Authors: L. Radu, D. Caruntu, M. White, J. Wiley, C.J. O’Connor and P. Hanson
Affilation: University of New Orleans, United States
Pages: 279 - 282
Keywords: paramagnetic, nanoparticle, super paramagnetic resonance
Currently, there is an increasing interest in using magnetite nanoparticles in biological and medical applications. The interest is driven by a combination of their biocompatibility, chemical stability and magnetic properties. Magnetite nanoparticles with diameter 10 – 12 nm were studied by super paramagnetic resonance at X-band frequencies (9.8 GHz). The particles were studied in a variety of solvents and with various surface modifications by ligands such as polypeptides and proteins. The characteristic lines and lineshapes of Fe(2+) and Fe(3+) highlight the sensitivity of the technique to ligand-dependent changes in the coordination sphere at the surface of the particles. For example, studies of the magnetite nanoparticles in methanol solutions at temperatures from 150 K to 320 K showed that the EPR linewidth values are almost linearly temperature dependent. This data details the transition from superparamagnetic to ferromagnetic behavior to reveal the blocking temperature of the particles. Similarly, lineshape parameters relating to the anisotropy and crystal structure (?Beff, geff, A) revealed a ligand-dependent SPR spectrum as well as information about the chemical environment around the Fe(2+) and Fe(3+) cations.