Nano Lett. http://doi.org/k3k (2013)

Credit: © 2013 ACS

The development of techniques enabling the localized modification of the electric properties of graphene is an essential step to fully exploit this material as a versatile platform for electronic devices. Zhou et al. now demonstrate the use of dip-pen nanolithography to pattern Rhodamine 6G on nanosheets of exfoliated graphene with submicrometre resolution. The bulk functionalization of graphene with this aromatic molecule induces an n-doping effect on its conductivity. Accordingly, the nanosized stripes of Rhodamine 6G locally modify the electrostatic potential of graphene as measured by Kelvin probe force microscopy. A stable molecular assembly is achieved when Rhodamine 6G dimers, instead of monomers, are deposited from aqueous solutions: their different electrostatic arrangement favours the formation of ordered one-dimensional chains that closely pack together and bind to the underlying surface by π–π stacking. Such chemical attraction between the planar honeycomb structure of graphene and aromatic molecules is the key to reliable positioning of localized dopants by means of dip-pen nanolithography.