Room temperature NO2 gas sensing properties of DBSA doped PPy–WO3 hybrid nanocomposite sensor

• Novel route of preparation of DBSA doped PPy–WO3 hybrid sensor.
• DBSA doped PPy–WO3 hybrid sensor showed maximum sensitivity 71% to NO2.
• DBSA doped PPy–WO3 hybrid sensor working at room temperature.
• Sensing mechanism of DBSA doped PPy–WO3 hybrid sensor discussed using an impedance spectroscopy.

We demonstrate the chemiresistive NO2 gas sensor based on DBSA doped PPy–WO3 hybrid nanocomposites operating at room temperature. The sensor was fabricated on glass substrate using simple and cost effective drop casting method. The gas sensing performance of sensor was studied for various toxic/flammable analytes like NO2, C2H5OH, CH3OH, H2S and NH3. The sensor shows higher selectivity towards NO2 gas with 72% response at 100 ppm. Also the sensor can successfully detect low concentration of NO2 gas upto 5 ppm with reasonable response of 12%. Structural, morphological and compositional analyses evidenced the successful formation of DBSA doped PPy–WO3 hybrid nanocomposite with uniform dispersion of DBSA into PPy–WO3 hybrid nanocomposite and enhance the gas sensing behavior. We demonstrated that DBSA doped PPy–WO3 hybrid nanocomposite sensor films shows excellent reproducibility, high stability, moderate response and recovery time for NO2 gas in the concentration range of 5–100 ppm. A gas sensing mechanism based on the formation of random nano p–n junctions distributed over the surface of the sensor film has been proposed. In addition modulation of depletion width takes place in sensor on interaction with the target NO2 gas has been depicted on the basis of schematic energy band diagram. Impedance spectroscopy was employed to study bulk, grain boundary resistance and capacitance before and after exposure of NO2 gas. The structural and intermolecular interaction within the hybrid nanocomposites were explored by Raman and X-ray photoelectron spectroscopy (XPS), while field emission scanning electron microscopy (FESEM) was used to characterize surface morphology. The present method can be extended to fabricate other organic dopent-conducting polymer–metal oxide hybrid nanocomposite materials and could find better application in the gas sensing.

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