Controlled Growth of Carbon Nanotubes with Specific Chirality Achieved
Carbon nanotubes are funny little things as they come in so many forms with so many different properties. For example, some are great conductors of electricity while others are semiconductors, and all of this is determined by their structure. One critical characteristic of a nanotube's structure is its chirality and finally researchers at Aalto University, A.M. Prokhorov General Physics Institute RAS, and the Center for Electron Nanoscopy of Technical University have found a way to grow nanotubes with preferred chirality.
A simple example of chirality is handedness, as some objects twist in the right-handed direction or in the opposite, left-handed direction. Carbon nanotubes are more complicated though and require two chiral indices to be described. The researchers discovered that by reducing a solid solution in carbon monoxide they were able to form special cobalt nanoparticles to serve as a catalyst. From these catalysts the researchers were able to grow nanotubes with a 90% preference to being semiconducting and a 53% preference to having the chiral indices (6, 5), at 500 ºC. After dropping the temperature to 400 ºC, the researchers found the preferred chiral indices shifted to (7, 6) and (9, 4).
That is a lot of numbers relating to a complex topic, but what it boils down to is that the researchers have achieved something that could lead to a better understanding of how nanotubes grow. From there nanotubes with specific properties could be more easily produced, and thus used in devices and technologies.
Source: Aalto University