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Nanoscroll formation by casacade intercalation–exfoliation method was investigated for a high iron-content kaolin and after the removal of its iron-bearing mineral constituents (goethite, hematite) by 11 M HCl treatment. Hindered kaolinite nanoscroll formation was observed by TEM in both cases, where the 11 M HCl treatment only slightly improved the occurrence of nanoscrolled shapes. The presence of minor amounts of well-dispersed, resilient Fe was observed after the exfoliation of 11 M HCl-treated sample, which was identified as structural Fe3+/Fe2+ in the octahedral sheet of kaolinite by Mössbauer and X-ray absorption spectroscopy. Iron substitution in the nanokaolinite TO layers was probed by computational chemistry. The computational results indicate inner coordination changes and elongation of bonds in the iron-substituted TO structure, and the increased curvature values offer an explanation for the observed experimental results for hindered nanoscroll formation. Graphical abstract

Comparison of the Mossbauer spectra of the as-prepared native iron oxide nanoparticles (IONs) and the citrate-functionalized IONs demonstrates differences in the spectral shapes at room temperature and variations of the 57Fe hyperfine parameters at 80 K. The observed differences are claimed to result from capping the IONs with citrate, thus decreasing the particle-particle interaction while promoting interaction of the outer atomic layers of the IONs with the surface molecular coating.

The effect of coating with nine different carboxylic acids (glycolic, propionic, lactic, malic, tartaric, citric, mandelic, caproic and caprylic) on nanostructured magnetite (D ~ 10 nm) was studied by Raman and photoacoustic, magnetic and 57Fe Mossbauer measurements. Mossbauer spectra of frozen suspensions showed dominantly magnetically split envelopes at lower temperatures, which were evaluated by hyperfine field distribution method. Mossbauer and Raman spectroscopy indicated similar variation of relative occurrence of magnetite and maghemite phases. These results are discussed on the basis of the hypothesis that different carboxylic acids can promote either the oxidation or reduction of iron oxide nanoparticles.

For the ubiquitous diazotrophic rhizobacterium Azospirillum brasilense, which has been attracting the attention of researchers worldwide for the last 35 years owing to its significant agrobiotechnological and phytostimulating potential, the data on iron acquisition and its chemical speciation in cells are scarce. In this work, for the first time for azospirilla, low-temperature (at 80 K, 5 K, as well as at 2 K without and with an external magnetic field of 5 T) transmission Mössbauer spectroscopic studies were performed for lyophilised biomass of A. brasilense (wild-type strain Sp7 grown with (57)Fe(III) nitrilotriacetate complex as the sole source of iron) to enable quantitative chemical speciation analysis of the intracellular iron. In the Mössbauer spectrum at 80 K, a broadened quadrupole doublet of high-spin iron(III) was observed with a few percent of a high-spin iron(II) contribution. In the spectrum measured at 5 K, a dominant magnetically split component appeared with the parameters typical of ferritin species from other bacteria, together with a quadrupole doublet of a superparamagnetic iron(III) component and a similarly small contribution from the high-spin iron(II) component. The Mössbauer spectra recorded at 2 K (with or without a 5 T external field) confirmed the assignment of ferritin species. About 20% of total Fe in the dry cells of A. brasilense strain Sp7 were present in iron(III) forms superparamagnetic at both 5 and 2 K, i.e. either different from ferritin cores or as ferritin components with very small particle sizes.

Iron-oxide nanoparticles were prepared by chemical coprecipitation method in inert gas atmosphere and also in air atmosphere in order to use them as possible nutrition source for plants. The samples were characterized by 57Fe Mossbauer spectroscopy, electron ¨ microscopy and PXRD measurements. The presence of considerable FeII contributions were indicated by 57Fe Mossbauer spectra. Furthermore TEM and XRD reflected nanomagnetite ¨ in washed and lyophilized samples prepared in inert gas atmosphere while the samples prepared in air atmosphere contained much higher amount of FeIII than characteristic of magnetite. In the case of samples prepared in inert gas, it was also shown that the immediate washing after the coprecipitation has a crucial influence on the FeII content of the nanomagnetites.

Frozen aqueous solution of hyperalkaline tin(II)-hydroxide was analysed by 119Sn Mossbauer spectroscopy at low temperature in order to determinate the structure of the hydroxo complex formed under hyperalkaline (pH > 13) conditions. Interestingly, the quadrupole doublet characteristic of this complex in the 119Sn Mossbauer spectrum exhibited asymmetry in the line intensities. Analysis of the temperature dependence of the Mossbauer spectra demonstrated that this phenomenon can be rationalised by the Goldanskii–Karyagin effect. The effect emerges due to the vibrational anisotropy of bonds in the tin complex formed in hyperalkaline solution, similarly to what has been found earlier for SnF2 with analogous Sn bond structure.

