Chemical in situ modulation of doping interactions between oligoanilines and nanocarbon films

The electronic properties of carbon nanotubes are commonly customized through doping with various moieties, however, the modification is permanent as long as the dopant is present. Here we present a family of dopants that can be switched on and off while in place via environmental stimuli, in particular redox conditions and exposure to acids and bases. Aniline oligomers are firmly attached to the carbon nanotubes and are not easily displaced by other dopants or through rinsing with solvent in either oxidation state. As opposed to the reduced form of the aniline oligomers, their oxidized form causes p-doping of the carbon nanotubes. Similarly, the free base and chloride salt form of the aniline oligomers can be distinguished by their doping impact on the carbon nanotubes. The switching of the doping state can be followed by X-ray photoelectron spectroscopy, Raman spectroscopy and especially also electrically (film resistance), opening up applications as switches and sensors.