Credit: © 2009 NPG

Graphene — an individual layer of carbon atoms — is a semimetal. However, thin strips of graphene called nanoribbons can be either semiconducting or metallic. Semiconducting nanoribbons display useful electronic properties that can be used for applications such as transistors. Several methods have been developed for the production of semiconducting nanoribbons, including lithographic and chemical approaches, but they all suffer from a number of drawbacks. Now, two independent research teams have shown that graphene nanoribbons can be produced from multiwalled carbon nanotubes.

Starting from the fact that a nanotube can be viewed as a graphene nanoribbon that has been rolled up to form a cylinder, the two groups have demonstrated different ways to unzip nanotubes lengthwise. Hongjie Dai and colleagues at Stanford University carried out plasma etching to cut open nanotubes that had been partially embedded in a polymer film (Nature 458, 877–880; 2009). James Tour and colleagues at Rice University, on the other hand, used a solution-based oxidative process to unfurl the nanotubes, followed by a chemical reduction step to remove chemical groups containing oxygen that have an adverse effect on the conductivity of the nanoribbons (Nature 458, 872–876; 2009). The development of similar chemical methods for the production of graphene sheets is currently the focus of much research (Nature Nanotech. 4, 217–224; 2009).

These transmission electron microscope images taken by Tour and co-workers show the nanotubes (left) and the nanoribbons (right). Both groups demonstrated the quality of their nanoribbons by using them to make field-effect transistors.