On diffusion of single-walled carbon nanotubes

The study is aimed at investigating the diffusion of single-walled nanotubes in liquids with the weight concentration of nanotubes varied from 0.00001 to 0.01%. Water solutions of sodium dodecylbenzene sulfate and polyvinylpyrrolidone, which are usually used as surfactants, are applied here as a carrier liquid. Their concentration is either equal to the concentration of nanotubes or twice greater. Depending on the concentration, the diffusion coefficient of nanotubes is found to change from 1.02·10⁻¹¹ to 0.7·10⁻¹² m²/s. Based on the data on the diffusion coefficient, the effective hydrodynamic size of nanotubes and their length are retrieved. The efficiency of nanotube separation by means of centrifugation and the changes in their characteristics during long-term storage are discussed.