Search

A vertical rod structure of Sn substituted Ni ferrite nanoparticles prepared by chemical co-precipitation method. From powder XRD results affirm that material has cubic structure with particle size range is 5–50 nm. Also, particle size is improved with increase of concentration. The SEM microstructure shows vertical rod structure and then fine powder nature even as increase of concentration. In addition, TEM microstructure revealed the particle size and it is matched with XRD results. The obtained dielectric result shows that material has low dielectric constant and loss with increase of concentration and sintering temperature. It is happened due to decrease of Fe 2+ ions at octahedral sites. The VSM analyses show that saturation and remnant magnetization are increased with respect to concentration. Also, the coercivity is decreased. These effects enhance soft magnetic nature. [ABSTRACT FROM AUTHOR]

Co-precipitated and 800 °C heat treated Ni-Cu-Zn nanoferrites with chemical formula Ni x Cu 0.1 Zn 0.9- x Fe 2 O 4 ( x =0.5, 0.6, 0.7) were prepared because of their potential use as multilayer chip inductors in electromagnetic applications. Their structural, magnetic properties and phase formation were studied using X-ray diffractometer (XRD), field emission scanning electron microscope (FE–SEM), vibrating sample magnetometer (VSM), Mössbauer spectrometer, thermogravimetric analyzer (TGA) and differential scanning calorimeter (DSC). The XRD patterns confirm the cubic spinel structure of the ferrite phase belonging to Fd3m space group. Lattice parameters and cation distributions were obtained by Rietveld refinement of the XRD patterns. The lattice parameter decreases with increase in Ni 2+ ion concentration. Rietveld analysis indicates that Cu 2+ ions predominantly occupy the B -sites and Ni 2+ ions partly going into B -sites but predominantly into A -sites. An excellent agreement is observed between the experimental lattice parameters and lattice parameters theoretically calculated using this cation redistribution. The inversion parameter (λ) observed for Fe 3+ ions by Mössbauer spectroscopy is different from that of Rietveld analysis. Magnetization and Mössbauer spectroscopic measurements indicate that the ferrite nanoparticles are mostly superparamagnetic. The cation redistribution is supposed to alter the magnetocrystalline anisotropy which in turn affects the magnetic parameters of the present ferrite samples. The reduced magnetization is attributed to core-shell interactions and possible canting of A - and B -shell magnetizations. TGA-DSC studies indicate that ferrite formation in the 800 °C heat treated samples is completed but grain growth increases as the particles are subject to the increased temperature. [ABSTRACT FROM AUTHOR]

Ferrite material nanoparticles comprised of manganese and zinc were chemically synthesized by the co-precipitation method. The designated ferrite X-ray diffraction peaks and characteristic ferrite absorption bands in Fourier transform infrared absorption spectra confirmed the formation of a spinel structure. Determination of the full width at half maximum values of the X-ray diffraction peaks and the corresponding calculations using the Scherrer formula suggested the generation of nano-grains. Micrographs obtained using a transmission electron microscope confirmed the nano-scale dimensions of the particles. Deviations in the characteristic resistivity and thermopower values in response to ambient sample temperature variations were experimentally observed and used for correlation-derived temperature-dependent transport behaviour analysis. Samples with a concentration x = 0.8 and 1.0 showed high thermopower values at reasonably low temperatures with moderate specific resistance. [ABSTRACT FROM AUTHOR]

CoFe 2 O 4 and MnFe 2 O 4 nanoparticles were obtained by hydrothermal synthesis method in aqueous and in gelatinous media, at 175 °C and 230 °C. The structural, morphological and magnetic characterization of all samples was performed using different techniques: XRD, SEM, TEM, SQUID magnetometry and 57 Fe Mössbauer spectroscopy. Their ability to be used as nanoheaters for magnetic hyperthermia applications was evaluated by determining their heating efficiency in aqueous suspension. The mean size of the CoFe 2 O 4 nanoparticles ranges from 4.2 to 6.7 nm, while larger nanoparticles with broader distributions were obtained for the MnFe 2 O 4 nanoparticles (from 4.4 to 17 nm). It was shown that both the temperature of the thermal treatment and the medium influence the mean size and size distribution of the nanoparticles, with the gelatin-assisted synthesis method producing nanoparticles with the highest specific heating ability. MnFe 2 O 4 nanoparticles synthesized at 175 °C in gelatine medium display one of the best reported heating efficiency for manganese ferrite with values comparable to those of commercial magnetic nanoparticles. [ABSTRACT FROM AUTHOR]

