Side-Chain Role in Chemically Sensing Conducting Polymer Field-Effect Transistors

Abstract

The role of polymer side chains in conferring selectivity to a sensing organic thin-film transistor is investigated. Alkyl-and alkoxy-substituted regioregular polythiophenes are used as active layers, and a set of volatile organic compounds carrying different chemical functionalities are employed as analytes. The responses of both polymer-based transistor and quartz crystal microbalance sensors are evaluated and compared; the sensing mechanisms involving weak interactions between the analyte functionalities and the polymers' side chains are discussed as well.

Organic Thin-Film Transistors as Plastic Analytical Sensors

“…In addition, grain boundaries play a critical role, because the sensor response increases when the grain size is reduced or L is raised (39,40). Moreover, upon exposure, a mass uptake is recorded along with an increase or decrease in I ds (43). The OTFT's sensing mechanism can be plausibly depicted as the analyte molecules being adsorbed or trapped at the grains' surface, and this changes the height of E B and eventually the film mobility and V t .…”

“…Recently, we have investigated the role of chemically different linear chains, both as substituents of polythiophene sensing layers and as analyte molecules, in conferring recognition properties to an OTFT device (43). Alkyl-and alkoxy-substituted regioregular polythiophene thin films were exposed to different volatile molecules.…”

A Nitrogen Dioxide Sensor Based on an Organic Transistor Constructed from Amorphous Semiconducting Polymers

“…In other words, the OFET is used as an 'amplified chemiresistor', as reported previously in the literature. [11][12][13][14][15] However, fully characterized OFETs offer access to more sensing parameters than just I SD . Analysis of the saturated transfer characteristics of the OFET allows for the separate extraction of the carrier mobility, l, and threshold voltage, V T ; other parameters, such as the conductivity at zero or reverse gate bias (depletion), are also readily accessible.…”

“…These materials are widely used in the OFET community, but are not tailored to be selective or responsive sensor materials (albeit some selectivity as a function of the side-chain substitution pattern has been reported for thiophenes). [11,12,15] The odors studied in the past have typically been vapors of common polar solvents such as alcohols, [11][12][13][14][15][16][17] usually at saturation level (> 100 ppm for hexanol, but only ≈ 10 ppm for nonanol). [15] Recently, OFETs based on polythiophene derivatives have been used for the selective multi-parameter sensing of some common organic acids at concentrations lower than saturation.…”

“…[15] Recently, OFETs based on polythiophene derivatives have been used for the selective multi-parameter sensing of some common organic acids at concentrations lower than saturation. [18] Crystalline grain boundaries in the semiconductors have been identified as sensing 'hotspots'; [12] the I SD response to a specific odor at a given concentration strongly depends on the characteristic grain size and the OFET channel length. In extreme cases, even the sign of the I SD response can change as a function of these variables.…”