Chitosan/polyaniline nanofibers coating on the quartz crystal microbalance electrode for gas sensing

In situ polymerization of aniline using ammonium peroxydisulphate (APS) as an oxidizing agent in the presence of chitosan (Cs) was used to synthesize Cs/polyaniline (PANI) nanofibers. The structure and morphology of the Cs/PANI nanofibers powder were characterized by using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), UV–visible spectroscopy and scanning electron microscope (SEM). The surface of the Cs/PANI seems like interconnected nanofibers with diameters of approximately 50 nm. A film of the Cs/PANI nanofibers was built onto a quartz crystal microbalance (QCM) electrode by drop casting and this film was used to develop a sensor to measure the concentration of volatile organic vapors such as amines and alcohols in air. The frequency shifts (Δf) of the QCM, due to the vapor adsorption onto the Cs/PANI nanofibers film, were measured and related to the vapors’ concentrations. Linear relationships existed between the Δf (Hz) and the analytes’ concentrations. The sensor showed a good sensitivity, reproducibility and reversibility. The influence of different temperatures on the vapor adsorption onto the Cs/PANI nanofibers film was studied. The kinetics of diffusion of the gases and the diffusion coefficients (D), were discussed.