Polyaniline/silver nanocomposites: Dielectric properties and ethanol vapour sensitivity

Polyaniline/silver (PANI/Ag) nanocomposites were prepared by in-situ oxidative polymerization of aniline monomer in the presence of different concentrations of Ag nanoparticles. The formation of PANI/Ag nanocomposite was characterized by UV-vis spectroscopy, energy dispersion X-ray (EDX) and transmission electron microscopy (TEM). TEM images showed that the particle size increased with increasing Ag concentration in the composite, owing to the aggregation effect. The AC conductivity and dielectric properties of pure PANI and PANI/Ag nanocomposites were measured in the frequency range of 10(3)-10(6) Hz. Higher conductivity, dielectric constant and dielectric loss of PANI/Ag nanocomposites than those of pure PANI were observed. The conductivity of the nanocomposites increased with increasing Ag concentration. The gas-responses of the PANI/Ag nanocomposite towards low concentrations of ethanol was examined and compared with that of the pure PANI. The nanocomposite was found to possess superior ethanol sensing capacity compared to pure PANI and it showed linear relationship between the responses and the ethanol and/or Ag concentration. The Fourier transform infrared (FT-IR) spectroscopy was used to explain the sensing mechanism. (C) 2009 Elsevier B.V. All rights reserved.