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Intravenous iron-carbohydrate nanomedicines are widely used to treat iron deficiency and iron deficiency anemia across a wide breadth of patient populations. These colloidal solutions of nanoparticles are complex drugs which inherently makes physicochemical characterization more challenging than small molecule drugs. There have been advancements in physicochemical characterization techniques such as dynamic light scattering and zeta potential measurement, that have provided a better understanding of the physical structure of these drug products in vitro. However, establishment and validation of complementary and orthogonal approaches are necessary to better understand the 3-dimensional physical structure of the iron-carbohydrate complexes, particularly with regard to their physical state in the context of the nanoparticle interaction with biological components such as whole blood (i.e. the nano-bio interface)., (Copyright © 2023. Published by Elsevier B.V.)

Enzymes and protein's immobilization on magnetic nano supports is emerging as a promising candidate in the food, medical field, and areas of environmental studies. This work presents a study on purified Bacillus thermoamylovorans lipase (BTL) by utilizing tetraethoxysilane (TEOS)-modified magnesium nano ferrite (MgNF) of 20 nm size. Its structural and morphological studies were investigated by powder X-ray diffractometry, high-resolution transmission electron microscopy, etc. Binding of BTL with MgNF was supported by using Fourier transform infrared spectroscopy. Magnetic behavior was examined by the vibrational sample magnetometer and Mössbauer spectrometer graphs. The enzymatic activity of BTL before and after immobilization was studied at different temperatures and reaction time. As per the Lineweaver-Burk plot, immobilized lipase has more biological affinity for fatty acids in comparison to the free lipase, and K max values of immobilized and free BTL were computed as 6.6 and 7.5 mM respectively, with excellent reusability(> 50%) even till 13 consecutive assay runs. Graphical Abstract.

We explore the solventless synthesis of iron oxide nanomaterials obtained on thermal conversion of iron(III)citrate in presence of malonic acid and glucose as co-precursors in varying weight ratios and physical characterization of the materials obtained. Pure phase of hematite was found only for a particular combination of precursor and co-precursor and else a mixture of hematite and magnetite. Significant effect of the co-precursors on the nature and size of the synthesized materials was noticed. Gradual conversion of hematite to magnetite with increasing amount of co-precursor was established. Morin transition was observed in the temperature dependent magnetization study for the hematite materials. Absorption spectroscopy exhibited three different electronic transitions that take place within the 3d5 shell of the octahedrally coordinated Fe3+ ions for hematite materials. The optical (direct and indirect) band gaps estimated from the Tauc's plot showed particle size dependence. From photoluminescence study the transitions of trapped electrons in various defect states of oxygen vacancies were observed which led to the appearance of nonradiative peaks. In the Raman spectra the significant bands of hematite (A1g and Eg bands) were noted. From morphology study the hematite nanomaterials appear as clusters of large irregular shaped particles of various sizes. Formation of hematite nanomaterials as observed by XRD studies was supplemented by the SAED patterns obtained in the HRTEM study. Present study established that nano-sized pure hematite materials can be thermally synthesized at comparatively lower temperature on thermal decomposition of iron(III)citrate by varying the weight ratio of suitable co-precursors. [ABSTRACT FROM AUTHOR]

In this work we produce Ba-hexaferrite nanoparticles by the ionic coordination reaction method and study the influence of La and Co ions on the magnetic properties of Ba 0.7 La 0.3 Fe 12-x Co x O 19 for x = (0.0, 0.25, 0.50, 0.75 and 1.0) nanoparticles. The crystalline and morphological properties were studied by X-ray diffraction and scanning electron microscopy techniques. The magnetic properties of samples were studied in a vibrating sample magnetometer under an applied field of ±6 T. The Fe occupancy in the three octahedral (12 k , 2 a , and 4 f 2), one tetrahedral (4 f 1) and one trigonal bipyramidal (2 b) sites was studied by Mössbauer spectroscopy. The samples are single domain nanoparticles with crystallite sizes in the range 71.5-50.1 nm, decreasing with the Co doping. The results suggest that the sample with x = 0.25 had the largest (BH) max of 6.98 kJ/m3, this effect is mostly due to the occupancy of 4 f 2 sites by Co2+. For x > 0.25, the Co2+ occupy mainly both the 4 f 2 and 12 k sites, the presence of oxygen vacancies is discussed. [ABSTRACT FROM AUTHOR]

Pulsed laser ablation in liquids was utilized to prepare NiFe2O4 (NFO) and CoFe2O4 (CFO) nanoparticles from ceramic targets. The morphology, crystallinity, composition, and particle size distribution of the colloids were investigated. We were able to identify decomposition products formed during the laser ablation process in water. Attempts to fractionate the nanoparticles using the high-gradient magnetic separation method were performed. The nanoparticles with crystallite sizes in the range of 5–100 nm possess superparamagnetic behavior and approximately 20 Am2/kg magnetization at room temperature. Their ability to absorb light in the visible range makes them potential candidates for catalysis applications in chemical reactions and in biomedicine. [ABSTRACT FROM AUTHOR]

Mössbauer spectra of Feridex, an MRI enhancement agent, show that it contains superparamagnetic γ-Fe2O3 nanoparticles. From spectra in magnetic fields applied at room temperature the magnetic moment of the particles was measured to be 11,250 μB, from which the diameters of the single-domain particles are estimated to be about 8 nm. This is smaller than the hydrodynamic particle size of 30 nm which includes a protective coating of dextran. The particles are monodisperse, as shown by the continuous change from a broad superparamagnetic line to a magnetic 6-line pattern as the temperature is lowered below the blocking temperature TB of about 90 K. The magnetic moments and blocking temperature are consistent with those of γ-Fe2O3 samples of known sizes. [ABSTRACT FROM AUTHOR]

