Highly selective and sensitive room temperature NO2 gas sensor based on polypyrrole thin films

Polypyrrole (PPy) was successfully prepared via chemical oxidation polymerization technique using pyrrole as a monomer and ammonium per sulphate (APS) as oxidant. PPy sensors were fabricated on glass substrates using spin coating technique and characterized using FTIR, SEM, AFM and TEM techniques as well as gas sensing performance of prepared sensors towards various reducing and oxidizing gases were studied. Formation of polypyrrole was confirmed by FTIR spectrum. SEM analysis revealed that, polypyrrole film has highly porous granular morphology suitable for gas sensing application. The AFM analysis showed interconnected granular, porous morphology. The gas sensing studies demonstrate that, the PPy sensor showed outstanding gas sensing properties towards NO2 gas operating at room temperature with good selectivity and excellent repeatability. Furthermore, the PPy sensor is able to detect up low concentration of (10 ppm) NO2 gas with reasonable sensitivity (12%) and can be reliably used to monitor the concentration of NO2 gas over the range 10–100 ppm. The plausible response mechanism of PPy sensor towards NO2 gas operating at room temperature is also discussed.