An array comprised of four magnonic gas sensors based on magnetic nanoparticles layers of CuFe 2 O 4 , MnFe 2 O 4 , ZnFe 2 O 4 and CoFe 2 O 4 was developed and tested with dymethylformamide, isopropanol, xylene and toluene. Magnonic gas sensors were composed of an yttrium iron garnet (YIG) epitaxial thin film as a magnetostatic spin waveguide combined with a spin-coated layer of magnetic nanoparticles as a sensitive layer. The magnetostatic spin waves (MSW) were very sensitive to perturbations produced in the magnetic properties of the nanoparticle layers due to interaction with gases, allowing the detection of low concentrations of gases. Finally, the sensitive layers of the magnetic nanoparticles revealed a differentiated response in regard to the gases used to test the array. Therefore, the gases could be discriminated and classified using pattern recognition techniques, such as principal component analysis and artificial neural networks. [ABSTRACT FROM AUTHOR]

Sn substituted Cu ferrite nanoparticles were synthesized (x=0.04, 0.06) by chemical co-precipitation method. The prepared samples were sintered at 300 °C, 600 °C, 900 °C. From XRD analyses the particle size increased due to sintering temperature. The lattice parameter decreased while increasing the concentration of Sn elements and sintering temperature. From SAED pattern of TEM results, the superimposition of bright spots confirms the polycrystalline nature. FT-IR results show the octahedral and tetrahedral stretching sites respectively. The remarkable change of dielectric constant and loss was found to be in the range of 100 KHZ- 700 MHZ. [ABSTRACT FROM AUTHOR]

Ferrite nanoparticles (FeO) have been produced by the direct low-pressure plasma-chemical synthesis. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), vibration magnetometry (VSM), and Mössbauer spectroscopy (NGR) were used for measurements, showing that the produced nanoparticles have an average size of 9.4 nm, a crystalline phase of magnetite, possess a property of superparamagnetism at room temperature, and have a blocking temperature of 89 K. The peculiarities of nanoparticle behavior in the magnetic field, related to a large specific surface area, are discussed. [ABSTRACT FROM AUTHOR]

Mg, Ca, Mn, Co, Ni, Cu, Zn, Mn-Zn, and Co-Zn metal ferrite and mixed metal ferrite nanoparticles were synthesized by co-precipitation method and were characterized by using transmission electron microscopy, X-ray diffraction, and nitrogen adsorption techniques. Transmission electron microscopy data indicated the formation of metal ferrite and mixed metal ferrite nanoparticles with particle sizes varying from 2 to 88 nm. X-ray diffraction data indicated the formation of metal ferrite and mixed metal ferrite nanoparticles with spinel phase. The metal ferrite nanoparticles were found to be mesoporous and exhibited surface area values in the range of 62–257 m 2 /g. The ferrite nanoparticles were used in decontaminating sulfur mustard and the reactions exhibited first order behavior. Out of them, Ni, Zn, and Co-Zn ferrite nanoparticles showed greater decontamination efficiency in comparison to other ferrite nanoparticles. While Ni, Zn, and Co-Zn ferrite nanoparticles decontaminated 99.99% of sulfur mustard within 10 h other ferrite nanoparticles took about 16 h to degrade the same. The metal ferrite and mixed metal ferrite nanoparticles degraded toxic sulfur mustard into relatively non toxic products like chloro ethyl vinyl sulfide, hydroxy ethyl vinyl sulfide, hemisulfur mustard, and 1,4-oxathiane. The promising decontamination properties of metal ferrite nanoparticles against sulfur mustard were attributed to the basic sites, Lewis acid sites, and the presence of these sites was confirmed by CO 2 and NH 3 temperature programmed desorption. [ABSTRACT FROM AUTHOR]

