MWCNT debundling

Note that UV-Vis spectroscopy can be used in exactly the same way to monitor the debundling of MWCNTs in an aqueous surfactant solution of SDS-MWCNT dispersions. The procedure described can be directly adapted to the study of systems containing MWCNTs [see Figure 3.11]. ... 

With the simple and efficient UV-Vis tool to monitor the sonication-driven debundling of SWCNTs and MWCNTs, the optimum debundling conditions can be determined to produce stable surfactant-CNT dispersions that can be further stored and employed to make conductive nanocomposites. Finding trends in the general debundling behavior of several types of CNTs, as well as selecting the right power of sonication and the optimum CNT and surfactant concentrations, are dealt with in this section. 

Figure 3.11 displays the dispersion dynamics of different concentrations of MWCNTs in aqueous SDS solutions. For each UV-Vis spectrum, the absolute concentration of the MWCNT dispersion effectively measured was made identical by using the appropriate dilution factor. Therefore, the absorbance measured represents the state of dispersion of the CNTs at the end of the debundling, which proves to be the same for MWCNT concentrations up to 1.4 wt%. Please note that it was verified that, in all the cases, enough SDS molecules were present in order to enable the debundling of all the CNTs that can potentially be exfoliated. 

Figure 3.12 shows the plateau value of the absorbance at the end of the debundling of two different SDS-MWCNT dispersions, for which the CNT concentrations range from 0.05 wt% to 1.5 wt%, plotted as a function of the CNT concentration. For all the SDS-CNT dispersions, the UV-Vis absorbance was constant as long as the CNT concentration was kept below a critical concentration, being equal to 1.5 wt% for the batch MWA P041206 (open circles, batch 2) and... 

Figure 3.12 Plateau value of the absorbance at the end of the debundling of thin MWCNTs coming from two different Nanocyl batches, plotted in function of the CNT concentration. The closed squares ( ) correspond to the value of the absorbance at 260 nm, for dispersions containing MWCNTs The weight ratio SDSiCNT was kept constant at 1.5 1. The open circles (O) deal with the results of the debundling of MWCNTs of a different batch the absorbance was recorded at 251 nm and the weight ratio SDS CNT was always equal to 2. For both batches of MWCNTs, all samples were diluted by an appropriate factor to get a final concentration 6.7 x 10" wt% before the UV-Vis anal5Tsis.

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