CoFe₂O₄–polypyrrole (PPy) nanocomposites: new multifunctional materials

Abstract

Spinel ferrites (iron cobalt oxide) were prepared by the microemulsion method at different temperatures and sodium dodecyl sulphate (SDS) surfactant concentrations. Subsequently, a quantity of the different samples were coated with an intrinsically conducting polymer (ICP) shell of polypyrrole. The polymer shell was synthesized by a chemical route after the ferrites particle production. By combining in a single material the electrical conductivity of ICPs and the magnetic properties of nanopowder ferrites, new multifunctional materials have been developed. Different CoFe2O4 grain size particles were obtained ranging from 3 to 30 nm, as determined by x-ray diffraction (XRD). Particles with grain size below a critical size exhibit a superparamagnetic behaviour. These superparamagnetic particles, without and with a conducting polymer shell, were analysed by transmission electron microscopy (TEM) to find the grains’ morphology and the growth evolution of the polypyrrole shell in the ferrites grains. The electrical conductivity of the nanocomposite was measured by the four points probe method, showing values of 120 ± 4 S cm−1 at ambient temperature. The behaviour of the magnetization and the coercivity with temperature, from nearly 0 K to the ambient, were measured in a vibrating sample magnetometer (VSM).

Comparison of surface and bulk doping levels in chemical polypyrroles of low, medium and high conductivity

“…Figure 1 shows the XPS N 1s core-level spectra for a series of chemical PPys of low ( < 75 S/cm), medium (75 < < 200 S/cm) and high ( > 200 S/cm) conductivity up to the state-of-the-art value of 288 S/cm. 18,30,31 As can be seen, in all cases the single major N 1s core-level component at 399.9 eV (-NH-structure) is present accompanied by two high BE tails attributable to positively charged nitrogens (-NH Cstructure). 27 These peaks are assigned by Malitesta et al 34 to polaron (401.4 eV) and bipolaron (403.0 eV) structures.…”

“…18,30,31 . The structure-conductivity relationships for these PPys as determined by wide-angle X-ray scattering (WAXS), 13 C cross polarized/magic angle spinning nuclear magnetic resonance ( 13 C CP/MAS NMR) and Fourier transform infrared spectroscopy (FTIR) techniques have been reported recently.…”

Synthesis of Co3O4/Poly(N‐vinylcarbazole) Core/Shell Composite With Enhanced Optical Property

“…PNVC is a well-studied vinyl polymer of outstanding thermal stability and photophysical properties. [12] Coating of the Co 3 O 4 nanoparticles outer surfaces with functional polymers such as polypyrrole (PPY) [13] or polyaniline (PANI), [14] by using chemical and electrochemical methods, has been reported. However, the synthesis of the polymer coated uniform Co 3 O 4 nanoparticles has remained a great scientific challenge, because it is very difficult to control the agglomeration of conjugated polymers during polymerization/precipitation.…”

Magnetic and Electron Transport Behaviors of Conductive‐Polymer Nanocomposites

“…frequency-permeability responses for high frequency applications [55,58]. By combining in a single material the electrical conductivity of the polymer and the magnetic properties of the nanoparticles, magnetopolymeric materials can be built and have many potential applications [55].…”

“…By combining in a single material the electrical conductivity of the polymer and the magnetic properties of the nanoparticles, magnetopolymeric materials can be built and have many potential applications [55]. The insulating properties of the ferrites have the advantage of reducing the eddy current losses and some of the soft ferrites have been extensively investigated for RF applications such as AC/DC converters, wide-band transformers, antennas, and electromagnetic interference (EMI) shielding.…”