Study of Polypyrrole-Coated MWCNT Nanocomposites for Ammonia Sensing at Room Temperature

The nanocomposite of polypyrrole (PPy) and carboxylated multi-walled carbon nanotubes (MWCNT) was synthesized by in situ chemical oxidative polymerization method using HCl as a dopant and Ammonium persulphate (APS) as an oxidant. The MWCNTs were carboxylic functionalized and were ultrasonicated to obtain uniform dispersion within the PPy matrix. Surface morphology of nanocomposites was investigated by Field Emission Scanning Electron microscopy (FE-SEM) and revealed that the functionalized MWCNTs were well embedded. X-Ray diffraction (XRD), Fourier Transform Infrared (FT-IR) Spectroscopy, Raman spectroscopy and UV-Vis spectroscopy were used to characterize the synthesized PPy-MWCNT nanocomposite. It was found that in situ polymerized PPy layer matrix was formed on carboxylated MWCNT and there was uniform dispersion of MWCNTs within the PPy matrix with significant interaction between PPy and MWCNTs. The response of the prepared PPy-MWCNT nanocomposite sensors was studied in the form of sensitivity towards Ammonia gas (NH3). The synergistic effects of the PPy-coated MWCNTs improve the gas sensing properties. Results showed that the sensitivity increased with NH3 concentration and it was also affected by the MWCNT content in PPy matrix. Furthermore, the sensor in pellet form reported here is robust, cost effective and relatively stable at room temperature.