Z. Klencsár

57Fe Mössbauer spectroscopy and electron paramagnetic resonance studies of human liver ferritin, Ferrum Lek and Maltofer®

A human liver ferritin, commercial Ferrum Lek and Maltofer® samples were studied using Mössbauer spectroscopy and electron paramagnetic resonance. Two Mössbauer spectrometers have been used: (i) a high velocity resolution (4096 channels) at 90 and 295K, (ii) and a low velocity resolution (250 channels) at 20 and 40 K. It is shown that the three studied materials have different superparamagnetic features at various temperatures. This may be caused by different magnetic anisotropy energy barriers, sizes (volume), structures and compositions of the iron cores. The electron paramagnetic resonance spectra of the ferritin, Ferrum Lek and Maltofer® were decomposed into multiple spectral components demonstrating the presence of minor ferro- or ferrimagnetic phases along with revealing marked differences among the studied substances. Mössbauer spectroscopy provides evidences on several components in the measured spectra which could be related to different regions, layers, nanocrystallites, etc. in the iron cores that coincides with heterogeneous and multiphase models for the ferritin iron cores.

Structural features of the La-Sr-Fe-Co-O system

Abstract:A structural study has been performed on the La0.8Sr0.2FexCo1-xO3 (x = 0.025 to 0.3) system displaying large magnetoresistance (MR) at room temperature. A detailed analysis of the crystal structure and microstructure was done by X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM and SEM). The atomic resolution TEM images and the appearing superreflections in the corresponding SAED patterns revealed that a superstructure is formed due to the presence of iron. The correlation between the ordered microstructure and the observed large MR ratio is discussed. 57Fe Mössbauer spectroscopy was utilized to gain information on the valence state of iron in the sample with x = 0.3. The lattice parameters of Fe- doped La0.8Sr0.2FexCo1-xO3 compounds were found to increase monotonously with increasing Fe content. The valence state of iron was found to be Fe3+.

Evidence for Pr3+ in EuBa1.3Pr0.7Cu3O7-δ by 141Pr Mössbauer spectroscopy

Abstract The polycrystalline compound EuBa 1.3 Pr 0.7 Cu 3 O 7− δ has been prepared and investigated by the means of 141 Pr Mossbauer spectroscopy. The observed 141 Pr Mossbauer isomer shift, δ (at T =4.2 K)=0.10 (15) mm/s relative to PrF 3 , reflect a valence state of 3+ for Pr located at the Ba site in EuBa 1.3 Pr 0.7 Cu 3 O 7− δ . Magnetic order of the Pr sublattice was not observed at T =4.2 K in contrast with the compound Eu 0.3 Pr 0.7 Ba 2 Cu 3 O 7− δ where magnetic order of the Pr sublattice appears at T =12 K. Our results explain why Pr behaves very similar to other 3+ cations (La, Nd) when substituted for Ba in this system, and suggests that suppression of superconductivity by Pr substituted at the rare earth site is a consequence of the hole filling effect.

Blood Meal-Based Compound. Good Choice as Iron Fertilizer for Organic Farming

Prevention of iron chlorosis with Fe synthetic chelates is a widespread agronomical practice but implies high costs and environmental risks. Blood meal is one of the main fertilizers allowed to be used in organic farming. Through this work a novel blood meal fertilizer was audited. Measurements such as FTIR, Raman, electron paramagnetic resonance, and Mössbauer spectroscopy, UV-visible properties, stability against pH, and batch experiments were performed to characterize and assess the reactivity on soil constituents and agronomic soils. The spectroscopy findings give clear indications that Fe is in the ferric oxidation state, is hexacoordinated, and has a low-spin form suggesting a similar structure to hemin and hematin. A spectrophotometric method at 400 nm was validated to quantify blood meal concentration at low electrolyte concentrations. Batch experiments demonstrated high reactivity of blood meal fertilizer with soil constituents, mainly in the presence of calcium, where aggregation processes are predominant, and its ability to take Fe from synthetic Fe (hydr)oxides. The beneficial profile of blood meal by a providing nitrogen source together with the capability to keep the Fe bound to porphyrin organic compounds makes it a good candidate to be used as Fe fertilizer in organic farming.

Different 57Fe microenvironments in the nanosized iron cores in human liver ferritin and its pharmaceutical analogues on the basis of temperature dependent Mössbauer spectroscopy

Mössbauer spectra of human liver ferritin and its pharmaceutical analogues Ferrum Lek and Maltofer® measured at various temperatures within the range of 295-83K were fitted using five quadrupole doublets related to different 57Fe microenvironments in various layers/regions of the ferrihydrite and akaganéite iron cores. The observed anomalous temperature dependences of some Mössbauer parameters were considered as a result of low temperature structural rearrangements in different layers/regions in the iron core.