Two tandem oxidative two-component reactions (O-2CRs) and Ugi-type (OU-3CRs) of of petroleum naphtha have been investigated for the synthesis of 2-phenyl-1 H-benzo [ d]imidazole, 2-aryl-4-quinazolinone and 3,4-dihydroquinoxalin-2-amine derivatives using six new biopolymer-supported ferrite nanocatalysts: CoFe2O4@wool-SO3H, MnFe2O4@wool-SO3H, ZnFe2O4@wool-SO3H, MnCoFe2O4@wool-SO3H, ZnCoFe2O4@wool-SO3H and CrCoFeO4@wool-SO3H. The best results are obtained with the CrCoFeO4@wool-SO3H catalyst. All of the catalysts were characterized using flame atomic , X-ray diffraction, thermogravimetric analysis, scanning and energy-dispersive spectroscopy. To the best of our knowledge, this approach can be considered as the first example of O-2CRs and OU-3CRs of of petroleum naphtha with ferrite nanocatalysts, which would be very useful from a practical point of view. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Nanostructured Co 1- x Zn x Fe 2 O 4 (0 ≤ x ≤ 0.5) catalyst synthesized by the microwave combustion method was employed for the photocatalytic degradation of rhodamine B (RhB) under visible light. Doping of Zn 2+ ions in the cobalt ferrite matrices were confirmed by the diffraction peak-shift towards lower angles. The Williamson-Hall method was used to calculate the crystallite size considering the strain components. The conduction band (CB) and valence band (VB) edges of all the samples were calculated using optical studies. Photoluminescence analysis performed at an excitation wavelength of 330 nm disclosed the rate of recombination of electron-hole pairs and the defects present. Photocatalytic degradation of RhB with pure cobalt ferrite system was performed at pH 2.0 by varying the time, initial concentration and addition of hydrogen peroxide to behave like a Fenton like process. However the effective photodegradation of all zinc doped cobalt ferrite were done at optimal RhB concentration of 6 mg/l at identical operational conditions. Among all the samples Co 0.6 Zn 0.4 Fe 2 O 4 exhibited an enhanced degradation efficiency of 99.9% at visible light exposure time of 210 min. The degradation pathway followed first order rate rather than the second order rate kinetics. Based on the values of CB and VB edges in the Co 0.6 Zn 0.4 Fe 2 O 4 system, possible routes for the degradation of RhB are suggested. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new effort to estimate the type of electron density by correlation within the Theoretical and experimental results of the composite material for multifunctional application. • X = 0.2 nano ceramic has a lower crystallite size (10 nm) with good morphology and a larger surface area (114 cm2/g) with an optical bandgap of 2.9 eV (absorption and transmission in the visible region), suggesting that it can be a suitable candidate for visible light active photocatalyst. • X = 0.3 refractive index (n) is equal to 2.4 which can be applied in the field of non-linear optics including thin lens-eyewear applications where a lesser amount of sample material is needed to achieve the favored effect. • X = 0.4 shows lattice energy of 2.73 eV with a higher elastic modulus (R = 158 GPa, B = 476 GPa, Y = 428 GPa) and poison ratio of 0.35 (similar to steel) with an average force constant of 0.4 x10-2N/m which can be utilized in high-frequency electronic noise filter applications including designing and fabricating ferrite core/ beads. • Due to magneto-static interaction, grains with maximum multiple-domains and magnetization are noticed for X = 0.4 which is (0.0058) and Bohr magneton (0.035μB) can be used in self-regulated magnetic hyperthermia and X-Ku (0.8–18 GHz) band frequency range (high frequency) applications. • All prepared multiphase (BaTiO 3) (1-X) + (ZnFe 2 O 4) X magnetic samples are permanent magnets and can also be used for bandgap engineering. Particulate (BaTiO 3) (1-x) + (ZnFe 2 O 4) x (x = 0.1, 0.2, 0.3, 0.4) Nano ceramic composites was synthesized using physical mixing route (<500°). Dual phases of triclinic (BaTiO 3) and cubic (ZnFe 2 O 4) structures were revealed by XRD. The optical and magnetic properties of the ceramic composite were correlated with Structural parameters including crystallite size, stress, micro-strain, unit cell volume, lattice parameters, dislocation, and X-ray density. The concentration of Zinc Ferrite (ZnFe 2 O 4) influences molecular elastic properties that are assessed by FTIR. The Comparison between crystallite and particle size was deliberated using SEM results. The particle size varies from 23 nm to 50 nm. The magnetic hysteresis loop from Vibrating Sample Magnetometry taken at room temperature shows soft and weak ferromagnetic behavior with high magneto static interaction (0.005). As the concentration of Zinc ferrite in Barium Titanate increases, the magnetic saturation varies from 0.744 emu/g to 0.852 emu/g and reaches a maximum of 0.852 emu/g with lowest coercivity value of 13.115 Oe. The overall correlation between physical properties can be used to theoretically estimate the electron density of the prepared composite which is responsible for specific opical and magnetic properties in the composite. [ABSTRACT FROM AUTHOR]

