NH3-detecting room temperature PANI-TiO2-based flexible gas sensor with EIS-validated sensing mechanism

Abstract

PANI-metal oxide nanocomposites have been studied extensively to improve sensor performance at room temperature. To date, researchers have utilized PANI-TiO2 for sensing NH3, but no elucidation of the sensing mechanism has been reported. In this research work, PANI-TiO2 nanocomposite-based flexible gas sensor for detecting NH3, operating at room temperature, has been investigated. The novelty lies in elucidating the sensing mechanism using electrochemical impedance spectroscopy (EIS) study. Effects of the operating temperature and different humidity levels of the CDA environment on the sensing parameters of the devices are also studied. PANI-TiO2 (10 wt% TiO2 with respect to aniline) device showed the best response of 9.88% against 2 ppm of NH3 at 21 °C. The sensor can detect NH3 as low as 2 ppm within 10 seconds. A low deviation of 3.5% in sensor response after 100 bending cycles was observed. Further, the sensor maintained a near-consistent response even after seven months of fabrication. Moreover, linearity was observed in the I-V analysis, providing further evidence that devices are ohmic. Furthermore, the contributions of the bulk, grain boundary, depletion region, and resistance between the electrode and the sensing film in the sensor response were identified by the EIS studies.