Electrolyte‐Gated Organic Field‐Effect Transistor for Selective Reversible Ion Detection

Abstract

An ion-sensitive electrolyte-gated organic field-effect transistor for selective and reversible detection of sodium (Na(+) ) down to 10(-6) M is presented. The inherent low voltage - high current operation of these transistors in combination with a state-of-the-art ion-selective membrane proves to be a novel, versatile modular sensor platform.

Innate cation sensitivity in a semiconducting polymer

“…While the response to monovalent cations (Na However, for Ca 2+ concentrations > M t is immediately obvious that increasing Ca 2+ concentration leads to increased threshold, and reduced carrier mobility. This is a remarkable observation because we have not deliberately introduced any cation-sensitive component to the OTFT, like the PVC membrane in the work of List-Kratochvil et al [5]. The threshold shift is an innate property of the PBTTT OTFT itself.…”

“…The threshold shift is an innate property of the PBTTT OTFT itself. Nevertheless, we can sense Ca For quantitative analysis, we use the Nikolsky-Eisenman equation 2b [9], which is a refinement of the Nernst equation 2a [5].…”

“…Since then a number of water-gated organic TFTs (OTFTs) have been demonstrated that respond selectively to water-borne analytes due to specific sensitisers that were introduced into the transistor architecture [2,3]. This provides an alternative to the traditional ion-sensitive field between semiconductor and water-borne analyte [4] Of particular interest to the present work is the report by List-Kratochvil et al on a water-gated transistor that is sensitised for the selective detection of Na + ions with an ion-selective PVC membrane [5]. However, the design of List-Kratochvil et al is rather sophisticated, employing a two compartment water cell (an analyte and a reference compartment), separated by the PVC membrane.…”

“…Fig 3b also shows a systematic decline of the product of carrier mobility and specific capacitance with increasing Ca 2+ concentration, albeit we have no theoretical model for this shift. In the previous work on ion-sensitive water gated transistors by List-Kratochvil et al [5], only a threshold shift was observed in response to cation exposure, but no change of mobility. In the more sophisticated design of List-Kratochvil et al [5] there is no direct contact between sample solution and semiconductor: The semiconductor remains in contact with a reference solution of fixed ion concentration.…”

“…In the previous work on ion-sensitive water gated transistors by List-Kratochvil et al [5], only a threshold shift was observed in response to cation exposure, but no change of mobility. In the more sophisticated design of List-Kratochvil et al [5] there is no direct contact between sample solution and semiconductor: The semiconductor remains in contact with a reference solution of fixed ion concentration. In our simpler transistor design, the analyte solution (of varying concentration) is in direct contact with the semiconductor.…”