Size dependent heating efficiency of multicore iron oxide particles in low-power alternating magnetic fields

Aggregates of superparamagnetic nanoparticles, so called multicore particles get much attention due to collective magnetic behaviour. Despite the fact that saturation magnetization and coercivity of multicore particles are lower than for single particles of comparable size, they can generate large amount of heat in alternating magnetic field. This makes them promising for magnetic hyperthermia. However, correlation between internal magnetic structure of multicore particles and their heating ability in alternating magnetic fields are not clear yet. Detailed experimental investigations are required to determine the optimal sizes of multicore particles and the alternating magnetic field parameters to obtain maximal heat. In this study, we demonstrated how hydrodynamic size of multicore particles influences alternating magnetic field energy absorption. Dense aggregates composed of bare magnetic iron oxide nanoparticles of 13 nm were obtained by coprecipitation. Further peptization allowed to gain aqueous dispersions of multicore particles with various hydrodynamic size, varing from 85 to 170 nm, due to electrostatic stabilization. Multicore particles dispersions have saturation magnetization of 40 A m(2)/kg(Fe3O4) and coercivity of 79.6 A/m regardless of their size. Dispersion of 85 nm multicore particles is stable and provides specific loss power of 42 W/g(Fe). Further increase of hydrodynamic size leads to low stability and loss of the ability to generate heat in alternating magnetic field.Ministry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504