Polycrystalline nanoferrites with chemical formula Mg x Zn 1−x Fe 2 O 4 ( x =0.5, 0.6, 0.7) have been synthesized by co-precipitation technique and then subsequently heated to 800 °C in order to investigate structural, thermal and magnetic properties. The samples are characterized by using XRD, FTIR, TGA-DSC, SQUID and Mössbauer spectroscopy techniques. The synergic effect of heat treatment with substitution of Mg 2+ , results in random variation of lattice parameter ( a ) and crystallite size ( D ). FTIR studies revealed the formation of cubic spinel structure. The broadening at octahedral bands for compositions x =0.6 and 0.7 attributes to distribution of ferrite particles of different sizes in these samples. The characteristic feature of hysteresis loops reflects the nature of ferrite particles in the state of superparamagnetism. The saturation magnetization at room temperature has been reported for composition x =0.7 is 44.03 emu/g. The variation of coercivity is due to variation in magnetic anisotropy which is predominately affected by the exchange interactions arising from the nature of nanoparticles. The blocking temperatures are in the range of 10–30 K and their variation is in the line of change in magnetocrystalline anisotropy but not due to variation in crystallite sizes. The Zeeman splitting at tetrahedral (A) and octahedral (B) sites for composition x =0.6 is expected due to increase in size of core of the nanoparticles/or increasing of magnetocrystalline anisotropy. The range of isomer shift values and quadruple splitting values are evident for the presence of Fe 3+ ions and the absence of Fe 2+ ions in the present systems. The present ferrite nanoparticles in the superparamagnetic state are the potential candidates for biomedical applications like cancer treatment through hyperthermia. The results are interpreted in terms of cation redistribution presuming exchange coupling energy variation on magnetocrystalline anisotropy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Different ferrite nanoparticles were used in the urea biosensor. • The contribution of bandgap values of ferrite nanoparticles was investigated. • Nf/PANI/CuF/Urs biosensor showed high sensitivity and selectivity to urea. • The biosensor displayed urea detection with a detection limit of 0.17 µM. • Nf/PANI/CuF/Urs biosensor was applied to soil and milk samples. A new enzymatic electrochemical biosensor has been developed with the PANI/Nafion composite system containing ferrite nanoparticles with four different transition metals. The ferrite nanoparticles containing copper, cobalt, nickel, and zinc metals were synthesized by the co-precipitation method and their surfaces were modified with tetraethoxysilane and (3-aminopropyl) triethoxysilane to obtain –NH 2 function in order to develop the purposed sensing system. The modified and unmodified ferrite nanoparticles were characterized by physically, chemically, and morphologically. Ferrite nanoparticles with suitable for enzyme immobilization were integrated on the GCE surface and covered with PANI/Nafion. According toelectrochemical measurements, it was determined that copper ferrite nanoparticles, which have the lowest bandgap value, significantly increased the biosensor performance. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to monitor biosensor production and evaluate its performance. A detection limit of 0.17 µM and a wide linear range of 0.5–45.0 µM were obtained for the urea detection with the DPV method with the sensing system (Nf/PANI/CuF/Urs). The biosensor has been successfully applied to soil and milk samples with high accuracy. In addition, it has been determined that the proposed method has good reproducibility, selectivity, and stability. [ABSTRACT FROM AUTHOR]

We report the structural, vibrational, surface composition, and magnetic properties of as-prepared and annealed (600–1200 °C) MFe 2 O 4 (M = Ni, Co) samples to investigate the cation distribution. Rietveld refinement of X-ray diffraction data indicated a spinel structure for all samples. Raman and X-ray photoelectron analyses suggest the presence of an inverse spinel structure in the samples. Furthermore, the mixed valence states (Fe2+, Fe3+, Ni2+/Co2+) of the cations and their occupancies over tetrahedral and octahedral sites have been evaluated. We have noticed a systematic increase in saturation magnetization (M S) (10.7–43.5 emu/g for NiFe 2 O 4 , 36.1–83 emu/g for CoFe 2 O 4) with increasing annealing temperature up to 1000 °C, and then M S slightly decreased for the samples annealed at 1200 °C. Furthermore, the values of coercivity (H C) varied over the ranges 15–125 Oe for NiFe 2 O 4 and 300–1644 Oe for CoFe 2 O 4 , suggesting that these materials are promising candidates for biomedical and high-frequency applications. • Structural and magnetic properties of NiFe 2 O 4 and CoFe 2 O 4 investigated to study the cationic distribution. • Raman analysis revealed the formation of inverse spinel structure in samples. • CFO showed enhanced magnetization (36.1–83 emu/g) compared with NFO (10.7–43.5 emu/g). • XPS revealed the mixed valence states (Fe2+, Fe3+, Ni2+/Co2+) of cations and their occupancies over A- and B-sites. [ABSTRACT FROM AUTHOR]

