One-pass separation of single-wall carbon nanotubes by gel chromatography with a gradient of surfactant concentration

We have investigated the diameter-selective separation of carbon nanotubes by one-pass gel chromatography with a gradient of surfactant concentration. The formation of surfactant gradient in a column was successfully measured and is explained by a simple diffusion process even in the gel. We found that the diameter of eluted nanotubes is inversely proportional to the surfactant concentration of eluate. The detailed analysis of the movement of the nanotubes in the gel revealed that the separation mechanism was qualitatively explained by a model based on the trapping and de-trapping events of the nanotube–surfactant micelle on the gel surface, where the probability of the trapping and de-trapping events is proportional to the product of the diameter of the nanotubes and the surfactant concentration. (paper)