The effect of Er content on sol-gel derived CoFe2−xErxO4, (x = 0.00, 0.01, 0.03, 0.05) nanoparticles was investigated by XRD, FTIR, SEM, Mössbauer spectroscopy, magnetic and dielectric measurements. The formation of cubic spinel structure and the presence of molecular bonding of functional groups were confirmed by XRD and FTIR spectroscopy. The average crystallite size is reduced from 61 to 18 nm with the increase of Er content. The decrease in crystallite size is due to the suppression of grain growth upon Er3+ occupation at the octahedral site. SEM study revealed the formation of nano size particles which dispersed uniformly. Mössbauer spectra, taken at room temperature (RT) confirmed the presence of ferromagnetic sextets demonstrating the existence of Fe both in the tetrahedral and octahedral sites. The magnetic properties were measured at 300 K, 100 K and 5 K using a Physical Properties Measurements System (PPMS). The saturation magnetization (Ms) of CoFe2O4 was found to be 95.92 emu/g which is much higher than the bulk ferrite (80.8 emu/g) and the maximum Ms 120 emu/g was found for 0.01 Er content. The coercivity increases with the increase of Er content which has a direct relationship with crystallite size and single-domain behavior of nanoparticles. The maximum coercivity is found to be 855 KA/m at 5 K which is the highest compared to the rare earth doped ferrites. The impedance analysis fallouts the relative permittivity and dielectric loss decrease while AC conductivity increases with increasing frequency for all samples. The obtained results signify CoFe2−xErxO4 as a potential candidate for magneto-electric sensors and high frequency electromagnetic devices application.

We report on the synthesis and characterization of single phase Sm doped Co-ferrites nanoparticles, CoFe (2− x) Sm x O 4 with x = {0.0, 0.05, 0.10, 0.15, 0.20}. The samples were characterized by X-ray diffraction, Mössbauer spectroscopy at 12 K and 300 K, transmission electron microscopy and vibrating sample magnetometry. The particle size, saturation magnetization and coercivity field are found to decrease with the increase of Sm3+ concentration. The particles had sizes from 5.6 nm to 9.5 nm. The cation distribution obtained by X-ray diffraction and mössbauer spectroscopy corresponds to a partially inverted ferrite. The magnetocrystalline anisotropy energy was determined from hysteresis curves. Since the samples are composed of superparamagnetic and thermally blocked nanoparticles, we used a combination of Langevin and hyperbolic tangent functions to fit the magnetization curves, the results were in close agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Pulsed laser ablation in liquids was utilized to prepare NiFe2O4 (NFO) and CoFe2O4 (CFO) nanoparticles from ceramic targets. The morphology, crystallinity, composition, and particle size distribution of the colloids were investigated. We were able to identify decomposition products formed during the laser ablation process in water. Attempts to fractionate the nanoparticles using the high-gradient magnetic separation method were performed. The nanoparticles with crystallite sizes in the range of 5–100 nm possess superparamagnetic behavior and approximately 20 Am2/kg magnetization at room temperature. Their ability to absorb light in the visible range makes them potential candidates for catalysis applications in chemical reactions and in biomedicine.

In this investigation, we have used the thermal treatment method for the preparation of nickel and manganese ferrite nanoparticles. All the samples were calcined at different temperatures from 420 to 570 °C. The results of XRD demonstrated the variation of average nanocrystallite size as a function of calcination temperature. Mossbauer spectra of calcined NiFe2O4 nanoparticles at 570 °C exhibit two sextets, indicating the samples are ferromagnetic, while calcined MnFe2O4 nanoparticles at 420 °C reveal simultaneous presence of two paramagnetic doublets with a central magnetic sextet. The Mossbauer spectroscopy is also applied here for investigating the magnetic hyperfine characteristics and cation distribution of the above-mentioned ferrite nanoparticles. Mossbauer results demonstrate that higher calcination temperature assistances M2+ ions enter into the octahedral sites, while simultaneously Fe3+ ions transfer from the octahedral (B) sites to the tetrahedral (A) sites. As the results indicate, magnetic properties of the samples can be attributed to the hyperfine parameters such as hyperfine field and cation distribution. The results of Mossbauer showed the change in hyperfine parameters along with changing temperature and nanocrystallite size. [ABSTRACT FROM AUTHOR]

• Nanopowder Fe 0.66 Co 0.34 @C has a high saturation magnetization (189 emu/g). • Nanoparticles with an average linear size of 9 nm have been obtained. • Annealed nanoparticles Fe 0.66 Co 0.34 @C are based on ordered FeCo alloy. A series of nanoparticles of the bimetallic core and carbon shell type Fe x Co 1-x @C (x = 0.4 – 0.8) have been obtained by the gas condensation synthesis method. The microstructural peculiarities and magnetic behaviour of the nanoparticles is analysed depending on the composition and thermal treatment. Collateral phases, which are difficult to detect by traditional methods, are identified. The 59Co,57Fe NMR and 57Fe Mossbauer spectroscopies have shown that homogeneity of the composition and removal of carbon from the metallic core can be reached by annealing. The combination of methods has quantified the fraction of superparamagnetic particles, the proportion of paramagnetic inclusions. A simplified visual interpretation of the 59Co NMR spectra is proposed for binary FeCo alloys. [ABSTRACT FROM AUTHOR]

This study focuses on the synthesis of FeRh nanoparticles via pulsed laser ablation in liquid and on controlling the oxidation of the synthesized nanoparticles. Formation of monomodal γ-FeRh nanoparticles was confirmed by transmission electron microscopy (TEM) and their composition confirmed by atom probe tomography (APT). For these particles, three major contributors to oxidation were analysed: (1) dissolved oxygen in the organic solvents, (2) the bound oxygen in the solvent and (3) oxygen in the atmosphere above the solvent. The decrease of oxidation for optimized ablation conditions was confirmed through energy-dispersive X-ray (EDX) and Mössbauer spectroscopy. Furthermore, the time dependence of oxidation was monitored for dried FeRh nanoparticles powders using ferromagnetic resonance spectroscopy (FMR). By magnetophoretic separation, B2-FeRh nanoparticles could be extracted from the solution and characteristic differences of nanostrand formation between γ-FeRh and B2-FeRh nanoparticles were observed.

