Fig. 2: Tunable ion selectivity of graphene-based polyethylene terephthalate nanochannel (GPETNC).

a I–V curves of the GPETNC in different chloride salt solutions with concentrations of 0.1 M. Error bars were the standard deviations from the average of three independent records. b Normalized conductance g_i of cation i for the GPETNC at different voltages. c Ion selectivity of the GPETNC at different voltages. d Comparison of ion selectivity of the GPETNC and other nanoporous atomically thin membranes (NATMs) in experiments. The selectivity of different cations was normalized by that of K⁺. Based on the type of experimental settings, selectivities exhibited here were divided into three groups: conductance (gray), permeation (yellow), and mobility (blue), which indicated that they were obtained by comparing the normalized ion conductance^22,43,54, the ion permeation rate^12,15,16,55, and the mobility ratio of cation against chloridion^56,57, respectively. The light blue region is the range of tunable selectivity of the GPETNC at different voltages in this work (see Supplementary Fig. 5 for the original data). The NATMs in references include graphene^16,22,43,54, graphene oxide with various modifications^12,15,16,55, molybdenum disulfide (MoS₂)⁵⁶, and composite structures of graphene, MoS₂, and hexagonal boron nitride (hBN)⁵⁷.