According to a press release (3 January 2002), researchers at the University of Illinois at Urbana-Champaign and the University of Pennsylvania have discovered that carbon nanotubes packed with fullerene spheres, like so many peas in a pod, have tunable electronic properties. They reported their work in the 3 January 2002 issue of Science.
"Our measurements show that encapsulation of molecules can dramatically modify the electronic properties of single-wall nanotubes," said Ali Yazdani, a professor of physics at UI. "We also show that an ordered array of encapsulated molecules can be used to engineer electron motion inside nanotubes in a predictable way."
To explore the properties of these novel nanostructures, Yazdani and coworkers used a low-temperature scanning tunneling microscope to image the physical structure of individual peapods and to map the motion of electrons inside them. The encapsulated fullerenes modify the electronic properties of the nanotube without affecting its atomic structure. "In contrast to unfilled nanotubes, peapods exhibit additional electronic features that are strongly dependent on the location along the tube," Yazdani said. Because the local electronic properties of single-wall nanotubes can be selectively modified by the encapsulation of a single molecule, the technique might one day be used to define on-tube electronic devices.
Update: An article on the Wired website ("Nanotech Fine-Tuning", by Mark K. Anderson, 4 January 2002) provides some additional coverage, with some perspective from Yazdani, as well as Cees Dekker and Calvin Quate.