Gas sensitivity of a composite of multi-walled carbon nanotubes and polypyrrole prepared by vapor phase polymerization

A composite of multi-walled carbon nanotubes (MWCNTs) and polypyrrole (Ppy) has been synthesized by vapor phase polymerization, and characterized by Fourier transformed infrared spectra, Raman spectra, thermal gravimetric analysis, X-ray diffraction study and scanning electron microscopy. Its gas sensitive characteristics towards NH3 vapor were investigated at room temperature. It was found that the composite exhibited a higher sensitivity than both Ppy and MWCNTs separately. In addition, the response was reversible even when the concentration of NH3 vapor was as high as 12,500 ppm, in contrast to the usually observed unrecoverable response of carbon nanotubes and their composite to low concentration NH3 vapor at room temperature. The oxidizing agents and dopants used for preparation of the composite have a great effect on its gas sensitive characteristics, which is related to its morphology and contact with the electrode.