Pressing Carbon Nanotubes Triggers Better Ion Selectivity

Abstract

The selective transport of K+ or Na+ in acqueous solutions by biomembranes is highly efficient in ion separation but hardly achieved by artificial devices. Inspired by the gates in voltage-gated potassium channels, our computational modeling indicate that biomimetic ion selectivity via nanopores can be achieved by membrane-spanning single-walled carbon nanotubes (CNTs) functionalized with carboxyl groups. It follows that the ion selectivity of the membrane-spanning CNTs can be acquired by pressing the functionalized CNT nanopores in the deformable biomimetic nanopores. According to free energy calculations by umbrella sampling, the free energy barrier difference between the permeation of K+ and Na+ through the functionalized CNT nanopores can be up to about 14.0 kJ/mol, resulting in a K+/Na+ conduction ratio around 260:1. The membrane-spanning single-walled carbon nanotubes with mechanically deformable nanopores may be of critical importance in design and fabricate many nanoscale devices and nanofiltratio...