NEWS OF THE WEEK

ΝΑΝΟ ΡΕΑ POD Interactions between the fullerene molecules and nanotubeare controlled by the functional group.

N A N O T E C H N O L O G Y

FUNCTIONALIZED C60 PEAS IN A POD Fullerene derivatives are inserted into carbon nanotubes at low temperatures

U SING SUPERCRITICAL CAR-bon dioxide, scientists in England have inserted ful­

lerene molecules with exterior or­ganic functional groups into sin­gle-walled carbon nanotubes

(SWNTs). The team also showed that encapsulation of the functionalized fullerenes can be enhanced or inhibited by altering the functional group.

The work was carried out by Andrei N. Khlobystov and David A. Britz of Oxford University, Martyn Poliakoff and Jiawei Wang of the University of Not­tingham, and their coworkers [Chem. Commun., 2004,176}.

SWNTs incorporating fuller­enes such as C60 or C70 have so-called pea pod structures. They are designated Cn@SWNT and are generally prepared in the gas phase at 300 to 500 °C. Organic functional groups decompose in this temperature range.

"We have demonstrated that filling SWNTs in supercritical

C 0 2 allows insertion of the C60

molecules bearing chemical func­tionalities at low temperatures without affecting the functional groups," Khlobystov tells C&EN "Our low-temperature technique opens up the possibility of gener­ating new forms of nanotube-based structures and, in turn, the poten­tial to explore applications such as catalysis, molecular separations, and nanoscale drug delivery"

Khlobystov and colleagues showed that fullerenes with ex-

A W A R D S

Harry Gray Wins Wolf Prize In Chemistry

T he 2004 Wolf Foundation Prize in chemistry has been awarded to Harry B. Gray, the Arnold 0. Beckman Professor of Chemistry and founding director of the Beckman Institute at California Institute of Technology. Gray is being recognized for pioneering work in bioinorganic chem­

istry—-specifically, for contributions to unraveling novel principles of structure and long-range elec­tron-transfer processes in proteins.

Among other accomplishments, Gray is credited with using specially modi­fied proteins to measure the rate of electron transfer between redox centers positioned at fixed distances from one another in the proteins. He and his coworkers demonstrated that electron transfer can occur at significant rates even between centers separated by some 20 A.

Electron-transfer reactions in proteins provide the basis for energy produc­tion in cells of all living organisms. Yet "until Gray's work, little was known about the chemical factors that govern electron transfer in biological sys­tems," the award panel notes.

"It's really great to be recognized for work that was done with students and very close friends," Gray tells C&EN. "We've been collaborating on this work for years, and it has been a lot of fun. The recognition is icing on the cake for work that has been so enjoyable."

The $100,000 prize will be presented by Israel's president at a special ceremony at the Israeli Parliament in May.-MITCH JACOBY

terior ester groups can enter S W N T s in supercritical C 0 2 at temperatures as low as 30 to 50 °C, forming C6 1(COOC2H5)2-@SWNTpea pod structures.

High-resolution transmission electron microscopy (HRTEM) revealed that the pea pod struc­tures formed in 60% of the nano­tubes observed.

"This is the first example of a nano pea pod containing func­tionalized fullerenes," Khloby­stov says.

The group also used HRTEM to show that fullerenes bearing car-boxylic acid groups, C61(COOH)2, aggregate by hydrogen bonding to form a dimeric supramolecular complex. The dimer sterically hin­ders encapsulation and preferen­tially coordinates to the outside walls of the SWNTs.

The low-temperature filling technique takes advantage of the hybrid gas-liquid properties of su­percritical C 0 2 such as low vis­cosity and zero surface tension.

"There is also no solvent resi­due," points out Poliakoff, an ex­pert on the use of supercritical fluids. "The method is an inter­esting application of C 0 2 that opens up exciting new possibili­ties for nano technology"

The Oxford group is particu­larly interested in using the tech­nique to generate nanotubes con­taining geometrically regular arrays of magnetically active mol­ecules, such as organic radicals or metal-containing fullerenes.

"These structures are candi­date materials for solid-state quantum computing," Britz says. "The supercritical C 0 2 method enables us to assemble such ar­rays using thermally unstable molecules that exhibit unique magnetic properties. We can ef­fectively create one-dimensional molecular arrays with periodic and controlled spacing."

The group also notes that SWNTs containing electroni­cally active functionalities could potentially be useful for creating nanotube-based electronic de-vices.-MICHAEL FREEMANTLE

1 2 C & E N / J A N U A R Y 2 6 , 2 0 0 4 H T T P : / / W W W . C E N - O N L I N E . O R G