Hydration-mediated ion selectivity in twisted graphene nanoribbon transistors

Organic mixed ionic-electronic conductors (OMIECs) that possess ion selectivity are essential for high-fidelity bioelectronic interfaces, yet achieving precise ionic discrimination without compromising electronic performance remains a formidable challenge. Here, we report a modular structural design to achieve cation-selective channeling by engineering twisted graphene nanoribbons (twGNRs) with macrocyclic side chains. Unlike traditional host-guest complexation, which often leads to irreversible ion trapping and slow kinetics, we demonstrate that twGNRs functionalized with 15-crown-5 (twGNR-15c5) exhibit a hydration-mediated steric filtering mechanism. In this system, twGNR-15c5 preferentially accommodates the smaller hydrated K + shell while impeding larger hydrated Na + and Li + ions at low operational voltages. Organic electrochemical transistors (OECTs) based on twGNR-15c5 show pronounced K + selectivity, hysteresis-free operation, and more than a 3-fold increase in current upon KCl addition to NaCl solutions. By decoupling ion recognition from the conductive graphitic backbone, this work establishes a generalizable framework for single-component OMIECs with ionic selectivity and dual electrical-optical response.