High levels of covalently functionalised single walled carbon nanotubes (SWCNT) have been produced using a rapid atmospheric pressure microwave reflux in a 1:1 mix of concentrated nitric and sulphuric acids. The resulting product shows high solubility (0.74 mg/ml at pH 11) and also displays a maximum solubility dependency based on the pH of the solution. The presence of sulphone and sulphonate functional groups has been shown using EDXA, TGA and IR analysis. The structural and electronic characteristics of the nanotubes were monitored using Raman spectroscopy and SEM imaging. Spray coating was used to form transparent conducting thin films from the functionalised nanotubes. The films demonstrated sheet resistances from 300 Ω / and a 25-85% optical transmission at 800 nm. This method provides a fast and effective route to the formation of conductive nanotube thin-films without the need for surfactant stabilisation of the solution. In addition the functionalisation was shown to be a fully reversible process sensitive to thermal treatment. Film formation removed the nanotube functionalisation and restored the pristine nanotube structure.
Keywords: Nanotubes, Functionalisation, Microwave, Solubility, Conducting, Film
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