Molecular ammonia sensing of PEDOT:PSS/nitrogen doped MXene Ti3C2T x composite film at room temperature

Abstract

The irrational NH3 emission routinely poses a significant threat to human health and environmental protection even at low dose. In addition, high miniaturization and low power-consumption has been the critical requirements of Internet of Things. To meet these demands, it is greatly pressing to develop a novel gas sensor with the capability to detect trace NH3 without external heating or light-irradiation elements. In this work, the organic conducting conjugated polymer PEDOT:PSS was combined with inorganic nitrogen-doped transition metal carbides and nitrides (N-MXene Ti3C2T x ) for chemiresistive NH3 sensing at room temperature (20 oC). By means of the organic–inorganic n–p heterojunctions via the synergistic effect, the results show that the composite film sensor with the optimal mass ratio of 1:0.5 between N-MXene and PEDOT:PSS components delivered favorable NH3 sensing performance than individual N-MXene or PEDOT:PSS counterparts in terms of higher response and quicker response/recovery speeds under 20 oC@36%RH air. Besides, decent repeatability, stability and selectivity were demonstrated. The incorporated N atoms served as excellent electron donors to promote the electron-transfer reactions and augment the sorption sites. Simultaneously, partial oxidation of MXene brought about some TiO2 nanoparticles which acted as spacers to widen the interlayer spacing and probably suppress the MXene restacking during the film deposition, thus favoring the gas diffusion/penetration within the sensing layer and then a quick reaction kinetic. The modulation of consequent build-in field within the heterojunctions was responsible for the reversible NH3 sensing. In addition, pre-adsorbed water molecules facilitated to establish a swift adsorption/desorption balance. The proposed strategy expanded the application range of MXene based composite materials and enrich the current sensing mechanisms of NH3 gas sensors.