Polydopamine-Functionalized 2D Sub-Nanochannels for Efficient and Diverse Multi-Stimuli Responsive Ion Transport Sensing

The functionalization of two-dimensional nanochannels (2D nanochannels) or even subnanoconfinements using diverse responsive molecules represents a wonderful combination for smart ion channels. However, this combination requires the careful chemical design of responsive molecules to maintain the elaborate structure of the 2D channel. Herein, we report the functionalization of 2D channels using polydopamine (PDA), which acts as an adhesive agent for binding responsive molecules to graphene oxide (GO) nanosheets and partially reduces GO to rGO, resulting in the formation of a stable 2D stacking structure. The positively charged two-dimensional channels, formed through interactions between analyte molecules and PDA, induce a rapid increase in ionic current, driven by deprotonation under nanoscale or subnanoscale confinement. Simulation results demonstrate a linear relationship between the current response ratio and decreasing positive charge density on the surfaces of the two-dimensional channels. The universal adhesion of PDA provides 2D channels with the ability to respond to temperature, potassium ions, and UV irradiation individually or in combination.