First prepared at Rice University in the laboratory of Dr. John L. Margrave, the E. D. Butcher Professor of Chemistry, fluoronanotubes have unique chemical properties not found in pure carbon nanotubes. They are reactive rather than inert and soluble rather than insoluble. This chemical accessibility allows scientists and engineers to use nanotubes in new materials and applications.
Single-walled carbon nanotubes (SWNTs) are hollow tubes of pure carbon that measure just one nanometer, or billionth of a meter, in diameter. SWNTs are single molecules that can contain thousands or even millions of carbon atoms. They're excellent conductors of electricity and heat, and they can also be electrical semiconductors. They show tremendous promise in applications including advanced composites, sensor technology, fuel cells, and molecular electronics, but a major obstacle to fully exploiting their properties is their tendency to get tangled into knotted bundles.
By attaching thousands of fluorine atoms to the sides of nanotubes, researchers in Margrave's group created a set of "chemical handles" that allow chemists and engineers to manipulate nanotubes using common and well-understood methods of organic chemistry. Fluorinating nanotubes reduces their tendency to self-agglomerate, and it renders the disentangled tubes soluble.
Fluoronanotubes also serve as a gateway to a host of nanotube "derivatives," which have other molecules attached to their sides. Some of the new materials Margrave's team has made include "nano-nylon", nano-esters, nano-ethers, nanoic acids and nano-salts.
Fluorinating nanotubes also makes it easier for scientists and engineers to exploit their incredible strength. SWNTs are 100 times stronger then steel at one-sixth the weight. With their tendency to clump together, though, engineers haven't been able to use them effectively in creating superstrong composite materials. Research by Margrave and others at Rice has shown that disentangling SWNTs via fluorination makes it easier to disperse them evenly in polymers and ceramic composites.
"Fluoronanotubes are truly unique materials that will play a major role in the development of carbon nanotechnology," said Margrave. "New materials, new systems for encapsulating and delivering pharmaceutical medicines and new, more versatile polymer composites will all result from the use of fluoronanotubes as an intermediary between the crude, tangled masses of nanotubes produced in high-temperature reactors and the ultimate applications that benefit society."
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Those participating in Margrave's fluoronanotube research include former doctoral student Edward T. Mickelson, who carried out the first synthesis and characterization of fluoronanotubes; former doctoral students Ivana Chiang and Zhenning Gu, who built upon Mickelson's work; Robert Hauge, distinguished faculty fellow; Richard E. Smalley, university professor, Gene and Norman Hackerman Professor of Chemistry and professor of physics; Valery Khabashesku, faculty fellow; Shyam Shukla, visiting professor of chemistry from Lamar University; Gaëlle Derrien, postdoctoral research associate; graduate students Haiqing Peng, Lei Zhang and Yu Liu; and undergraduate researchers Joel Stevens, Ian Tonks, Paul Reverdy and Justin Cratty.
The fluoronanotube research is sponsored by the Robert A. Welch Foundation and the Texas Advanced Technology Program. Additional assistance was provided by Carbon Nanotechnologies Inc., Rice's Center for Nanoscale Science and Technology and MarChem Inc.