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The helicity sorting and optical resolution of single-walled carbon nanotube (SWNT) derivatives were investigated to elucidate their fundamental properties and to fully understand their application scope. Herein, the helicity sorting and optical resolution of functionalized SWNTs (SWNTs-xylyl), which were prepared by reductive alkylation using 1,2-bis(bromomethyl)benzene, were achieved for the first time via gel chromatography using an agarose gel as the stationary phase. By applying a stepwise elution, three surfactant types (6,4) SWNTs-xylyl, (11,–5) SWNTs-xylyl, and (6,5) SWNTs-xylyl were successfully separated and characterized. The circular dichroism spectra of (11,–5) SWNTs-xylyl and (6,5) SWNTs-xylyl were mirror images of each other along the abscissa, confirming the successful enantiomeric separation of these functionalized SWNTs. Both of the SWNTs-xylyl enantiomers showed red-shifted near-infrared (NIR) photoluminescence (PL) peaks, which were assigned to quantum defects formed by the chemical modification process. The intensity of the red-shifted PL peak of SWNTs-xylyl significantly increased after the separation. Compared to the sample before the separation, the purified (6,5) SWNTs-xylyl exhibited a considerable red-shifted PL with reduced concentration quenching effects. Owing to these properties, the helicity sorting and optical resolution of functionalized SWNTs may have practical applications as efficient NIR optical materials.
Maeda et al. (Mon,) studied this question.