The magnetic properties of copper ferrite (CuFe2O4) nanoparticles prepared via sol–gel auto combustion and facile solvothermal method are studied focusing on the effect of nanoparticle arrangement. Randomly oriented CuFe2O4 nanoparticles (NP) are obtained from the sol–gel auto combustion method, while the solvothermal method allows us to prepare iso-oriented uniform spherical ensembles of CuFe2O4 nanoparticles (NS). X-ray diffractometry (XRD), atomic absorption spectroscopy (AAS), infra-red (IR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), 57Fe Mossbauer spectroscopy and vibrating sample magnetometer (VSM) are used to investigate the composition, microstructure and magnetic properties of as-prepared ferrite nanoparticles. The field-dependent magnetization measurement for the NS sample at low temperature exhibits a step-like rectangular hysteresis loop (MR/MS ∼ 1), suggesting cubic anisotropy in the system, whereas for the NP sample, typical features of uniaxial anisotropy (MR/MS ∼ 0.5) are observed. The coercive field (HC) for the NS sample shows anomalous temperature dependence, which is correlated with the variation of effective anisotropy (KE) of the system. A high-temperature enhancement of HC and KE for the NS sample coincides with a strong spin–orbit coupling in the sample as evidenced by significant modification of Cu/Fe–O bond distances. The spherical arrangement of nanocrystals at mesoscopic scale provokes a high degree of alignment of the magnetic easy axis along the applied field leading to a step-like rectangular hysteresis loop. A detailed study on the temperature dependence of magnetic anisotropy of the system is carried out, emphasizing the influence of the formation of spherical iso-oriented assemblies.

Influence of spherical assembly of copper ferrite nanoparticles on magnetic properties: orientation of magnetic easy axis

Manganese–nickel ferrites powder with general formula MnxNi1−xFe2O4 (x = 0.0, 0.2, 0.4) were synthesized through oxalate precursor route and sintered at 1000 °C. The X-ray diffraction (XRD) patterns were measured for the prepared samples to confirm the existence of single-phase structure. The crystallite size was estimated and found to be within the range 125–170 nm. To study the radiation effect on the structure and magnetic properties, a representative group of the investigated samples were irradiated by γ-rays of 60Co source with a dose of 310 kGy. The XRD spectra were performed for the irradiated samples and compared with that of the pristine samples to estimate changes in the structure. The obtained results showed that the crystallite size increased by a factor of 10–16% after gamma irradiation. The lattice parameter also was increased due to the conversion of Fe3+ (0.64 A) to Fe2+ (0.76 A). The formula of the cation distribution of the ferrites samples was suggested at x = 0, 0.2, 0.4 before and after irradiation. The theoretical lattice parameter, sample density and porosity were calculated and compared with that obtained from the experimental data. Good agreement was found between theoretical and experimental structural data which confirms the proposed formula of cations distribution. The hysteresis curves were measured using vibrating sample magnetometer (VSM) for the unirradiated and irradiated samples and the saturation magnetization was estimated. The obtained results showed increase in saturation magnetizations (Ms) for all the samples by irradiation due to redistribution of the cations between A and B sites and changing the net magnetic moments. Theoretical calculation of magnetic moments and saturation magnetization using the proposed cations distribution of A and B sites confirmed the experimental results. The positron annihilation lifetime spectroscopy (PALS) was used to investigate the defects and changes in electron density after irradiation. The PAL parameters (τ1, I1, τ2, I2 and mean lifetime) show that the irradiation affects the size and concentration of the vacant type defects. The results reveal that there are some large voids (with radius ranged from 0.28 to 0.38 nm and mean value of 0.34 ± 0.04 nm in the studied samples). The obtained results indicate the high sensitivity of PALS technique to the enhanced structure changes due to gamma rays irradiation.

Effect of γ-rays irradiation on Mn–Ni ferrites: Structure, magnetic properties and positron annihilation studies

A solvothermal method was used to prepare zinc ferrite spinel oxide (ZnFe2O4) using ethylene glycol and 1,4 butanediol as solvent diols, and the influence of diols on the physical properties of ZnFe2O4 particles was investigated. The produced particles were characterized by X-ray powder diffraction (XRD), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and nitrogen adsorption isotherms, and the catalytic activity for the organic pollutant decomposition by heterogeneous photo-Fenton reaction was investigated. Both solvents produced particles with cubic spinel structure. Microporous and mesoporous structures were obtained when ethylene glycol and 1,4 butanediol were used as diols, respectively. A higher pore volume and surface area, as well as a higher catalytic activity for the pollutant degradation were found when 1,4 butanediol was used as solvent.

https://www.mdpi.com/1996-1944/7/9/6281/pdf

Effects of Solvent Diols on the Synthesis of ZnFe2O4 Particles and Their Use as Heterogeneous Photo-Fenton Catalysts

