Composites of Fe2O3 nanosheets with polyaniline: Preparation, gas sensing properties and sensing mechanism

Fe 2 O 3 nanosheets were in-situ deposited on the interdigitated gold electrodes by hydrothermal treatment of the electrospun nanofibers containing FeCl 3 and poly(vinyl butyral). As-prepared electrode was further dip-coated with water-dispersible polyaniline (PANI) to fabricate a resistance gas sensor based on Fe 2 O 3 /PANI nanocomposite. The structure and morphology of the nanocomposite were investigated by X-ray diffraction pattern, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. It was found that the nanocomposite sensor exhibited much higher response magnitude towards low concentration of NH 3 (0.5–10.7   ppm) than the sensors based on either PANI or Fe 2 O 3 at room temperature (∼20   °C), indicating an obvious synergetic effect. The nanocomposite sensor was featured with ultra high response magnitude (relative resistance change of ∼3070% towards 10.7   ppm of NH 3 ) and excellent selectivity towards NH 3 . A sensing mechanism has been put forward, which takes into account of the conducting network comprising of bulk PANI and composites of PANI and Fe 2 O 3 nanosheets. It was proposed that the p/n heterojunction established between Fe 2 O 3 nanosheets and PANI coating played a major role in the highly desirable sensing performance of the composite.