Preparation and characterization of polyaniline cadmium sulfide nanocomposite for gas sensor application

Polyaniline (PANT) was prepared by chemical oxidative polymerization of aniline monomers as emeraldine salt form. By the same method, polyaniline cadmium sulfide nanocomposites were synthesized in the presence of different percentages (10-50 wt.%) of cadmium sulfide (CdS) which was prepared by using sol gel method. The optical band gap was decrease with increasing of CdS concentration, that is obtained from UV-VIS measurements. From SEM and AFM, there is uniform distribution for cadmium sulfide nanoparticles in the PANI matrix. The electrical measurements of nanocomposites exhibit the effect of crystallite size and the high resistivity of CdS on the resistivity of nanocomposites. Emeraldine salt PANI, CdS and PANI CdS nanocomposites were investigated as gas sensors. From this investigation, the sensitivity of PANI CdS for NO2 gas increase with the increasing of operation temperature and the optimum sensitivity was obtained at 200 degrees C. The sensitivity of nanocomposites at best temperature (200 degrees C) was increased and faster response time with the increasing of CdS contents.