Trivalent iron sulfide (Fe S ) particles were synthesized using a modified polyol method. These particles exhibited a needle-like shape (diameter = 10-50 nm, length = 350-1000 nm) and generated a clear XRD pattern. Mössbauer spectra of the product showed a paramagnetic doublet at room temperature and distributed hyperfine magnetic splitting at low temperature. The Curie temperature of this material was determined to be approximately 60 K. The data suggest that the Fe S had a structure similar to that of maghemite ( γ-Fe O ) with a lattice constant of a = 10.6 Å. The XRD pattern calculated from this structure was in agreement with the experimental pattern and the calculated hyperfine magnetic field was also equivalent to that observed in the experimental Mössbauer spectrum. [ABSTRACT FROM AUTHOR]

Lepidocrocite, a widespread environmentally relevant iron oxyhydroxide, has been investigated for decades using 57Fe Mössbauer spectroscopy and magnetic measurements. However, a coherent and comprehensive interpretation of all the data is still lacking due to seemingly contradictory interpretations. On one hand, temperature dependence of magnetic susceptibility and Mössbauer spectra resemble those of superparamagnetic nanoparticles with diameters less than 10 nm even though physically particles are lath-shaped with lengths on the order of 100-300 nm. On the other hand, in-field Mössbauer spectra show that lepidocrocite is an antiferromagnet and becomes paramagnetic above 50-70 K, a temperature close to the blocking temperature deduced from susceptibility data. The present study investigates a well-characterized synthetic sample of lepidocrocite, includes modelling of Mössbauer spectra and dc and ac magnetization data, and proposes a solution to this paradox. The new data are coherent with the presence of two entities in lepidocrocite: a bulk antiferromagnetic matrix and sparse ferrimagnetic nanosized inclusions (d = 3.4 nm), akin to maghemite, embedded within. The presence of nanosized ferrimagnetic inclusions is confirmed for the first time by Mössbauer spectroscopy.

The successful synthesis of nanoparticles of Fe-bearing kuramite, (Cu,Fe)SnS, is reported in this study. Nanocrystalline powders were obtained through a mild, environmentally friendly and scalable solvothermal approach, in a single run. The sample was the object of a multidisciplinary investigation, including X-ray diffraction and absorption, scanning electron microscopy and microanalysis, electron paramagnetic resonance, diffuse reflectance and Mössbauer spectroscopy as well as SQUID magnetometry. The nanoparticles consist of pure Fe-bearing kuramite, exhibiting tetragonal structure. The valence state of the metal cations was assessed to be Cu, Sn and Fe. The material presents a band gap value of 1.6 eV, which is fully compatible with solar cell applications. The uptake of Fe by nanokuramite opens a compositional field where the physical properties can be tuned. We thus foster the application of Fe-bearing nanokuramite for photovoltaics and energy storage purposes. [ABSTRACT FROM AUTHOR]

δ-FeOOH is a synthetic analogue of a relatively uncommon mineral feroxyhyte (δ′-FeOOH). The conventional syntheses of δ-FeOOH start from the Fe(II) salt and proceed by a rapid oxidation of iron(II) hydroxide with H 2 O 2 . The new synthesis route to δ-FeOOH nanodiscs reported in this work is based on the γ -irradiation of a deoxygenated iron(III) chloride alkaline aqueous colloidal solution in the presence of 2-propanol and diethylaminoethyl-dextran hydrochloride (DEAE-dextran). γ -irradiation of the colloidal solution enabled the strong reducing conditions thus favouring the reduction of Fe(III) to Fe(II). Under such strong reducing conditions the white suspension characteristic of Fe(OH) 2 was formed. When the white suspension came into contact with oxygen from air it rapidly oxidized into stable green-gray suspension characteristic of Fe(II)-Fe(III) hydrochloride known as Green Rust I. In the conventional process of sample isolation the green-gray stable suspension transformed to δ-FeOOH reddish powder that consists of rather uniform regular nanodiscs. The synthesized δ-FeOOH nanodiscs are magnetic and contain a magnetically ordered component in the Mössbauer spectrum at room temperature. It is expected that the results of this work will have a strong impact on finding new synthetic routes to the δ-FeOOH. [ABSTRACT FROM AUTHOR]

The iron oxide FeO, the mineral magnetite sometimes called ferrosoferric oxide, is notoriousy non-stoichiometric even in bulk form so its formula may be written FeO. In nanoparticle form, where it has applications in medicine and information technology, it is even more susceptible to oxidation. In this paper we report synthesis and studies of superparamagnetic FeO nanoparticles with controlled diameters of 5.3, 10.6 and 11.9 nm. In room temperature spectra, departures from stoichiometry δ of up to 0.02 were estimated from the relative amounts of Fe / Fe and from their isomer shifts. This cannot be used for very small particles of diameter 10.6 nm and less as they are superparamagnetic at room temperature and do not show hyperfine splitting owing to fast relaxation. Such particles have promise for use in enhancing MRI signals. The magnetic spectrum is restored by the application of a relatively small magnetic field (10 kG). As the temperature is lowered the relaxation slows down and 6-line magnetic hyperfine patterns appear below a blocking temperature T. The values of T obtained are lower than those of many other researchers reported in the literature, suggesting that our particles are less affected by magnetic interactions between them. At low temperatures all the spectra are similar and closely resemble that of bulk FeO confirming that departures from stoichiometry are small. [ABSTRACT FROM AUTHOR]