A new method is developed to synthesize magnetic carbon microspheres decorated with carbon nanofibers and iron nanoparticles (nanofurry microspheres) for separation techniques in chemistry and biology. Microspheres are synthesized by carbonizing polystyrene–divinylbenzene-based, iron-loaded ion exchange resins. The phase composition, magnetic properties, and surface area and morphology of these materials are characterized by various techniques. It is detected that superparamagnetic (SPM) magnetite is present in microspheres exclusively upon carbonization at 400–500 °C, elemental iron, both α- and γ-Fe, is the major component at 600 °C, and cementite dominates between 700 and 1000 °C. Nanofiber formation is observed to be pronounced at high temperatures. The synthesized carbon microspheres have high surface area (100–300 m2 g−1) and can be separated easily by a magnet or by filtration. Saturation magnetization of selected samples is obtained between 5 and 28 emu g−1, depending on the phase composition. The novel microcomposites are expected to be effective adsorbents or support materials in various chemical processes, for example in water and air cleaning, catalysis, and biotechnological separations. Preliminary experimental studies for Cr(VI) removal from water and for platinum deposition are provided.

A relationship between the photocatalytic effect and the local structure of 50Fe2O3⋅ (50−x)SiO2⋅xTiO2 glass abbreviated as 50FSxTi prepared by sol-gel method was investigated by 57Fe-Mossbauer spectroscopy (FeMS), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR) and ultraviolet-visible diffuse reflectance spectroscopy (UV-VIS). Mossbauer spectra of 50FSxTi glass before annealing showed a doublet with the isomer shift (δ) and quadrupole splitting (Δ) of 0.41±0.01 mm s−1 and 0.75±0.02 mm s−1, indicating that Fe3+ formed FeO6 octahedra (O h). A comparable δ of 0.36±0.02 mm s−1 and the larger Δ of 0.92±0.02 mm s−1 values were confirmed for 50FSxTi after annealed at 400 ∘ C for 3 h. These results indicates that the coordination number of iron polyhedra decreases from 6 to 4 due to annealing. UV-VIS diffuse reflectance spectra of 50FS10Ti yielded two optical band gap energies (E g’s) of 2.05 eV and 3.55 eV. This result implied that 50FS10Ti has two optical band gaps in the visible area and UV area. A bleaching test performed by 10 mL of MB aqueous solution and 40 mg of powder 50FS10Ti glass sample showed that MB absorbance decreased from 3.16 to 0.43 after UV-visible light irradiation for 2 h with the first order rate constant (k) of $1.6\times 10^{-2}~ \min ^{-1}$ . These results prove that titanium containing iron silicate glass with the composition of 50Fe2O3⋅40SiO2⋅10TiO2 has the UV and visible light responsive photocatalytic effect.

Constant current electrochemical deposition technique was used to obtain quaternary alloys of Sn-Fe-Co-Ni from a gluconate electrolyte, which to date have not been reported in the literature. For the characterization of electroplated alloys, 57Fe and 119Sn Conversion Electron Mossbauer Spectroscopy (CEMS), XRD and SEM/EDAX were used. XRD revealed the amorphous character of the novel Sn-Fe-Co-Ni electrodeposited alloys. 57Fe Mossbauer spectrum of quaternary deposit with composition of 37.0 at% Sn, 38.8 at% Fe, 16.8 at% Co and 7.4 at% Ni displayed a magnetically split sextet (B = 28.9T) with broad lines typical of iron bearing ferromagnetic amorphous alloys. Magnetically split 119Sn spectra reflecting a transferred hyperfine field (B = 2.3T) were also observed. New quaternary Sn-Fe-Co-Ni alloys were successfully prepared.

A series of novel [Fe(MeiPrGlyoxH)2(amine)2] complexes have been synthesized [(MeiPrGlyoxH2 = methylisopropylglyoxime, amine = 3,5-dimethylpyridine, 4-(dimethylamino)pyridine, 4-(phenylamino)phenol, 2-imidazolidone)] and characterized by 57Fe Mossbauer, FTIR, UV–Vis spectroscopy, mass spectrometry, AFM and thermoanalytical methods. Quantum chemical (DFT) computations of [Fe(MeiPrGlyoxH)2(3,5-dimethyl-Py)2] (Py = pyridine) complex were also performed. The square-planar structure of [Fe(MeiPrGlyoxH)2] moiety is similar to that of [Fe(MeEtGlyoxH)2]. The incorporation of branching alkyl chains (isopropyl) in the complexes alters the Fe–N bond length and results in high-spin iron(II) state.

Liquids trapped in the pores of certain silicate glasses (such as Corning Vycor ‘thirsty’ glass) were found to display frozen solutions like behavior at temperatures much higher than their actual freezing point. For example, recoilless γ-resonance absorption was observed for Mossbauer active solutes such as 119Sn and 57Fe salts at room temperature (i.e., without the need of quenching). Thus capillary Mossbauer spectroscopy (CMS) proved to be a new and useful experimental tool with great potential in solution chemistry. As part of a research project concerned with the hydrolysis of SnII salts, we attempted to perform 119Sn CMS measurements for solutions containing stannous ion in a range of aqueous environments. Somewhat surprisingly, we found that under ambient conditions, SnII aqueous liquid solutions, both the acidic and the basic systems, are essentially CMS-silent. This can be attributed to the strong temperature dependence of Lamb–Mossbauer factor of SnII species, which may result in the complete disappearance of Mossbauer pattern well below room temperature. These observations can also explain why previous publications concerned with the use of CMS dealt exclusively with SnIV and not with SnII containing liquids.

