Method for dispersing in water: In solid form SWNTs are highly entangled and associated in macroscopic particles. It requires significant effort to break such an association and bring the material in solution. Sonicate 50 mg of material in 2 ml water for 30 min. Add 8 ml of water and sonicate for additional 90 min. Typically, after this procedure all material is completely dispersed according to visual observation. For quantitative measurement of the solubility, allow the dispersion to stand overnight at room temperature. Because of the high optical density of concentrated dispersion, dilute an aliquot from the upper layer of the studied dispersion by a factor of 100. The concentration of the diluted solution is estimated from the recorded NIR spectra using a plot of the absorbance at 9750 cm-1 compared to the concentration of a standard solution (see reference).
