Polypyrrole coated magnetite nanoparticles from water based nanofluids

The synthesis and characterization of hybrid structures obtained by coating Fe3O4 magnetic nanoparticles from water based nanofluid with a polypyrrole (PPy) layer are reported. The thin amorphous layer of polypyrrole surrounding the crystalline magnetic core was observed by HRTEM. The FTIR spectra of the nanocomposites show that the absorption bands characteristic for pyrrole ring vibrations significantly shifted to lower frequencies in the nanocomposite spectra, which indicates a higher degree of oxidation of the PPy shell covering the magnetite as compared with conventional PPy. The existence of superparamagnetism in the investigated nanocomposites is evidenced by the missing hysterezis loop in the magnetization versus applied magnetic field dependences. The comparison between the physical size of nanoparticles determined from TEM analysis and the magnetic size deduced from magnetization measurements is discussed. The surface modification of magnetite by polypyrrole coating results in an increase in the saturation magnetization and of the apparent magnetic diameter of the nanoparticles. This novel effect is attributed to a charge transfer process from the conducting polymer to the surface iron ions of magnetite, producing an increase in the surface contribution to the overall magnetic moment of the nanoparticles.