NEWS OF THE WEEK
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 fullerene 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 chemistry-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
AWARDSHarry Gray Wins Wolf Prize In Chemistry