While rolling a newspaper makes it hard to read, rolling carbon into a nanotube makes it relatively easy to "read" its type -- whether armchair or zigzag or some variation in between. What's impossible is controlling how the tube will roll. The process tends to be willy-nilly, leaving researchers the task of separating the nanotubes they need from the bulk through ultracentrifugation or other expensive procedures.
Yakobson said it would be a real game-changer if they could, for instance, grow batches of pure armchair nanotubes for use in such projects as armchair quantum nanowire (AQW). As imagined by Rice's late Nobel Laureate Richard Smalley, AQW could revolutionize the nation's power grid by carrying 10 times the amount of electricity as copper at only one-sixth the weight.
Yakobson's work may open a path to do so. A nanotube's chirality is determined by the combination of energies at play in its nucleation. "When it just emerges from the 'primordial soup' of carbon, the edge of the tube is essentially the same as the edge of graphene," he said.
"At first, it's just a cap. There's no stem yet. You're frying these caps on a skillet, and they're bubbling," he said. "The probability for different bubbles to emerge is controlled by energy around the edge."
The chirality of the nascent nanotube is set when atoms in the cap self-assemble a sixth pentagon (necessary to mold the hexagons into a dome). "That's where we can, I think for the first time, make some quantitative judgment about how different chiral structures emerge," Yakobson said.
It may be worth chemists' efforts to look more closely at the energy between the catalyst and carbon structure. "This has some promise," he said. "If you can tweak this pref
|Contact: David Ruth|