Conducting and magnetic behaviors of polyaniline coated multi-walled carbon nanotube composites containing monodispersed magnetite nanoparticles

High conductivity and supermagnetism of polyaniline (PANI)-coated multi-walled carbon nanotube (MWCNT) composites containing monodispersed 6 nm iron oxide (Fe₃O₄) nanoparticles has been successfully synthesized by in situ chemical oxidative polymerization using anionic surfactant dodecylbenzenesulfonic acid sodium salt. Hydrophilic 6 nm spherical Fe₃O₄ nanoparticles fabricated by the thermal decomposition process were chemically modified using 11-aminoundecanoic acid tetramethylammonium salt. The modified nanoparticles were further mixed with carboxylic acid containing multi-walled carbon nanotubes (c-MWCNTs) in an aqueous solution to form one-dimensional Fe₃O₄ coated c-MWCNT template and PANI/c-MWCNT nanocomposite were then synthesized via in situ chemical oxidative polymerization in HCl solution. Structural and morphological analysis using FESEM, HRTEM and XRD showed that the fabricated Fe₃O₄ coated c-MWCNT/PANI nanocomposites are one-dimensional core (Fe₃O₄ coated c-MWCNT)–shell (PANI) structures. The electrical conductivity of 1 wt% Fe₃O₄ coated c-MWCNT/PANI nanocomposites at room temperature is 37.7 S/cm, which is decreased to 28.6 S/cm with the loading of 5 wt% Fe₃O₄ nanoparticles. The magnetic properties of Fe₃O₄ coated c-MWCNT/PANI nanocomposites exhibit supermagnetism with saturation magnetization in the range of 0.04–0.15 emu/g, which increases as the amount of Fe₃O₄ nanoparticles increases.