Nitrogen dioxide (NO2) sensing performance of p-polypyrrole/n-tungsten oxide hybrid nanocomposites at room temperature

Abstract

Polypyrrole (PPy)–tungsten oxide (WO3) hybrid nanocomposite have been successfully synthesized using different weight percentages of tungsten oxide (10–50%) dispersed in polypyrrole matrix by solid state synthesis method. The sensor based on PPy–WO3 was fabricated on glass substrate using cost effective spin coating method for detection of NO2 gas in the low concentration range of 5–100ppm. The gas sensing performance of hybrid material was studied and compared with those of pure PPy and WO3. It was found that PPy–WO3 hybrid nanocomposite sensor can complement the drawbacks of pure PPy and WO3. The structure, morphology and surface composition properties of PPy–WO3 hybrid nanocomposites were employed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The presence of WO3 in PPy matrix and their interaction was confirmed using XRD, FTIR techniques. The porous surface morphology was observed with addition of WO3 in PPy matrix which is useful morphology for gas sensing applications. TEM image of PPy–WO3 hybrid nanocomposites shows the average diameter of 80–90nm. X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical composition of nanocomposites. It was observed that 50% WO3 loaded PPy sensor operating at room temperature exhibit maximum response of 61% towards 100ppm of NO2 gas and able to detect low concentration of 5ppm NO2 gas with reasonable response of 8%. The hybrid sensor shows better sensitivity, selectivity, reproducibility and stability compared to pure PPy and WO3. The proposed sensing mechanism of hybrid nanocomposite in presence of air and NO2 atmosphere was discussed with the help of energy band diagram. Furthermore, the interaction of NO2 gas with PPy–WO3 hybrid nanocomposites sensor was studied by cole–cole plot using impedance spectroscopy.