Electrostatic Gatekeeper Ion Rectification and Electrochemical Fouling Recovery of Carbon Nanotube Membranes

摘要

By reducing diameter of carbon nanotubes (<1.5nm) and increasing functional chemistry density at we are able to mimic protein channel electrostatic paddles functionality and demonstrate ion exclusion of small ions. Prior studies with larger multiwalled CNTs could have only modest rectification of large Ru(bipyr)_3~(2+) cations [1]. Recent results with charged entrances showed significant electroosmotic pumping at low ionic concentrations (<～20mMol) [2]. In this work, highly charge and sterically bulky dye molecules resulted in significant ionic rectification factors (4-7) for small ions (KCl, LiCl, ZnSO4 and BaCl2) in high ionic strength (0.1M) aqueous solutions. Mass transport studies of electrically neutral molecule, caffeine through these CNTs indicate that an enhanced charge repulsion instead of steric hindrance mechanism dominates the ionic rectification phenomenon. Electrochemical Impedance Spectroscopy (EIS) measurements are also employed to investigate the underlying mechanism of the ionic rectification.