Magnetic nanoparticles Tomi Kainuvaara Nanoparticles KE-31.5530 03.05.2011
General • Can be exploited in variety of applications • Magnetism is, to a large extent, a nanoscale phenomenon • Three different types • Ferrite(oxides) NPs are the most explored • Metallic NPs are phyrophoric and reactive to oxidizing agents • Metallic NPs with a shell: higher magnetization and higher stability
Coating • Uncoated MNPs have some limitations • Aggregation, biodegradation, iron oxide NPs get easily oxidized when exposed to air • Surface ligands and surfactants provide stabilizing organic shells • Polymer is the best material for drug delivery • Proteins, silanes and silica
Synthesis • For exampel co-precipitation, thermal decomposition, microemulsion, different gas phase methods, high pressure hydrothermal methods and sol-gel methods • Often fail to provide addition features • Scale-up, toxicity, safety, cost
Properties • Determined by all energy contributions • Critical size • Spin waves • Bloch’s law • Magnetization relaxes when the magnetic field is switched off • Spin-glass behavior, moment flip time • Coercivity
Iron oxides • Most popular magnetic nanoparticle formulations • Magnetite, maghemite and hematite • Magnetite exhibits the strongest magnetism of any tansition metal oxides. • Iron has strong magnetic moment due to four unpaired electrons in its 3d orbitals.
Applications • Data storage • Ferrofluids in sealing • Detection and treatment of cancer • Magnetic hyperthermia • Magnetite and maghemite are by far the most commonly employed materials for biomedical applications • Waste water treatment, catalysts, MRI
References • Vázquez, M., Luna, C., Morales, M.P., Sanz, R., Serna, C.J., Mijangos, C., Magnetic nanoparticles: synthesis, ordering and properties,Phys. B, 354 (2004) 71-79. • Lin, X-M., Samia, A.C.S., Synthesis, assembly and physical properties of magnetic nanoparticles,J. Magn. Magn. Mater., 305 (2006) 100-109. • Chomoucka, J., Drbohlavova, J., Huska, D., Adam, V., Kizek, R., Hubalek, J., Magnetic nanoparticles and targeted drug delivering,Pharmacol. Res., 62 (2010) 144-149. • Yallapu, M.M., Othman, S.F., Curtis, E.T., Gupta, B.K., Jaggi, M., Chauhan, S.C., Multi-functional magnetic nanoparticles for magnetic resonance imaging and cancer therapy, Biomaterials, 32 (2011) 1890-1905. • de Dios, A.S., Díaz-García, M.E., Multifunctional nanoparticles: Analytical prospects,Anal. Chim. Acta, 666 (2010) 1-22. • Teja, A.S., Koh, P-Y., Synthesis, properties, and applications of magnetic iron oxide nanoparticles, Prog. Cryst. GrowthCharact. Mater., 55 (2009) 22-45. • http://en.wikipedia.org/wiki/Magnetic_nanoparticles,taken29.04.2011.