Abstract: Ferrite nanoparticles are promising future materials for applications in medicine, ferrofluids, technical designing and other fields. The as-prepared CuAl x Cr0.8−x Fe1.2O4 nanoparticles (0≤x≤0.8) have been prepared by the chemical co-precipitation method. A study of the structure and other physical properties of the samples was carried out by using X-ray, infrared, Mössbauer and vibrating sample magnetometer (VSM) patterns and particle size distributions. The results revealed the ultrafine nature of the particles, where the crystallite size and the average particle size have been deduced. The values of the lattice parameters and crystallite size were dependent on the substitution factor x, while the oxygen parameter was higher than the standard value and independent on x. In addition to six absorption bands, a triple band attributed to the retained water in the samples was observed in the infrared spectra. The absorption bands indicated the existence of Fe2+ ions in the sample sublattices. The Mössbauer and VSM patterns proved the presence of small magnetic field in the samples, where the saturation magnetization, coercivity, hyperfine interaction parameters, cation distributions and magnetization were dependent on x. [Copyright &y& Elsevier]

Purpose: This paper reports a technique that enables the quantitative determination of the concentration of gold nanoparticles (GNPs) through the accurate detection of their fluorescence radiation in the diagnostic x-ray spectrum. Methods: Experimentally, x-ray fluorescence spectra of 1.9 and 15 nm GNP solutions are measured using an x-ray spectrometer, individually and within chicken breast tissue samples. An optimal combination of excitation and emission filters is determined to segregate the fluorescence spectra at 66.99 and 68.80 keV from the background scattering. A roadmap method is developed that subtracts the scattered radiation (acquired before the insertion of GNP solutions) from the signal radiation acquired after the GNP solutions are inserted. Results: The methods effectively minimize the background scattering in the spectrum measurements, showing linear relationships between GNP solutions from 0.1% to 10% weight concentration and from 0.1% to 1.0% weight concentration inside a chicken breast tissue sample. Conclusions: The investigation demonstrated the potential of imaging gold nanoparticles quantitatively in vivo for in-tissue studies, but future studies will be needed to investigate the ability to apply this method to clinical applications. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis of chromium doped Ni–Mg ferrite with a chemical formula Ni0.5Mg0.5Fe2−xCrxO4 (0≤x≤1.0 in a step of 0.2) was investigated in this study. The elemental analysis as obtained from energy dispersive X‐ray (EDAX) is in close agreement with the expected composition from the stoichiometry of the reactant solutions used. X-ray diffraction (XRD) analysis reveals that all the samples posses a single phase cubic spinel structure. The lattice constant determined from XRD decreases with the Cr3+ substitution. The crystallite size estimated lies within the range of 30–35nm. Field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) confirm the homogeneous and well defined surface morphology of the synthesized samples. Fourier transform infrared spectroscopy (FT-IR) is employed to determine the local symmetry in crystalline solids and to shed light on the ordering phenomenon. Magnetization results obtained from the vibrating sample magnetometer (VSM) confirm that the substitution of Cr3+ for Fe3+ caused a decrease in the saturation magnetization from 29.78 to 5.88emu/g and coercivity from 198.71 to 60.01Oe. The dependence of the Mössbauer parameters, viz., line width, isomer shift, quadrupole splitting and hyperfine magnetic field on Cr3+ substitution have been analyzed. Neel''s molecular field model is used to explain the variation of the hyperfine magnetic field with increasing Cr3+ substitution. [Copyright &y& Elsevier]

Abstract: Magnetite (Fe3O4) nanoparticles were successfully synthesized by a sol–gel method. The obtained nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive analysis by X-ray (EDAX), transmission electron microscopy (TEM), superconducting quantum interference device (SQUID) and Mössbauer spectrometry. XRD and Mössbauer measurements indicate that the obtained nanoparticles are single phase. TEM analysis shows the presence of spherical nanoparticles with homogeneous size distribution of about 8nm. Room temperature ferromagnetics behavior was confirmed by SQUID measurements. The mechanism of nanoparticles formation and the comparison with recent results are discussed. Finally, the synthesized nanoparticles present a potential candidate for hyperthermia application given their saturation magnetization. [Copyright &y& Elsevier]

Microstructure, magnetic and transport properties of magnetoresistive CuFeNi ( x = 5, 10 and 15 at.%) melt-spun ribbons were studied for the as-spun and annealed for 2 h at 400 to 600 °C samples. The microstructure was characterised by means of X-ray diffraction, transmission electron microscopy, energy filtered transmission electron microscopy and Mössbauer spectrometry (MS). Magnetic and transport measurements such as magnetization, zero field cooled/field cooled and giant magnetoresistance (GMR) measurements at 5 and 300 K were performed. The aim of this work is to study the influence of the microstructure of as-spun and annealed ribbons on magnetic and transport properties at 5 and 300 K. We have precisely determined the nature of precipitation of nanoparticles, the relative proportion and the magnetic properties of each phase in such a system using MS at both temperatures. We report the conclusive observation of the magnetic behaviour of each phase which was correlated to the structural data to explain the GMR properties that are observed. The influence of magnetic interactions between nanoparticles on magnetic and magnetoresistive properties of these ribbons was determined. We have clearly shown the existence and the nature of the magnetic interactions that reduce the GMR. [ABSTRACT FROM AUTHOR]

Abstract: The intracellular biosynthesis of superparamagnetic (blocking temperature 5.6K) 2-lines ferrihydrite (Fh2L) nanoparticles was observed within living Euglena gracilis microalgae. [Copyright &y& Elsevier]

Mössbauer and x-ray diffraction spectroscopic analyses were carried out on ZnFe2O4 nanoferrite of average size 17 nm after γ-irradiation with three absorbed doses of 291 kGy, 582 kGy and 873 kGy using 60Co source. The obtained Mössbauer analysis data were unchanged before and after irradiation for the investigated sample. A broad paramagnetic doublet spectrum was observed which is refereeing to octahedral high spin Fe3+ in the B-site of the ZnFe2O4 structure. The x-ray powder diffraction analysis has revealed that there is slight shift in some of the diffracted lines of the characteristic XRD pattern due to irradiation which is attributed to change in the lattice parameter. The estimated net magnetic moment was decrease after irradiation due to redistribution of the cations occupying the tetrahedral and octahedral sites. These results are discussed in the light of γ-rays interaction with ferrite lattice. [ABSTRACT FROM AUTHOR]

