Synergetic effect of electrochemical doping and long-range charge transport in solution-processed organic/inorganic hybrid chemiresistors for ultrasensitive NO2 detection

Abstract

Molecular-level electrochemical doping of solution-processed conjugated polymers (CPs) with solid-state ionic liquids (SILs) has emerged as a key technology for obtaining highly selective and sensitive chemiresistors. However, their responsivity and signal-to-noise ratio (SNR) still need to be significantly improved before commercialization. Herein, we demonstrate highly selective, sensitive, and flexible organic/inorganic hybrid chemiresistors for nitrogen dioxide (NO2) detection, exploiting the synergetic effects of: 1) the electrochemical doping of a polymer electrolyte by a SIL, and 2) the long-range charge transport by a two-dimensional (2D) MXene. The SIL with a long alkyl chain enables the molecular-level electrochemical doping of the polymer electrolyte, while the 2D MXene provides a long-range charge transport pathway, facilitating the operation of the device under low-bias conditions (<= 1 V). Notably, during NO2 exposure, additional electrochemical doping can be selectively and sensitively carried out in the hybrid chemiresistors owing to the presence of [NO2](-) anions. Therefore, the hybrid chemiresistors exhibit outstanding sensing capabilities, including an excellent sensitivity (Delta R/R-0 = 48 % at 10 ppm) and ultralow limit of detection (similar to 53 ppb). Based on the excellent reliability of the hybrid chemiresistor over 1000 bending cycles, our approach shows promising potential for achieving stable electrochemical reactions in emerging flexible sensing technologies.