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9 pags., 7 figs., 1 tab., Here we report the first example of nanoMIL-100 particles modified with monomeric cyclodextrin derivatives of different length by exploiting strong interactions between non-saturated iron trimers at the external surface and carboxylate functionalities located at the end of biocompatible and flexible linkers of cyclodextrins. The main results revealed that, after the functionalization, the cyclodextrins are selectively located at the external surfaces covering the nanoparticles. Z potential measurements show that this functionalization induced changes respect to the bare nanoMIL-100 particles, however, the presence of the cyclodextrins does not modify the size neither porosity of the nanoparticles. The amount of cyclodextrins attached, investigated by thermogravimetry, increases with the length of the linker between CD cavity and nanoparticle surface, reaching up a 9 % wt. Auger spectroscopy suggested a clear predominant sp character after the functionalizations (vs. sp predominance in the unmodified nanoMIL-100). This study supposes the creation of an alternative family of hybrids based on carboxylated monomeric cyclodextrins., Authors would like to thank to Center for the Development of Nanoscience and Nanotechnology CEDENNA AFB180001 basal project. TC would like to thank to Fondo Nacional para el Desarrollo Científico y Tecnologico (FONDECYT POSTDOCTORADO) proyect 3180454. Financial support from the Spanish Agencia Estatal de Investigacion under project RTI2018-095303-B-C51 is gratefully acknowledged. This work was done under the LIA-M3-1027 CNRS Collaborative Program. The present work has been funded by ‘Unidad de Excelencia María de Maeztu’ MDM-2015-0538 granted to ICMol, and the Generalidad Valenciana (Prometeo/2019/076 program of excellence). M.G.M. ac-knowledges funding from the MINECO (Ram on y Cajal contract).

8 pags., 4 figs., 5 tabs. 1 app., Manganese nickel oxides with a spinel-related structure, NiMnO (x = 0.5 or 0.75), were synthesized by an ultrasound-assisted sol-gel method. Inductively coupled plasma atomic optical emission spectroscopy and energy-dispersive X-ray spectroscopy analysis showed good agreement with the nominal oxide compositions. The Rietveld refinement of the X-ray data indicated that both NiMnO and NiMnO crystallize in the Fd3m space group, having cell parameter a of 0.8439 and 0.8392 nm, respectively. Scanning electron microscopy images showed agglomerated particles with sizes ranging from 300 nm to 1.4 μm, approximately. The magnetization curves showed paramagnetic behavior at room temperature, whereas ferromagnetic behavior was observed at 5 K. Zero-field-cooling and field-cooling magnetization measurements indicated the presence of three magnetic transitions, at T = T = 107 K, T = 98 K, and T = 54 K for NiMnO and at T = T = 101 K, T = 93 K, and T = 68 K for NiMnO X-ray photoelectron spectroscopy analysis revealed the presence of Ni, Mn, Mn, and Mn. The results provided by the different techniques allow us to propose the following cation distributions for these oxides: Mn Mn [Ni Mn Mn ]O and Ni Mn [Ni Mn Mn ]O ., This work was supported from the Chilean agency Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)(Fondecyt grants 1150371 and 3180042). JLG also thanks Dirección de Investigación Científica y Tecnológica (DICYT) 51831 EM DAS project.JCD thanks CONICYT Basal Centro para el Desarrollo de la Nanociencia y la Nanotecnología (CEDENNA) FB0807 project and JFM thanks theSpanish MINECO (project MAT2015-64110-C2-1-P)

5 pags., 2 figs., 2 tabs., The study of non-precious metal catalysts (NPMCs) as alternatives to platinum for oxygen reduction is crucial if the use of fuel cells is to become more widespread. Among NPMCs, pyrolyzed catalysts (Fe-N-C) are particularly promising in both basic and acid media. The characterization of active sites and the understanding of the oxygen reduction reaction (ORR) mechanism are crucial for the design of active Fe-N-C catalysts. In this study, we have tested the involvement of the metal centre in the ORR process at pH 13 for two pyrolyzed iron porphyrins. The pyrolyzed catalysts present a FeN4 active site structure similar to that of the porphyrin precursors. Regarding the mechanism, we have found evidence for the crucial role of the Fe(II) centres. There is a direct relation between the Fe(III)/(II) redox transition of the catalysts and the onset potential of the ORR, showing that the electrogeneration of Fe(II) from Fe(III)OH– controls the catalysis. The poisoning of iron centres with CN− induces a decrease in the ORR activity. However, the onset potential for H2O2 generation remains unchanged. The Tafel plots show two different slopes at high and low overpotentials. Based on these results, we propose two different mechanisms, both dependent on the redox potential of the catalysts and the FeO2 binding energy., This work was supported by Fondecyt Regular Projects 1161117,1181037. Fondecyt Postdoctoral Projects 3170330, 3180509, and Conicyt Scholar ships 1160955,21160212

