Speaker
Description
Cobalt-ferrite (CoFe$_2$O$_4$) nanoparticles (NPs) are valued for their strong magnetism, chemical stability, and mechanical strength, making them useful in multiple fields. In biomedicine, they enable targeted drug delivery, hyperthermia cancer treatment, and MRI contrast enhancement. To employ them in various applications, covering their surface with some specific layer is often inevitable. The layer usually facilitates several functions simultaneously. It prevents agglomeration, promotes the stability of the NP dispersion, provides biocompatibility, and enables further modification by a specific ligand.
Using the thermal decomposition method, we have prepared monodispersed CoFe$_2$O$_4$ NPs of average size $12$ nm as documented by transmission electron microscopy, scanning electron microscopy, and X-ray powder diffraction. For their employment in biomedical applications (magnetic hyperthermia), hydrophobic oleic acid (OA) that covers the surface of as-prepared NPs has to be replaced by a hydrophilic ligand. For this purpose, we have exchanged OA with polyacrylic acid (PAA), obtaining excellent stability of the NP dispersion in water (documented by dynamic light scattering). Further experimental methods (X-ray photoelectron spectroscopy, zeta potential measurements) have also reconfirmed the successful ligand exchange process. However, it is known that bonding some ligands may significantly affect the NP surface layer and, consequently, its magnetic performance. In this context, we have examined and compared the magnetic properties of the as-prepared system (CoFe$_2$O$_4\\@$OA) and the system after ligand exchange (CoFe$_2$O$_4\\@$PAA). The analysis of experimental data obtained in the temperature range of $5-300$ K and applied fields up to $5$ T evidenced that replacing OA with PAA has no deleterious impact on the magnetic characteristics of the prepared NPs.
Acknowledgements
This work was supported by the Slovak Research and Development Agency under the contracts No. APVV-20-0512 and VEGA 1/0470/25, by the Slovak Academic Information Agency and by the EU NextGenerationEU through the Recovery and Resilience Plan for Slovakia under project No. 09I03-03-V04-00325.
