Aggregates of single-walled carbon nanotube bundles in a surfactant solution

We have carried out small angle X-ray scattering (SAXS), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and 1H NMR studies as a function of temperature on 0.1 wt.% single-walled carbon nanotubes (SWCNTs) dispersed aqueous (D2O) cetyl trimethylammonium bromide (CTAB) solution. We find that the single-walled carbon nanotubes in this system aggregate to form bundles and depending on the temperature of the system, the bundles aggregate and exhibit four different structures namely, Y-shaped structures, net-like structures, domains of small spherical structures and sheet-like structures. Our DSC thermogram also showed peaks at these structural transition temperatures of the CNT aggregates. Our SEM and 1H NMR studies reveal that the CTAB micelles are adsorbed on the CNT aggregates and the adsorption depends on the temperature and structure of the CNT aggregates.