Detecting Minute Chemical Vapors via Chemical Interactions between Analyte and Fluorinated Thiophene–Isoindigo Conjugated Polymer Transistor

Abstract

Detecting and discriminating chemical vapors are essential for environmental monitoring and medical diagnostics. In this study, highly sensitive chemical vapor sensors fabricated from fluorinated thiophene−isoindigo donor−acceptor conjugated polymers are realized through understanding the interaction of the fluorine functional group and different chemical vapors. The polymers possess the merits of facile synthesis for high quality materials, good field-effect transistor performance, and stability in air and humid environments. The transistor exhibits extremely high detecting capability for minute chemical vapor down to the ppb range. The detecting sensitivity of the transistor depends on the chemical structure of the polymer and the nature of analytes. Polar molecules such as amines with potential hydrogen bond donor can adsorb in close vicinity to conducting channels due to the formation of a hydrogen bond with fluorine atoms, enhancing the sensitivity significantly. Chemical vapors such as acetone and xylene interacting with the polymers via dipolar and van der Waals forces, respectively, have to accumulate sufficient amounts in the polymer films or at the dielectric interface. Through understanding functional group−analyte interactions, polymers can be designed for multiparameter sensing, paving ways toward ultrasensitive sensors and accurate discrimination of different kinds of chemical vapors.

π‐Extension of Isoindigos (IIDs) through C—H/N—H Activation and Alkyne Annulation†

“…[ 1‐2 ] It contains two amide groups and an exocyclic double bond in its conjugated structure (Scheme 1a), showing planar geometry, [ 3 ] electro‐deficient character, off‐axis dipole moment, and strong intermolecular interactions. [ 4 ] As a result, IID and its derivatives have been found wide applications in organic photovoltaics, [ 5 ] organic field‐effect transistors, [ 4 ] organic thermoelectrics, [ 6‐7 ] organic electrochemical transistors, [ 8 ] chemical sensors, [ 9‐10 ] organic spin valves, [ 11 ] organic phototransistors, [ 12 ] pharmaceuticals [ 13 ] and other areas. [ 14‐16 ] For instance, Reynolds and coworkers firstly utilized it as a building block for organic semiconductors and synthesized an isoindigo‐thiophene oligomer, which was used in organic solar cell in 2010.…”

Semiconducting Polymers Based on Isoindigo and Its Derivatives: Synthetic Tactics, Structural Modifications, and Applications

“…[ 165 ] For P121 – P123 (Figure 9h), the FH hydrogen bonds formed between polymers and ammonia molecules attracted ammonia molecules to polymers, thus increasing the HOMO energy levels and leading to larger hole‐injection barriers, both of which were negative to the hole transport. [ 169 ] Therefore, the sensing response of sensors based on these polymers to ammonia showed linear correlation to the fluorine content of polymers. However, the structure features of P121 that high fluorine content and no additional thiophene spacer led to baseline drift and slow recovery rate.…”

“…Finally, P122 ‐based OFET possessed the highest response sensitivity of 100 ppb for ammonia in 1 min (Figure 9i). [ 169 ]…”

Side-Chain-Assisted Transition of Conjugated Polymers from a Semiconductor to Conductor and Comparison of Their NO2 Sensing Characteristics

“…Chemiresistive sensors utilize a change in resistance to detect the target gas; therefore, CP as a detection platform should have electrical conductor-like properties [ 31 , 32 , 33 ]. FET-based sensors, on the other hand, adopt semiconducting CPs to monitor current changes due to charge carrier mobility and/or concentration, which enable the delivery of multiparameter response characteristics, such as charge–carrier mobility, threshold voltage, on/off current, and conductivity [ 34 , 35 , 36 ]. Various CPs have been implemented in chemiresistive- and FET-type electronic sensors, and their advantages have been reported in terms of detection sensitivity, selectivity, and fast recovery.…”