Electrically Tunable Ion Selectivity of Charged Nanopores

Selective ion transport through nanoscale pores or channels has attracted considerable attention because of its fundamental role in essential biological activities such as the propagation of action potentials as well as in diverse applications from nanofiltration to biosensing. However, a precise and continuous control of ion selectivity over a wide range remains a challenging task. Here, we show by molecular dynamics simulations that ion transport through a graphene nanopore can be modulated by electrically biasing the graphene membrane. The nanopore selectivity between cations and anions can be continuously and reversibly tuned by varying the sign and magnitude of the electric charge on graphene. We further show that this tunable selectivity is attributed to the electrostatic adsorption induced diffusion of charged ions on oppositely charged surfaces, which promotes the permeation of these ions. Our work opens a new avenue for developing nanofluidic devices and mass-selective membranes with finely controlled selectivity.