Gas sensing properties of surface acoustic wave NH3 gas sensor based on Pt doped polypyrrole sensitive film

In this paper, we demonstrated the fabrication and gas sensing properties of room temperature surface acoustic wave (SAW) NH3 gas sensors based on polypyrrole (PPy) film of different layers and Pt doped 2 layer PPy film. The PPy film was deposited on the photolithography patterned sensitive area by layer-by-layer (LBL) self-assembly method. The doping of Pt was conducted by immersing substrates with PPy film in the solution of H2PtCl6 and then reduced by NaBH4. Gas sensing properties of SAW devices with different layer of PPy films and Pt doped 2 layer PPy film were investigated and compared. We found that device with 2 layer PPy film shows best performance among devices with different layers of PPy films. Response and stability of device with 2 layer PPy could be further improved by the doping of Pt. Gas sensing properties of our device in different carrier gases (air and N2) were also investigated. Fourier transform infrared (FTIR) spectroscopy, energy dispersive X-ray spectrometry (EDS) and scanning electron microscopy (SEM) techniques were used for the characterization of each sensitive film. Besides, the sensing mechanism was also discussed.