Dispersions in vitals (a) have coagulated CNTs in the body and at the bottom by means of bath sonication for 8 hrs, (b) appear free-homogenous with probe sonication for 3 minutes, and (c) keep free-homogenous even after 4 months of sitting at room temperature. The concentration of MWCNTs is 2500 mg/L and the MWCNTs/SDS ration is 1:10. (d) MWCNTs of (c) was diluted to 25 mg/L with deionized water.
It is clear that MWCNTs are not completely soluble in water by using bath Sonicator for 8 hrs; there was much sedimentation of MWCNTs at the bottom of a small bottle (Fig. a). Upon operating 20 kHz applied by a probe Sonicator, the MWCNTs are entirely dispersive in aqueous solution, forming a homogeneous-free solution (Fig. b). Remarkably, there is no sedimentation observed even after four months of sitting at room temperature (Fig. c).