Ammonia gas-sensing behavior of uniform nanostructured PPy film prepared by simple-straightforward in situ chemical vapor oxidation

Abstract

Abstract A highly uniform nanostructured polypyrrole (PPy) film prepared by a simple, straightforward in situ route of chemical vapor oxidation has been demonstrated as a sensitive substrate for NH3 gas sensing. The structure of PPy film was investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The binding characteristics of the functional groups of the PPy film were examined by Fourier transform infrared and Raman spectroscopy. NH3 sensing properties of the PPy film were evaluated by its resistive response to gas concentrations from 45 to 350 ppm at different temperatures ranging from 25 to 100°C. The sensing response maximum value was 142.6% when exposed to 350 ppm of NH3 gas at room temperature (25°C). The sensing response of PPy film shows an excellent linear relationship and high selectivity toward NH3. The NH3 sensing mechanism is due to the physisorption and chemisorption interactions of NH3 molecules and the adsorptive sites of PPy (polaron and bipolaron charging carriers).