Iron(III)-containing aqueous solutions of 5-methylresorcinol (5-MR), 5-n-propylresorcinol (5-n-PR) and 4-n-hexylresorcinol (4-n-HR) at pH ~ 3 were studied by means of 57Fe transmission Mossbauer spectroscopy. Kinetic considerations were applied to the redox reactions. Density Functional Theory (DFT) calculations were performed for the alkylresorcinol (AR) molecules and their non-alkylated analogue (resorcinol). Mossbauer spectra consisted of quadrupole doublets assigned to high-spin Fe(III) and Fe(II) species. From changes in their relative spectral areas, a gradual reduction of Fe(III) by all the ARs studied was observed. However, significant differences were found for the reduction rates among the ARs. The following series of the reduction rates was established by means of Mossbauer spectroscopy: 4-n-HR ≫ 5-MR > 5-n-PR, supplemented by rate constants calculated using a kinetic model. DFT calculations resulted in the following series: 4-n-HR ≫ 5-n-PR > 5-MR ≫ resorcinol (the latter is not oxidised under the conditions applied). The reversed order of the experimentally observed 5-MR and 5-n-PR oxidation rates may be explained in terms of their different kinetic parameters related to their structure.

A relationship between physical properties and local structure of 20Li2O·10Fe2O3·xWO3·(70–x)V2O5 glass, abbreviated as xLFWV glass (x = 0 − 25 in mol%), was investigated by 57Fe-Mossbauer spectroscopy, Fourier transform infrared spectroscopy (FT-IR), differential thermal analysis (DTA), leaching test using 20 vol% HCl and DC two- or four-probe method. 57Fe-Mossbauer spectra of xLFWV glass showed an increase of quadrupole splitting (Δ) from 0.67 to 0.73±0.02 mm s − 1 and a constant isomer shift (δ) of 0.39±0.01 mm s − 1 with an increase of ‘x’ from 0 to 25. This suggests that FeIIIO4 tetrahedra gradually increase their local distortion along with a substitution of WO3 for V2O5. DTA of xLFWV glass showed an increase in glass transition temperature (T g) from 252 to 298 $_{\pm 5}^{\circ}$ C with an increase of ‘x’. Composition dependency of T g and Δ indicates that FeIII atoms occupy substitutional sites of WO6 octahedra as network former (NWF), since a large slope of 680 K (mm s − 1) − 1 was obtained in T g − Δ plot. Comparable electrical conductivities (σ) of 2.5 × 10 − 6, 1.9 × 10 − 6, 8.4 × 10 − 7 and 2.9 × 10 − 6 S cm − 1 obtained for xLFWV glasses with ‘x’ of 0, 10, 20 and 25, respectively increased to 2.4 × 10 − 2, 2.4 × 10 − 3, 3.5 × 10 − 4 and 8.8 × 10 − 5 S cm − 1 after annealing at 400 °C for 100 min. Smaller Δ values of 0.58 and 0.67±0.02 mm s − 1 obtained in annealed xLFWV glasses with ‘x’ of 0 and 10, respectively indicate that structural relaxation occurs in VO4 units of vanadate glass units, as had been observed in other vanadate glasses.

N-containing fully saturated (L-prolinate) or aromatic (indole-2-carboxylate) heterocyclic anions were immobilised in CaFe-layered double hydroxide with the dehydration-rehydration method from aqueous ethanol or acetone. The structure of the resulting organic-inorganic hybrids was characterised mainly with powder X-ray diffraction and 57Fe Mossbauer spectroscopy, and as supplementary analysis scanning electron microscopy, energy dispersive X-ray spectroscopy with elemental mapping and molecular modelling were also applied. It was found that the solvent mixture used for the synthesis caused enormous difference in the interlayer spacings of the obtained inorganic-organic hybrids.

Preliminary 57 Fe transmission Mossbauer spectroscopic data were ob- tained for the first time for live cells of the plant-growth-promoting rhizobacterium Azospirillum brasilense (wild-type strain Sp245) grown aerobically with 57 Fe III - nitrilotriacetate (NTA) complex as a sole source of iron. The results obtained have shown that live cells actively reduce part of the assimilated iron(III) to iron(II), the latter amounting up to 33 % of total cellular iron after 18 h of growth, and 48 % after additional 3 days of storage of the dense wet cell suspension in nutrient-free saline solution in air at room temperature (measured at 80 K). The cellular iron(II) was found to be represented by two quadrupole doublets of different high-spin forms, while the parameters of the cellular iron(III) were close to those typical for bacterioferritins.

Mossbauer spectroscopy has been used to investigate the nature of the Zinc-Iron alloys present within the Hot Dip Galvanized (HDG) layers of steel with a silicon content of 0.35 %. The investigation also studied the impact of the powder coating pretreatment on the nature of the alloy layers. The acid etching process within the pretreatment process in particular would be expected to have a significant impact on the HDG layer. This study utilized 57Fe Mossbauer spectroscopy to examine identically processed samples prior to and post pre treatment. XRD and 57Fe CEMS measurements were performed on hot galvanized S355J2 + N samples, forming sandwiched structure. Both XRD and CEMS reveal the presence of dominant steel phase in accordance with its estimated occurrence on the surface of the sandwiched samples. Minor Γ-Fe3Zn10, ζ-FeZn15 and solid solution Fe-Zn as well as minor Fe-Si phases could also be identified.

