NEWS OF THE WEEK

M A T E R I A L S C H E M I S T R Y

CUSTOM TAILORING CARBON NANOTUBES Reactions modify, differentiate the electronic properties of nanotubes

T HE PRACTICAL CONSEQUEN-

ces of covalent chemistry on the electronic proper­

ties of single-walled carbon nano-tubes are highlighted in two new­ly published papers.

Robert C. Haddon and co­workers at the University of Cal­ifornia, Riverside, have shown that metallic nanotubes func-tionalized with dichlorocarbene take on semiconducting proper­ties [Science, 301,1501 (2003)}. The effect is due to a change in the hybridization of carbon atoms in the nanotube wall from sp2 to sp3. The change causes the electronic band gap to widen to that of a semiconductor.

'Any control of nanotube prop­

erty is useful" because nanotubes are being explored for various ap­plications based on their electri­cal conductivity, notes Michael S. Strano, assistant professor of chemical and biomolecular engi­neering at the University of Illi­nois, Urbana-Champaign. Indeed, Strano, chemistry professors James M. Tour and Richard E. Smalley at Rice University, and coworkers have developed selec­tive covalent chemistry that dif­ferentiates between metallic and semiconducting single-walled car­bon nanotubes [Science, 301,1519 (2003)}.

The chemistry is reduction of a diazonium salt by a carbon nanotube to form a carbon-car­

bon bond. "The first step involves the nan­otube donating an electron to the re­agent," Strano says. "Valence electrons in metallic nanotubes are more reactive than those in semicon­ducting ones, so they donate first." And in a mixture of metallic and semiconducting nanotubes, the metal­lic ones react com­pletely before any of the semiconducting ones are touched.

Heating removes the new covalent bonds and restores the original nanotube. Thus, the chemistry can be used to physi­cally separate metal­lic nanotubes and to recover them in the pristine state. Work is underway to demonstrate this application, Strano says.-MAUREEN R0UHI

N = N

REACTIVITY Selective chemistry can be used to separate metallic nanotubes from a mixture.

H I G H - T E C H B U S I N E S S

NAN0TECH CONGRESS PAINTS BROAD SWATH Business, government attendees cover wide-ranging topics at inaugural event

W! 4 4 1 M M E CAN USE SMALLNESS

to become great," No­bel Peace Prize Laure­

ate Shimon Peres told attendees at the first World Nano-Econom-ic Congress held in Washington, D.C., last week. The former Israeli prime minister is championing sci­ence and technology particularly nanotechnology to promote peace and prosperity

"Nanotechnology has the greatest promise for all of us," Peres continued. "That's why I appreciate what you are doing and how we will be helped by your knowledge and potential in serv­

ing humanity," he told attendees. In a similar vein, Chemistry

Nobel Laureate and Rice Uni­versity professor Richard E. Smalley tackled the issue of glob­al energy supply, his agenda for the past year. "It is the single most important problem facing hu­manity today," he said, and solv­ing it may lead to answers to oth­er pressing questions around food, water, the environment, poverty, and terrorism.

" The energy problem is also spe­cial because we can do something about it," Smalley pointed out. "It's got a techno-fix." Nanotechnology

he believes, will offer revolutions in energy production, storage, transmission, and utilization.

Meanwhile, emerging societal, ethical, and health issues—as well as the disconnect between nano-tech research and commerciali­zation—were on the minds of about 280 people from the busi­ness and government communi­ties, as was finding the requisite public and private funding to help address the issues and bridge the gap. Attendees from start-up firms were attentive to the advice offered by those from corpora­tions and venture-capital firms.

On a positive note, Rep. Brad Sherman (D-Calif.) said he antic­ipates that the Nanotechnology R&D Act (S. 189),which would establish a federal nanotech pro­gram and received bipartisan sup­port in the House in May, will soon be passed in the Senate and then signed into law by President George W Bush.—ANN THAYER

"To know to learn is more important than to learn to know because the world is always

-Shimon Peres

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