Understanding Coupled Transport in Semiconducting Polymers for Analysis of Energetic Trace Materials

Organic electrochemical transistors provide a means to examine the intimately coupled mass and charge transport that occurs in polymer mixed conductors. Here, we evaluate this coupled transport while applying polymer blends in the detection of improvised explosives, in particular ammonium nitrate. Specifically, our OECT devices utilized either a conductive poly(3,4-ethylene dioxythiophene) poly(styrene sulfonate) blend or a semiconducting poly[3,4-propylene dioxythiophene-(2,2,4,4-tetramethylpiperdin-1-yl)oxyl] homopolymer as their active layer materials. Exhibiting distinct conductivities and operation modes, their behavior is compared over a range of electrolyte compositions and concentrations while illustrating the device’s sensing capabilities. The polymers’ behavior is elucidated by modeling their transport exhibited when gated with dilute electrolytes reminiscent of anticipated sensor analytes. Additionally, OECTs that include a molecularly imprinted polymer (MIP) cast atop the device structure produce size-exclusive electrolyte gating. By properly preparing the OECT sensor, we explain the contributions of both the channel and electrolyte gate composition in ion and charge transport in these mixed conducting macromolecular systems.