Sn-Fe thin films were electrodeposited by constant current deposition on copper substrates using an aqueous gluconate based electrolyte with varying concentrations of the organic additive peptone. Good quality metallic deposits were obtained with surface morphologies which varied with the concentration of peptone present in the electrolyte. The effect of peptone concentration on the deposition process was studied using electrochemical polarization curves and EDX analysis. The effect of peptone concentration on deposit structure and surface morphology was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and 57Fe and 119Sn conversion electron Mossbauer spectroscopy (CEMS). It was concluded that the addition of small amounts of peptone to the electrolyte slightly increased the bath stability and led to changes in the alloy composition of the electrodeposits. It was found that increases in the peptone content increased the amount of the crystalline structure in the deposits with corresponding reductions in the amounts of amorphous structure present in the deposits.

The effects of the Mg(II)/Fe(III) ratio on the structure and Fe microenvironments in MgFe LDH substances were investigated. The LDHs were prepared by the co-precipitation method with Mg(II)/Fe(III) ratios from 2:1 to 6:1. The materials were characterized by 57Fe Mossbauer spectroscopy and powder X-ray diffractometry. The 57Fe Mossbauer spectra exhibited asymmetric doublet corresponding to high-spin Fe(III) microenvironments in all LDH structure. It was found that the quadrupole splitting decreased with increasing Mg(II)/Fe(III)ratio reflecting change in the electric field gradient due to the incorporation of different amounts of iron into the Mg-containing layers.

A relationship between electrical conductivity (σ) and local structure of 15Li2O·10Fe2O3·xSnO2·(70–x)V2O5·5P2O5 glass (x = 0–20 mol%), abbreviated as xLFSVP glass, was investigated by 57Fe- and 119Sn-Mossbauer spectroscopies, differential thermal analysis (DTA) and dc-four probe method. A small increase in quadrupole splitting (Δ) for FeIII was observed from 0.70 to 0.74± 0.02 mm s − 1 with an increase of “x”, whereas isomer shift (Δ) values of 0.40±0.01 mm s − 1 were independent of “x”. This result suggests that local distortion of FeIIIO4 tetrahedra was slightly increased in SnO2-containing vanadate glasses, which was reflected as an increase in glass transition temperature (Tg) from 266 to 285±5 °C. A slope of 675 K / (mm s − 1) obtained in ‘Tg vs. Δ plot’ proved that FeIII occupied the site of network former (NWF). An isothermal annealing of 10LFSVP glass at 500 °C for 100 min resulted in a marked decrease of Δ from 0.72 to 0.56±0.02 mm s − 1, indicating that local distortion of FeO4 tetrahedra was reduced by the structural relaxation of 3D-network. In contrast, identical δ and Δ values of 0.07±0.01 and 0.53±0.02 mms − 1, respectively, were observed in 119Sn-Mossbauer spectra of 10LFSVP glass before and after the annealing. These results indicate that SnIVO6 octahedra are loosely bound in the glass matrix as a network modifier (NWM). A marked increase in σ from 7.4 × 10 − 7 to 9.1 × 10 − 3 S cm − 1 was observed in 20LFSVP glass after the isothermal annealing, indicating that structural relaxation of 3D-network evidently causes a marked increase in σ.

A relationship between waste-water cleaning ability and local structure of iron-containing soda-lime silicate glass, 15Na2O·15CaO·xFe2O3·(70-x)SiO2 (x = 10–50 in mass%), abbreviated as NCFSx glass, was investigated by means of 57Fe-Mossbauer spectroscopy, redox titration with KMnO4 for the determination of chemical oxygen demand (COD) and inductively coupled plasma optical emission spectroscopy (ICP-OES). Mossbauer spectra of NCFSx glass with “x” of 10 and 30 were composed of two doublets: one due to FeIIIO4 tetrahedra (Td) with isomer shift (δ) of 0.23–0.26 mm s − 1 and quadrupole splitting (Δ) 1.01–1.04 mm s − 1, and the other due to FeIIO6 octahedra (Oh) with δ of 1.00–1.03 mm s − 1 and Δ of 2.03–2.05 mm s − 1. Absorption area for FeII(Td) was decreased from 9.7 to 6.5 and 0.0 % when “x” was increased from 10 to 30 and 50. A leaching test performed with 500 mL of artificial waste water and 2.0 g of NCFS50 revealed waste-water cleaning ability of soda-lime glass, e.g., COD was reduced from 280 to 55.2 mg L − 1 after 10 day-leaching. After 10 day-leaching, it proved that iron was dissolved into waste water to a level of 5.3\(_{7} \times 10^{-1}\) mg L − 1. These results prove that organic matter could be effectively decomposed with iron-containing soda-lime silicate glass.

As-quenched and stress field annealed FINEMET ribbons were irradiated with 246 MeV energy Kr, 470 MeV energy Xe and 720 MeV energy Bi ions and investigated by 57Fe Mossbauer spectroscopy and XRD methods. The change in relative areas of the 2nd and 5th lines in the Mossbauer spectra indicated significant changes in the magnetic anisotropy of both as-quenched and stress annealed FINEMET due to irradiation with swift heavy ions. Differences were observed between the effect of irradiations with various ions having different energy and fluence. The effect of irradiation on the magnetic orientation in FINEMET was explained in terms of radiation induced defects. The swift heavy ion irradiation can be applied to produce FINEMET ribbons with more favorable soft magnetic properties for technological applications.

