Synthesis and Characterization of Rare-Earth Orthoferrite LnFeO3 Nanoparticles for Bioimaging: Synthesis and Characterization of Rare-Earth Orthoferrite LnFeO3 Nanoparticles for Bioimaging

A combination of sol-gel synthesis and thermal decomposition was developed for preparing nanosized, perovskite-type LnFeO(3) (Ln = Eu, Gd, Tb) powders. Perovskite-type powders with crystalline particles of 100 nm average size, as determined by transmission electron microscopy (TEM), could be obtained after a thermal treatment at 800 degrees C. The perovskite nanoparticles (NPs) were further characterized by X-ray powder diffraction and Mossbauer spectroscopy. These were in agreement with the pure perovskite LnFeO(3) structure with the expected Zeeman sextet corresponding to a magnetically ordered phase. Magnetization measurements [M(H)] at 5 K and 300 K showed a behavior that is dominated by antiferromagnetic interactions and weak ferromagnetism in EuFeO3, while for Ln = Gd, Tb, they were dominated by the low ordering temperature Ln magnetic sublattice. The colloidal aqueous NPs suspensions exhibited no significant leaching of free Ln(3+) ions. Their relaxivities define them as potential T-2 MRI contrast agents for further biomedical applications. The NPs showed fast uptake and no cytotoxicity at concentrations below 62.5 mu g/mL with respect to Hela cells.