Electric jolt forms graphene nanoribbons
doi:10.1038/nindia.2011.49 Published online 11 April 2011
Researchers have used an electric field to convert both multi- and single-walled carbon nanotubes into smooth graphene nanoribbons. These nanoribbons could be useful for designing novel nanosized electronic devices.
Graphene is a thin, one-atom-thick layer of carbon whose electron mobility is around ten times that of silicon. However, existing methods for producing graphene nanoribbons such as chemical oxidation have major drawbacks, including poor quality and low yields.
The use of strong reducing agents in chemical oxidation poses difficulties in controlling layer thickness. To find a suitable alternative method, researchers resorted to an electrochemical oxidation process in which they applied electric fields to carbon nanotubes in two steps.
Applying a two-step potential variation (0.70 V anodic, followed by 0.75 V cathodic, each for six hours) converted the majority of the nanotube material to nanoribbons. The first step produced graphene oxide and the second step reduced the graphene oxide to yield graphene nanoribbons.
The process produced long, straight-edged bilayer nanoribbons with widths of 70–110 nm and thicknesses of 1.6–1.9 nm. The nanoribbons were strikingly similar to the dimensions of high-quality graphene prepared by chemical methods. The graphene nanoribbons were transparent and very stable under an incident electron beam.
"This study opens new ways for the preparation of high-quality graphene in good yield, having profound implications for certain applications such as fuel cells and lithium battery electrodes," says lead researcher Vijayamohanan K. Pillai. This method, he says, can help avoid problems that arise in high-temperature processes such as chemical vapour deposition.
The authors of this work are from: Physical and Materials Chemistry Division, National Chemical Laboratory, Pune, Central Electrochemical Research Institute, Chennai, Karaikudi, and Indian Institute of Technology, Mumbai, India.