Abstract: Superparamagnetic nickel ferrite single phase nanoparticles with the average crystallite size of ∼9nm have been synthesized at a low temperature (220°C) by the sol–gel auto-combustion method. In the present study the as prepared powder was further calcined at different temperatures for 4h, resulting in nanoparticles of larger size. The nanoparticles exhibited superparamagnetic behavior and changes in cation distribution as revealed by the Mossbauer, Raman and X-ray diffraction studies. The Mossbauer spectra collected at 5K and under 5T applied magnetic field showed mixed spinel structure and canted spin order for the nanoparticles, whereas there is collinear spin order with inverse spinel structure for larger particles. The vibrational spectra of the nanoparticles showed a redshift and broadening in the Raman line shape due to confinement effects. [Copyright &y& Elsevier]

Nano nickel-zinc-indium ferrite (NZIFO) (Ni0.58Zn0.42InxFe2-xO4) particles with varied quantities of indium (x = 0, 0.1, 0.2) have been chemically synthesized through a reverse micelle reaction and investigated by X-ray diffraction, transmission electron microscopy and by magnetic and Mossbauer spectral studies. The dependence of Mossbauer parameters, viz, isomer shift, quadrupole splitting, linewidth and hyperfine magnetic field on In3+ concentration have been discussed. Mossbauer results are also supported by magnetization data. With these interesting ferromagnetic properties indium substituted nano nickel-zinc ferrites have potential applications in magnetic storage data. The dependence of Mossbauer parameters on nano NZIFO particles at 5 K and 300 K has been studied. The values of Bloch exponent (α) are in well accordance with that reported for bulk materials. [ABSTRACT FROM AUTHOR]

Abstract: The effect of high energy ball milling on the hematite for milling periods of times ranging from 1 to 48h was investigated by Rietveld analysis based on XRD patterns and Mössbauer spectroscopy. An expansion of the unit cell parameters was observed. Both Scherrer method and Rietveld analysis show an evident decrease of the grain size with the increase of the milling time. Moreover, some dependence of the lattice parameters on the grain size was observed. Mössbauer spectroscopy measurements reveal that there are two kinds of particles which co-exist in the sample: nanostructured and micrometric hematite. The magnetic hyperfine field is affected by the grain size. [Copyright &y& Elsevier]

Abstract: Fe-rich FePt nanoparticles with an average size of 5nm were prepared using a reverse micelle route. As synthesized FePt powders were disordered face centered cubic in structure. DSC thermogram displays phase transformation at 575°C, based on which heat treatments were carried in the temperature range of 500–600°C. XRD patterns show that the degree of ordering increased with the increase in heat treatment temperature. An utmost coercivity of 3.2kOe was observed for 600°C heat-treated sample. The M–H loops were asymmetric in nature suggesting the presence of a second phase, Fe-oxide (Fe3O4) that is also observed from the XRD patterns. Mössbauer spectra reveals that on heat treatment the super-paramagnetic phase transforms into an ordered face centered tetragonal phase. The presence of 23% super-paramagnetic phase even after heat-treating at 600°C reveals that the phase transformation is incomplete. [Copyright &y& Elsevier]

In this study the synthesis of very small magnetite nanoparticles is reported. Analysis of the (311) X-ray diffraction line indicates nanoparticle with 2.2 nm average diameter. The as-synthesized nanosized magnetite sample was submitted to a chemical oxidation process for conversion to maghemite. However, the yielding of the chemical oxidation process, as indicated by the analysis of the Mössbauer data, was about 20%. This finding indicates a strong size-dependence of the oxidation process, reducing the yielding of the chemical process used as the nanoparticle size reduces down to extremely low values. [ABSTRACT FROM AUTHOR]

Abstract: Li–Zn ferrites substituted with Ni having the compositional formula Li0.4−0.5 x Zn0.2Ni x Fe2.4−0.5 x O4 where x=0.02⩽x⩽0.1 in steps of 0.02 were fabricated by the citrate precursor method. This method has been employed to get nanosized particles and good magnetic properties. The spinel phase structure of the prepared ferrites was confirmed by XRD analysis. The effect of Ni concentration on magnetic properties such as saturation magnetization and Curie temperature were investigated. A good knowledge of these magnetic properties is desirable from application point of view. The values observed are large and both quantities were found to decrease with substitution. The saturation magnetizations were found to vary from 78 to 94emu/gm while the Curie temperature which limits the operating temperature of the system ranges between 563 and 584°C. Mössbauer data were also recorded at room temperature and the hyperfine parameters like isomer shift, quadrupole splitting and internal magnetic field estimated. The results obtained and mechanisms involved are discussed. [Copyright &y& Elsevier]

α-Fe2O3 nanoparticles were obtained by a mechanical alloying of micrometer-sized powder at different milling times. Samples were characterized by X-ray powder diffraction, scanning electron microscope (SEM), Mössbauer spectrometry, and vibrating sample magnetometer (VSM). A qualitative and quantitative phase analyses using the Rietveld method have been performed based on the XRD data. The results did not reveal any phase change during the milling. The average particle size decreases with a prolongation of milling times, while the lattice parameters, unit cell volume, and microstrain increase. Mössbauer measurement shows that there are two components, one nanometric and other micrometric. The magnetic hysteresis loops shows that the samples are typical of ferromagnet with superparamagnetic fraction in the material. [ABSTRACT FROM AUTHOR]

Abstract: The effect of the presence of palladium ions in a highly alkaline precipitation system on the formation of iron oxides was investigated using X-ray powder diffraction (XRPD), Mössbauer and FT-IR spectroscopies, field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). Acicular α-FeOOH particles precipitated in a highly alkaline medium with the addition of tetramethylammonium hydroxide (TMAH) were used as reference material. The initial addition of palladium ions to that precipitation system had a significant effect on the formation of iron oxide phases and their properties. In the presence of palladium ions, the initially formed α-FeOOH has been transformed to α-Fe2O3 crystals in the form of hexagonal bipyramids via a dissolution–reprecipitation mechanism with a simultaneous formation of metallic palladium nanoparticles. These palladium nanoparticles acted as a catalyst for the reductive dissolution of α-Fe2O3 particles and the formation of Fe3O4 crystals in the form of octahedrons. Increase in the initial concentration of palladium ions in the precipitation system accelerated the transformation process α-FeOOH→α-Fe2O3 →Fe3O4 and influenced changes in the shape of α-Fe2O3 and Fe3O4 particles. [Copyright &y& Elsevier]

