Silver nanoparticles were synthesized by reduction of silver nitrate (AgNO3) with sodium borohydride (NaBH4). The polyaniline/silver (PANI/Ag) nanocomposites were prepared by in-situ chemical oxidation polymerization of aniline solution containing different silver concentrations (0.5, 1.5 and 2.5 mole%). The crystal structure and surface morphology of the synthesized PANI/Ag nanocomposites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM micrographs of the nanocomposites showed almost homogeneous particle dispersion. The particle size of the nanoparticles calculated from XRD and TEM analyses increased with increasing Ag concentration in the nanocomposite. The acetone vapour sensitivity of pure PANI and PANI/Ag nanocomposites were examined at different acetone concentrations. Typical vapour sensor parameters (dynamic responses, response time, sensitivity, reproducibility) obtained for nanocomposite sensor were compared with corresponding parameters for pure PANI sensor. In comparison with pure PANI sensor, the PANI/Ag nanocomposite sensors exhibited fastest response, good reproducibility and long-term stability. The effects of Ag content on the sensing characteristics of the nanocomposite sensors were also investigated. The sensing mechanism was discussed on the basis of FT-IR spectroscopy.
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