Room-Temperature-Operated Fe2O3/PANI-Based Flexible and Eco-Friendly Ammonia Sensor With Sub-ppm Detectability

In this work, a room temperature (RT; ∼27 °C) operated ferric oxide/polyaniline (Fe2O3;sol;PANI) composite-based flexible ammonia (NH3) sensor with substantial sensing performance is reported. Initially, interdigitated electrodes (IDEs) were screen printed (using graphene-carbon based ink) on a bio-degradable paper substrate. Further, PANI nanofibers were electrospun on printed IDEs, followed by drop casting a layer of Fe2O3. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) studies were performed to confirm the composite formation followed by scanning electron microscopy (SEM) analysis to examine the sensing surface morphology. The ammonia sensing performance was examined within the range 0.5 ppm (i.e., 500 ppb) to 50 ppm, with a 1.99% response achieved even at 0.5 ppm. The response/recovery times were noted as 950 s / 250 s, towards 0.5 ppm of ammonia. Additionally, selectivity towards interference gases including carbon dioxide (CO2), nitrogen dioxide (NO2), carbon monoxide (CO) and sulfur dioxide (SO2) were also investigated. The proposed sensing mechanism of the composite material towards ammonia gas detection is also presented.