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The use of magnetic nanoparticles in C–C coupling reactions enables the facile recovery of the catalyst under environmentally friendly conditions. Herein, the synthesis of Pd/Fe@Fe3O4 nanoparticles by the reduction of Pd2+ and oxidation of Fe on the surface of preformed Fe@Fe3O4 is reported. The nanoparticles were characterized using a variety of analytical techniques (transmission electron microscopy, Mössbauer spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction) to determine their size, structure, and chemical composition. The catalytic efficiency of these nanoparticles in classical Suzuki–Miyaura coupling reactions was investigated. The nanoparticles achieved high catalytic activity with the application of local heating by an alternating magnetic field. An investigation was conducted at identical temperatures to compare global heating with the application of an external magnetic field; magnetic heating demonstrated excellent substrate conversion in lesser time and at a lower temperature. The catalyst could also be recycled and reused three times, with ~ 30% decrease in the substrate conversion, which is most likely due to the agglomeration of the Pd nanoparticles or poisoning of the Pd catalyst. This approach, which takes advantage of the catalytic activity and magnetic susceptibility of magnetic nanoparticles, can be applied to several organic transformations to improve their efficiency, We are grateful for financial support provided by the Government of Spain through project PGC2018-095642-B-I00. In addition, A. Villacampa and L. Duque acknowledge the Community of Madrid for Predoctoral contracts PEJD-2019-PRE/IND-15356 and PEJ-2019-AI/IND-12506, respectively, co-financed by the European Social Fund through the Youth Employment Operational Program and the Youth Employment Initiative (YEI)

15 pags., 9 figs., 2 tabs., Pyrolyzed non-precious metal catalysts have been proposed as an alternative to substitute the expensive and scarce noble metal catalysts in several conversion energy reactions. For the oxygen reduction reaction (ORR), the pyrolyzed catalyst M−N−C (M: Fe or Co) presents remarkable catalytic activity in acid and alkaline media. These pyrolyzed materials show a high heterogeneity of active sites being the most active in the MNx moieties. The activity and stability of these catalysts are also conditioned by other structural parameters such as the area, the N-doping, and by the presence of metal particles. In this study, we explore the use of FeO nanoparticles as templates and as iron sources to synthesize Fe−N−C. The best performance for the ORR in acidic media was reached with the catalysts using nanoparticles covered by PANI and iron salts as the precursor, with an onset potential of 0.85 vs. RHE and a direct 4-electrons mechanism. We corroborated the use of the catalysts’ redox potential as reactivity descriptors and discussed the detrimental role of the presence of FeC metallic particles in the mechanism. Based on the experimental results, we performed DFT calculations to explore the influence of N-doped species on the electronic density of the iron centers of FeN4 active sites, and we propose a theoretical model for increasing the activity based on the distance and ratio of N-doping to iron center., This work was supported by Fondecyt Regular Project 1161117, Conicyt Scholarship 21160212, Fondecyt Postdoctoral Projects 3180509 and 3170330, and Anillo Project ACT-192175. By MICIN grant PGC2018-095642-B-I00, MCIN/AEI/10.13039/501100011033 RTI2018-095303-B-C51, by ERDF A way to making Europe, and by CISC grant 2021AEP056.

Catalyst stability has become a challenging issue for advanced oxidation processes (AOPs). Herein, we report an alternative method based on 3D printing technology to obtain zero-valent iron polylactic acid prototypes (ZVI@PLA) in a single step and without post etching treatment. ZVI@PLA was used to activate persulfate (PS) for the removal of Tetracycline (TC) in recirculating mode under two different heating methodologies, thermal bath and contactless heating promoted by magnetic induction (MIH). The effect of both heating methodologies was systematically analysed by comparing the kinetic constant of the degradation processes. It was demonstrated that the non-contact heating of ZVI by MIH reactivates the surface of the catalyst, renewing the surface iron content exposed to the pollutant solution, which makes the ZVI@PLA catalyst reusable up to 10 cycles with no efficiency reduction. In contrast, by using a conventional thermal bath, the kinetic constant gradually decreases over the 10 cycles, because of the superficial iron consumption, being the kinetic constant 5 times lower in the 10th run compared to MIH experiment. X-ray diffraction and Mössbauer spectroscopy confirmed the presence of metallic iron embedded in the ZVI@PLA prototype, whose crystalline structure remained unchanged for 10th cycles of MIH. Moreover, it was proven that with no contact heating technology at low magnetic fields (12.2 mT), the solution temperature does not increase, but only the surface of the catalyst does. Under these superficial heated conditions, kinetic rate is increased up to 0.016 min compared to the value of 0.0086 min obtained for conventional heating at 20 °C. This increase is explained not only by PS activation by iron leaching but also by the contribution of ZVI in the heterogeneous activation of persulfate., This research was funded by the Madrid Government (Comunidad de Madrid-Spain) under the Multiannual Agreement with Universidad Autónoma de Madrid in the line of action encouraging youth research doctors, in the context of the V PRICIT (Regional Programme of Research and Technological Innovation), (SI1-PJI-2019-00366) and by the Spanish Ministry of Science, innovation, and Universities under projects PGC2018-095642-B-I00 and PID2019-104600RB-I00

11 pags., 7 figs., 3 tabs., Fe-N-C pyrolyzed materials have been proposed as substitutes of the noble-based catalyst for energy conversion reactions. However, their use as electrochemical sensors has not been deeply explored. In the present work, different Fe-N-C pyrolyzed catalysts were synthesized for the amperometric sensing of the HO reduction in neutral media. The catalysts were characterized by BET, TEM, FESEM, XPS, Mössbauer spectroscopy, and cyclic voltammetry. The catalysts present an N-doped graphitic matrix with a macroporous structure and mesoporous contribution. Different amounts of N-pyridinic, N-pyrrolic, N-graphitic, N-oxides, and FeN4 sites have been detected on the catalysts. Among the different active sites present in the catalysts, the FeN4 structure is proposed as the most catalytic active site for the hydrogen peroxide reduction reaction (HPRR). Under optimal conditions (0.61 V vs. NHE, 0.00 V vs. Ag/AgCl), the materials show a lineal amperometric response in the range of 0.08 and 14 µM, with a sensitivity of 31.3 µA µM cm, and a detection and quantification limits of 0.25 µM and 0.75 µM respectively. The amperometric results indicate that the best performance is reached when increasing the amount of FeN4 active sites, and the redox potential of the FeN4 species becomes more positive. The Fe-N-C catalyst stands out for the more positive working potential than other materials proposed in the literature., We are grateful to FONDECYT Grant 1170352 & ANID- PFCHA/PhD fellowship No. 21160955 awarded to C. Candia-Onfray. F.J. Recio and N. Menendez are grateful to The Spanish Ministry of Economy and Competitiveness funded this research under project PGC2018-095642-B-I00.

