Inverse gas chromatography of as-received and modified carbon nanotubes.

The surface properties of chemical vapor deposition (CVD)-grown, multiwalled carbon nanotubes (CNTs) have been studied using inverse gas chromatography (IGC). By adapting known IGC methodologies to these challenging materials, the surface character of a broad range of CNT materials can be reliably compared and quantified in terms of dispersive and specific surface energies, electron acceptor and donor numbers, and adsorption capacities. The effect of CNT surface modification by high temperature annealing, thermal oxidation, and grafting of methyl methacrylate was explored. The IGC surface characterization of these materials was consistent with results from other surface-sensitive analytical techniques, including X-ray photoelectron spectroscopy (XPS), titration, and electron microscopy, confirming the validity and sensitivity of our approaches. The same IGC methodologies were successfully applied to characterize three as-received CNT materials which differed significantly in their specific surface areas and functional surface group concentrations.