Spinel type nano-sized ferrite compounds AFe 2 O 4 (A = Co, Mg and Mn) have been successfully prepared by self-propagating combustion method using glycine as fuel at 400 °C under air atmosphere for 4 h. The crystal structure, chemical composition, morphology and magnetic properties of the synthesized samples were characterized by X−ray diffraction, Fourier transform infrared spectroscopy, X−ray photoelectron spectroscopy, Energy dispersive X−ray, Scanning and Transmission electron microscopy and vibrating sample magnetometer. The chemical reaction and role of fuel on the nanoparticles formation were discussed. The XRD pattern of the synthesized samples shows the formation of pure phase with average crystallite size of 97, 57 and 98 nm from Scherrer formula and 86, 54 and 87 nm from Williamson and Hall (W–H) formula respectively. FTIR absorption spectra revealed that the presence of strong absorption peaks near 400–600 cm −1 corresponds to tetrahedral and octahedral complex of spinel ferrites. The relative concentrations of electronic states of elements such as cobalt (Co 2+ and Co 3+ ), iron (Fe 2+ and Fe 3+ ) and manganese (Mn 2+ and Mn 3+ ) oxidation states were studied from XPS and it is found that 55% of Fe ions are in Fe 2+ state and the remaining is in Fe 3+ state and thus the cationic distribution of Fe ions occurred in both tetrahedral and octahedral sites. SEM analysis indicates the presence of pore like morphology which is nearly homogenous because of combustion process. EDS analysis confirms the presence of elements in the ferrite samples. By replacing the active ‘A’ site cations in AFe 2 O 4 (A = Co, Mg and Mn) samples show the different magnetic properties. The parameters like saturation magnetization, coercivity and remnant magnetization obtained from M − H loops are studied in room temperature. [ABSTRACT FROM AUTHOR]

The importance of magnetic interactions within an individual nanoparticle or between adjacent ones is crucial not only for the macroscopic collective magnetic behavior but for the AC magnetic heating efficiency as well. On this concept, single-(MFe 2 O 4 where M=Fe, Co, Mn) and core–shell ferrite nanoparticles consisting of a magnetically softer (MnFe 2 O 4 ) or magnetically harder (CoFe 2 O 4 ) core and a magnetite (Fe 3 O 4 ) shell with an overall size in the 10 nm range were synthesized and studied for their magnetic particle hyperthermia efficiency. Magnetic measurements indicate that the coating of the hard magnetic phase (CoFe 2 O 4 ) by Fe 3 O 4 provides a significant enhancement of hysteresis losses over the corresponding single-phase counterpart response, and thus results in a multiplication of the magnetic hyperthermia efficiency opening a novel pathway for high-performance, magnetic hyperthermia agents. At the same time, the existence of a biocompatible Fe 3 O 4 outer shell, toxicologically renders these systems similar to iron-oxide ones with significantly milder side-effects. [ABSTRACT FROM AUTHOR]

The effect of Zn-Ti substitution on the infrared spectroscopy, elastic, dielectric, and resistivity properties of CoZnTiFeO ferrites (where x= 0.0-0.4 in steps of 0.1) is investigated in the paper. All the samples were synthesized by the sol-gel method. Infrared spectroscopy shows two major absorption bands indicating that the prepared samples are in spinel structure. Elastic properties and dielectric properties are measured at room temperature and Zn-Ti is substitution dependent. The dc resistivity is measured using a two-probe method in the temperature range 300 to 650 K. The dielectric constant decreased whereas dc resistivity increased with the Zn-Ti substitution. The elastic constant decreases with increases in Zn-Ti ions. [ABSTRACT FROM AUTHOR]

Nanocrystalline spinel ferrite was prepared by sol-gel auto-combustion technique and sintered at 600 °C for 12 h. Single-phase cubic spinel structure of zinc ferrite was confirmed through X-ray diffractometry. Several structural and magnetic properties of ZnFeO NPs were studied after Co γ-irradiation with total gamma dose of 50 and 100 kGy. An average crystallite size was determined from the full width at half maximum of strongest reflection (311) by using Scherrer's approximation. Williamson-Hall plot (graph against βcos θ and 4sin θ) was used to re-evaluate the measured crystallite size and to estimate the strain distribution in terms of η%. Lattice constant ( α) initially increased slightly to 8.441 Å with γ-50 kGy and then decreased dramatically with total dose of γ-100 kGy. Frustrated behaviour in peak shift to lower and higher 2 θ side can be seen in XRD after γ-irradiation to ZnFeO NPs. FT-IR spectra confirmed the formation of ferrite phase and redistribution of cations in (A) and [B] sites of ZnFeO spinel structure. In the first derivative peak of ESR spectroscopy, gyroscopic spitting factor ( g-value) and linewidth (∆H) were used to deliberate the γ-radiation damage in investigated ferrimagnetic nanoparticles. Experimental results revealed that the saturation magnetization ( M ), coercivity ( H ) and magneton number ( n ) of ZnFeO NPs were found to be increased after gamma irradiation dose of γ-100 kGy. Graphical Abstract: [ABSTRACT FROM AUTHOR]

