CoFe2O4–polypyrrole (PPy) nanocomposites: new multifunctional materials

Abstract

Spinel ferrites (iron cobalt oxide) were prepared by the microemulsion method atdifferent temperatures and sodium dodecyl sulphate (SDS) surfactant concentrations.Subsequently, a quantity of the different samples were coated with an intrinsicallyconducting polymer (ICP) shell of polypyrrole. The polymer shell was synthesized by achemical route after the ferrites particle production. By combining in a singlematerial the electrical conductivity of ICPs and the magnetic properties ofnanopowder ferrites, new multifunctional materials have been developed. DifferentCoFe2O4 grain size particles were obtained ranging from 3 to 30 nm, as determined byx-ray diffraction (XRD). Particles with grain size below a critical size exhibit asuperparamagnetic behaviour. These superparamagnetic particles, withoutand with a conducting polymer shell, were analysed by transmission electronmicroscopy (TEM) to find the grains’ morphology and the growth evolution ofthe polypyrrole shell in the ferrites grains. The electrical conductivity of thenanocomposite was measured by the four points probe method, showing values of120 ± 4 S cm−1 at ambient temperature. The behaviour of the magnetization and the coercivity withtemperature, from nearly 0 K to the ambient, were measured in a vibrating samplemagnetometer (VSM).