Abstract: Highly crystalline CoFe1.9RE0.1O4 ferrite nanoparticles, where RE=La, Ce, Nd, Sm, Eu, Gd, Tb, and Ho, have been synthesized by forced hydrolysis in polyol. X-ray diffraction (XRD), transmission electron microscopy (TEM), electron energy-loss spectroscopy (EELS), 57Fe Mössbauer spectrometry, Co K-edge X-ray absorption spectroscopy and magnetic measurements using a SQUID magnetometer were employed to investigate the effect of the substitution RE3+ ions for Fe3+ ones on the structure, the microstructure, the chemical homogeneity, and the magnetic properties of the cobalt ferrite system. All the produced particles are superparamagnetic at room temperature. Nevertheless, the substitution causes reduction of the blocking temperature which is mainly ascribed to partial cation exchange among the spinel-like sublattices of CoFe2O4 induced by the insertion of the relatively large RE3+ ions. The low-temperature saturation magnetization and coercivity appear to be greatly affected by the nature of RE3+ ions—maxima values were found for Gd3+ and Eu3+, respectively. [Copyright &y& Elsevier]

Nanoparticles of several titanates and zirconates in the range of 20-60 nm have been obtained using the reverse micellar route. Important oxides like CeO2 (mixture of nanorods; 7 nm diameter and 30 nm length and nanoparticles; 10 nm), ZrO2 (3-4 nm) and SnO2 (8 nm) have also been synthesized. Nanorods and nanoparticles of CaCO3 in all three forms (aragonite, vaterite, and calcite) have been obtained using reverse micelles as nanoreactors. The specific reactions vary depending on the nature of the target nanomaterial. For synthesis of ternary oxides like BaTiO3, a modified and convenient route using microemulsions (avoiding Ba-alkoxide) has evolved. Monophasic tin dioxide (SnO2) was obtained when liquid NH3 was used as precipitating agent. Transmission electron microscopy (TEM) studies show that the SnO2 nanoparticles are highly uniform and particle size was found to be 6-8 nm at 500 °C. The gas sensing characteristics of SnO2 have also been investigated using n-butane, which shows high sensitivity and fast recovery time. Reverse micelles have been used, for the first time, to mimic the conditions suitable for the room-temperature synthesis of the high-temperature and -pressure orthorhombic phase of calcium carbonate (aragonite). Other forms of calcium carbonate (vaterite and calcite) could be obtained by varying the atmospheric conditions. At a lower temperature (5 °C), homogeneous and monodisperse spheres of vaterite are obtained. The spherical particles aggregate after longer aging (168 h) to form nanorods, and the self-assembly is clearly seen at various stages by electron microscopy images. The samples were well characterized using powder X-ray diffraction (PXRD), line-broadening studies, TEM, variation in the dielectric properties with frequency and temperature, were measured on disks sintered at high temperature. [ABSTRACT FROM AUTHOR]

Nanocrystalline Fe3Mo3N, FeMoN2 and Ni3Mo3N interstitial nitrides having particle sizes of 32, 50 and 80 nm respectively, were synthesized by molybdate precursor route. The nanocrystalline nature was examined by XRD and SEM. Both, the field and temperature dependence of magnetic characteristics indicate paramagnetic behavior of the materials and the possible presence of magnetic contamination in the nitride materials. We examine the Mössbauer spectroscopic investigations in order to probe the magnetic characteristics and contaminations therein. X-ray photoelectron spectroscopy (XPS) study corroborates the possible presence of magnetic oxide phases at the surface of the Fe3Mo3N and Ni3Mo3N nano-particles. In summary, this paper investigates the magnetic properties of newer nitrides with appropriate corroboration with the Mössbauer and XPS studies. [ABSTRACT FROM AUTHOR]

Abstract: Aqueous solution of a globular protein named bovine serum albumin was homogeneously mixed with ferrous and ferric ions and allowed to gel at ambient conditions. Gels were then oxidized using sodium hydroxide, in the presence of magnetic field of magnitude 0.13T. The effect of magnetic field on the above biomimetic synthesis was a reduction in particle size and a directional assembly of synthesized super paramagnetic particles into a regular pattern in the protein film. The microstructural revelation was complimentary to Mössbauer results and magnetic measurement studies, i.e., an interesting variation in the magnetic behaviour of self-assembled super paramagnetic particles as a function of dc magnetic field induced ordering. [Copyright &y& Elsevier]

Abstract: We report a novel technique to produce ultra-fine crystallites (<50nm) of Sr2FeMoO6 at relatively low temperatures. Powders that were fired at 850°C for 2h have almost a single-phase structure. Longer annealing times improve cationic ordering and increase the saturation magnetization. Several thermal conditions were tried to get samples with different amounts of disorder. Mössbauer spectra at room temperature show broad and complex absorption lines for all samples, reflecting the effect of multiple metal neighbor environments on the magnetic field of iron ions and the different relaxation regimes caused by the chemical disorder. Spectra taken at low temperatures allowed resolving the spectra into three magnetic sextets that were assigned to Fe atoms with well-ordered first neighbors Mo environments, disordered Mo environments, and Fe ions in B′ crystallographic sites with six Fe first neighbors. The magnetization data at room temperature yielded by a SQUID magnetometer show a significant reduction of the saturation magnetic moment with decreasing annealing temperature. These results indicate that there is a correlation between the defect concentration and the magnetic properties. [Copyright &y& Elsevier]