[EN] Novel 3D Fe/SiC honeycomb monolithic reactors with different morphologies (i.e. cell geometry, cell density and interconnected channel pattern) have been conceptually designed, digitally prototyped and manufactured by robocasting. Square, tronco-conical and triangular cell geometries with parallel channels presenting staggered or faced interconnections have been tested in the phenol hydroxylation reaction with hydrogen peroxide to produce dihydroxybenzenes, such as catechol and hydroquinone. The analysis of the valence state of iron in the monoliths by Mössbauer spectroscopy identified iron silicides, viz. FeSi and α-FeSi, as the iron catalytic species. The results demonstrate that an increased macro-channel tortuosity, favoured by a high density cell and a high number of not-facing inter-connected channels, facilitates the selectivity to the dihydroxybenzenes. In particular, 3D Fe/SiC monoliths with triangular cells provide an outstanding improvement with respect to the commercial process, not only because of their superior performance (S=99.1% and Y=29.6% at 80 ºC) and stability (over 8 days on stream) but also in sustainability (i.e. operation in flow-reactor, no need of catalyst filtration, water as unique solvent). The additive manufacturing has allowed the smart integration of the catalytic phase into the monolithic structure, enabling, by this way, to architecture the reactor independently on its chemical composition., The authors thank the financial support by the Community of Madrid through the project S2018/EMT-4341 and the Government of Spain through the projects: PGC2018-095642-B-I00 and RTI2018-095052-B-I00 (MCIU/AEI/FEDER, UE). Also, G. Vega acknowledges the Community of Madrid for the Predoctoral contract PEJD-2018-PRE/AMB-9019, co-financed by the European Social Fund through the Youth Employment Operational Program and the Youth Employment Initiative (YEI) 2018. The authors would like to thank Alvaro Pérez for performing the BET and TGA measurements.

Peroxydisulfate (PDS, S2O82−)-based advanced oxidation processes have been developed as an alternative to those based on OH, as PDS activation yields a much more stable radical like SO4 − that can maintain the oxidation ability of water treatment systems for longer time. Here, the electrochemical PDS activation has been investigated using reticulated vitreous carbon (RVC) substrate modified with Fe3O4 nanoparticles (NPs) as cathode. The NPs were exhaustively characterized by different surface analysis techniques (TEM, SEM) and Mossbauer spectroscopy. Cyclic voltammetry and linear sweep voltammetry with a rotating disk electrode allowed concluding that the main electrocatalytic role in the cathodic PDS activation to SO4 − corresponded to the Fe(II) active sites continuously promoted upon cathodic polarization. These sites were less catalytic for O2 reduction reaction, although it was still feasible with n = 2.7 electrons as determined from Koutecky-Levich analysis. Both cathodic reactions followed an inner-sphere reaction mechanism. The Fe3O4-modified RVC cathodes were employed to electrolyze Methylene Blue aqueous solutions at pH 3.5, employing different current values and PDS concentrations. Dissolved O2 was purged to impede the competitive cathodic H2O2 production and Fenton’s reaction. The occurrence of dye adsorption/electrosorption on the cathode reduced the mass transport limitations, enhancing the reaction between SO4 − and organic molecules. The best operation conditions to reach total and fast color removal at 18 min were 2 mM PDS and 10 mA, yielding > 80% TOC abatement at 45 min. Reproducible degradation profiles were found after 5 runs, thereby ensuring the stability of the Fe3O4-modified RVC, with no iron sludge production.

Uniform cobalt ferrite nanoparticles have been synthesized using an electrochemical synthesis method in aqueous media. Their colloidal, magnetic, and relaxometric properties have been analyzed. The novelty of this synthesis relies on the use of iron and cobalt foils as precursors, which assures the reproducibility of the iron and cobalt ratio in the structure. A stable and biocompatible targeting conjugate nanoparticle-folic acid (NP-FA) was developed that was capable of targeting FA receptor positivity in HeLa (human cervical cancer) cancer cells. The biocompatibility of NP-FA was assessed in vitro in HeLa cells using the MTT assay, and morphological analysis of the cytoskeleton was performed. A high level of NP-FA binding to HeLa cells was confirmed through qualitative in vitro targeting studies. A value of 479 Fe+Co mM􀀀1s􀀀1 of transverse relaxivity (r2) was obtained in colloidal suspension. In addition, in vitro analysis in HeLa cells also showed an important effect in negative T2 contrast. Therefore, the results show that NP-FA can be a potential biomaterial for use in bio medical trials, especially as a contrast agent in magnetic resonance imaging (MRI)., We are grateful for the financial support provided by the Spanish Ministry of Economy and Competitiveness who funded this research under project PGC2018-095642-B-I00 and to the Fondo Social Europeo-Gobierno de Aragón, Ministerio de la Economía y Competitividad del Gobierno de España for the public funding of Proyectos I+D+I—Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad (project n. BIO2017-84246-C2-1-R).

[EN] The search for more efficient, scalable, reproducible and standardized synthesis methods able to control particle size and crystallinity is still a challenge in nanotechnology. The one-pot microwave-assisted polyol process has been optimized for the synthesis of well-defined ferrite nanoparticles. Highly uniform and crystalline γ-Fe2O3, CoFe2O4 and ZnFe2O4 nanoparticles, with diameters below 14 nm have been prepared by an easy and reproducible one-pot microwave-assisted heating procedure in a polyol medium. A pure single phase and cubic spinel structure were confirmed by powder X-ray diffraction and Raman spectroscopy. Depending on the metal precursors, nanoparticles display magnetic features from superparamagnetic behaviour (Fe- A nd Zn-ferrites) to ferrimagnetism (Co ferrite) at room temperature. The iron oxidation state of 3+ and its short-range order coordination were studied by XAS (X-ray absorption spectroscopy). External field Mössbauer spectra, recorded at low temperature, confirmed the ferrimagnetic order with a Fe3+ and M2+ partial cationic distribution within both the A and B sites in zinc and cobalt ferrite, respectively. According to these results, the ferrite stoichiometry was (Zn0.70Fe0.30)[Zn0.30Fe1.70]O4 and (Co0.28Fe0.72)[Co0.72Fe1.28]O4. This journal is, This research was funded by the Spanish Ministry of Economy and Competitiveness under grants MAT2017-88148-R, MAT2017-86540-C4-1-R, RTI2018-095303-A-C52, and PGC2018-095642-B-I00. E. M. acknowledges financial support from the Juan de la Cierva Formación (FJCI-2015-23702) and to Comunidad de Madrid – Jóvenes Doctores project (SI1-PJI-2019-00366). L. G. acknowledges financial support from the Ramón y Cajal program (RYC-2014-15512). The authors would like to acknowledge the use of the Advanced Microscopy Laboratory (INA-Universidad de Zaragoza). A. S. and A. E. acknowledge financial support from the Comunidad de Madrid for the ‘‘Atracción de Talento Investigador’’ contracts (No. 2017-T2/IND5395 and 2018-T1/IND10058). A. E. is also grateful to the 2018/NMT-4321 and SEV-2016-0686 projects. The European Synchrotron (ESRF),Ministerio Español de Ciencia, Innovación y Universidades (MCIU) and Consejo Superior de Investigaciones Cientificas (CSIC) are acknowledged for the provision of synchrotron radiation facilities. We also thank the BM25- SpLine staff for the technical support beyond their duties.

