Synthesis, characterization and functionalization of nearly mono-disperse copper ferrite Cu_xFe_3-xO₄ nanoparticles

Magnetic nanocrystals are of great interest for a fundamental understanding of nanomagnetism and for their technological applications. Cu _xFe_3-xO₄ nanocrystals (x ≈ 0.32) with sizes ranging between 5 and 7 nm were synthesized starting from Cu(HCOO)₂ and Fe(CO)₅ using oleic acid and oleylamine as surfactants. The nanocrystals were characterized by high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), magnetization studies and Mössbauer spectroscopy. The Cu_xFe_3-xO₄ particles are superparamagnetic at room temperature 300 K with a saturation magnetization of 30.5 emu g^-1. Below their blocking temperature of 60 K, they become ferrimagnetic, and at 5 K they show a coercive field of 122 Oe and a saturation magnetization of 36.1 emu g^-1. The Cu _xFe_3-xO₄ nanoparticles were functionalized using a hydrophilic multifunctional polymeric ligand containing PEG(800) groups and a fluorophore. By virtue of their magnetic properties these nanoparticles may serve as contrast enhancing agents for magnetic resonance imaging (MRI).