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.
We demonstrated single-walled carbon nanotube aggregation at electrode edges by local electric field enhancement by a focused laser irradiation. It was revealed that the formation of nanobubbles and their induced fluid motion play an important role in carrying nanotubes to the electric field enhancement region around the laser irradiation spot from the laser power dependence of the aggregation on electrode edges. Furthermore, we found that metallic nanotubes preferentially aggregated near irradiation spots by the investigation of the laser irradiation time dependence of the aggregation. This technique is useful for manipulating and bridging nanotubes between electrodes for device applications.
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