Modification of ferrihydrite nanoparticles with boron is investigated using Mössbauer spectroscopy and powdered X-ray diffraction. These materials were heated to temperatures up to 600°C. The addition of the boron in the fabrication of ferrihydrite nanoparticles raises the transition temperature of the phase transformation of ferrihydrite to hematite. Evidence is that the boron does not penetrate the iron oxihydroxide structure, but attaches itself to the surface of the particles. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles of cobalt ferrite (CoFe2O4) have been synthesized in a homogeneous aqueous solution without any template and subsequent heat treatment. The average particle size could be varied in the range of 2–14 nm by controlling coprecipitation temperature of Co2+ and Fe3+ ions in alkaline solution although the size distribution is pretty wide. As the precipitation temperature increased in the range of 20–80°C, the average particle size also increased. However, there is a considerable change in XRD crystallinity and the average size of the nanoparticles at the precipitation temperature between 40°C and 60°C. While the nanoparticles prepared at the temperature below 40°C show superparamagnetic relaxation at room temperature with blocking temperatures between 75 and 200 K, the samples prepared at the temperature higher than 60°C consist of both superparamagnetic and ferrimagnetic nanoparticles that result in magnetic coercivity at room temperature. Mo¨ssbauer spectra of the samples also confirmed their magnetic properties and wide size distribution in each sample. The analysis of the spectra gave a rough estimation of the ratio of superparamagnetic and ferromagnetic nanoparticles in each sample at various temperatures. [Copyright &y& Elsevier]

• Cubic spinel structure of sol-gel derived CoFe 2−x Er x O 4 was confirmed by XRD analysis. • Mössbauer spectra confirmed the presence of ferromagnetic sextets. • The maximum value of M s was found to be 120 emu/g for 0.01 Er content. • The coercivity increases with Er due to the single domain nature of nanoparticles. • The obtained results signify CoFe 2−x Er x O 4 as a potential candidate for devices application. The effect of Er content on sol-gel derived CoFe 2−x Er x O 4 , (x = 0.00, 0.01, 0.03, 0.05) nanoparticles was investigated by XRD, FTIR, SEM, Mössbauer spectroscopy, magnetic and dielectric measurements. The formation of cubic spinel structure and the presence of molecular bonding of functional groups were confirmed by XRD and FTIR spectroscopy. The average crystallite size is reduced from 61 to 18 nm with the increase of Er content. The decrease in crystallite size is due to the suppression of grain growth upon Er3+ occupation at the octahedral site. SEM study revealed the formation of nano size particles which dispersed uniformly. Mössbauer spectra, taken at room temperature (RT) confirmed the presence of ferromagnetic sextets demonstrating the existence of Fe both in the tetrahedral and octahedral sites. The magnetic properties were measured at 300 K, 100 K and 5 K using a Physical Properties Measurements System (PPMS). The saturation magnetization (M s) of CoFe 2 O 4 was found to be 95.92 emu/g which is much higher than the bulk ferrite (80.8 emu/g) and the maximum M s 120 emu/g was found for 0.01 Er content. The coercivity increases with the increase of Er content which has a direct relationship with crystallite size and single-domain behavior of nanoparticles. The maximum coercivity is found to be 855 KA/m at 5 K which is the highest compared to the rare earth doped ferrites. The impedance analysis fallouts the relative permittivity and dielectric loss decrease while AC conductivity increases with increasing frequency for all samples. The obtained results signify CoFe 2−x Er x O 4 as a potential candidate for magneto-electric sensors and high frequency electromagnetic devices application. [ABSTRACT FROM AUTHOR]

A comparatively new and important cost and time effective Polyol method has been utilized for the preparation of FeS 2 nanoparticles (NPs), while their crystallite size, bonding as well as nearest neighbor atomic information was obtained from XRD, FTIR, Mössbauer, FE-SEM, EDX spectroscopy techniques. The average crystallite size was found to be ∼28 nm and a very small tangential strain due to the spherical shape of the particle was seen in the prepared sample. The bond length of Fe–S bond was estimated to be ∼0.29 nm and that of S –S bond was ∼0.22 nm using VESTA software confirming the Pyrite FeS 2 structure in agreement with the XRD of these NPs. Also, the sample shows an octahedral geometry. Both XRD and Mössbauer spectra indicate that no impurity phase is present in these Pyrite NPs. Using Mössbauer, the average electric Quadrupole splitting (ΔE Q) and average isomer shift (δ), for Pyrite FeS 2 at 300 K are found to be 0.596 ± 0.0039 mm/s and 0.311 ± 0.0023 mm/s respectively. From the Isomer shift, +2 oxidation state is confirmed. The FTIR revealed various vibrations modes of FeS 2 nanoparticles (Fe S, S –S and Fe–S bonds at their respective positions). Corresponding FE-SEM and EDX measurements revealed the formation of agglomerated spherical particles with the Fe:S ratio of ∼1:1.46 confirming the pyrite structure. • FeS 2 nanoparticles (NP) were prepared by cost and time effective Polyol method. • Small tangential strain was observed among ∼28 nm size crystallites. • Pyrite NP have Fe–S and S –S bond lengths of ∼0.29 nm and ∼0.22 nm respectively. • From the Isomer shift in Mössbauer spectrum, +2 oxidation state is confirmed. • Agglomerated spherical particles with the Fe: S ratio of ∼1:1.46 confirm the pyrite structure. [ABSTRACT FROM AUTHOR]

