One‐Spot Synthesized Crystalline Graphene/PANI for Wearable Ionic Transistor Textiles

Here, we report a one‐spot, temperature‐controlled AC electropolymerization strategy for converting graphene oxide and aniline into a crystalline, processable reduced graphene oxide (rGO)/polyaniline (PANI) composite for wearable ionic transistor textiles. By tuning the electropolymerization temperature from 4°C to 55°C under a low‐frequency triangular AC waveform, followed by mild postreduction, conformal polycrystalline PANI nanodomains are grown directly on rGO sheets. Low‐temperature synthesis yields the highest structural ordering and the lowest fraction of protonated imine species, directly linking growth conditions to mixed ionic–electronic transport behavior. The resulting rGO/PANI composite functions as an electrolyte‐gated transistor with stable operation and amplified gate response. Furthermore, the composite can be stencil printed onto cotton textiles to realize ratiometric Na ⁺ /K ⁺ sensing at constant ionic strength, highlighting its potential for scalable, wearable ion‐sensing architectures.