MAGNETIC PROPERTIES AND SIZE DISTRIBUTION OF MAGNETITE NANOPARTICLES COVERED BY OLEIC ACID

The particle size and particle size distribution are very important to biomedical applications because the uptake of nanoparticles is strongly dependent on particle size. Oleic acid coated magnetite nanoparticles were synthesized by using chemical co-precipitation. The average particle size and particle size distribution measured by different techniques are compared. The crystallite sizes estimated by X-Ray Diffraction (9.32 nm) and the average particle size calculated by Transmission Electron Microscopy (9.46 nm) are very similar. Atomic Force Microscopy revealed an average diameter of 1030 nm, which is bigger than estimated by other techniques due to the oleic acid layer covering the nanoparticles. The distribution of magnetic sizes of nanoparticles was also estimated through the magnetic response of the system, using the Langevin model (9.11 nm). Anisotropy constant (K-a = 4.74 * 10(5) erg/cm(3)) and blocking temperature (< T-B > = 118 K) were obtained.