Fig. 5: Schematic illustration of the mechanism of ion sieving and rectification in graphene-based polyethylene terephthalate nanochannel (GPETNC).
From: Multifunctional graphene heterogeneous nanochannel with voltage-tunable ion selectivity
The distribution and transport direction of anions and monovalent cations at negative voltages (a), divalent cations at negative voltages (b), monovalent cations at positive voltages (c), and divalent cations at positive voltages (d). Ion selective graphene subnanopores are on the base side of the conical polyethylene terephthalate nanochannel, where the voltage is applied. For monovalent cations (a, c), the graphene effective charges heavily decrease with the increase of applied voltage (curved arrow) due to the significant voltage-dependent cation enrichment near the graphene (dashed box). However, for divalent cations (b, d), the graphene effective charges slightly decrease with the increase of applied voltage (curved arrow), because the change of the cation enrichment degree is slight (dashed box).
