Molecular ammonia sensing of PEDOT:PSS/nitrogen doped MXene Ti ₃ C ₂ T <i> _x </i> composite film at room temperature

Abstract

The irrational NH₃emission 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 NH₃without 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_<i>x</i>) for chemiresistive NH₃sensing at room temperature (20^oC). By means of the organic-inorganic<i>n</i>-<i>p</i>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 NH₃sensing 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 TiO₂nanoparticles 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 NH₃sensing. 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 NH₃gas sensors.