Effect of oxidizing agent on ammonia sensing of DBSA doped polyaniline nanocomposite thin film

Abstract

Dodecylbenzene sulphonic acid (DBSA) doped polyaniline (PANI) film have been successfully prepared by simple dispersion polymerization method. In this article stress has been given to compare the structural, morphological, spectral and gas sensing properties of DBSA doped PANI film using two different oxidising agents, namely ammonium per sulphate (APS) and potassium dichromate (PDC). The composite film oxidized by APS responses more to ammonia (NH3) vapour as compared to that prepared using PDC. Prior to vapour sensing investigation the composite film has been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersion X-ray, UV–visible spectroscopy, fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) in order to investigate its structural, morphological, spectral properties and thermal stability respectively. Structure analysis shows better crystallinity nature of the APS oxidized film through the presence of sharper peaks in the XRD plot. The morphological studies, done through FESEM measurements, reveal more ordered nearly uniform one dimensional shapes in APS oxidized film. The UV–visible absorption spectra indicate better conductivity for the APS oxidized film. FTIR spectra confirm cross linking in the DBSA doped composite film from the presence of extra bands apart from those of PANI and DBSA. APS doped film is found to possess improved thermal and environmental stability as compared to the PDC oxidized film. It is observed that at room temperature (300 K), the response of the APS oxidized PANI film is found to be 63 % towards 100 ppm of NH3 gas. Also it shows better sensitivity, stability and correlations compared to the PDC oxidized film.