REIPI/GEIH Study Group., Sigma factor B (SigB) controls the expression of Staphylococcus aureus genes including virulence factors and plays a role in the bacterial secretion system through membrane vesicle production. Inhibition of SigB could attenuate SigB dependent virulence and secretion system. The objective of this study was to determine the effects of rhodomyrtone on SigB and virulence factors related to SigB. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values of rhodomyrtone against 67 clinical methicillin-resistant S. aureus isolates were 0.25–8 μg/ml, which were similar to those of vancomycin. Using luciferase gene fused to SigB dependent promoters of asp23, five time reduction in SigB activity was observed when the bacteria were treated with rhodomyrtone for 3 h. Rhodomyrtone significantly reduced SigB activity in a concentration dependent manner in exponentially growing cells (P, This work was financially supported by The Royal Golden Jubilee Ph.D. Program (Grant No. PHD/0033/2553) and TRF Senior Research Scholar (Grant No. RTA 6180006), the Thailand Research Fund. M.J.R.O. was funded by the 'XXII Programa Propio de Fomento de la Investigación', University of Córdoba.

9 pags., 10 figs., 2 tabs., The performance of microbial fuel cells (MFCs) is highly dependent on the electrode materials. The electrode surface can be modified to provide a favorable environment for biofilms to enhance electron transfer from the bacteria to the anode. In this work, Faujasite zeolite-Y (ZY) was exchanged with iron (Fe) and was used to modify glassy carbon/graphite electrodes (GC/gr-ZY) evaluating its effect in electroactive biofilm development for application in microbial fuel cells. The novel material was evaluated as an anode in MFCs by comparing its performance with GC/gr and GC/gr-ZY electrodes. The results show that when using a GC/gr-ZY electrode, an electroactive biofilm with good electrochemical activity for acetate degradation can be generated on the electrode surface. The maximum current density obtained with a GC/gr-ZY-BF electrode (where BF is biofilm) was 7.7 times higher than that of a GC/gr anode. The modification generates a less hydrophobic electrode surface that facilitates microbial cell attachment, thereby improving bioelectricity production. By using scanning electron microscopy, a homogeneous microbial community with bacteria that had a similar short rod-shaped morphology was observed. Furthermore, electrochemical impedance spectroscopy demonstrated that the charge transfer resistance (R) decreased as the biofilm grew, revealing that the presence of the biofilm facilitated the electrochemical reaction. After 7 days of MFC operation, the GC/gr-ZY bioanode showed a reduction in R from 212.9 ± 1.81 Ω to 151.5 ± 1.46 Ω which was 2.4 times lower than that achieved with GC/gr. The biofilm on GC/gr-ZY was characterized using cyclic voltammetry, and the results showed a larger oxidation peak (169.8 μA cm) than that of the GC/gr electrode (36.5μA cm), further supporting the better electron-transfer properties of the modified electrode. Additionally, this result confirms the capability of biofilms to act as bioelectrocatalysts under acetate-oxidizing conditions., This work was supported by the grants CONICYT-PCHA/Doctorado Nacional/2015-211160606 from CONICYT (Chile), CONICYT/FONDAP/15130015 and FONDECYT 1140207.

As a hazardous waste, pickling waste liquor must be properly treated. An alternative consists in promoting the formation of ferrous salts from this residue, due to its higher ferrous content. Since FeCl2·4H2O is widely used in several applications, obtaining pure crystals of this material appears to be an interesting prospect. However, this compound has scarcely been investigated. In the present work, FeCl2·4H2O crystals have been obtained from pickling waste liquors. Their structural and morphological characteristics have been investigated by X-ray diffraction, scanning electron microscopy as well as Mössbauer spectroscopy. In addition, the photoluminescence study of the obtained samples was also assessed. It was observed that after some aging time, the obtained crystals change in colour from green to more yellowish. So, the aged sample has also been evaluated, and their structural characteristics are compared with the original crystals. Despite this, the obtained crystals exhibit a FeCl2·4H2O structure, which is not modified with the aging of the sample.

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.

