Phase evolution induced by polypyrrole in iron oxide–polypyrrole nanocomposite

Nanocomposite of polypyrrole and iron oxide were prepared using simultaneous gelation and polymerization processes. Varied amounts of pyrrole were added to a solution containing an Fe(III) salt as precursor and 2-metoxy ethanol as solvent. The particles were found to be nanocrystalline. However, the composites exhibited mixed phase, belonging to both the corrundum α-Fe2O3 (nonmagnetic) and the cubic phase, Fe3O4, which is ferromagnetic. The presence of both the phases is clearly seen from the X-ray diffraction (XRD) studies. Electrical conductivity study of powders showed a slight variation in conductivity for lower concentration of pyrrole, with a sudden increase in conductivity at 15% of pyrrole concentration, that could be explained on the basis of percolation theory which predicts that at a certain amount of concentration of conducting polymer a full conducting path is formed for the flow of current. The properties of nanocomposites formed by combining conducting polymers and oxides nanoparticles are strongly dependent on concentration of polymer and have brought out more fields of applications such as smart windows, toners in photocopying, conductive paints, drug delivery, rechargeable batteries. These nanocomposites were used for humidity and gas sensors.