Comparative study on purity evaluation of singlewall carbon nanotubes

Here we present a comparative study on Raman spectroscopy and optical absorption spectroscopy (OAS) as two main techniques being used for the purity evaluation of singlewall carbon nanotubes (SWCNT). The raw material was produced by the standard laser ablation technique using cobalt and nickel as catalysts (40 wt.% SWCNT). The presence of impurities influences the measurement of the properties of the carbon nanotubes. Therefore, the systematic purification study and its comparative estimation using the above mentioned characterization tools are presented. In order to reduce the catalyst particles content the diluted aqua regia was applied. In order to eliminate the amorphous carbon and fullerenes (unwanted forms of carbon) the high temperature annealing was used. The measurements were performed in suspension (dimethylformamide (DMF)) and on thin film deposited on potassium bromide crystal. This gave additional information about the effect of the sample preparation technique sensitivity on the purity of SWCNT evaluation.