Highly sensitive, reproducible, selective and stable CSA-polypyrrole NO2 sensor

Camphor sulfonic acid (CSA) doped polypyrrole (PPy) thin film sensors were prepared by spin coating method on glass substrates. Structure and morphology of the CSA doped in PPy films were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM), respectively, which proved that there is a strong synergetic interaction between the CSA and PPy. The prepared gas sensors were tested for different concentrations of nitrogen dioxide gas at room temperature conditions by sensing the changes in surface resistivity of the films with respect to time and the results compared with the data on pure PPy sensor. The CSA doped PPy sensor exhibited better sensitivity, selectivity and stability to NO2 when compared with PPy alone. It was revealed that 30% CSA doped PPy sensor operating at room temperature could detect NO2 gas at low concentration (10 ppm) with high selectivity (Q = 13% compared to H2S) and high sensitivity (S = 52%), with better stability (73%). Plausible NO2 sensing mechanism of the CSA doped PPy sensor is discussed. Also, the synergetic interaction between CSA-PPy and NO2 is carried out using impedance spectroscopy and the results are explored.