Growing Opportunities with Collapsed Nanotubes

Category: Science & Technology
Posted: June 21, 2012 11:34AM
Author: Guest_Jim_*

If you take a piece of paper and roll it into a cylinder you will notice that the greater the diameter of the cylinder, the more easily you can distort the shape. Though several thousand times smaller, carbon nanotubes have a similar relation between diameter and distortion. Researchers at Rice University decided to investigate collapsed nanotubes to find how they can be made, and what they are capable of doing.

Carbon nanotubes are essentially rolled up sheets of graphene, which are atom-thick sheets of carbon. Nanotubes are grown using a catalyst, which allows carbon atoms to collect and bond into the hexagonal pattern they like. Researchers have considered unzipping nanotubes to make nanoribbons of graphene, but this does not always result in clean edges to the ribbons. By collapsing nanotubes like this though, the edges will always be perfect. The key to collapsing the nanotubes was to make them really wide. Systems tend to the state of lowest energy, and at a certain point the collapsed state requires less energy than remaining a cylinder.

Once collapsed, there are two main parts of the nanotube; the flat top and bottom, and the bulged sides. The flat parts act like graphene, because really, that is what they are, while the edges act like buckyballs, a 3D carbon structure. This differentiation allows for different properties between the sections. For example, edge chemistry could be used to make the edges non-conductive, making it difficult for the top and bottom sections to electrically communicate. This could open up a new realm of physics and electronic properties. Using double-walled nanotubes (essentially one nanotube inside of another) could make things even more interesting as there will be four layers of graphene and two sets of buckyball-like edges.

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