Structural and magnetic characterization of nanosized gamma-iron oxide particles precipitated in polymer matrices

The synthesis, characterization and application of magnetic nanoparticles have been receiving much attention in recent years due to their potential technological and biomedical applications. In particular, nanosized gamma-Fe 2O3 particles are considered as one of the most desirable material for biomedical applications especially for targeted drug delivery.; Nanosized gamma-Fe2O3 particles have been synthesized in polystyrene resin and alginate biopolymer matrices by employing the methods used by Ziolo et al. and Kroll et al. Aqueous solutions of FeCl2, FeCl3 and mixtures of FeCl2 and FeCl3 were ion exchanged repeatedly with polymer matrices to prepare nanosized gamma-Fe 2O3 particles. The samples have been characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Mossbauer Spectroscopy (MS), and Superconducting Quantum Interference Device SQUID magnetometry. The XRD is used to identify the iron oxide phase present and to find the particle size. TEM images were used to find the particle morphology and the size distribution. The particle size distribution was found to depend on the number of loadings and the type of cations, Fe(II) and Fe(III), used in the starting solutions in the synthesis process for the particles precipitated in resin. No such dependence was observed for the particles in alginate. By increasing the number of loadings, particle size, amount of iron, saturation magnetization and other magnetic properties of gamma-Fe2O3 nanoparticles can be influenced.; Mossbauer spectroscopy studies have confirmed that Fe exists only as Fe(III) ions in both resin and alginate nanocomposites, and the phase present is that of gamma-Fe2O3. The zero-field-cooled and field-cooled magnetic measurements using SQUID magnetometry showed a superparamagnetic behavior of these nanocomposites. The data were analyzed to determine the blocking temperature distribution (log-normal). In general, polymers loaded with Fe(II) ions showed bigger size particles with a wider size distribution. Above the blocking temperature, the M-H curves were fitted to a modified Langevin function to find the particle size distribution. The average particle size was found to be somewhat larger than the values found from XRD and TEM measurements indicating possible inter particle dipolar interaction. Below the blocking temperature, the temperature dependence of coercivity is not consistent with the T1/2 behavior as predicted by Neel and Brown for a non-interacting particles system. Further, the saturation magnetization value was also found to be lower than that for bulk gamma-Fe2O 3. The role of the resin and alginate matrices and the effect of inter- and intra-particle interactions need to be further investigated.