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Medscape

The role of cobalt ferrite magnetic nanoparticles in medical science

Nanoparticles of CoFe2O4 and CoIn0.15Fe1.85O4 ferrites were prepared by citrate gel route and characterized to understand their structural, electrical, and magnetic properties. X-ray diffraction and Raman spectroscopy were used to confirm the formation of single phase cubic spinel structure. The average grain sizes from the Scherrer formula were below 50 nm. Microstructural features were obtained by scanning electron microscope and compositional analysis by energy dispersive spectroscopy. The hysteresis curve shows enhancement in coercivity while reduction in saturation magnetization with the substitution of In3+ ions. Enhancement of coercivity is attributed to the transition from multidomain to single domain nature. Electrical properties, such as dc resistivity as a function of temperature and ac conductivity as a function of frequency and temperature were studied for both the samples. The activation energy derived from the Arrhenius equation was found to increase in the doped sample. The dielectric cons...

Magnetic and electrical properties of In doped cobalt ferrite nanoparticles

Compositions of polycrystalline Mg–Zn mixed ferrites with the general formula Mg1−xZnxFe2O4 (0≤x≤1) were prepared by the standard double sintering ceramic method. The structural properties of these ferrites have been investigated using X-ray diffraction and infrared absorption spectroscopy. The lattice parameter, particle size, bonds length, force constants, density, porosity, shrinkage and cation distribution of these samples have been estimated and compared with those predicted theoretically. Most of these values were found to increase with increasing Zn content. The energy dispersive (EDS) analysis confirmed the proposed sample composition. The scanning electron microscope (SEM) and transmission electron microscope (TEM) micrographs showed aggregates of stacked crystallites of about 200–800 nm in diameter. Far infrared absorption spectra showed two significant absorption bands. The wave number of the first band, ν1, decreases with increasing Zn content, while the band, ν2 shifts linearly towards higher wave numbers with Zn contents, over the whole composition range. The room temperature electrical resistivity was found to decrease as Zn-content increases. Values of the vacancy model parameters showed that the packing factors Pa and Pb decrease, the fulfillment coefficient, α, remains almost constant and the vacancy parameter, β, strongly increases with increasing Zn content in the sample. The small values of Pa, Pb, α and the strong increase of the vacancy parameter, β, indicate the presence of cation or anion vacancies and the partial participation of the Zn2+ vacancies in the improvement of the electrical conductivity in the Mg–Zn ferrites.

Infrared and structural studies of Mg1–xZnxFe2O4 ferrites

Magnetic spinel cobalt ferrite nanoparticles with variable composition (CoxFe3-xO4; x = 0.1, 0.5, 0.7 and 1.0) were synthesized. The nanoparticles were characterized by various surface techniques. Average sizes and surface areas of ferrites were determined in the ranges of 11–34 nm and 18.5–49.1 m2/g, respectively. Surface analysis of the nanoparticles confirmed the spinel type structures in which Co(II) incorporated into the crystal lattice. The synthesized catalysts were used to dissociate peroxomonosulphate (PMS) into reactive sulfate radicals ( SO 4 • − ) and further into hydroxyl radicals ( H O • ) to degrade a target pollutant, 2-phenylbenzimidazole-5-sulfonic acid (PBSA) in absence of heat and light. As the molar ratio of cobalt (i.e., x) in the ferrite catalyst increased from 0.1 to 1.0, PBSA degradation enhanced from 24 to 75% in 240 min. The removal of PBSA increased significantly with the increase in PMS concentration up to 0.1 mM, followed by a decrease at PMS levels of >0.1 mM. Nitrogen content in PBSA was mineralized by the cobalt ferrite-PMS system mostly into NO3− and NH4+ ions with minor formation of NO2−. Only 32% TOC removal was observed over a 240 min reaction time, indicating carbon content in PBSA was not completely mineralized. A chemical probe method, based on free radical scavenging, revealed the contribution of both SO 4 • − and H O • species in PBSA degradation. Fifteen reaction intermediates were identified using LC/Q-TOF-ESI–MS analysis. Hydroxylation, elimination of sulfonate moiety, and ring cleavage processes were involved in the major degradation pathways. Catalyst reuse experiments demonstrated PBSA degradation efficiency either retained or increased with each subsequent reuse. The magnetic spinel Co-ferrite nanoparticles can be applied effectively to activate PMS without energy aiding for degrading harmful emerging organic contaminants in water.

