Ion flow under an applied electric field in semiconducting and metallic carbon nanotubes

Measurements made by Li et al. showed that the flow rates of potassium ions through 11-nm-long, subnanometer diameter, metallic and semiconducting carbon nanotubes under an applied electric field are almost the same. In contrast, measurements of the electrical conductivity of potassium chloride solution through 100-μm-long metallic and semiconducting carbon nanotubes with diameters between 2.6 and 5.4nm by Cui et al. show that the ionic conductivity in the semiconducting nanotubes is larger than that of the metallic nanotubes. A possible theoretical origin of these differences is proposed in this article.