Catalysts supported on aluminium pillared clays (Al-PILCs) using Fe and Pd or Rh as active phases have been prepared and tested for a two-step treatment of p-chloro-m-cresol (PCMC) in water by catalytic hydrodechlorination (HDC) followed by catalytic wet peroxide oxidation (CWPO) under ambient-like conditions (25 °C, 1 atm). Both processes were first studied independently. HDC was investigated with Pd and Rh monometallic catalysts as well as Pd-Fe and Rh-Fe bimetallic ones. The bimetallic Pd-Fe catalyst showed the best performance, allowing complete dechlorination in less than 1 h reaction time. On the other hand, CWPO of PCMC with a monometallic Fe catalyst allowed complete conversion of that pollutant but with only about 33% reduction of total organic carbon (TOC) after 4 h. Then, a two-step approach consisting in HDC of PCMC followed by CWPO has been tested for the first time in two different ways. The first one used a Pd-Fe bimetallic catalyst in both steps while in the second approach monometallic Pd and Fe catalysts were used for HDC and CWPO, respectively. The HDC in alkaline medium allowed reducing significantly Fe leaching. This second approach yielded complete dechlorination followed by higher mineralization (>55%) with better efficiency of H2O2 consumption.

The M-1212 family of cuprates, with general formula $$\hbox {M}_{{x}}\hbox {Cu}_{1-{{x}}}\hbox {Sr}_{2}\hbox {RECu}_{2}\hbox {O}_{7+{\delta } }$$ (M = transition metal; RE = Rare Earth), can be stabilized at room pressure and continues to be the basis for the study of superconducting cuprates by means of different total or partial substitutions. Here, we explore two interesting possibilities through substitution of the Cu in the chains (forming the charge reservoir layer) by Mo and Fe, leading to the $$\hbox {Mo}_{0.3}\hbox {Cu}_{0.7}\hbox {Sr}_{2}\hbox {RECu}_{2}\hbox {O}_{7+\delta }$$ (RE: Tm and Yb) and $$\hbox {Fe}_{{x}}\hbox {Cu}_{1-{{x}}}\hbox {Sr}_{2}\hbox {YCu}_{2}\hbox {O}_{7+\delta }$$ (x = 0.5) systems respectively—followed by RED/OX processes. Oxidation techniques such as ozonisation and high-pressure-oxygen treatment have been used to increase the critical temperature $$T_\mathrm{c}$$ of the present compounds, looking at the crystal structural evolution of these materials in relation with the $$T_\mathrm{c}$$ enhancement. We have considered, in particular, some of the structural parameters that seem to go in parallel with the $$T_\mathrm{c}$$ increasing: inter and intra-bilayer spacing, apical distance and buckling angle at the superconducting plane. Although the $$\hbox {Mo}_{0.3}\hbox {Cu}_{0.7}\hbox {Sr}_{2}\hbox {RECu}_{2}\hbox {O}_{\mathrm{y}}$$ system does not show superconductivity as synthesized in air, a $${T_\mathrm{c}}\approx 32\,\hbox {K}$$ is achieved after oxygen or ozone flowing at low temperature and it increases by almost three times to a $${T_\mathrm{c}} \approx $$ 83 K under high-pressure-oxygen treatment . On the other hand, the $$T_\mathrm{c}$$ for the $$\hbox {Fe}_{0.5}\hbox {Cu}_{0.5}\hbox {Sr}_{2}\hbox {RECu}_{2}\hbox {O}_{\mathrm{y}}$$ system is increased from $${T_\mathrm{c}} \approx 30\,\hbox {K}$$ up to $${T_\mathrm{c}} \approx 50\,\hbox {K}$$ after oxygenation under ozone annealing.

BACKGROUND: The environmental risk from the application of synthetic chelates has led to the use of biodegradable complexes to correct Fe deficiency in plants. In this article, the Fe oxidation state, the Fe:ligand ratio, and the molecular weight distribution for heptagluconate (G7) and gluconate (G6) are considered as key factors for the efficacy of complexes as fertilizers. Complexes with different Fe:ligand ratios were prepared and analyzed by gel filtration chromatography (GFC). The ability of Fe:ligand ratios to provide Fe to tomato in hydroponics and soybean in calcareous soil was tested and compared with synthetic chelates (Fe3+:HBED and Fe3+:EDTA). RESULTS: G7 presented greater capacity to complex both Fe(II) and Fe(III) than G6, but the Fe(II) complexes exhibited poor stability at pH 9 and oxidation in solution. Gel filtration chromatography demonstrated the polynuclear nature of the Fe3+:G7 at various ratios. The effectiveness of the Fe fertilizers depend on the Fe3+:ligand ratio and the ligand type, the Fe3+:G7 (1:1 and 1:2) being the most effective. Fe3+:G7 (1:1) also presented a better response for the uptake of other micronutrients. CONCLUSION: Fe3+:G7 molar ratios have been shown to be critical for plant Fe uptake under hydroponic conditions and with calcareous soil. Thus, the Fe3+:G7 at equimolar ratio and 1:2 molar ratio can be an environmentally friendly alternative to less degradable synthetic chelates to correct Fe chlorosis in strategy I plants, This work was supported by the State Research Agency, Ministry of Science, Innovation and Universities of Spain (projects AGL2013-44474-R and RTI2018-096268-B-I00) and the Comunidad de Madrid (Spain) and Structural Funds 2014-2020 (ERDF and ESF) (project AGRISOST-CM S2018/BAA-4330). SIV would like to thank the Consejo Nacional de Ciencia y Tecnología (CONACYT, Mexico) for supporting her grant through PhD studentship number 278934, and the Consejo de Ciencia, Tecnología e Innovación de Hidalgo (CITNOVA, Mexico)

