Modifying Water Flow, Ion Selectivity, and Salt Rejection in Carbon Nanotubes via Surface Adsorption

Chemical modification of carbon nanotubes is seen as an attractive way to control the rapid flow of liquids, gases, and solutes through their interior. However, precise covalent modification of nanotubes can be difficult. Here, we use molecular dynamics simulations to show that adsorption of polar molecules on the outside surface of carbon nanotubes provides an alternative means to control the rate and selectivity of transport in the pores. Specifically, adsorbing molecules with highly localized charges can significantly influence flow rates and generate selective ion transport. Strategic or patterned adsorption of charged polymers on the outside of carbon nanotubes may provide an avenue to precisely control flow through the nanotube interior.