Hyperthermic and Relaxometric Properties of Cobalt Ferrite Nanoparticles (original) (raw)
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Nanoscale, 2016
The possibility to finely control nanostructured cubic ferrites (M II Fe 2 O 4) paves the way to design materials with the desired magnetic properties for specific applications. However, the strict and complex interrelation among the chemical composition, size, polydispersity, shape and surface coating renders their correlation with the magnetic properties not trivial to predict. In this context, this work aims to discuss the magnetic properties and the heating abilities of Zn-substituted cobalt ferrite nanoparticles with different zinc contents (Zn x Co 1−x Fe 2 O 4 with 0 < x < 0.6), specifically prepared with similar particle sizes (∼7 nm) and size distributions having the crystallite size (∼6 nm) and capping agent amount of 15%. All samples have high saturation magnetisation (M s) values at 5 K (>100 emu g −1). The increase in the zinc content up to x = 0.46 in the structure has resulted in an increase of the saturation magnetisation (M s) at 5 K. High M s values have also been revealed at room temperature (∼90 emu g −1) for both CoFe 2 O 4 and Zn 0.30 Co 0.70 Fe 2 O 4 samples and their heating ability has been tested. Despite a similar saturation magnetisation, the specific absorption rate value for the cobalt ferrite is three times higher than the Zn-substituted one. DC magnetometry results were not sufficient to justify these data, the experimental conditions of SAR and static measurements being quite different. The synergic combination of DC with AC magnetometry and 57 Fe Mössbauer spectroscopy represents a powerful tool to get new insights into the design of suitable heat mediators for magnetic fluid hyperthermia. † Electronic supplementary information (ESI) available. See
Nanomaterials
Using magnetic nanoparticles for extracorporeal magnetic heating applications in bio-medical technology allows higher external field amplitudes and thereby the utilization of particles with higher coercivities (HC). In this study, we report the synthesis and characterization of high coercivity cobalt ferrite nanoparticles following a wet co-precipitation method. Particles are characterized with magnetometry, X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy (TEM) and calorimetric measurements for the determination of their specific absorption rate (SAR). In the first series, CoxFe3−xO4 particles were synthesized with x = 1 and a structured variation of synthesis conditions, including those of the used atmosphere (O2 or N2). In the second series, particles with x = 0 to 1 were synthesized to study the influence of the cobalt fraction on the resulting magnetic and structural properties. Crystallite sizes of the resulting particles ranged between 10 and 18 nm,...
Pharmaceutics, 2021
The clinical translation of magnetic hyperthermia (MH) needs magnetic nanoparticles (MNPs) with enhanced heating properties and good biocompatibility. Many studies were devoted lately to the increase in the heating power of iron oxide MNPs by doping the magnetite structure with divalent cations. A series of MNPs with variable Zn/Fe molar ratios (between 1/10 and 1/1) were synthesized by using a high-temperature polyol method, and their physical properties were studied with different techniques (Transmission Electron Microscopy, X-ray diffraction, Fourier Transform Infrared Spectroscopy). At low Zn doping (Zn/Fe ratio 1/10), a significant increase in the saturation magnetization (90 e.m.u./g as compared to 83 e.m.u./g for their undoped counterparts) was obtained. The MNPs’ hyperthermia properties were assessed in alternating magnetic fields up to 65 kA/m at a frequency of 355 kHz, revealing specific absorption rates of up to 820 W/g. The Zn ferrite MNPs showed good biocompatibility a...
Tuning the magnetic properties of ferrite nanoparticles by Zn and Co doping
Materials Letters, 2017
This work describes the synthesis of ferrite nanoparticles and the zinc and cobalt doping effect on tuning their magnetic properties. The zinc doping led to formation of a secondary crystalline phase (ZnO), which meant that the Zn and Co individual ions show different physical-chemical affinities for the two types of lattice sites. Zerofield cooling and field cooling curves were elaborated to study the magnetization unblocking process of these nanoparticles. The metal doping effect led to large differences in the magnetization curves. The zinc-doped samples were shown to exhibit classical magnetization unblocking, being superparamagnetic below the room temperature. The cobalt doping increased the blocking temperature to above room temperature. The amount of cobalt did not change the coercive field of the doped samples. The coercive field of zinc-doped samples followed the same trend, but with a much lower value (0.6 kOe) when compared with cobalt-doped samples (18 kOe), showing a great change in magnetic anisotropy. The current synthesis approach offered a facile way to synthesize ferrite nanoparticles with metal doping-tunable magnetic properties by an environmentally friendly and facile sol-gel approach using water as solvent. This finding motivated us to think these ferrite nanoparticles can be attractive for biomedical and/or technological applications, although further studies other than these are still required.
Fizika tverdogo tela, 2023
The results of studies of the properties of co-deposition of magnetic nanoparticles (MNPs) of Co 1−x Znx Fe 2 O 4 spinel ferrites synthesized (at x = 0.0; 0.1; 0.2; 0.4; 0.6) in order to synthesize magnetic particles for biomedical applications. X-ray diffraction (XRD), raman spectra, magnetic measurements and Mossbauer spectroscopy (MS) were used to study the Co 1−x Znx Fe 2 O 4 MNPs. It was found that the synthesized MNPs Cox Zn 1−x Fe 2 O 4 are singlephase. According to the results of XRD measurements, it was found that the average sizes of crystallites are 13 nm for CoFe 2 O 4 (x = 0) and, with an increase in the Zn concentration, they decrease to 7 nm for Co 1−x Znx Fe 2 O 4 (x = 0.6), which is consistent with the Mössbauer data, which showed that the sizes of crystallites vary from 14 to 8 nm. In the raman spectra of the Co 1−x Znx Fe 2 O 4 MNPs in the region of ∼ 620 cm −1 , splitting of the A 1g , line is observed, indicating that the studied particles have an inverse spinel structure. The change in the ratio between intensities of A 1g (1) and A 1g (2) peaks is indicative of a significant redistribution of Co 2+ and Fe 3+ cations between tetrahedral and octahedral positions in Co 1−x Znx Fe 2 O 4 MNPs as the quantity of Zn increases, which is confirmed by the Mössbauer data. It is found that small sizes of MNPs result in a strengthening of the effects of size and an effect of surface on the magnetic structure of the surface layer. The MS analysis has shown that there is a layer on the MNP surface, the magnetic structure of which is different from from the structure of the crystallite volume. With increase in the quantity of Zn ions thickness of this layer increases and at x = 0.6 the particle becomes completely paramagnetic. Mössbauer studies have shown that Co 0.8 Zn 0.2 Fe 2 O 4 (x = 0.2) particles are in the superparamagnetic state and their magnetic blocking temperature is ∼ 315 K, which is the most acceptable for the treatment of cancer by the magnetic hyperthermia method.