Design of an electrochemically gated organic semiconductor for pH sensing

[Display omitted] •PEDOT:BTB is a potentiometric pH transducer.•PEDOT:BTB can spontaneously modulate the conductivity of a charge transport layer.•Spontaneous electrochemical gating imparts pH sensitivity.•Gateless and referenceless pH sensor realised in a simple two-terminal configuration.•A textile chemical sensor for pH detection is fabricated. Since the development of potentiometric ion-selective electrodes, remarkable steps have been taken towards progressive simplification and improved robustness of pH sensing probes. In particular, the design of compact sensing architectures using solid-state components holds great potential for portable and wearable applications. Here we report the development of an electrochemically gated device for pH detection, combining the robustness of potentiometric-like transduction with an extremely simple and integrated geometry requiring no reference. The sensor is a two-point probe device comprising two thin polymeric films, i.e. a charge transport layer and a pH-sensitive layer, and exhibits a sensitivity of (8.3 ± 0.2) × 10−3 pH unit−1 in the pH range from 2 to 7. Thanks to the versatility and robustness of the optimised design, a textile pH sensor was fabricated whose performance is comparable with that of glass sensors.