The effect of elution speed control on purity of separated large-diameter single-walled carbon nanotubes in gel chromatography

Large-diameter single-walled carbon nanotubes (SWNTs) have unique properties compared to small-diameter ones, for example, higher electrical conductivities, higher charge carrier mobilities, smaller bandgaps, and longer lengths, which can broaden SWNT applications. However, because the preparation methods result in mixtures of metallic SWNTs (m-SWNTs) and semiconducting SWNTs (s-SWNTs); such as in the case of small-diameter SWNTs, they must be separated and used for specific applications to obtain optimal performance characteristics. In this study, we show that simple elution speed control can increase the purity of separated large-diameter SWNTs in gel chromatography. According to the results, the flow rate of the eluant (i.e., the elution speed during gel column chromatography) greatly affects the purity of the separated m-SWNTs. We controlled the elution speed by changing the pressure inside the column during the separation process and experimentally investigated the relationship between the purity of the separated m-SWNTs and elution speed. By adjusting the elution speed to 0.13 ml/min, we obtained large quantities of pure m-SWNTs. Moreover, high-purity s-SWNTs were obtained for a wide elution speed range. Thus, highly pure m- and s-SWNTs can simultaneously be prepared by simply controlling the elution speed in single-column gel chromatography.