MnZnFe2O4 ferrite was successfully synthesized using metallic chlorides and polyvinylpyrolidone, by Co-precipitate method. Deferent concentrations of PVP (0.1, 0.3, 0.5, 0.7, and 0.9) wt%, were used as capping agent to stabilize the particles and prevent them from agglomeration. The PVP content had a vital influence on enhancing the properties of the ferrite nanoparticles. From X-ray data the degree of crystallinity and the Lattice constants (a) of the nanoparticles increased from (8.92 nm) and (8.344 A) to (19.94 nm) and (8.395 A) respectively with increasing PVP concentrations. The morphology and average particle size of the MnZn ferrite nanoparticles were evaluated by scanning electron microscopy (SEM), the values were in a good agreement with the XRD results. Fourier transform infrared spectroscopy (FT-IR) confirmed the cubic structure with octahedral and tetrahedral, also indicated the formation of bond between PVP and surface of metallic hydroxide of ferrite nanoparticles. Vibrating sample magnetometer (VSM) analysis was performed for all samples at room temperature, results showed that the specimens exhibited a paramagnetic behavior in the absence of PVP while in the presence of PVP they have super paramagnetic characteristics. The values of saturation magnetization (Ms) (1.78–17.67 emu/g), remnant magnetization (Mr) (0.0022–0.0696 emu/g) also increased with increasing pvp concentration. Polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites were used it alone or as a combination therapy with NIR laser, and alternating magnetic field (AMF) as anti-proliferative agent against breast cancer cell lines AMJ-13, MCF-7,and ovarian cancer cell line SKOV-3 as well as against normal cell line HBL. While, its capability to induce apoptosis was detected using different techniques which is acridine orange/ethidium bromide (AO/EtBr) staining and mitochondrial membrane potential (MMP), and flow cytometry assay membrane potential (MMP). q-PCR was used to investigate the changes in the expression of P53 gene. The influence of Polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites in viability of breast and ovarian cancer cells alone or when they used as a combination therapy with laser photo-thermal therapy and alternating magnetic field (AMF) was also tested using MTT assay. Our results in the present study demonstrated that the inhibition activity of Polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites against treated cancer cell lines increased when Polyvinylpyrrolidone loaded-MnZnFe2O4 nanocomposites used with NIR laser, while highly increased cytotoxic activities were observed after exposure of Polyvinylpyrrolidone loaded-MnZnFe2O4 nanocomposites to induction heating with AMF. Treated cancer cells with polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites significantly increased ROS synthesis, with subsequent reduction of the MMP. The results of the current study show that tested compounds suppressed cancers cells’ proliferation and has a growth inhibitory effect on different cancer cells, resulting in apoptosis as a novel pathway that involves mitochondrial damage mechanism via activated P53. Taken together the present data suggest that the Polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites could be promising therapy protocol for cancer cells.

Polyvinylpyrrolidone Loaded-MnZnFe2O4 Magnetic Nanocomposites Induce Apoptosis in Cancer Cells Through Mitochondrial Damage and P53 Pathway

Co and Zn ferrites with general formula CO1-XZnXFe2O4 (x = 0; 0,2 and 0,8) were synthesized by combustion reaction method, using urea as fuel. The structure of inverse-spinel-type ferrite were characterized through XRD using Rietveld refinement method to identify, quantify phases and determine lattice parameters. The crystallites had mean size of 37,33 nm, 43,66 nm and 51.88 nm with the increment of Zn2+, respectively. Samples were sintered in a resistive oven at 900 °C for 3 hours. Analysis by SEM indicated that the particles have irregular sizes and high concentration of open pores. The magnetic properties were measured using a vibrating sample magnetometer (VSM), through which a decrease in the magnetization variation was observed as the non-magnetic Zn2+ concentration increases. The permittivity and loss tangent were determined using vector network analyzer equipment, permittivity increases with the increase of zinc concentration and the tangent loss measurements were small for all ferrites synthesized in this work.

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Tunable Magnetic and Electrical Properties of Cobalt and Zinc Ferrites CO1-XZnXFe2O4 Synthesized by Combustion Route

powder under open air. Formation of both normal and inverse spinel ferrite phases was noticed after 30 minutes and 2.5 hours ball milling respectively and the content of inverse spinel phase increased with increasing milling time. The phase transformation kinetics towards formation of ferrite phases and microstructure characterization of ball milled ZnFe

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Microstructural Changes and Effect of Variation of Lattice Strain on Positron Annihilation Lifetime Parameters of Zinc Ferrite Nanocomposites Prepared by High Enegy Ball-milling

Dipankar Das

Papers

Microstructural Changes and Effect of Variation of Lattice Strain on Positron Annihilation Lifetime Parameters of Zinc Ferrite Nanocomposites Prepared by High Enegy Ball-milling