Ultra-sensitive, highly selective and completely reversible ammonia sensor based on polythiophene/SWCNT nanocomposite

Abstract

Herein, we report polythiophene (PTh) based single-walled carbon nanotubes (SWCNT) nanocomposite (PTh/SWCNT) as a gas-sensor with extraordinary sensitivity and reproducibility at the room temperature (27 °C). The structures and morphologies of as-synthesized PTh/SWCNT nanocomposites were confirmed by scanning electron microscopy (SEM), transmittance electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD) techniques. These materials were studied for comparative stability of DC electrical conductivity under temperature ageing conditions; thus, PTh/SWCNT-3 (nanocomposite having 15 wt% of SWCNT with respect to the monomer, i.e. thiophene) was observed to be the most stable material. The change in conductivity of PTh/SWCNT-3 was calculated on exposure to the ammonia-vapours. It was noticed that the incorporation of SWCNT in PTh showed excellent sensitivity as compared to PTh, resulting in a significantly lower detection limit of 05 ppm in addition to the complete reversibility as well as excellent selectivity. The faster response, as well as the complete reversibility, may be attributed to relative higher surface-area of PTh/SWCNT-3, accessibility of appropriate sensing corridors and active sites. Most importantly, PTh/SWCNT-3 showed excellent selectivity towards ammonia than different tested volatile hydrocarbons. Finally, the sensing-mechanism was explained on the basis of involvement of polarons of PTh during adsorption and desorption of analyte gas.