We study the magnetic field induced hyperthermia in water based phosphate coated Fe 3 O 4 nanofluids, synthesized by a co-precipitation method using ferrous and ferric salt solutions, ammonia and orthophosphoric acid. The specific absorption rate (SAR) values were measured at a fixed frequency of 126 kHz and at extremely low field amplitudes. The SAR values were determined from the initial rate of temperature rise curves under non-adiabatic conditions. It was observed that the SAR initially increases with sample concentration, attains a maximum at an optimum concentration and beyond which SAR decreases. The decrease in SAR values beyond the optimum concentration was attributed to the enhancement of dipolar interaction and agglomeration of the particles. The system independent intrinsic loss power (ILP) values, obtained by normalizing the SAR values with respect to field amplitude and frequency, were found to vary between 158–125 nHm 2 kg −1 , which were the highest benchmark values reported in the biologically safe experimental limit of 1.03–0.92×10 8 Am −1 s −1 . The very high value of ILP observed in the bio-compatible phosphate coated iron oxide nanofluids may find practical applications for these nanoparticles in tumor targeted hyperthermia treatment. [ABSTRACT FROM AUTHOR]

A series of Ni x Zn 1− x Fe 2 O 4 ( x =0.5, 0.6 and 0.7) ferrite nanoparticles have been synthesized using a co-precipitation technique, in order to understand the doping effect of nickel on their structural and magnetic properties. XRD and FTIR studies reveal the formation of spinel phase of ferrite samples. Substitution of nickel has promoted the growth of crystallite size ( D ), resulting the decrease of lattice strain ( η ). It was also observed that the lattice parameter ( a ) increases with the increase of Ni 2+ ion concentration. All particles exhibit superparamagnetism at room temperature. The hyperfine interaction increases with the increase of nickel substitution, which can be assumed to the decrease of core–shell interactions present in the nanoparticles. The Mössbauer studies witness the existence of Fe 3+ ions and absence of Fe 2+ ions in the present systems. These superparamagnetic nanoparticles are supposed to be potential candidates for biomedical applications. The results are interpreted in terms of microstructure, cation redistribution and possible core–shell interactions. [ABSTRACT FROM AUTHOR]

The application of ferrite magnetic nanoparticles (MNPs) in medicine finds its rapidly developing emphasis on heating mediators for magnetic hyperthermia, the ever-promising “ fourth leg ” of cancer treatment. Usage of MNPs depends largely on the preparation processes to select optimal conditions and effective routes to finely tailor MNPs. Microwave heating, instead of conventional heating offers nanocrystals at significantly enhanced rate and yield. In this work, a facile mass-production microwave hydrothermal synthetic approach was used to synthesize stable ferromagnetic manganese and cobalt ferrite nanoparticles with sizes smaller than 14 nm from metal acetylacetonates in the presence of octadecylamine. Prolonging the reaction time from 15 to 60 min, led to ferrites with improved crystallinity while the sizes are slight increased. The high crystallinity magnetic nanoparticles showed exceptional magnetic heating parameters. In vitro application was performed using the human osteosarcoma cell line Saos-2 incubated with manganese ferrite nanoparticles. Hyperthermia applied in a two cycle process, while AC magnetic field remained on until the upper limit of 45 °C was achieved. The comparative results of the AC hyperthermia efficiency of ferrite nanoparticles in combination with the in vitro study coincide with the magnetic features and their tunability may be further exploited for AC magnetic hyperthermia driven applications. [ABSTRACT FROM AUTHOR]

