Scientists Unbound Carbon-60 Molecular Bonds

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Scientists at Rice University in Houston say they've found a way to control the bonds between the atoms of a molecule.

Discovered at Rice in 1985, the molecule in question is carbon-60, also known as the buckminsterfullerene, which is said to look like a soccer ball.

Researchers led by Rice physicists Yajing Li and Douglas Natelson determined they could loosen the bonds holding the atoms together by applying a certain voltage and running an electric current through a single molecule.

The scientific team explained their discovery this week in the online Proceedings of the National Academy of Sciences.

"In general, if we can manipulate the charge distribution on molecules, we can affect their vibrations," Natelson said in a statement. "This doesn't mean we're going to be able to arbitrarily dial around the strength of materials or anything like that," but "we can start thinking, in the future, about controlling things in a better way."

The effect of the electric current is detected when a carbon-60 molecule attaches to a gold surface in a special nano antenna Natelson's group constructed a few years ago to trap small numbers of molecules.

Natelsen said that once the molecules are in place in the antenna, and nestled between two electrodes, the researchers can subject them to various conditions, including cold, heat, energy from a laser and, of course, an electric current.

The resulting changes in the molecule are then measured through spectroscopy, a way of gathering information from the frequencies of light the particle emits.

After Natelsen and his colleagues gained the ability to analyze molecular vibrations and the bonds between the atoms in a molecule, they also saw how applying an electric current seemed to leave the bonds between the atoms looser, similarly to how guitar strings that start out taught can end up loose after a certain amount of force is applied to them.

"Think of these molecules as balls and springs," Natelson said. "The atoms are the balls and the bonds that hold them together are the springs. If I have a collection of balls and springs and I smack it, it would show certain vibrational modes."

Using the nano antenna, the researchers saw the carbon-60 atomic bonds became weaker, or floppier, under the electric charge, but reverted back to their original strength when the charge was removed.

The discovery of the structurally-stable carbon-60 molecules which, aside from soccer balls, have also been likened to geodesic spheres, earned a Nobel Prize for two Rice professors and kick-started the nanotechnology revolution, Natelsen said.

The new research has taught scientists "how to put them on surfaces, what you can do to them and have them still be intact," he said, comparing the potential manipulation of carbon-60 to the molecular manipulation of graphene, the single-atomic-layer form of carbon which has a variety of research and commercial uses.

"I don't want to make some grand claim that we've got a general method for tuning the molecular bonding in everything," Natelson said, "but if you want chemistry to happen in one spot, maybe you want to make that bond really weak, or at least make it weaker than it was."

A long-sought goal in the chemistry community has been "to gain precise control over where and when bonds break," Natelsen said. "We're offering ways to think about doing that."