The preparation of polypyrrole–Fe 3O 4 nanocomposites by the use of common ion effect

Abstract

Fe 3O 4 nanoparticles were successfully disposed with FeCl 3 solution to prevent their aggregation in the solution by the application of common ion effect principle. A large amount of Fe 3+ was absorbed onto the surface of the Fe 3O 4 nanoparticles and formed positively charged (Fe 3+) shell. Consequently, the surface of the Fe 3O 4 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 Fe 3O 4 nanoparticles treated with FeCl 3 solution were encapsulated by polypyrrole (PPy) matrix, and the dispersion of the resulting Fe 3O 4 nanoparticles was more stable than that of the control sample without FeCl 3 treatment. This kind of Fe 3O 4 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–Fe 3O 4 composites was higher than that of pure PPy, and went on increasing as the Fe 3O 4 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.