulnanotechnolgies and materials.A team of researchers at Rice University, led by chemistRichard Smalley, have brought carbon nanotubes officially into the world ofchemistry by cutting them into pipes and attaching molecules to their open ends,providing the ability to bind nanotubes to a variety of other chemical groups orsurfaces.Smalley and his team have demonstrated this ability bytethering the pipes to gold particles 10 nanometers in diameter. A nanometer isone-billionth of a meter.The research is published in the May 22 issue of Science in apaper titled, “Fullerene Pipes.”Since nanotubes were discovered in 1991, scientists have beenworking to develop ways to unlock the potential of these carbon fibers that are100 times stronger than steel yet only one-sixth the weight, and that possessinteresting electrical properties.Two areas that stand to gain by the development of nanotubesare molecular electronics and high-strength composite materials. Both areasrequire knowing how to manipulate the nanotubes.Molecular electronics involves shrinking components to themolecular level, increasing density and speed, thereby vastly increasingcomputing power. Fullerene pipes, with their molecular nature and electricalproperties, might be used as connectors and components for molecularelectronics. With their newly demonstrated controlled chemistry, nanotubes mightalso be integrated with other polymers to make super-strong composite buildingmaterials.To create the fullerene pipes, Smalley and the researchersfirst purify the raw nanorope material in large batches using nitric acid,followed by a filtration technique similar to dialysis, yielding about 10-20percent pure nanoropes by weight. Then the nearly endless ropes, which are madeof several nanotubes nestled parallel to one another, are separated and cut intoindividual open-ended pipes ranging in length from 100-300 nanometers.The cutting method involves sonic bombardment with high-energysound waves, in combination with concentrated sulfuric and nitric acids. Thewalls of the nanotubes are attacked by the sonication, creating a hole, and theoxidizing acids etch around the remainder of the tube. The cutting takes placeover a period of one to three hours. The acid treatment leaves the open edge ofthe pipe with carboxylic acid groups hanging onto the end, which can easily beconverted to the acid chloride.When mixed with water and soap-like molecules to keep themseparated, the cut pieces, which are molecularly perfect and chemically clean,are in a form which allows them to be sorted by length using a type ofchromatography. They can then be manipulated by exposing the ends to additionalchemicals, such as alkane thiol chains attached by amide links. The alkane thiolchains for this research were provided by chemist Randall Lee’s research groupat the University of Houston.The thiol group on the end of a fullerene pipe was used tocreate a chemical bond with a gold sphere, a connection easily and convenientlyimaged by atomic force microscopy.The attachment of the thiol group and the gold sphere aremerely examples of much richer possibilities for the chemistry of fullerenepipes.This research was supported by the National Science Foundation,the Office of Naval Research, the Advanced Technology Program of Texas and theRobert A. Welch Foundation.### last_img

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