10 pags., 5 figs., 2 tabs., In this work, we report a new octanuclear cluster based on FeIII and the ligand 1H-imidazole-4,5-dicarboxylic acid, [Et3NH]12[Fe8(IDC)12]middot10DMF 13H2O (1), with a metal core containing eight FeIII connected by only one type of organic ligand. A peak at 573 m/z in the mass spectra of the compound suggests the adduct species {[Fe8(IDC)12]+8H}4-. By X-ray photoelectron spectroscopy, the oxidation state of the iron cation was confirmed to be 3+, also identifying the presence of a quaternary nitrogen species, which act as a countercation of the anionic metal core [Fe8(IDC)12]12-. Mössbauer spectra recorded at different temperatures show an isomer shift and quadrupole splitting parameters that confirm the existence of only FeIII-HS in the structure of 1. X-ray analysis reveals that compound 1 crystallizes in the orthorhombic system space group Ibam, confirming a molecular cluster structure with an almost regular cube as geometry, with the FeIII atoms located at the corners of the cube and connected by κ2N,O:2κ2N,Oâ IDC3- bridges. Additionally, the magnetic measurements reveal a weak antiferromagnetic coupling in the Fe8III coordination cluster (J =-3.8 cm-1). To the best of our knowledge, 1 is the first member of the family of cubes assembled with 1H-imidazole-4,5-dicarboxylic acid and FeIII cation, exhibiting high pH stability over a broad pH range, making it an ideal candidate for the design of supramolecular structures and metal-organic frameworks., The authors acknowledge FONDECYT 1170887, Proyecto Anillo CONICYT ACT 1404 grant, CONICYT-FONDEQUIP/PPMS/EQM130086, CONICYT-FONDEQUIP/ EQM140060, Chilean-French International Associated Laboratory for Multifunctional Molecules, and Materials LIAM3- CNRS N°1027 for financial support. The authors also acknowledge Financiamiento Basal, AFB180001, CEDENNA and Laboratory of Analyses of Solids (L.A.S-UNAB). JFM acknowledges financial support from the Spanish Agencia Estatal de Investigacion (AEI) through Project No. RTI2018- ́ 095303-B-C51 and the Comunidad de Madrid through Project. NANOMAGCOST-CM P2018/NMT-4321. NM acknowledges Agencia Estatal de Investigacion Espanola PGC2018- 095642-B-I00 proyect.

11 pags., 10 figs., 2 tabs., The development of heterogeneous Fenton-based electrochemical advanced oxidation processes is important for the removal of organic pollutants at industrial level in the near future. This work reports the application of heterogeneous photoelectro-Fenton (HPEF) with UVA light as an enhanced alternative to the more widespread heterogeneous electro-Fenton (HEF) process. The treatment of the antibiotic cephalexin using chalcopyrite as a sustainable catalyst was studied using an undivided IrO/air-diffusion cell. XPS analysis showed the presence of Fe(III), Cu(I) and Cu(II) species on the surface. The amount of Fe ions dissolved upon chalcopyrite exposure to continuous stirring and air bubbling was proportional to chalcopyrite content. In all cases, the occurrence of pH self-regulation to an optimum value near 3 was observed. The HEF and HPEF treatments of 100 mL of 50 mg L cephalexin solutions with 0.050 M NaSO have been studied with 1.0 g L chalcopyrite at 50 mA cm. Comparative homogeneous EF and PEF with dissolved Fe and Cu catalysts were also performed. HPEF was the most effective process, which can be mainly explained by the larger production of homogeneous and heterogeneous [rad]OH and the photodegradation of the complexes formed between iron and organics. The effect of applied current and catalyst concentration on HPEF performance was assessed. Recycling experiments showed a long-term stability of chalcopyrite. Seven initial aromatics and six cyclic by-products of cephalexin were identified, and a plausible degradation route that also includes five final carboxylic acids is proposed., Financial support from FONDECYT project 11180772 (CONICYT, Chile) as well as from project CTQ2016-8616-R (AEI/FEDER, EU) is acknowledged. A. Thiam is grateful to the ‘Becas Iberoamérica. Santander Universidades’ program.

