Influence of aggregation on magnetic and optical properties of CoFe2O4 superparamagnetic nanoparticles

Magnetic nanoparticles (MNP) attract persist attention due to their unique magnetic, electrical, catalytic and optical properties, which in the most cases differ from the properties of the bulk material [1]. Superparamagnetism... [ view full abstract ]

Magnetic nanoparticles (MNP) attract persist attention due to their unique magnetic, electrical, catalytic and optical properties, which in the most cases differ from the properties of the bulk material [1]. Superparamagnetism is one of extremely important MNP property for their application in biomedicine. The absence of remanence after elimination of the external magnetic field decrease probability of MNP aggregation that makes superparamagnetic MNPs a perfect candidate for drug delivery using blood flows without dangerous of obstruction of vessels. The drawback of using MNPs is that isolated MNPs are weakly magnetized, in contrast to the aggregated MNPs. Therefore control of MNP aggregation with keeping their supperparamagnetic properties is an emerging challenge in drug delivery area [2].

In present work, we investigated magnetic and optical properties of both isolated and aggregated superparamagnetic CoFe₂O₄ nanoparticles synthesized by the co-precipitation method and coated by chiral ligands. We applied magnetic circular dichroism (MCD) spectroscopy to probe the magnetic, optical and structural properties of MNPs. Analysis of transitions in the MCD spectra of single MNPs shows that Co²⁺ ions occupied both tetrahedral and octahedral cites. Also it was found that all MCD band intensities dependence on applied magnetic field is proportional to MNP magnetization curve. MNP aggregation leads to changing MCD signal intensity as well. Correlation between MCD band intensity and MNP magnetization allowed making assumptions about an influence of aggregation on MNP magnetic properties.

[1] Owens, F. J., Physics of magnetic nanostructures. John Wiley & Sons: 2015.

[2] Amiri, S.; Shokrollahi, H., The role of cobalt ferrite magnetic nanoparticles in medical science. Materials Science and Engineering: C 2013, 33 (1), 1-8.