A combined electrochemical/chemical method was developed in order to synthesize manganese ferrite nanoparticles. The synthesis was carried out in an electrochemical cell containing iron as anode and cathode electrodes and an electrolyte solution of manganese chloride and tetrabutyl ammonium bromide. A usual XRD, STEM compositional mapping images and ICP analysis showed the formation of spinel structure and the presence of Mn, Fe and O in the nanoparticles (NPs) with a stoichiometry Mn0.5Fe2.5O4. The nanoparticle size, shape, and morphology were characterized using electron microscopy and X-Ray absorption spectroscopy, and SQUID measurements were carried out to determine the magnetic behavior. This sample was compared with a same composition manganese ferrite obtained by electrochemical synthesis. Keywords: Electrochemical synthesis, Superparamagnetic, Nanoparticles, Manganese ferrite

Nominal granular iron oxide-aluminum thin films have been prepared by simultaneous deposition of iron oxide nanoparticles, grown by the gas-phase aggregation technique, and an aluminium matrix, grown by conventional magnetron sputtering. Composition, structure and magnetic behavior have been analyzed by different techniques including TEM and AFM microscopies, EDX, RBS, X-ray absorption and Mössbauer spectroscopies and SQUID magnetometry. Both, structure and magnetic behavior, are found to be highly dependent on the preparation conditions. In particular, our work shows that for low matrix/nanoparticle ratios the aluminum is able to partially displace the iron oxide and form a core-shell iron metal-iron oxide structure. For higher ratios, on the other hand, the oxygen atoms become very diluted and their role negligible. In this case a core-shell structure consisting of an iron metal core and an iron-aluminum alloy shell is formed. Magnetization measurements indicate that in the first case the core and the shell are magnetically coupled while in the second case the two phases are magnetically uncoupled, the Fe-Al alloy presenting strong coercivity., This work was partially supported by the Spanish Ministry of Economy and Competitiveness under contract projects MAT2010-16022, MAT2011-27573-C04-04, MAT2012-37109-C02-02 and MAT2012-37276-C03-01. Further support has been given by the Comunidad de Madrid project P2013/MIT-2740 and by the Aragón DGA NETOSHIMA grant. MAL-M acknowledges CSIC and the European Social Fund for a JAE-Doc contract.

We studied the adsorption/degradation process of methylene blue in a Fenton like process using iron oxide nanoparticles as a source of Fe2+ ions, where the nanoparticles were prepared via a facile electrochemical synthesis method. The degradation kinetics were studied using 2 g L−1 of catalyst and 100 ppm of pollutant at pH 3.5. The influence of temperature on this process was evaluated using two different setups: conventional heating in a thermostatic bath and selective heating using an alternating magnetic field. The magnetic induction heating process led to a greater degradation of the pollutant compared with the thermostatic bath. In addition, the optimal concentration of Fe2+ in solution was evaluated in a Fenton homogeneous process to achieve the same degradation efficiency when using a nanoparticle-assisted Fenton-like process. A concentration of 0.5 ppm Fe2+ in solution yielded the same degradation achieved by using 2 g L−1 of iron oxide nanoparticles. The kinetic analysis fit the pseudo-first-order kinetics and indicated a linear increase in the apparent rate constant with increasing temperature. The activation energy of the degradation process obtained by fitting the Arrhenius equation was 58 kJ mol−1.

Ferrites of iron, cobalt, and nickel were used as a non-enzymatic sensor for detection of hydrogen peroxide. X-ray diffraction (XRD) and transmission electron microscopy revealed that the nanoparticles obtained by electrochemical route and varying the parameters synthesis show similar size of around 20 nm and a relation metal/iron equal to 1/2. The effect of pH, temperature, amount of nanoparticles, and potential has been studied to obtain the best sensor properties in terms of sensitivity and linear response. The mechanism has been attributed to the oxidation of Fe2+, Co2+, and Ni2+ in the octahedral position of the spinel that enhances the catalytic reduction of hydrogen peroxide. The best sensor has been obtained with magnetite (iron ferrite) with a detection limit of 7.3 × 10−6 M and a sensitivity of 4.0 × 10−4 μA/M. The magnetite was also applied to determine hydrogen peroxide in commercial contact lens cleaner Novoxy® with satisfactory results.

This article describes the preparation of hybrid gradient porous surfaces by using the breath figures approach. In a first step gradient porous surfaces were created from polymeric blends consisting of a linear polystyrene as major component and amphiphilic copolymers of poly(styrene-co-acrylic acid) as minor component. THF was used as solvent conducting to porous surfaces with a gradual variation of the pore size in a radial manner due to the long evaporation time. A detailed investigation of the influence of chemical composition of the copolymer (i.e. ratio styrene/acrylic acid) on the porous films was carried out. These films were successfully employed to prepare hybrid gradient surfaces by incorporating of magnetic nanoparticles inside the cavities. For this purpose two different strategies were explored. On one hand a magnetic nanoparticles aqueous suspension was placed on the porous surface with a magnet below the film, and subsequently the colloidal suspension was removed. Alternatively, the magnetic suspension was placed onto the surface and left until complete evaporation. A further step of peeling off the top layer also conducts to the decoration of the nanoparticles exclusively in the interior of the holes. Both strategies allow the preparation of hybrid surfaces with a variation of the content of magnetic nanoparticles magnetic inside the holes as a function of the radial position.

et al., Superparamagnetic iron oxide-based nanoparticles (SPIONS) have attracted an enormous amount of attention for their potential use in biomedical applications, due to their good biocompatibility and low toxicity. The current study considers citric acid-conjugated manganese ferrite and its synergy to be used in MRI and in hyperthermia treatment, thus showing theragnostic applications. High colloidal stability was obtained with this functionalization. SPIONS with superparamagnetic behavior of crystal sizes of approximately 20 nm were obtained via an electrochemical synthesis method. One of the highest specific absorption rate (SAR) values was achieved in this work (1661 W g–1), under a magnetic field of 30 mT at 717 kHz frequency, compared with other magnetic ferrites in the literature. These nanoparticles dissipate heat through Néel relaxation and, together with the high SAR value obtained, indicate an excellent material for hyperthermia treatment of cancer. In addition, these nanoparticles exhibit transverse relaxivity behavior, with an r2 value of 394 mM–1 s–1, i.e., at least two times higher than the value of a commercial magnetic contrast agent based on iron oxides. Finally, no toxicity effects of these nanoparticles are evidenced; as a result, these nanoparticles are appropriate for in vivo application., This work was supported by the project MAT-2012−37109-C02-02 and CTQ2013-48767-C3-3-R, from the Ministerio de Economia y Competitividad of Spain. E. Mazario also acknowledges the Ministerio de Economia y Competitividad of Spain for mobility grant EEBB-I-13- 07517 and fellowship FPI (BES-2010-03109).