NiCoFeO nanoparticles with x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5 (named NC0, NC10, NC20, NC30, NC40, and NC50, respectively) were synthesized by wet chemical co-precipitation method. The prepared nanoparticles were crystallized in the cubic spinel structure of space group Fd3m with a narrow size distribution from 13 to 24 nm. The saturation magnetization was strongly influenced with Co concentrations. The cation distribution, the spin canting, and the presence of Fe ions along with Fe ions were responsible for the variation in saturation magnetization. Cation distribution estimated from saturation magnetization suggested the mixed spinel structure of NiCoFeO system. The calculated g values from electron spin resonance spectra were consistent with the variation of saturation magnetization. UV-vis diffuse spectra indicated that NiCoFeO samples were indirect band gap materials and band gap decreased with increasing Co concentration. Dielectric constant and dielectric loss showed frequency-dependent dispersion along with enhancement dielectric constant with increasing Co concentration. The complex impedance analysis confirmed that the conduction process predominantly takes place through grain boundaries. [ABSTRACT FROM AUTHOR]

Ferrites of iron, cobalt, and nickel were used as a non-enzymatic sensor for detection of hydrogen peroxide. X-ray diffraction (XRD) and transmission electron microscopy revealed that the nanoparticles obtained by electrochemical route and varying the parameters synthesis show similar size of around 20 nm and a relation metal/iron equal to 1/2. The effect of pH, temperature, amount of nanoparticles, and potential has been studied to obtain the best sensor properties in terms of sensitivity and linear response. The mechanism has been attributed to the oxidation of Fe, Co, and Ni in the octahedral position of the spinel that enhances the catalytic reduction of hydrogen peroxide. The best sensor has been obtained with magnetite (iron ferrite) with a detection limit of 7.3 × 10 M and a sensitivity of 4.0 × 10 μA/M. The magnetite was also applied to determine hydrogen peroxide in commercial contact lens cleaner Novoxy® with satisfactory results. [ABSTRACT FROM AUTHOR]

In this paper we report the structural, vibration, and electronic-structure parameters (bonding and valence of cations) of single phase cubic mixed spinel nanoparticles of (Zn δ Mn γ Fe 1−( γ + δ ) )[Ni x Zn 0.5− δ Mn 0.5− γ − x Fe 1+( γ + δ ) ]O 4 where x = 0.05–0.45 with an aim to determine cation-distribution i.e. δ and γ in these samples. The Raman spectroscopy has established that only Fe and Zn cations occupy tetrahedral interstitial sites in a FCC anion lattice in nearly equal fraction, and Mössbauer spectra have shown that Fe 3+ cations are present at both, tetrahedral and octahedral interstitial sites and Ni 2+ cations are situated at the octahedral sites in all the substituted samples. The photoelectron spectra also revealed the presence of Fe 3+ cations at both the interstitial sites. The best possible cationic distribution in Ni substituted Mn–Zn ferrites has been estimated by reiteratively calculating the intensity ratios of various pairs of X-ray diffraction peaks and matching with the observed intensity ratios. [ABSTRACT FROM AUTHOR]

We have investigated the critical behavior of Zn 0.6−x Ni x Cu 0.4 Fe 2 O 4 (x = 0, 0.2 and 0.4) ferrite nanoparticles near the ferromagnetic-paramagnetic (FM-PM) phase-transition temperature ( T C ). Experimental results reveal that all samples undergo a second-order phase transition. Through various techniques such as modified Arrott plot, Kouvel-Fisher method and critical isotherm analysis, the estimated critical exponents are close to those expected for three-dimensional Heisenberg class for x = 0 ( β = 0.386 ± 0.002, γ = 1.271 ± 0.012 and δ = 4.387 at T C = 305 K). Whereas for a high amount of Ni, these exponents belong to a different universality class ( β = 0.716 ± 0.063, γ = 0.807 ± 0.008 and δ = 2.010 at T C = 565 K for x = 0.2 sample) and ( β = 0.785 ± 0.004, γ = 0.797 ± 0.002 and δ = 2.061 at T C = 705 K for x = 0.4 sample). This is due to the fact that the substitution of Zn 2+ (non-magnetic ions) by Ni 2+ (magnetic ions) increases the A – B interaction sites of AB 2 O 4 spinel ferrite which in turn increases the magnetic disorder when increasing Ni content. Using the magnetic entropy change equation: | Δ S M m a x | = a ( H ) n , we have studied the relationship between the exponent n and the critical exponents of our samples. The obtained n value are 0.641, 0.843 and 0.873 for x = 0, 0.2 and 0.4, respectively. These values are in good agreement with those deducted from the critical exponents using the KF method. [ABSTRACT FROM AUTHOR]