Cobalt ferrite nanoparticles with controlled composition-peroxymonosulfate mediated degradation of 2-phenylbenzimidazole-5-sulfonic acid

Self-regulated cobalt zinc ferrite system as a potential nanoplatform for the synergistic effect of hyperthermia-chemo agent for cancer therapy.

Observed variations in density, grain size and initial permeability (μ ic ) in two series of Ni-Zn-Sc ferrites with varying concentrations of zinc and scandium have been discussed in terms of their microstructural and compositional changes. Initial amounts of scandium enhanced densification and sintering in both the series. Subsequent concentrations of only scandium caused reduction in μ ic in Series-I, whereas simultaneous substitutions of zinc and scandium together resulted an increase in μ ic in Series-II. Conclusions have been drawn towards the domination of the microstructural changes in series-1 and compositional changes in series-II in the study of initial permeability.

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Initial permeability dependence on the microstructural and compositional changes in Ni-Zn-Sc ferrites

Dimensional Effects Resulting from High Dielectric Constants in NiZnSc-Ferrites

The effect of the substitution of paramagnetic trivalent chromium ions in stoichiometric magnesium–manganese ferrites has been studied with the composition Mg0.9Mn0.1Cry Fe2-yO4 where y varies from 0.0, 0.1 to 0.9 in steps of 0.2. The single-phase cubic spinel structure of these samples has been confirmed from X-ray diffraction analyses. Mossbauer spectra of these samples studied at room temperature (300 K) showed two characteristic ferrimagnetic Zeeman sextets for lower concentration of Cr3+ followed by relaxation phenomenon corresponding to y=0.9. The dependence of Mossbauer parameters, viz. isomer shift, quadrupole splitting, line width and hyperfine magnetic field on Cr3+ concentration have been discussed. The variation of hyperfine magnetic field with increasing Cr3+ content has been explained on the basis of Neel's molecular field model.

MÖSSBAUER STUDY OF Mg0.9Mn0.1CryFe2-yO4 SPINEL FERRITES

The present study aims to develop low magnetic anisotropy Ni-Zn nanoferrites with cobalt substitution. The results enable the development of nanoferrite samples with superior magnetic properties suitable for high-frequency core applications through an understanding of the influence of cobalt in the manipulation of the magnetic anisotropy of the nanoferrite. Ni0.65-xZn0.35CoxFe2O4 (x varies from 0.00 to 0.24 in steps of 0.04) particles were synthesized by sol–gel method using polyvinyl alcohol as a chelating agent. X-ray diffraction patterns of all the samples showed sharp peaks corresponding to spinel structure with no extra phases. Transmission electron micrographs depict uniform size distribution of particles in the range 185 to 247 nm. Magnetic properties were measured at 300 K and 5 K. Excellent control to reduce the magnetic anisotropy to a negligible amount can be achieved by incorporating minute amounts of cobalt in nickel-zinc ferrite.

K. H. Rao

Papers

Self-regulated cobalt zinc ferrite system as a potential nanoplatform for the synergistic effect of hyperthermia-chemo agent for cancer therapy.

Initial permeability dependence on the microstructural and compositional changes in Ni-Zn-Sc ferrites

Dimensional Effects Resulting from High Dielectric Constants in NiZnSc-Ferrites

MÖSSBAUER STUDY OF Mg0.9Mn0.1CryFe2-yO4 SPINEL FERRITES

Control of Coercivity and Magnetic Anisotropy Through Cobalt Substitution in Ni-Zn Ferrite