Preparation of polypyrrole-Fe3O4 nanocomposites by the use of common ion effect

Fe3O4 nanoparticles were successfully disposed with FeCl3 solution to prevent their aggregation in the solution by the application of common ion effect principle. A large amount of Fe3+ was absorbed onto the surface of the Fe3O4 nanoparticles and formed positively charged (Fe3+) shell. Consequently, the surface of the Fe3O4 nanoparticles became the active site to polymerize pyrrole monomers. The obtained composites were then characterized by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The TEM photos indicated that Fe3O4 nanoparticles treated with FeCl3 solution were encapsulated by polypyrrole (PPy) matrix, and the dispersion of the resulting Fe3O4 nanoparticles was more stable than that of the control sample without FeCl3 treatment. This kind of Fe3O4 nanoparticles was a stable composite system, and the thickness of PPy layer was about 10 nm. The formed composites showed unique electrical and magnetic behavior. The room temperature conductivity of PPy-Fe3O4 composites was higher than that of pure PPy, and went on increasing as the Fe3O4 content in the composites elevated, reaching a maximum at about 11.36 S cm(-1). The saturated magnetization (M-s = 6.89-16.98 emu g(-1)) also increased linearly with the Fe content in the composites, however, the coercive force (H-c) was very low (H-c = 5-12 Oe). As a result, the obtained composites by this method were suitable for the preparation of soft magnetic material. (C) 2003 Elsevier Science B.V. All rights reserved.