K2Fe3(OH)2(SO4)3(H2O)2 was prepared by hydrothermal synthesis. The crystal structure is the isomorphous phase of K2Co3(OH)2(SO4)3(H2O)2. Mossbauer spectra of K2Fe3(OH)2(SO4)3(H2O)2 were measured at low temperatures between room temperature and 14 K, and the hyperfine interactions were analyzed. The Neel temperature is 39 K. Two paramagnetic Fe2 + species were observed in the Mossbauer spectrum at room temperature, and Mossbauer spectra measured below 38 K were decomposed into four magnetic subspectra. From the temperature dependence, it is found that the local electron density at each site is largely deviating at low temperatures, which may induce the giant coercivity.

The thermal behavior of tin containing oxalate, EDTA, and inositol-hexaphosphate were investigated. The end products of synthesis were identified by Mossbauer-, XRD analyses, and FTIR studies. The thermal decompose of the samples was studied by DTA-TG analysis. The simultaneously obtained DTA and TG data makes it possible to follow the thermal decomposition of the investigated samples. The tin oxalate decomposed in the temperature range of 520–625 K through tin carbonate formation and finally yielded CO2 and SnO. The tin EDTA complex first lost its hydrate bound water till 520 K. The followed thermal events related to the pyrolysis of anhydrous salt. The intense exothermic process that exists in the temperature range of 820–915 K is due to the formation of SnO2. The tin sodium inositol-hexaposphate lost its hydrate bound water (~10%), up to 460 K. The following sharp exothermic process, in the temperature range of 680–750 K is due to the decomposition and parallel oxidation of organic part of the molecule. At the end of this process, a mixture of phosphorous pentaoxide, sodium carbonate, and tin dioxide is obtained.

Tin(II/IV) phosphate was prepared by various synthetic methods. The different methods resulted in tin phosphate with different properties, i.e., different crystalline form and behaviour during thermal treatment. The prepared materials have 3 mol water of crystallisation, which they lose in different ways. Total mass loss was between 20 and 30%. This could be connected with water loss, going generally in two steps in parallel with endothermic processes. At the end of thermal treatment, tin pyrophosphate is obtained, irrespective of the method of preparation used.

A relationship between the water purifying effect and structure of 0.5xNa2O·0.5xCaO·5Fe2O3·(95–x)SiO2 glass (Na2O/CaO = 1; NCFS glass) with ‘x’ of 20 and 50 were investigated by means of 57Fe-Mossbauer spectroscopy, X-ray diffraction (XRD), induced coupled plasma optical emission spectroscopy (ICP-OES), as well as absorption spectroscopy, pH and oxidation-reduction potential (ORP) measurements. In the case NCFS glass with ‘x’ of 20, dissolved amounts of total Fe, Na + , and Ca2 + were respectively estimated to be 13.6, 39.1 and 36.7 mg/l, after 10 day-leaching test. On the other hand, the dissolved amounts of total Fe, Na + and Ca2 + were determined to be 34.3, 647.6 and 667.6 mg/l, respectively when ‘x’ was 50. The original pH value of 6.0 was increased to 10.0 and 11.6 after leaching test of NCFS glasses with ‘x’ of 20 and 50, respectively. At the same time, the ORP value was decreased from 30.0 to −195.8 and −284.7 mV in the glasses with ‘x’ of 20 and 50, respectively.

57Fe Mossbauer spectroscopy was used to study the effect of iron concentration on the oxidation state and microenvironments of iron in Fe–polygalacturonate compounds prepared by a novel method from pectin. The iron concentration of the coordination compounds was determined by inductively coupled plasma optical emission spectrometry analysis. The Mossbauer spectra of the studied compounds could be decomposed into three markedly different quadrupole doublets referring to three microenvironments. Two of these have ferrous and one has ferric oxidation state. In the applied concentration range the relative occurrence of the ferric component was found to increase considerably with iron concentration. At the same time, with increasing iron concentration the relative occurrence characteristic of the three components showed saturation behaviour up to the iron concentration at which for each pair of galacturonic acid units there is on average one iron atom in the system, which iron concentration value is interpreted as to be related to the complete fill up of certain iron complexation sites of the polygalacturonate chains.

The compound Fe[C(SiMe3)3]2 has been prepared and investigated by the means of powder X-ray diffractometry and 57Fe Mossbauer spectroscopy. The compound’s unique geometry, in which iron is linearly coordinated by the two C(SiMe3)3 ligands, results in a unusual electronic structure of iron, which is visualized as an extreme high hyperfine magnetic field of 157.5(8) T as sensed by the 57Fe nucleus at T = 20 K. In order to obtain information on the electronic structure of iron and on the bonds to the ligands, DFT (density functional theory) calculations were carried out on Fe[C(SiMe3)3]2. The high-spin state of iron was found to be energetically favored: an Fe(II) electron configuration of 3d5.83 4s0.72 is predicted, where the 4s electron density is only slightly polarized, and most of the unpaired electrons have 3d character. By assuming a linear crystal field, and associated 3d level scheme as a starting point, it is suggested that the extreme high hyperfine magnetic field, observed along with an apparently negative quadrupole splitting, is perpendicular to the C–Fe(II)–C bond axis, and can be decomposed mainly into contact (B c ≈ 44 T), dipolar (B d ≈ 14 T), and orbital (B L ≈ 99 T) hyperfine magnetic field contributions.

