Hui Gui, Jason K. Streit, Jeffrey Fagan, Angela R. Hight Walker, Chongwu Zhou, Ming Zheng
This work expands the redox chemistry of single-wall carbon nanotube (SWCNT) by investigating its role in a number of SWCNT sorting processes. Using a polyethylene glycol (PEG)/dextran (DX) aqueous two-phase system, we show that electron-transfer reaction between redox molecules and SWCNTs triggers reorganization of the surfactant coating layer, leading to strong modulation of nanotube partition in the two phases. While the DX phase is thermodynamically more favored by an oxidized SWCNT mixture, the mildly reducing PEG phase is able to recover SWCNTs from oxidation and extracts them successively from the DX phase. Remarkably, the extraction order follows SWCNT bandgap: semiconducting tubes of larger bandgap first, followed by semiconducting tubes of smaller bandgap, then non-armchair metallic tubes of small but nonvanishing bandgap, and finally armchair metallic tubes of zero bandgap. Furthermore, we show that redox-induced surfactant reorganization is a common phenomenon, affecting colloidal SWCNT's buoyancy in a density gradient field, affinity to polymer matrices, and solubility in organic solvents. These findings establish redox modulation of surfactant coating structures as a general mechanism for tuning a diverse range of SWCNT sorting processes.