Strategy for High Concentration Nanodispersion of Single-Walled Carbon Nanotubes with Diameter Selectivity

Nanodispersion of single-walled carbon nanotubes (SWCNTs) have been systematically investigated with the use of sodium dodecyl sulfate (SDS) and poly(vinylpyrrolidone) (PVP) surfactant in deionized water. A high concentration of nanodispersed SWCNTs up to 0.08 mg/mL was achieved with introduction of an additional dispersant of PVP by optimizing surfactant concentration, sonication time, and centrifugation speed, which was crucial to obtaining a high concentration of SWCNTs in the supernatant solution. We also demonstrate that diameters of the nanodispersed nanotubes can be sorted out by controlling the centrifugation speed, and furthermore, the saturated SWCNT concentration was nearly constant, independent of the initial concentration at high centrifugation speed. Two dispersion states were identified depending on the centrifugation speed: (I) an intermediate mixed state of nanodispersion and macrodispersion and (II) nanodispersion state. This was verified by Raman spectroscopy, scanning probe microscopy, optical absorption spectroscopy, and photoluminescence measurements. The obtained SWCNT solution was stable up to about 10 days. Some aggregated SWCNT solution after a long period of time was fully recovered to initial state of dispersion after resonication for a few minutes. Our systematic study on high concentration nanodispersion of SWCNTs with selective diameters provides an opportunity to extend the application areas of high quality SWCNTs in large quantity.