Saturation of Specific Absorption Rate for Soft and Hard Spinel Ferrite Nanoparticles Synthesized by Polyol Process

Abstract

Spinel ferrite nanoparticles represent a class of magnetic nanoparticles (MNPs) with enormous potential in magnetic hyperthermia. In this study, we investigated the magnetic and heating properties of spinel soft NiFe2O4, MnFe2O4, and hard CoFe2O4 MNPs of comparable sizes (12–14 nm) synthesized by the polyol method. Similar to the hard ferrite, which predominantly is ferromagnetic at room temperature, the soft ferrite MNPs display a non-negligible coercivity (9–11 kA/m) arising from the strong interparticle interactions. The heating capabilities of ferrite MNPs were evaluated in aqueous media at concentrations between 4 and 1 mg/mL under alternating magnetic fields (AMF) amplitude from 5 to 65 kA/m at a constant frequency of 355 kHz. The hyperthermia data revealed that the SAR values deviate from the quadratic dependence on the AMF amplitude in all three cases in disagreement with the Linear Response Theory. Instead, the SAR values display a sigmoidal dependence on the AMF amplitude, with a maximum heating performance measured for the cobalt ferrites (1780 W/gFe+Co), followed by the manganese ferrites (835 W/gFe+Mn), while the nickel ferrites (540 W/gFe+Ni) present the lowest values of SAR. The heating performances of the ferrites are in agreement with their values of coercivity and saturation magnetization.

The Effect of Zn-Substitution on the Morphological, Magnetic, Cytotoxic, and In Vitro Hyperthermia Properties of Polyhedral Ferrite Magnetic Nanoparticles

“…According to magnetic characterization, the ZnF01 particles are, at RT, in a ferromagnetic state with a H c of 18 mT (14.3 kA/m). Therefore, the typical evolution of SAR values with H presents a sigmoidal shape that can be fitted phenomenologically with a simple logistic function (Section S7, Table S3), as shown in our previous papers [23,45,47]. In other words, the main contribution to SAR is given by the energy losses quantified by the area of the dynamic hysteresis loops.…”

“…In this context, the substitution of Fe 2+ (d 6 ) cations in B sites with Mn 2+ (d 5 ) cations, bearing a larger magnetic moment of 5µ B per formula unit due to their five unpaired valence electrons, led to an increase of the saturation magnetization (M s ) of ferrite particles and thus to an enhancement of their heating capabilities [17][18][19][20][21]. The replacement of Fe 2+ (d 6 ) cations in B sites by more anisotropic Co 2+ (d 7 ) cations, conducted to ferrite particles with larger coercivity values and a wider hysteresis loop, which improved considerably the production of heat under AMF [22][23][24][25]. A particular different situation is offered by the diamagnetic Zn 2+ (d 10 ) cations once incorporated in the spinel structure, as they can produce significant enhancement of the ferrite particle s magnetic moment, compared to pure Fe 3 O 4 [26][27][28].…”

Sonophotocatalytic Degradation of Malachite Green by Nanocrystalline Chitosan-Ascorbic Acid@NiFe2O4 Spinel Ferrite

“…Because the NIFE Depending on the different synthesis protocol, such as the sol gel, combustion, and coprecipitation methods, the values of saturation magnetization (m s ) of NIFE MNPs vary [42]. Following the coprecipitation method, the reported saturation magnetization values of bulk NIFE MNPs in the literature were found to be 50 emu•g −1 [43], 44.22 emu•g −1 [44], and 47.4 emu•g −1 [45]. From the M-H curve of CTAS@NIFE given in Figure 5, the m s value was found to be 43.57 emu g −1 .…”

Heating ability of elongated magnetic nanoparticles

“…The use of such assemblies can significantly reduce the concentration of magnetic nanoparticles introduced into the tumor to obtain a positive therapeutic effect. In recent years, a significant amount of works [5][6][7][8][9][10][11][12][13][14][15][16][17] have been devoted to the creation of various assemblies of magnetic nanoparticles suitable for magnetic hyperthermia. Basically, iron oxide nanoparticles were studied [5][6][7][8][9][10] because of their low toxicity and high saturation magnetization, although nanoparticles of other chemical compositions, such as metallic iron nanoparticles [11][12][13], and various ferrites [14][15][16][17] were also examined.…”