Ion-Selective Organic Electrochemical Transistor Sensors Using Molecularly Imprinted Polymers

Organic electrochemical transistors (OECTs) have emerged as attractive candidates for biosensing and bioelectronic applications, and they show great potential to serve as compact platforms for ion analysis. OECTs contain electronically active polymer layers whose charge transport properties can be modulated by electrolytes possessing ion concentrations as low as 1 μM. However, standard OECTs typically suffer from a lack of selectivity to electrolyte composition, a prerequisite for viable implementation into ion-sensing applications. To introduce this needed species selectivity, we have incorporated a molecularly imprinted polymer (MIP) into an OECT employing a poly(3,4-ethylene dioxythiophene) and poly(styrene sulfonate) polymer blend (PEDOT:PSS) as the channel active layer material. The MIP-OECTs were challenged with three cations: the sodium ion, the ammonium ion, and the tetrabutylammonium ion. The MIP did not limit the performance of the OECT when gated with electrolytes containing sodium ions, but the barrier did reduce the gating capabilities of electrolytes containing ammonium ions and tetrabutylammonium ions due to size-exclusion effects. In particular, the MIP-OECT was not responsive to tetrabutylammonium ions at concentrations up to 1 mM. Additionally, electrolyte mixtures were used to test the potential for interference in MIP-OECTs. Ammonium ions produced negligible interference when detecting sodium ions; however, tetrabutylammonium ions completely suppressed the gating capabilities of sodium ions. This MIP-OECT platform demonstrates how electrolyte gating can be engineered to exhibit greater selectivity such that MIP-coated OECTs can be utilized as advanced sensor technologies.