Nickel ferrite nanoparticles (NiFe 2 O 4 ) were synthesized by electrochemical method and used as catalyst for direct oxidation of glucose, NADH and methanol. Characterization of these nanoparticles was carried out by X-ray diffraction, Mossbauer spectroscopy, and colloidal properties such as hydrodynamic radius and Zeta potential. To evaluate the catalytic properties of these nanoparticles against the oxidation process, paste graphite electrodes mixing nickel ferrites and different conductive materials (graphite, carbon nanotubes) and binders agents (mineral oil, 1-octylpyridinium hexafluorophosphate ( n OPPF6)) were used. The results prove good catalytic properties of these materials, with an oxidation potential around 0.75, 0.5 and 0.8 V for glucose, NADH, and methanol, respectively.

A ferromagnetic γ-Al 2 O 3 -supported iron catalyst has been prepared and its activity and stability in catalytic wet peroxide oxidation (CWPO) have been compared with those of a previous iron-based conventional catalyst using the same support. Both catalysts were characterized by nitrogen adsorption–desorption isotherms, ICP, TXRF, XRD, XPS, elemental analysis and Mossbauer spectroscopy. The behavior of these catalysts in CWPO of chlorophenols has been related with the nature of the dominant iron species (magnetite or hematite). The results showed that the magnetic catalyst improved significantly the decomposition of H 2 O 2 leading to an increased degradation and mineralization of chlorophenols. Complete conversion of those target pollutants and more than 75% TOC reduction were achieved after 4 h under stoichiometric H 2 O 2 dose, 100 mg L −1 initial chlorophenol concentration, 1 g L −1 catalyst, pH 3 and 50 °C temperature. Moreover, complete dechlorination of all the chlorophenols tested was achieved, being the residual organic by-products short-chain acids without significance in terms of ecotoxicity. The catalyst showed a remarkable stability in long-term continuous experiments with limited Fe leaching, below 5% of the initial loading after 100 h on stream. An additional clear advantage of the new catalyst is its easy separation and recovery from the reaction medium by applying an external magnetic field.

Using the electrochemical route, cobalt ferrite nanoparticles (NPs) with two different sizes were synthesized and stabilized in water by coating with citric acid. The specific absorption rate (SAR) values of aqueous suspensions of magnetic nanoparticles with crystal sizes of 13 and 28 nm were investigated in the frequency range 32–101 kHz and up to 51 mT. SAR values were higher for the larger NPs and reached 133 W/g. Numerical simulations are used for a quantitative analysis of hyperthermia experiments and seem to indicate that the larger NPs are multidomain. Cytotoxicity analysis was also performed in HeLa tumor cells; a null cytotoxicity of these nanoparticles in cell tissues were obtained.

We report a detailed work of composition and location of naturally formed iron biominerals in plant cells tissues grown in iron rich environments as Imperata cylindrica. This perennial grass grows on the Tinto River banks (Iberian Pyritic Belt) in an extreme acidic ecosystem (pH∼2.3) with high concentration of dissolved iron, sulphate and heavy metals. Iron biominerals were found at the cellular level in tissues of root, stem and leaf both in collected and laboratory-cultivated plants. Iron accumulated in this plant as a mix of iron compounds (mainly as jarosite, ferrihydrite, hematite and spinel phases) was characterized by X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), Mossbauer spectroscopy (MS), magnetometry (SQUID), electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX; TEM-EDX; HRSTEM). A low fraction of phosphorous was detected in this iron hyperaccumulator plant. Root and rhizomes tissues present a high proportion of ferromagnetic iron oxide compounds. Iron oxides-rich zones are localized in electron dense intra and inter-cellular aggregates that appear as dark deposits covering the inner membrane and organelles of the cell. This study aims to contribute to a better understanding of the mechanisms of accumulation, transport, distribution of iron in Imperata cylindrica.

A new electrochemical method to synthesize cobalt ferrite nanoparticles has been developed. Magnetic measurement, Mossbauer spectroscopy, X-ray diffraction, inductive coupled plasma spectroscopy, and transmission electron microscopy were carried out to characterize the cobalt ferrites synthesized at different temperatures between 25 °C and 80 °C. These techniques confirm the efficiency of the electrochemical method. At room temperature a mixture of different compounds was obtained with a particle diameter around 20 nm, while at 80 °C the synthesis of cobalt ferrite leads to a stoichiometric spinel, with a crystallite size of 40 nm measured by Scherrer equation. The temperature was defined as an important parameter to obtain stoichiometric ferrites and different diameters.

Iron nanoclusters have been deposited by the gas-phase aggregation technique to form multilayered structures with outstanding exchange-bias ( H E ) values up to H E = 3300 Oe at low temperatures. In order to explain the observed magnetic properties, composition and crystallographic phase have been determined by X-ray absorption spectroscopy. A metal-oxide core–shell arrangement has to be discarded to explain the large obtained values of H E since structural results show nanoclusters formed by the antiferromagnetic α-Fe 2 O 3 oxide. Moreover, nanoparticles of few nanometers formed by substoichiometric α-Fe 2 O 3 explain the observed weak ferromagnetism and let to understand the origin of large exchange bias by the interaction between different spin sublattice configurations provided by the low iron coordination at surface.

