Electrostatic Modulation for Enhanced Ion Selectivity in Gate-All-Around Multilayer Stacked Graphene Nanopore.

Biological ion channels exhibit exceptional gating capabilities for regulated transport and filtration across cell membranes. This study explores similar gating functions in artificial nanopores using graphene membranes. By applying direct voltage, we can dynamically control ion distribution around nanopores, allowing for real-time triggering, dynamic flow control, and adaptability to varying pore sizes. We investigate electrostatic modulation of ion transport in a stacked nanoporous graphene configuration, which mitigates defects from growth and transfer processes. Nanopores are created using oxygen plasma, enabling fine-tuning of ion transport. External voltage enhances ion conductivity at positive voltages and reduces it at negative voltages, demonstrating significant modulation by the surface potential-induced electric double layer (EDL). Voltage-dependent ion enrichment and depletion within the nanopores affect the effective surface charge density, facilitating controllable ion sieving. Results show that nanopores, with sizes comparable to hydrated ion diameters, achieve high and tunable voltage-gating functionality, enabling efficient on-demand ion transport. Voltage-gating effectively tunes ion selectivity in multilayer stacked graphene membranes, with negative voltages impeding divalent cations and positive voltages mimicking biological K nanochannels. This research lays the foundation for developing nanopores with tunable ion selectivity for applications in energy conversion, ion separation, and nanofluidics.