Sublimable Surfactant for Carbon Nanotube Dispersion: Effect of the Length of 10-n-Alkyl Side Chains of Flavin on Sublimation

We investigated the sublimation properties of 10-n-alkyl side chains of flavins (n = 4–9, and 12) to address the issue of surfactant residue in single-walled carbon nanotubes (SWNTs). Thermogravimetric analysis under vacuum indicated that the 10-octyl-alkyl side chain of flavin sublimated at a lower temperature than the other flavins, with a saturation vapor pressure of 0.1 Pa at 200 °C. This allowed sublimation without the competing thermal reaction. Therefore, the 10-octyl-alkyl side chain of flavin is a surfactant that can separate and disperse semiconducting SWNTs for the effective utilization of their electrical properties. Moreover, it can be subsequently removed via sublimation. The flavin containing an octyl-alkyl chain (10-octyl-7,8-dimethyl-10H-benzo[g]-pteridine-2,4-dione) sublimated with a saturation vapor pressure of 0.1 Pa at 200 °C. This allowed sublimation without the competing thermal reaction. Moreover, the flavin with octyl-alkyl chain is a surfactant that can separate and disperse semiconducting SWNTs for the effective utilization of their electrical properties.