Two new oxynitride double perovskites of composition Sr{sub 2}FeMoO{sub 6-x}N{sub x} (x=0.3, 1.0) have been synthesized by annealing precursor powders obtained by citrate techniques in flowing ammonia at 750 Degree-Sign C and 650 Degree-Sign C, respectively. The polycrystalline samples have been characterized by chemical analysis, x-ray and neutron diffraction (NPD), Moessbauer spectroscopy and magnetic measurements. They exhibit a tetragonal structure with a=5.5959(1) A, c=7.9024(2) A, V=247.46(2) A{sup 3} for Sr{sub 2}FeMoO{sub 5.7}N{sub 0.3}; and a=5.6202(2) A, c=7.9102(4) A, V=249.85(2) A{sup 3} for Sr{sub 2}FeMoO{sub 5}N; space group I4/m, Z=2. The nitridation process seems to extraordinarily improve the long-range Fe/Mo ordering, achieving 95% at moderate temperatures of 750 Degree-Sign C. The analysis of high resolution NPD data, based on the contrast existing between the scattering lengths of O and N, shows that both atoms are located at (O,N)2 anion substructure corresponding to the basal ab plane of the perovskite structure, whereas the O1 site is fully occupied by oxygen atoms. The evolution of the Left-Pointing-Angle-Bracket Fe-O Right-Pointing-Angle-Bracket and Left-Pointing-Angle-Bracket Mo-O Right-Pointing-Angle-Bracket distances suggests a shift towards a configuration close to Fe{sup 4+}(3d{sup 4}, S=2):Mo{sup 5+}(4d{sup 1}, S=1/2). The magnetic susceptibility shows a ferrimagnetic transition with a reduced saturation magnetization compared tomore » Sr{sub 2}FeMoO{sub 6}, due to the different nature of the magnetic double exchange interactions through Fe-N-Mo-N-Fe paths in contrast to the stronger Fe-O-Mo-O-Fe interactions. Also, the effect observed by low-temperature NPD seems to reduce the ordered Fe moments and enhance the Mo moments, in agreement with the evolution of the oxidation states, thus decreasing the saturation magnetization. - Graphical Abstract: We have synthesized and studied the new oxinitride double perovskites Sr{sub 2}FeMoO{sub 6-x}N{sub x}. They present anionic ordering between O and N. The nitridation process improves the long-range Fe/Mo ordering. They show a ferrimagnetic transition with a reduced saturation magnetization compared to Sr{sub 2}FeMoO{sub 6}, due to the different nature of the double exchange interactions through Fe-N-Mo-N-Fe in contrast to Fe-O-Mo-O-Fe. We suggest a shift towards a configuration Fe{sup 4+}(3d{sup 4}, S=2):Mo{sup 5+}(4d{sup 1}, S=1/2). Highlights: Black-Right-Pointing-Pointer Synthesis and study of the new oxinitride double perovskites Sr{sub 2}FeMoO{sub 6-x}N{sub x} (x=0.3, 1.0). Black-Right-Pointing-Pointer Compounds present anionic ordering between O and N. Black-Right-Pointing-Pointer Nitridation process extraordinarily improves the long-range Fe/Mo ordering. Black-Right-Pointing-Pointer We suggest a shift towards a configuration Fe{sup 4+}(3d{sup 4}, S=2):Mo{sup 5+}(4d{sup 1}, S=1/2).« less

Catalysts based on Fe supported on γ-Al2O3 and active carbon (AC) have been prepared and tested for catalytic wet peroxide oxidation (CWPO) of cosmetic wastewaters. The catalysts were characterized by TXRF, XPS, XRD, SEM, elemental chemical analysis, Mossbauer spectroscopy and 77 K N2 adsorption–desorption. The catalytic performance was monitored in terms of COD, TOC and H2O2 conversions. The possible leaching of iron from the catalyst was also checked. The influence of the catalysts preparation conditions (calcination temperature and Fe content) as well as the operating temperature in the oxidation process has been studied with the purpose of optimization. Working at 85 °C with a Fe/γ-Al2O3 catalyst calcined at 300 °C and with 4% Fe content, a remarkable COD reduction (around 85%) has been reached. However, lower temperatures are sufficient to fulfill the locally allowable limit of COD for industrial wastewaters discharge into the municipal sewer system. A substantial improvement of biodegradability (BOD5/COD ratio) was observed. Thus, CWPO could be effectively applied whether as a treatment itself or as a pre-treatment addressed to improve subsequent biodegradability of these wastewaters. The Fe/γ-Al2O3 catalyst showed a reasonable stability, a relatively low decrease of activity (15%) being observed after three successive runs.

In this work, the preparation of a polypyrrol–magnetite composite with good magnetic and electric properties is described. Firstly, the method consists of the electrochemical synthesis of magnetite nanoparticles 20 nm in diameter and narrow size distribution, and secondly, the encapsulation of the nanoparticles in a polymer matrix during its formation by chemical oxidation of the monomer. Particles appear well dispersed in the polymer matrix by transmission electron microscopy (TEM) while no degradation, in terms of nanoparticles size or magnetic properties during the polymer formation, seems to take place as it was revealed by X-ray diffraction and Mossbauer spectroscopy. Saturation magnetization increases with the amount of magnetic material present in the composite, but conductivity decreases in such a way that the amount of magnetic material was optimized to 10% with respect to the monomer to obtain a composite with high electrical conductivity and magnetic response.

Catalytic wet air oxidation (CWAO) of phenol with iron/activated carbon catalysts (Fe/AC) at temperature of 400 K and 8 atm of total pressure is an efficient treatment to oxidize a resistant pollutant such as phenol into biodegradable species, mainly short chain acids. Extended studies employing activated carbon catalysts point out significant changes in the carbon as a consequence of the CWAO process. After the long-term experiments carried out in this work it was concluded that these modifications consist of loss of microporosity, temporary decrease of the mesoporosity, decrease of the carbon/oxygen ratio on the catalyst surface, more acidic pH slurry values, and aggregation of the α-Fe 2 O 3 crystallites. The causes that provoke these changes and the reasons why they do not alter significantly the CWAO efficiency were analyzed. The way of exposition of Fe/AC catalyst to the reactants plays an important role in its activity and selectivity towards complete mineralization, namely oxidation to CO 2 and H 2 O.

Magnetite (Fe 3 O 4 ) nanoparticles (NP) with sizes between 20 and 30 nm have been obtained by Fe electrooxidation in the presence of an amine surfactant, which acted as a supporting electrolyte and coating agent, controlling particle size and aggregation during the synthesis. The effect of different parameters on the nature and size of the particles as well as the mechanism of formation of the particles have been studied by different techniques. It was concluded that, under the electrochemical conditions used in this work, the NP mean size was found to be constant at around 20 nm when the electrooxidation current density is increased from 10 to 200 mA cm −2 . However, when the potential is over 6 V, particle size decreases from 30 to 20 nm and metallic iron appears as an impurity. The mechanism of particles formation has being clarified and the critical effect of the distance between electrodes for obtaining magnetic iron oxide nanoparticles has been understood. Finally, the presence of an electrostatic adsorbed surfactant coating the particles allows the functionalization of the particles easily by exchange reaction with biomolecules of interest, which makes this material very promising for future application in biotechnology.

