Carbon Nanotubes Rotate As They Grow

Experts from the Rice University, in the US, and the Universite Lyon1/CNRS, in France, have recently released the first videos depicting the atom-by-atom growth of carbon nanotubes. Much to their amazement, they noticed that, as individual atoms were added to the nanoscale constructs, the entire structure rotated, in very much the same way a mechanical clock's second hand exhibited its halting motion. The new investigation was conducted using funds provided by the National Science Foundation (NSF), the Air Force Research Laboratory, and the French L'Agence Nationale de Recherche (National Research Agency).

“The key issue for realizing the potential of carbon nanotubes has always been better control of their growth. Our findings offer new insights for better measurement, modeling and control of nanotube growth,” Universite Lyon1/CNRS expert Stephen Purcell, who has also been the leader of the science team, explains. “The images from Dr. Purcell's lab show the atom-by-atom 'self assembly' of a nanotube. The video offers compelling evidence of the rotational motion that accompanies nanotube growth. It brings to mind Galileo's famous quote, 'And yet, it does turn,'” RU Mechanical Engineering, Materials Science and Chemistry Professor Boris Yakobson, the co-author of the new study, adds.

The researcher was the one who proposed earlier this year, in February, that the carbon nanotubes grew as if individual atoms were “woven” on a spinning thread. The new experiments, conducted using a field emission microscope (FEM) probe, seem to suggest that the expert was correct, and that this is, indeed, the way in which the nanoscale constructs form. “The results support our predictions of how nanotubes grow. The video shows rotational movement during growth, as carbon atoms are added in pairs to the twisting, chiral network of carbon atoms that comprise the nanotube,” Yakobson says.

Carbon nanotubes are considered to be among the most promising materials in the world. Their applications range from constructing nanowires in nanoscale mass spectrometry devices to offering the groundwork for cables that would be used by space elevators. Their unique structure is almost impervious to radiations, conducts electricity as well as copper, and the tube itself is several times stronger than steel on the same scale. “Smart” materials are a distinct possibility with these structures, but, first of all, researchers need to understand exactly how to grow them. And this study is a major step forward.

Adapted from materials provided by the Rice University.