4,4'-[1,2-Ethenediylbis(4,1-phenyleneiminocarbonyl)]bis(N-butyl-N,N-dimethylbenzenemethanaminium) Dichloride

E1127 has strong interaction to the surface of single-walled carbon nanotube (SWCNT), and the positive charge on the stilbene core enables SWCNT to disperse in aqueous solution. UV irradiation makes closure of the stilbene moiety and elimination from the SWCNT surface which enables SWCNT to aggregate. After the aggregation, the dispersant can be easily removed by filtration, etc.

(1) Preparation of dispersions (Low power sonication)
3.6 mg of E1127 was dissolved in 3 mL of pure water (18.8 MΩ·cm, TOC < 3 ppb) or D₂O using a glass vial (ca. 0.12 wt%). The solution was then sonicated (80 W, 35 kHz) at room temperature. Heating by a dryer is also a useful method for solvation. 1.96 mg of SWCNTs was added into the solution of E1127. The E1127/SWCNT mixture was sonicated (80 W, 35 kHz, 1 h) at room temperature. The black-colored dispersion was then centrifuged to remove impurities such as amorphous carbons and metal particles (28500 x g, at 22 °C, 3 hrs). Upper 70 % of supernatant was corrected as a well-dispersed SWCNT dispersion.

(2) Preparation of dispersions (High power sonication)
10 mg of E1127 was dissolved in 20 mL of pure water (18.8 MΩ·cm, TOC < 3 ppb) or D₂O using a glass vial (ca. 0.05 wt%). The solution was then sonicated (80 W, 35 kHz) at room temperature. Heating by a dryer is also a useful method for solvation. 7.0 mg of SWCNTs was added into the solution of E1127. The mixture was sonicated (80 W, 35 kHz, 1 h) at room temperature. Subsequently, the dispersion was subjected ultrasonication (60 W, 19 kHz, 4 hrs) at room temperature. The black-colored dispersion was then centrifuged to remove impurities such as amorphous carbons and metal particles (28500 x g, at 22 °C, 3 hrs). Upper 70 % of supernatant was corrected as a well-dispersed SWCNT dispersion.

(3) Photoirradiation and precipitation
A well-dispersed SWCNT dispersion was transferred to a dialysis tube (cutoff MW of 1000) to remove excess amount of E1127 from the dispersion. The tube filled with the dispersion of E1127/SWCNT system was put into a glass beaker with 3 L of pure water (18.8 MΩ·cm, TOC < 3 ppb) and was stirred overnight. The dialyzed dispersion was transferred into quartz cells and irradiated by an LED light source (365 nm, 100 mW/cm²) for several hours under magnetically stirring. After 3 hrs of light irradiation, precipitation of SWCNTs was completed for the dispersion treated with low power sonication. The SWCNT dispersion prepared using high power sonication took 7 hrs to recognize precipitation.