6 pages, 3 figures.-- Research article., A comparative study of the roots, rhizomes and leaves of an iron hyperaccumulator plant, Imperata cylindrica, isolated from the banks of an extreme acidic environment, using complementary techniques: Mösbauer spectroscopy (MS), X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled to energy-dispersive X-ray microanalysis (EDAX) and transmission electron microscopy (TEM), has shown that two main biominerals, jarosite and ferrihydrate-ferritin, accumulate in the different tissues. Jarosite accumulates mainly in roots and rhizomes, while ferritin has been detected in all the structures. A model of iron management in I. cylindrica is presented., This work was supported by grants BOS2002-02148 from the CICYT and institutional grants to the Centro de Biología Molecular and the Centro de Astrobiología.

Mono- and dimetallic cobalt- and iron oxide nanoparticles deposited on the surface of a silica substrate have been prepared by an impregnation technique. Both the bulk and surface structures of these particles have been characterised by different physical and chemical techniques. The results provided by X-ray diffraction, Mossbauer and X-ray photoelectron spectroscopy show the formation of separate Co3O4 and Fe2O3 nanoparticles in oxide samples, but in no case were cobalt–iron mixed oxides detected. Quantitative data also showed that the dispersion degree of cobalt- and iron oxides is rather low. It was also observed that pretreatment of the supported metal oxide nanoparticles under a hydrogen atmosphere does not promote the formation of a metal–support interaction, although a cobalt–iron interaction is observed in the dimetallic systems. The diffraction patterns and photoelectron and Mossbauer spectra of these dimetallic samples provide conclusive proof for the formation of both metallic Co0 and iron-cobalt (Co7Fe3) alloy phases in the hydrogen-reduced samples. It was also found that the crystallite size of the alloyed Co7Fe3 phase increases with increasing iron content, i.e. 11 and 23 nm for samples containing 1 % and 5 % Fe added to the base Co sample, respectively, while that of Co0 was constant (10 nm). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

A new series of double perovskites of stoichiometry Sr2−xCexFeMoO6 (0 ≤ x ≤ 1) has been prepared by a wet chemistry procedure yielding very reactive precursors, which were subsequently annealed under reducing conditions. The compounds have been studied by X-ray (XRD), neutron powder diffraction (NPD), Mossbauer spectroscopy, magnetic and magnetotransport measurements in polycrystalline samples, aiming to investigate the effect of electron doping in the parent perovskite Sr2FeMoO6. The evolution of the crystal structure has been analyzed from NPD data; a transition from tetragonal (I4/m) to monoclinic (P21/n) has been observed at 0.2 ≤ x ≤ 0.4 as a result of the decrease of the tolerance factor due to the electron injection on B sites and the reduction in ionic size at A positions of the ABO3 perovskite. A bond valence study shows that an important fraction of the injected electrons is localized at Mo sites, which promotes the occurrence of antisite disordering between Fe and Mo cations. The magnetic properties are characteristic of ferromagnetic materials, with an ordering temperature of around 400 K, showing a non-monotonic behavior along the series, which is understood as a compromise between the steric and the electron injection effects. The introduction of a magnetic rare-earth in the Sr sublattice improves the magnetoresistive response at low temperatures, as a result of the polarization of the Ce3+ moments: a magnetoresistance (MR) factor of 45% is observed at 5 K for the x = 0.6 sample. For the first time we show that the introduction of a magnetic element in the A sublattice of a double perovskite can be used as an effective way to enhance the magnetoresistive response in this attractive family of oxides.

The effect of disorder due to anti sites on the charge-transfer processes in the double perovskite Sr2FeMoO6 has been assessed at the microscopic level, using 57Fe Mossbauer spectroscopy. We have followed over a very broad temperature range (from 673 to 4.2 K) the spectral response of three polycrystalline samples only differing in the levels of anti-site disorder of the B sublattice. Our measurements reveal an intricate charge-transfer pattern across TC that is connected to the levels of disorder present in each sample. It is found that the magnetic transition triggers a charge-transfer process between the ordered and anti-site disordered regions for moderate levels of disorder, while this process is completely disabled when disorder becomes dominant. The observed behavior is correlated to the macroscopic properties of the system.

We have studied the static and dynamic effects of pressure on the spin-transition in the temperature range of the thermal hysteresis loop for the compound Fe(phen)2(NCS)2. The high-spin fraction (nHS) as a function of pressure and temperature has been determined by optical reflectivity. In this compound, the pressure was found to upward shift the spin-transition temperature by 23 K per kbar. During the dynamic pressure pulse, a decrease in nHS is observed, with an irreversible (reversible) character in the descending (ascending) branch of the hysteresis loop. In this respect, pressure has a ‘mirror effect’ compared to the application of an intense and pulsed magnetic field, for which – as reported previously – an increase in nHS is observed, with an irreversible (reversible) character in the ascending (descending) branch of the hysteresis loop. To cite this article: A. Bousseksou et al., C. R. Chimie 6 (2003).

The Mn–Li ferrite system Li1−0.5xFe1.5x+1Mn1−xO4 (x = 1, 0.8, 0.6, 0.4, 0.2) has been studied by means of X-ray diffraction, Mossbauer spectroscopy and Mn K- and Fe K-edge XANES/EXAFS. All the samples show the spinel-related structure with the lattice constant a gradually decreasing between a = 0.8310 nm (x = 1) and a = 0.8301 nm (x = 0.2). Mossbauer and Fe K-edge XANES/EXAFS results have shown that the oxidation state of Fe is +3 and that the fractions of Fe3+ ions occupying the octahedral and tetrahedral sublattices do not change significantly along the series. Mossbauer data recorded under applied magnetic field indicate the existence in the Mn-containing samples of canted spin structures for the Fe3+ ions on both the tetrahedral and octahedral sites, the canting angle being larger for the octahedral sublattice. Mn K-edge XANES and EXAFS have shown Mn to be present as Mn3+ and Mn4+ and to occupy only octahedral sites. The XANES/EXAFS results have also shown that the Mn4+/Mn3+ ratio increases with increasing Li/Mn content. The results indicate that as the extent of Li/Mn insertion increases the new inserted Li+ ions occupy tetrahedral sites and that some of the Li+ ions initially occupying octahedral sites are also driven into tetrahedral positions.

Different solid/liquid "exchange" reactions involving divalent cations, protons, or ammonium ions have been performed at low/moderate temperatures (between 80 and 500 degrees C) on alpha-NaFeO2 dipped in molten salts (or acid) media. Several ferrites have been obtained which are nonstoichiometric with partially inverse spinel structures. When sodium is replaced by divalent cations (Mg2+, Co2+, Ni2+, and Zn2+), the obtained ferrites are hyperstoichiometric (cation/oxygen ratio higher than 3/4) whereas proton or ammonium reactions result in hypostoichiometric materials (cation/oxygen lower than 3/4). All these ferrites present a platelet-like morphology and show ferrimagnetic, soft magnet behavior.

