Novel Design of Amine-Functionalized Semiconducting Polymer Gel for Highly Sensitive NO2 Chemotransistor

Abstract

Organic semiconductor (OSC)-based gas sensors have attracted considerable attention due to their facile manufacturing process and effective contact with target gases at room temperature. However, OSCs lack binding sites for the introduction of functional groups, one of the strategy to improve sensitivity. In addition, they suffer from slow recovery time because their porous structure expedites deep penetration of gases into the films.

Here, we demonstrate a novel methodology of semiconducting polymer gel (SPG) based on a semi-interpenetrating diphasic polymer network (semi-IDPN), composed of semiconducting polymer and organosilica network. The SPG facilitates straightforward functionalization by silanol (Si-OH) groups in the film. We introduced electron-donating amine (NH2) functional groups via solution process, because they interact strongly with electron-withdrawing NO2 gas. A chemotransistor based on the NH2-functionalized SPG (NH2-SPG) exhibited extremely high sensitivity (990 % ppm-1 at 5 ppm), even at low concentrations, and excellent NO2 selectivity against common gases, including SO2, H2S, NH3, and hexane.

Furthermore, the recovery of chemotransistor was significantly improved because the surface NH2 groups suppressed deep penetration of gases into the film. These results demonstrate that our NH2-SPG-based chemotransistor affords not only high sensitivity and selectivity, but also full recovery, which are infeasible characteristics for conventional gas sensors. Our novel material design will open a new path for practical gas sensor applications.