Distinct chemical species of iron were investigated by Mössbauer spectroscopy during iron uptake into cucumber roots grown in unbuffered nutrient solution with or without 57Fe-citrate. Mössbauer spectra of iron deficient roots supplied with 10-500 microM 57Fe-citrate for 30-180 min and 24 h and iron-sufficient ones, were recorded. The roots were analysed for Fe concentration and Fe reductase activity. The Mössbauer parameters in the case of iron-sufficient roots revealed high-spin iron(III) components suggesting the presence of FeIII-carboxylate complexes, hydrous ferric oxides and sulfate-hydroxide containing species. No FeII was detected in these roots. However, iron-deficient roots supplied with 0.5 mM 57FeIII-citrate for 30 min contained significant amount of FeII in a hexaaqua complex form. This is a direct evidence for the Strategy I iron uptake mechanism. Correlation was found between the decrease in Fe reductase activity and the ratio of FeII-FeIII components as the time of iron supply was increased. The data may refer to a higher iron reduction rate as compared to its uptake/reoxidation in the cytoplasm in accordance with the increased reduction rate in iron deficient Strategy I plants.

Structural change of chrysotile caused by isothermal annealing and glassification was examined by 57Fe-Mossbauer spectroscopy, X-ray diffractometry (XRD), X-ray fluorescence analysis (XRF), differential thermal analysis (DTA) and scanning electron micrography (SEM). From 57Fe-Mossbauer spectra, it proved that FeII in the pristine chrysotile was oxidized to FeIII when annealed at 1,000°C. By contrast, FeIII was reduced into FeII when annealed at 1,300°C under in ambient atmosphere. Both forsterite (Mg2SiO4) and fayalite ((Fe, Mg)2SiO4) were precipitated when the chrysotile was annealed at higher than 1,000°C. Homogeneous glass samples were obtained by melting asbestos with waste-glass powder, Na2CO3 and K2CO3 at 1,300°C for 15 min. A constant isomer shift value of 0.23 ±0.01 mm s − 1 and an increase in the quadrupole splitting value from 0.70 ±0.02 to 1.01 ±0.02 mm s − 1 were observed in the glassified chrysotile.

Local structure and thermal durability of semiconducting xBaO·(90 − x)V2O5 · 10Fe2O3 glasses (x = 20, 30 and 40), NTA glass TM, before and after isothermal annealing were investigated by 57Fe-Mossbauer spectroscopy and differential thermal analysis (DTA). An identical isomer shift (\(\mathit{\delta}\)) of 0.39 ± 0.01 mm s − 1 and a systematic increase in the quadrupole splitting (Δ) were observed from 0.70 ± 0.02 to 0.80 ± 0.02 mm s − 1 with an increasing BaO content, showing an increase in the local distortion of FeIIIO4 tetrahedra. From the slope of the straight line in the T g–Δ plot of NTA glass TM, it proved that FeIII plays a role of network former. Large Debye temperature (Θ D) values of 1000 and 486 K were respectively obtained for 20BaO · 70V2O5 · 10Fe2O3 glass before and after isothermal annealing at 400°C for 60 min, respectively. This result also suggests that FeIII atoms constitute the glass network composed of tetrahedral FeO4, tetrahedral VO4 and pyramidal VO5 units. The electric conductivity of 20BaO · 70V2O5 · 10Fe2O3 glass increased from 1.6 × 10 − 5 to 5.8 × 10 − 2 S cm − 1 after isothermal annealing at 450°C for 2,000 min. These results suggest that the drastic increase in the electric conductivity caused by heat treatment is closely related to the structural relaxation of the glass network structure.

Fe[C(SiMe3)3]2 compound, in which iron is coordinated by two carbons, was prepared using the reaction of FeCl2 with (Me3Si)3CLi, and investigated by XRD, 57Fe Mossbauer spectroscopy and DFT calculations. 157.5 T hyperfine magnetic field was found at the site of the iron nucleus of this compound at 20 K. DFT calculations predict the quintet states to be clearly favored energetically over the lower spin states. The population analysis reveals considerable 4s as well as large unpaired 3d electron contributions, which can be responsible for the extremely high hyperfine field.

Mossbauer study of La1 − x Sr x 57Fe0.025Co0.975O3 (0.15 ≤ x ≤ 0.25) perovskites below their magnetic ordering temperature shows cooperative electronic and magnetic phase separation for all compositions investigated. It is shown that the increase of the Sr concentration results in a transition from superparamagnetism to long range ferromagnetism of Co clusters between x = 0.18 and 0.2. In-field Mossbauer measurements revealed the existence of frustrated magnetic interactions at x = 0.22.

Rutile-type Co x Ti1 − x O2 − d laser deposited on alumina substrate was studied after 57Co doping, using emission Mossbauer spectroscopy. It was found that although under certain conditions (i.e., which result in high conductivity) the thin rutile layers showed magnetooptical effect, the Mossbauer probe did not reveal any magnetic splitting, but showed paramagnetic Co3 + (Fe3 + ) in the films of low electric resistance. This supports that these samples have carrier induced magnetism which is also connected to the defect structure of the rutile films.

