Voltage-Gated Ion Transport in Two-Dimensional Sub-1 nm Nanofluidic Channels.

Voltage-gated nanofluidic systems have shown a wide range of potential applications in biosensors, energy harvest, and separation. Two-dimensional (2D) nanofluidic membranes fabricated with electrically conductive nanosheets have high ion conductivity and voltage-gated ion transport behaviors. However, the voltage-gating effect of the sub-nanometer-sized 2D channel membranes has not been well-investigated. In this work, a high-performance voltage-gated 2D nanofluidic device is constructed by assembling MXene nanosheets into a laminar membrane with sub-1 nm interlayer channels. By applying external voltage to the membrane, the ion conductivity of the device is enhanced by positive voltages and reduced by negative voltages, exhibiting a high voltage-gating on-off ratio of ∼10. The on-off ratio is found to be dependent on ion concentration and ion species. This work demonstrates that 2D membranes with interlayer spacings comparable to those of hydrated ion diameters can achieve high and tunable voltage-gating function, which provides a strategy to construct devices for highly efficient on-demand ion transport.