nanotech congress paints broad swath
TRANSCRIPT
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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