Nanocomposites of conducting polyaniline with ZnS nanoparticles (PAni/ZnS) have been synthesized by in- situ polymerization of aniline monomer using ammonium persulphate as oxidizing agent. The weight percentage of ZnS is varied from 1% to 28%. The formation of PAni/ZnS composites was assessed by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM) and UV-Vis spectroscopy. The broadening sharp peaks in the XRD patterns indicated the formation of nanocrystalline phase of ZnS with crystallite size of ~5.3 nm. The FESEM image shows a nanoparticular structure of ZnS and it is also seen that the ZnS nanoparticles are well dispersed in the polyaniline matrix. UV-Vis spectrum of composites shows two peaks at 340 nm and a broad peak in the range ~580 nm to 790 nm. The peak around ~340 nm corresponds to excitation of electron from valence to conduction band, is used to determine the nature and value of the optical band gap of composites. Photoluminescence studies were carried out by exciting the samples with an excitation wavelength of 320 nm. Two peaks are observed at a wavelength of ~365nm and 520 nm. The 365 nm emission is due to recombination of electrons at the sulphur vacancy donor level with holes trapped at the zinc acceptor level. The Peak at ~520 nm with less intensity could be due to some self activated defect centres related to Zn vacancies. Thermal stability of the sample was analysed by Differential Scanning Calorimetry. DSC thermogram shows 2 endothermic peaks at 125° C and 260 °C. DC conductivity of PAni and its composites have been measured in the temperature range from 25°C to 205°C. It is found that conductivity increases with the increase of ZnS concentration.
