Electrokinetic Transport of Methanol and Lithium Ions Through a 2.25-nm-Diameter Carbon Nanotube Nanopore

Abstract

The flow enhancement and molecular selectivity of carbon nanotubes make them unique nanopore conduits. In this study, we examine separately the transport of Li+ and methanol through a 2.25 nm-diameter, 200-μm long single-walled carbon nanotube (SWNT). Threshold voltages of 200 mV and 700 mV were found for Li+ and methanol, respectively, to exhibit pore blocking. As the applied electric field was increased, the pore-blocking currents for Li+ and for methanol were both found to generally increase in the range of 1 to 6 pA. A simple volumetric model for methanol and hydrated Li+ is consistent with these observations. For applied voltages between 200 and 1000 mV, the dwell times for Li+ transport varied from 200 to 1200 ms and scaled linearly with inverse electric field. These results indicate an electrophoretic mobility of 1.6 × 10–7 m2 V–1 s–1, in agreement with previous measurements of alkali metal ions in SWNTs. Conversely, for applied voltages between 700 and 1000 mV, the dwell times for methanol remaine...