The structure and composition of carbon nanotubes (CNTs) are extremely sensitive to the manner in which they are produced and purified and in consequence there is a need for reliable characterisation of these materials. Multiple characterisation techniques have been applied in the literature, but their comparability is questionable since a small subset is applied to a particular sample. We address this issue by applying a wide range of common analytical tools to each member of a wide set of CNT samples. Scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS), ultra-violet photoemission spectroscopy (UPS), x-ray photoemission spectroscopy (XPS) and Raman spectroscopy are applied sequentially to carbon nanotube (CNT) samples containing predominantly single, double and multi-wall species purified in the same manner.
There is qualitative agreement between the majority of the techniques regarding chemical purity and structural perfection of the samples, although the volume of sample analysed can lead to misleading results and must be considered. It is concluded that effective characterisation is not possible with a single technique and that HRTEM and XPS are among the most effective complementary analytical tools, able to ascertain detailed physical and quantitative chemical data respectively. However, all the techniques studied have disadvantages, which are discussed. These include the surprising finding that UPS and EELS data cannot be straightforwardly used to compare the quality of CNT species.
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