• Sn x Fe 3-2/3 x O 4 nanoparticles with different x were synthesized and characterized. • Sn2+ doping tunes dipping temperature/amplitude, irreversibility and Curie point. • Sn2+ doping reduces the dipping amplitude, until it disappears when x = 0.150. • Modified Bloch law and Curie–Weiss law was used to explain the M-T behavior. Sn x Fe 3−2x/3 O 4 nanoparticles were synthesized using the precipitation under reflux method by Sn2+ doping (x = 0.000−0.150). The structural and magnetic properties of the prepared materials were characterized using a host of techniques. We demonstrate that Sn2+ doping increases the size of the nanoparticles (12−50 nm) and protects them from oxidation to the γ-Fe 2 O 3 phase, making them useful for magnetic applications. Rietveld refinement data for the samples suggest that the dopant Sn2+ ions, while preferentially occupying the B sites at equilibrium, initially start with A-site occupation to maintain the charge balance. While the spin unsaturation at the surface of these nanoparticles, together with oxidation to maghemite, explains the observed decrease in magnetization of the Fe 3 O 4 nanoparticles, it does not for the doped samples, for which spin canting in B sites was preferred. [ABSTRACT FROM AUTHOR]

• Zn 0.5 Mn 0.5 Sm x Fe 2- x O 4 (0 ≤ x ≤ 0.05) nanoferrites were synthesized by glycol-thermal process. • The nanosizes particles are compared to bulk particles. • The field and temperature dependent magnetization data revealed superparamagnetic behaviour of the compounds. • The magnetic isotherms average moment is estimated to be about ≈ 10 4 μ B Zn 0.5 Mn 0.5 Sm x Fe 2- x O 4 (0 ≤ x 0.05) fine powders with average crystallite sizes in the range 12–17 nm were synthesized by glycol-thermal reaction. The as-prepared compounds were subjected to thermal annealing process at 1100 °C, after which the crystallite sizes increased to about 60 nm. XRD analysis confirmed a single-phase cubic spinel structure in all the compounds investigated. TEM images showed nearly spherical particles with uniform particle size distributions. SEM and FTIR have been used to study morphology and confirm phase formation, respectively. The Mössbauer spectrum for Zn 0.5 Mn 0.5 Fe 2 O 4 (x = 0) at room temperature may be resolved into two quadrupole doublets indicative of paramagnetic spin state. Sm3+ substituted compounds showed weak sextets in addition to broad doublets attributed to some particle magnetic moments in ordered magnetic phase. The Mössbauer spectra of the compounds annealed at 1100 °C exhibit magnetic split sextets indicative of ordered magnetic phase. The compounds have small coercive fields and high saturation magnetization (40 emu/g to 60 emu/g) which reduce with increasing Sm3+ content due to the paramagnetic nature of Sm3+ ions. Magnetic measurements as a function of field and temperature in as-prepared particles showed superparamagnetic behaviour with average moment of about ≈104 μ B. The average particle size obtained from the magnetic data corresponds well with that estimated from XRD analysis. [ABSTRACT FROM AUTHOR]

The degradation of methyl orange (MO) dye, in the presence of pure iron nanoparticles (Fe-NPs) and supporting them in natural zeolite-type clinoptilolite (Fe-Z), were studied. The degradation tests consisted of analyzing the dependence of pH, initial concentration of MO, contact time between systems Fe-NPs ↔ MO and Fe-Z ↔ MO, and temperature, respectively. The highest degradation percentages of MO ranging from 80 to 100% occurred at pH values between 3 and 10; below 3 and above 10, relatively low degradation percentages were measured. Whereas nearly 100% of MO degradation was obtained with pure Fe-NPs for all studied MO concentrations and from 30 °C to 50 °C, for the composite Fe-Z, the degradation of MO was both MO concentration and temperature dependent with the highest degradation percentages at 50 °C. Besides, while using pure Fe-NPs the degradation of 100% of MO was reached at a contact time of 6 h at temperatures between 20 °C and 50 °C. However, when using the composite Fe-Z, the degradation percentages of MO were from 80% to 90% which was reached in 17 h, for temperatures between 15 °C and 50 °C. The resulting kinetic degradation data of MO from pure and supported Fe-NPs was analyzed by considering several empirical models, from which the temperature dependent rate constants were obtained, with best values of ~0.2 h−1at 15 °C and ~1.86 h−1at 50 °C and establishing endothermic-degradation processes. By using these rate constants and the Arrhenius relation, an activation energy (E a) for the degradation process was determined, being for the Fe-NPs ↔ MO system slightly higher than for the Fe-Z↔ MO system. Image 1 • Iron nanoparticles degrade the methyl dye efficiently. • The composite iron nanoparticles-zeolite degrades methyl orange at a lower than iron nanoparticles. • The iron nanoparticles transform to magnetite after degradation of methyl orange. [ABSTRACT FROM AUTHOR]

Mn3+ substituted orthoferrites TbFe1-x MnxO3 (x = 0.00, 0.25, 0.50, and 0.75) nanoparaticles were prepared by the sot-gel method. The crystallographic and magnetic properties of powders were characterized by using X-ray diffractometer (XRD), Mössbauer spectroscopy, and scanning electron microscopy (SEM). The crystal structure was found to be a single phase of orthorhombic structure (Pbnm). For Mössbauer spectra, we have fitted the spectra to a model based on a random distribution of Fe and Mn ions on the octahedral sites. Mössbauer spectroscopy measurement showed that Néel temperature decrease with increasing Mn concentration x. The isomer shift indicate that the valance state of Fe ions is ferric (Fe3+). The result of SEM measurements showed that powders present average particle size of 36.5 nm for TbFe0.25 Mn0.75 O3. [ABSTRACT FROM AUTHOR]

Abstract: Many studies on cation substitution have been carried out in sintered magnets application, since intrinsic magnetic properties such as saturation magnetization depend on the cation configuration in the M-type hexagonal structure. La–Zn substituted Sr-ferrite nanoparticles were fabricated by a sol–gel method. Their magnetic and structural properties were characterized by using the XRD, VSM, TG/DTA, and Mössbauer spectroscopy. We focused on the Mössbauer effects of non-magnetic ions such as the Zn occupation of and 2b sites in the M-type hexagonal structure. As substitution x increased, the saturation magnetization increased, and took a maximum at before decreasing again. We interpret that it is closely related to Zn occupation of 4f 1 and 2b. This was thought to be caused by the preferential location of Zn2+ at the down-spin Fe3+ site. [Copyright &y& Elsevier]