The mixed zirconium, titanium, hafnium and first-row transition metal oxides (containing phosphorous oxide) were prepared using ion exchange method followed by calcinations at 1020 K during 12 h. The resulted mixed oxides were identified by XRPD method and studied their thermal behaviour by TG-DTA analysis. As a result of thermal analysis there were found one exothermic (with a peak at about 950 K), and one endothermic (with a peak at about 1300 K) processes, both without mass loss. The observation was valid for all investigated samples. The analysis of XRPD patterns of the investigated samples showed well-defined crystal phases characteristic of each oxide. The XRPD analysis also verified the phase transition of tetravalent metal oxides from orthorhombic to tetragonal, observed by DTA analysis.

Thin films prepared by vacuum evaporation of 57Fe and subsequent low energy ion implantation were investigated by conversion electron Mossbauer spectroscopy and AFM measurements. A sextet with Mossbauer parameters of δ = 0.1 mm/s and B = 26 T appearing in the CEM spectra was identified as amorphous iron. Passivation and phosphonation of the thin films revealed the high affinity of amorphous iron in chemical reactions.

The speciation of iron in aqueous solutions containing Fe3 + and selected chelates such as EDTA, EDDA, CDTA and HEDTA has been studied using transmission 57Fe Mossbauer spectrometry in frozen solutions. The protonation of various complexes as well as binuclear complex formation could be detected as a function of pH. Autoreduction of Fe3 + to Fe2 + was observed in several cases. Reaction with hydrogen peroxide proved to be rather different for the four ligands, while the dihapto complex [XFe(η 2-O2)]3 − had surprisingly identical Mossbauer parameters for X = EDTA, CDTA or HEDTA. Paramagnetic spin relaxation observed in the Mossbauer spectra was found to be strongly influenced by the identity of the chelating ligand, despite the basically spin-spin origin of the phenomenon.

The influence of water on the interaction between iron(III) and indole-3-acetic acid (IAA) was studied in different organic solutions using rapid-scan stopped-flow spectrophotometry and rapid-freeze/quench Mossbauer spectroscopy. Measurements were also performed in ethanol–water and acetone–water mixtures. The results showed that the interaction between FeIII and IAA resulted in dimeric FeIII–IAA complex within 1 s, followed by a slow second step to give Fe2+ and IAA(oxidized). No such products were formed in the absence of water. The visible and Mossbauer spectra reflect the nature of the organic solvent and that of the anion of iron(III) salts.

Emission and transmission Mossbauer studies of La0.8Sr0.2CoO3-δ perovskites doped with ∼0.02 stoichiometric units of oxygen vacancy or 2.5% iron corroborate the occurrence of electronic phase separation in these systems. The effect of the small perturbation of the CoO3 sublattice with either iron ions or oxygen vacancies on the bulk magnetization as well as on the Mossbauer spectra is in good agreement with the double exchange based cluster model. The magnetoresistance does not show any peak near the Curie temperature, but reaches -84% in a field of 7.5 T at T = 8 K. Below TC ≈ 180 K the Mossbauer spectra distinctly include the contribution from paramagnetic and ferromagnetic regions, providing direct evidence for phase separation. No contribution to the spectra from Fe4+ ions can be observed, which is an unambiguous evidence that at low concentration iron (either directly doped or formed from 57Co by nuclear decay) is accommodated in the cobaltate lattice as Fe3+ ion.

The effect of FeCl 3 in acetonic medium on the structure of Na-bentonite was studied using X-ray diffraction (XRD), 57 Fe Mossbauer spectroscopy, X-ray fluorescence spectroscopy and infrared spectroscopy to describe the structure of the bentonite before and after treatment. In the samples treated with FeCl 3 , an increase in the basal spacing was found by XRD, while a new magnetically split component assigned to Fe 3+ incorporated within the interlayer regions of montmorillonite showed up in the low-temperature Mossbauer spectra. The Mossbauer parameters observed were close to those of Fe oxyhydroxides, suggesting the presence of some kind of nanoparticles. These results show that the treatment with acetonic FeCl 3 solution is an effective method for introducing Fe into montmorillonite in the form of Fe 3+ accommodated in the interlayer region. The treated samples proved to be efficient Lewis catalysts in the acylation of aldehydes (benzaldehyde and 4-OH-benzaldehyde) by acetic acid anhydride.

In this paper we present 57Co emission Mossbauer and AC magnetic susceptibility studies of La0.8Sr0.2CoO3-δ perovskite. The observed coexistence of paramagnetic and magnetic subspectra in the 57Co emission Mossbauer spectra, as well as the difference of their isomer shifts support the existence of electronic phase separation in this perovskite, in good agreement with the double exchange based cluster model.

57Fe Mossbauer spectroscopy, X-ray diffraction, X-ray fluorescence spectroscopy and infrared spectroscopy were used to study the effect of FeCl3 and acetone on the structure of a Na-bentonite. XRD indicated the incorporation of Fe3+ ions into the interlayer space since the basal lattice spacing of montmorillonite increased to 1.6 from 1.24 nm after treatment with FeCl3 dissolved in acetone. Interlayer Na+ ions could be exchanged to Fe3+. Magnetically split Mossbauer subspectra with internal magnetic fields 41 and 46 T at 74 K, were associated with two main Fe3+ microenvironments within the interlayer regions. The resultant Fe-montmorillonite was successfully applied as a catalyst in the preparation of 1,1-diacetates from aromatic aldehydes and acetic acid anhydride.

