Credit: © 2009 NPG

Graphene nanoribbons are thin strips of hexagonally arranged carbon atoms with straight edges. To understand and make use of their interesting electronic properties, methods for their large-scale production are required. Now, two different methods have been reported for creating such nanoribbons that both use the same idea of 'unzipping' multiwalled carbon nanotube (MWCNT) side walls.

James Tour and co-workers at Rice University have developed1 a method that uses sulfuric acid and potassium permanganate. The proposed mechanism relies on the oxidation of C=C double bonds at an undefined point along the wall. This creates a diketone defect within the MWCNT wall that also makes adjacent C=C double bonds more susceptible to oxidation. Sequential cleavage therefore unzips the MWCNTs to create highly oxidized graphene nanoribbons that, once annealed, are metallic conductors.

Hongjie Dai and co-workers at Stanford University use2 a different 'plasma etching' method to unzip MWCNTs. The MWCNTs are embedded in a polymer film that acts as a mask, partially protecting the MWCNT but allowing the most exposed part of the side wall to be removed with argon plasma. The method can produce single-, bi- or multilayer-nanoribbons depending on the starting MWCNT and the etching time.