Structural Investigation of the Effect of Praseodymium in Eu1-xPrxBa2Cu3O7-δ and EuBa2-xPrxCu3O7-δ Perovskites by 151Eu and 141Pr Mössbauer Spectroscopy

Abstract151Eu and 141Pr Mössbauer spectroscopy was applied to study the effects of Pr substitution for Eu or Ba atoms in Eu1-xPrxBa2Cu3O7-δ and EuBa2-xPrxCu3O7-δ, respectively. It was found that there exists a correlation between the 151Eu isomer shift and the onset temperature of the superconducting transition, independent of the location of Pr. This shows that the extra electrons provided by the Pr increase the electronic density in the copper oxide planes and in the 4f orbitals of Eu31, simultaneously. The polycrystalline compound EuBa1.3Pr0.7Cu3O7-δ has been investigated by 141Pr Mössbauer spectroscopy. The observed 141Pr isomer shift, δ(4.2 K) = 0.10(15) mm/s relative to PrF3, reflects a valence state of 3+ for the Pr located at the Ba site in EuBa1.3Pr0.7Cu3O7-δ, being in contrast to the valence state of 3.4+ found earlier for Pr which was situated at the rare earth site. This means that the valence state of Pr substituted for Eu is different from that of Pr substituted for Ba. These results suggest that the suppression of superconductivity by Pr substituted for the rare earth atoms is a consequence of the hole filling effect.

151Eu Mössbauer study of Eu3C60

Abstract Eu 3 C 60 salt was synthesized via the liquid ammonia route. X-ray diffractometry data show the formation of a single phase material with lattice parameters close to Eu 3 C 60 prepared previously by solid state reaction. A detailed study of 151 Eu Mossbauer spectroscopy of Eu 3 C 60 salt is presented. It was found that the relative occurrence of Eu 2+ and Eu 3+ cations is equal to 4:1.

Fabrication of Yolk/Shell Partially Inverse Spinel Cobalt Ferrite/Mesoporous Silica Nanostructured Catalysts for Organic Pollutants Degradation by Peroxymonosulfate Activation

AbstractSulfate radical based advanced oxidation process has received popular attention in organic pollutants degradation recently, including which, cobalt ferrite heterogeneous catalyst was reported to be an effective activator. However, issues of particle aggregation and metal leaching still made the activity and stability not so satisfactory. In this study, well-defined partially inverse spinel cobalt ferrite/mesoporous silica ((CoxFe1−x)[Co1−xFe1+x]O4@mSiO2) nanostructured catalysts with uniform yolk/shell architecture were synthesized successfully through a hard-templating method for the first time. The prepared catalysts were characterized by various techniques including X-ray diffraction, transmission electron microscopy, N2 physical adsorption/desorption. And moreover, Mössbauer spectroscopy was employed to confirm the detailed structure of the partially inverse spinel cobalt ferrite. It was shown that the synthesized catalysts consisted of (Co0.21Fe0.79)[Co0.79Fe1.21]O4 nanoparticles encapsulated in mSiO2 hollow spheres and the content of cobalt ferrite can be controlled by varying experimental conditions. The catalysts were utilized as peroxymonosulfate catalytic activator for organic pollutant degradation. Both sulfate radical and hydroxyl radical were certified as intermediate active species during the dye pollutants degradation process. Compared to the conventional mSiO2 supported and naked cobalt ferrites, the yolk/shell nanostructured catalysts exhibited higher activity, excellent reaction stability and sintering resistance. It is clear that the design of such yolk/shell architecture can promote the development of highly efficient catalytic nanomaterials applied to degradation of organic pollutants.Graphical AbstractWell-defined yolk/shell (Co0.21Fe0.79)[Co0.79Fe1.21]O4@mSiO2 nanostructured catalysts were successfully synthesized through hard-templating method and exhibited excellent activity and stability in dyes degradation.

The effect of carboxylic acids on the oxidation of coated iron oxide nanoparticles

Abstract57Fe Mössbauer spectroscopy, XRD, and TEM were used to investigate the effect of mandelic- and salicylic acid coatings on the iron oxide nanoparticles. These two carboxylic acids have similar molecules size and stoichiometry, but different structure and acidity. Significant differences were observed between the Mössbauer spectra of samples coated with mandelic acid and salicylic acid. These results indicate that the occurrence of iron microenvironments in the mandelic- and salicylic acid-coated iron oxide nanoparticles is different. The results can be interpreted in terms of the influence of the acidity of carboxylic acids on the formation, core/shell structure, and oxidation of coated iron oxide nanocomposites.

Mössbauer spectroscopy of human liver ferritin and its analogue, Ferrum Lek, in the temperature range of 295-90 K: Comparison within the homogeneous iron core model

Human liver ferritin and its pharmaceutical analogue, Ferrum Lek, containing nanosized hydrous ferric oxides cores in the forms of ferrihydrite and akaganeite, respectively, were studied using Mossbauer spectroscopy with a high velocity resolution in the temperature range of 295-90 K. To simplify comparison, these spectra were fitted using one quadrupole doublet within the homogeneous iron core model. An unusual line broadening with a temperature decrease was observed in this way for human liver ferritin below ∼150 K and for Ferrum Lek below ∼130 K. Some anomalies were also observed below these temperatures for spectral area and quadrupole splitting. The Debye temperature for both iron cores was evaluated from temperature dependence of isomer shift using the temperature dependence of the second-order Doppler shift.