A relationship between the structure and water purifying ability of waste glass prepared from household garbage and Fe2O3 was examined by 57Fe-Mossbauer and induced coupled plasma (ICP) measurements. From the Debye temperature of waste glass, FeII proved to be loosely bound in the glass network as a network modifier. Dissolution amount of FeIII into artificial drain can be controlled from 0.14 to 0.35 mg/l by changing the Fe2O3 content. It proved that chemical oxygen demand (COD) decreases in proportion to the content of FeIII, indicating that iron causes decomposition of organic and phosphorus compounds.

EU0.8Sr0.2Fe x Co1−x O3−z CMR perovskites with different iron concentrations (x=0, 0.025, 0.075, 0.15, 0.3) were investigated by X-ray diffraction, AC magnetic susceptibility, magnetotransport, as well as 57Fe and 151Eu Mossbauer spectrometry. The valence state of europium ions was found to be trivalent, independently of the iron concentration. 57Fe Mossbauer spectra and magnetic susceptibility of the investigated perovskites presented complementary results for the magnetic transitions.

The chemical reactions between iron(III) and indole-3-acetic (IAA), -propionic (IPA), and -butyric (IBA) acids were studied in acidic aqueous solutions. The motivation of this work was that IAA is one of the most powerful natural plant-growth-regulating substances (phytohormones of the auxin series). Mossbauer spectra of the frozen aqueous solutions of iron(III) with indole-3-alkanoic acids as ligands (L), showed parallel reactions between Fe3+ and the ligands. Partly, it resulted in a complex formation which precipitated in aqueous solution and partly, in a redox process with iron(II) and the oxidised indole-3-alkanoic acids as products. The Mossbauer parameters of the Fe2+ species suggested a hexaaquo coordination environment. The chemical composition and coordination structure of the precipitated complexes were investigated using elemental analysis, Mossbauer spectroscopy, Fourier transform infrared (FTIR) and Raman spectroscopic techniques. The complexes were soluble in some organic solvents. So, Mossbauer, FTIR and solution X-ray diffraction measurements were carried out on the solution of complexes in acetone, hexadeutero acetone and methanol, respectively. The data obtained supported the existence of the μ-dihydroxo-bridging structure of the dimer: [L2Fe FeL2] (where L is indole-3-propionate, -acetate or -butyrate).

Hydrated microcrystalline compound, V1-xCrxOy·nH2O, where x

57Fe conversion electron Mossbauer spectroscopy, X-ray diffraction, electrochemical and magnetic measurements were used to study pulse electroplated Fe-P and Ni-Fe coatings. XRD and 57Fe CEMS measurements revealed the amorphous character of the novel pulse plated Fe-P alloys. CEM spectra indicated significant differences in the short range order and in the magnetic anisotropy between the Fe-P deposits pulse plated at medium long deposition time (t on=2 ms), with short relaxation time (t off=9 ms) and low current density (I p=0.05 Acm−2) or at short deposition time (t on=1 ms) with long relaxation time (t off=250 ms) and high current density (I p=1.0 Acm−2). The broad peaks centred around the fcc reflections in XRD of the pulse plated Ni-22 wt.% Fe deposit reflected a microcrystalline Ni-Fe alloy with a very fine, 5–8 nm, grain size. The CEM spectrum of the pulse plated Ni-22 wt.% Fe coating corresponded to a highly disordered solid solution alloy containing a minute amount of ferrihydrite. Extreme favourable soft magnetic properties were observed with these Ni-Fe and Fe-P pulse plated thin layers.

The microstructures of a wear induced surface glazed layers formed during sliding wear of Nimonic 80A against Stellite 6 at 20–750 °C using a speed of 0.314 m s-1 under a load of 7 N have been investigated using X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) in combination with energy dispersive X-ray (EDX) analysis. The defects formed in the glazed layers were measured by positron lifetime spectroscopy. The results indicate the formation of a wear resistant nanostructured glazed layer. Positron lifetime and Doppler-broadening measurements demonstrated that the defects (mainly dislocations) existed in the glazed layers at low temperatures which increasing wear test temperature led to decrease in defects density. Positron measurements also suggested that, at the annealing temperature (1200 °C), the presence of dislocations might lead to the formation of ordered or partially ordered regions in Nimonic 80A.

La0.8Sr0.257Fe0.05Co0.95O3-δ perovskite is investigated by 57Fe transmission and emission Mossbauer spectroscopy, X-ray diffraction, AC magnetic susceptibility and magnetotransport measurements. Temperature dependence of the 57Fe Mossbauer isomer shift, quadrupole splitting, magnetic hyperfine field, line broadening, and relative spectral area is presented in a detailed manner for La0.8Sr0.257Fe0.05Co0.95O3-δ . The oxidation state of iron is determined to be Fe3+, and the presence of preferential electronic charge compensation Fe3+ ↦ Fe4+ over that of Co3+ ↦ Co4+ is excluded. Relaxation of iron magnetic moments reflected by the 57Fe Mossbauer spectra of La0.8Sr0.257Fe0.05Co0.95O3-δ are interpreted as evidence for the existence of superparamagnetic like Co clusters and a corresponding cluster glass magnetic phase formed below T ≈65 K.