Co - Zn ferrite nanoparticles have been synthesized using carboxylate- hydrazine precursor via thermal decomposition route. The prepared precursor Co0.8Zn0.2Fe2(PhAc)3(N2H4)3 was characterized by hydrazine, metal analyses, infrared spectral and thermal analyses. Using appropriate annealing conditions, Co0.8Zn0.2Fe2O4 nanoparticles of average size 13 nm were synthesized by thermal treatment of the precursor. The nanoparticles were characterized by using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), High Resolution Transmission Electron Microscope (HRTEM) and Selected Area Electron Diffraction (SAED) techniques. The details of synthesis and characterization of the nanoparticles are reported in this paper. [ABSTRACT FROM AUTHOR]

Mechanical properties of multi-walled carbon nanotubes (CNT) reinforced epoxy nanocomposites, with and without any structural defect, were investigated using different weight percent values of pristine and covalently functionalized CNT. First, nickel ferrite (NiFe2O4) catalyst nanoparticles were prepared using the co-precipitate method followed by CNT growth via chemical vapor deposition, using acetylene as carbon feedstock. Through a combination of magnetic stirring and ultrasound vibration treatments in acetone, pristine, COOH-, or NH2-functionalized CNTs at 0.15, 0.60, 1.10 and 1.50 wt% were added to the Epon 828 epoxy. During each stage, extensive materials characterization was carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA)/differential thermal analysis (DTA) techniques. Tensile testing of the specimens revealed an increase in the elastic modulus and tensile strength values with maximum increase registered in the case of nanocomposites made from 1.1 wt% CNT-NH2 (+73%) or CNT-COOH (67%) addition. The energy absorbed during impact testing also increased by 86% upon addition of 1.50 wt% CNT-NH2. The presence of a small notch in the nanocomposite specimens yielded superior mechanical properties to those of the neat epoxy. Such enhancement in the mechanical properties can be attributed to better CNT dispersion in the nanocomposites and good interfacial bonding, as confirmed from microstructural examination of the fractured surfaces. [ABSTRACT FROM AUTHOR]

Rare earth ion (Er 3+ )-doped magnesium ferrite nanoparticles of basic composition MgFe 2− x Er x O 4 ( x =0, 0.02, 0.04, and 0.06) were synthesized for the first time by a combustion method with use of glycine as fuel. The synthesized nanoparticles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, UV-diffuse reflectance spectroscopy, and vibrating sample magnetometer analysis in order to study the structural, compositional, morphological, and magnetic changes with addition of dopant. The X-ray diffraction pattern revealed a single phase with cubic spinel structure, and from the Scherrer formula and the Williamson–Hall formula, the average grain sizes ranged from 35 to 56 nm and from 31 to 54 nm, respectively. The lattice parameter ( a ) increases with the increase of the Er 3+ concentration x in the lattice. The cation distributions among the tetrahedral (A) and octahedral (B) sites of spinel-type Er-doped magnesium ferrites were also investigated. The Fourier transform infrared spectroscopy spectra of synthesized samples illustrate that the higher-frequency bands lying in the range from 550 to 620 cm −1 and the lower-frequency bands lying in the range from 410 to 450 cm −1 are associated with the asymmetric stretching modes of the AB 2 O 4 type of spinel transition metal oxides. Information about the chemical elements and oxidation states of the samples was obtained from high-resolution core-level X-ray photoelectron spectroscopy spectra of Mg 1s, Fe 2p, Er 4d, and O 1s. Further information about the morphology of the nanoparticles was obtained by scanning electron microscopy. From UV-diffuse reflectance spectroscopy studies, the optical band gaps were found to range from 1.81 to 1.96 eV. The magnetic hysteresis curves clearly indicate the soft ferromagnetic nature of the samples. Various magnetic properties such as saturation magnetization, coercivity, and remanent magnetization obtained from M – H loops were observed to increase with Er 3+ substitution. [ABSTRACT FROM AUTHOR]

Zinc doped cobalt ferrite spinel nanoparticles were prepared by the microwave combustion method. All the samples were characterized by using X-ray diffraction technique (XRD), Scanning Electron Microscopy, energy dispersive X-ray analysis, UV–visible diffuse reflectance spectroscopy, Fourier transformed infrared (FT-IR) spectroscopy and vibrating sample magnetometry. The XRD patterns confirmed the formation of single phase CoFe 2 O 4 inverse spinel structure without impurities. The lattice parameter increased from 8.380 to 8.396 Å with increasing Zn 2+ fraction. The average crystallite sizes obtained by a Scherrer method varied between 46.22 nm and 30.79 nm. The estimated band gap energy values increases with an increasing zinc fraction (1.88–2.10 eV). The elemental composition of Zn, Co, and Fe was qualitatively obtained from energy dispersive X-ray (EDX) analysis. [ABSTRACT FROM AUTHOR]