Instead of the expected carbon−carbon coupling into oxalates, thermolysis at 30 °C of the cis-bis(alkoxycarbonyl) monomers (CO)4Fe(CO2R)2 (1) affords the novel trimetallic compounds [(CO)3Fe(μ,η2-C...

Herein a facile and versatile one step synthesis of magnetite nanoparticles coated with polydopamine is described. Magnetite nanoparticles are synthesized electrochemically by electrooxidation of iron in an aqueous medium in the presence of dopamine. The oxidative conditions and alkaline pH involved in the synthesis favor the self-polymerization of dopamine that adheres at the surface of the magnetic nanoparticles in a simultaneous process. It is shown that the size of the magnetite nanoparticles as well as the polydopamine coating can be controlled by varying the synthetic approach that is, adding dopamine at the beginning of the electrosynthesis, in the middle or at the end of the process. The particle size of the core varies between a few nanometers and 25 nm while the shell can reach thicknesses of up to ∼5 nm. The obtained hybrid nanoparticles were characterized by thermogravimetric analysis (TGA), infrared spectroscopy (FTIR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). In addition, the magnetic measurements of the different obtained materials were carried out showing a variety of magnetic behaviors depending on the synthetic procedure., This work was financially supported by the Spanish MINECO (Project MAT2012-37109-C02-02).

Nickel nanoferrites were obtained by means of four different synthetic wet-routes: co-precipitation (CP), sonochemistry (SC), sonoelectrochemistry (SE) and electrochemistry (E). The influence of the synthesis method on the structural and magnetic properties of nickel ferrite nanoparticles is studied. Although similar experimental conditions such as temperature, pH and time of synthesis were used, a strong dependence of composition and microstructure on the synthesis procedure is found, as electron microscopy, X-ray diffraction and Mössbauer spectroscopy studies reveal. Whereas by means of the CP and SC methods particles of a small size around 5–10 nm, respectively, and composed by different phases are obtained, the electrochemical routes (E and SE) allow obtaining monodisperse nanoparticles, with sizes ranging from 30 to 40 nm, and very close to stoichiometry. Magnetic characterization evidences a superparamagnetic behavior for samples obtained by CP and SC methods, whereas the electrochemical route leads to ferromagnetic ferrite nanoparticles.

In this paper we focus on the different types of hysteresis exhibited by spin transition compounds: thermal hysteresis, pressure hysteresis and light induced thermal hysteresis. We analyse the manner in which different Preisach-type models can be applied to reproduce major and minor hysteresis loops.

The hysteresis loops of the spin transition crystalline powder Fe(btr)2(NCS)2·H2O, pure or diluted in a Ni-homologue, have been recorded as a function of temperature and pressure. The phase diagrams in p, T axes have been determined. Pressure hysteresis loops, at constant temperature, have been obtained. A pressure-induced structural change is inferred from the data of the pure compound. The possible thermal quenching of the high-pressure structural phase is evidenced. A relationship between the shapes of the temperature and pressure loops is established.

Complex admittance measurements have been performed on α-NaFeO 2 and on the product Na 0.9 FeO 2 obtained by sodium extraction, both being polycrystalline powders. The electrical conductivity in both samples is proposed to be due to sodium ions hopping between octahedral positions through the adjacent, empty, tetrahedral ones characteristic of a rock-salt structural framework. The parent material shows an activation energy in the dc conductivity of 0.31 eV between 306 and 498 K. Removal of sodium, in spite of creating octahedral vacancies, results in lower conductivity values, and a higher activation energy of 0.58 eV in a similar temperature range.

We have constructed a low-temperature helium pressure device that incorporates optical-reflectivity detection and is useful for the study of thermochromic materials. We have tested the device up to 1600 bar (0.16 GPa) and down to 10 K. The performance of the device is illustrated by the results of constant-pressure and constant-temperature runs for the spin-transition solid [Fe(btr)2(NCS)2]·H2O. The data establish a consistent pressure-temperature phase diagram, which is discussed.

The first examples of compounds containing the [SnR2I3]– anion, i.e. [Bun4N][SnR2I3] (R = Me or Ph), have been prepared and characterized by IR, Raman and 119Sn Mossbauer spectroscopies, and X-ray powder diffraction data. The experimental data are consistent with a trigonal bipyramidal structure, with the R groups in equatorial positions, for the [SnR2I3]– anions. Octahedral [SnR2I4]2– anions could not be isolated and it is shown that the previously reported [Bun4N]2[SnMe2I4] is actually a 1∶1 mixture of Bun4NI and [Bun4N][SnMe2I3]. The X-ray powder structure of Cs2SnI6 has been refined by the Rietveld method. The compound crystallises in the cubic Fm3m space group with a = 11.6410(3) A and a Sn–I distance of 2.864(1) A. The Sn–I distances in Cs2SnI6, SnI4(bipy), SnI4(Ph3PO)2 and SnI4(Ph2SO)2 are related to the Mossbauer quadrupole splitting, showing that ligands that are weaker donors than I– (i.e. have a more positive partial quadrupole splitting) give rise to Sn–I distances that are shorter than for the [SnI6]2– anion.

Proton exchange reactions have been performed on α-NaFeO 2 at 150 °C in molten benzoic acid; a ferrimagnetic material showing the spinel structure was produced. Infrared spectroscopy was used to investigate the oxyhydroxide character of this product which, after thermal treatment at 300 °C yields the well known maghemite γ-Fe 2 O 3 , although some hydroxyl groups still seem to be present. Besides IR, X-ray diffraction, chemical and thermal analysis, Mossbauer spectroscopy and magnetization measurements are presented and discussed.

Undoped and 5%(Mn, In)-doped SnO 2 thin films were deposited on Si(1 0 0) and Al 2 O 3 (R-cut) by RF magnetron sputtering at different deposition power, sputtering gas mixture and substrate temperature. X-ray reflectivity was used to determine the films thickness (10–130 nm) and roughness (∼1 nm). The combination of X-ray diffraction and Mossbauer techniques evidenced the presence of Sn 4+ in an amorphous environment, for as-grown films obtained at low power and temperature, and the formation of crystalline SnO 2 for annealed films. As the deposition power, substrate temperature or O 2 proportion are increased, SnO 2 nanocrystals are formed. Epitaxial SnO 2 films are obtained on Al 2 O 3 at 550 °C. The amorphous films are quite uniform but a more columnar growth is detected for increasing deposition power. No secondary phases or segregation of dopants were detected.