Protocol for the characterization of single-wall carbon nanotube material quality

Single wall carbon nanotubes (SWCNTs) can be synthesized and purified by a number of techniques, and always contain certain amount of impurities of varying composition (mostly metal catalyst and non-tubular carbon), as well as defects resulting from purification. Particular purification route also affects homogeneity of nanotube material and its dispersability in organic solvents, which are important in the subsequent application development. A number of analytical characterization tools have been used successfully in the past years to access various properties of nanotube materials, but lack of standards makes it difficult to compare these measurements across the board. In this work we report on the protocol which standardizes measurements in TEM, SEM, TGA, Raman and UV-VIS spectrometer, consumes <30 mg of material, and was found to provide fast and reliable feedback in the development of purification techniques. The amount of residual metal catalyst is determined directly, and numerical measures are established for parameters such as homogeneity, thermal stability and dispersability, to allow easy comparison of SWCNT materials. Quantitative measurement of non-tubular carbon impurities still remains a problem, and we have to rely on qualitative electron microscopy observations. (C) 2004 Elsevier Ltd. All rights reserved.