[EN] The purpose of this work is to fabricate self-assembled microstructures by the sol–gel method and study the morphological, structural and compositional dependence of 3-Fe2O3 nanoparticles embedded in silica when glycerol (GLY) and cetyl-trimethylammonium bromide (CTAB) are added as steric agents simultaneously. The combined action of a polyalcohol and a surfactant significantly modifies the morphology of the sample giving rise to a different microstructure in each of the studied cases (1, 3 and 7 days of magnetic stirring time). This is due to the fact that the addition of these two compounds leads to a considerable increase in gelation time as GLY can interact with the alkoxide group on the surface of the iron oxide precursor micelle and/or be incorporated into the hydrophilic chains of CTAB. This last effect causes the iron oxide precursor micelles to be interconnected forming aggregates whose size and structure depend on the magnetic stirring time of the sol–gel synthetic route. In this paper, crystalline structure, composition, purity and morphology of the sol–gel coatings densified at 960 ºC are examined. Emphasis is placed on the nominal percentage of the different iron oxides found in the samples and on the morphological and structural differences. This work implies the possibility of patterning 3-Fe2O3 nanoparticles in coatings and controlling their purity by an easy one-pot sol–gel method., Spanish Ministry of Industry, Economy and Competitiveness for financing the project MAT2015-65445-C2-1-R, MAT2017-86450-C4-1-R, MAT2015-67557-C2-1-P, by the Comunidad de Madrid S2013/MIT-2850 NANOFRONTMAG and H2020 AMPHIBIAN Project ID: 720853. The authors are also grateful to the BM25-SpLine staff for their valuable technical support beyond their duties and for the financial support from the Spanish Ministry of Science, Innovation and Universities (MICIU) and The Spanish National Research Council (CSIC) under Grant No. PIE 2010- 6OE-013, The ESRF – The European Synchrotron, MICIU and CSIC are acknowledged for provision of synchrotron radiation facilities. A. S. acknowledges the Financial support from the Comunidad de Madrid for an “Atracción de Talento Investigador” contract (No. 2017-t2/IND5395).

In the present paper we describe a simple method to immobilize amino cyclodextrins (CDs) and methylated-amino cyclodextrins on gold surfaces. We also report on the effect that the presence of methyl groups in the broader rim of the cyclodextrin causes on the interaction with the guest molecule bentazon. By means of electrochemical measurements, X-ray photoelectron spectroscopy and contact angle experiments we have demonstrated that the CDs attach covalently to the gold surfaces by amide bond formation and that the CD cavity is oriented opposite to the gold surface. We have shown that methylated-CD/Au modified surfaces are more sensitive towards the recognition of the herbicide bentazon than the non-methylated variants. The association constants for the corresponding interactions of the immobilized CD with the guest molecule have been determined from surface plasmon resonance experiments. The magnitudes of these constants (30.8 ± 1.0 M and 80.5 ± 4.2 M for amino-CD and methylated-amino cyclodextrins, respectively) are consistent with the change of hydrophobicity caused by methyl groups. The results demonstrate the feasibility of using CD-gold modified surfaces to encapsulate herbicides such as bentazon within the macrocyclic receptor without necessity of carrying out the experiments in solution.

The Morrón de Mateo bentonite deposit has been studied as a natural analogue of the thermal effect on the bentonite barrier of a geological radioactive waste repository. This deposit was intruded by a volcanic dome that induced hydrothermal activity affecting the smectite clay minerals close to the dome. Previous studies of proximal bentonites indicated that Al-montmorillonites were transformed into Fe-rich smectites with intermediate composition between beidellite and saponite through gradual steps formed by smectites increasingly rich in Mg and Fe. In order to confirm the suggested transformation and the Fe distribution into the smectites, infrared and Mössbauer spectroscopy studies were performed. Infrared spectra of samples away from the dome show typical bands for montmorillonite type with prevailing Al in octahedral positions, while proximal samples also show bands of Fe-rich smectites. Mössbauer data confirm that Fe present in the fine fraction of bentonites is fundamentally located in the smectites structure, mainly as octahedrally coordinated Fe(III). Proximal smectites have a considerably more distorted octahedral environment for Fe(III) which probably stemmed from a significant degree of substitution of Al by Fe(III). These results confirm that an alteration process occurred related to the volcanic intrusion which produced an increase in temperature and Fe-rich solutions responsible for the transformation of Al-montmorillonites.

Co−doped stannates, Zn 2-x Co x SnO 4 (0.5 ≤ x ≤ 1.5), were produced by ceramic synthesis starting from the ZnSnO 4 phase. Morphology, structure, and composition of synthesized compounds were examined using scanning electron microscopy, X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). Using XPS, cobalt ions are shown to have an oxidation state of 2 + , and XRD patterns showed the same crystalline structure for all Zn 2-x Co x SnO 4 (0.5 ≤ x ≤ 1.5) phases, i.e., they are isostructural. The morphology of synthesized compounds shows appreciable differences in particle sizes which range from 80 nm to 500 nm, depending on how the ceramic was synthesized and the cobalt concentration. Co−doped stannates ⁄reduced graphene (rGO) composites were prepared and used to modify glassy carbon electrodes (GCE). The resulting electrodes were evaluated for the amperometric determination of hydrogen peroxide. The catalytic activity of composites towards the oxidation of hydrogen peroxide was highly dependent on quantity of cobalt in the ceramic compound, and also on the quantity of rGO present in the composite. The pure cobalt stannate phase with a ratio of 8:1 (ceramic:rGO) exhibited the best catalytic activity towards hydrogen peroxide oxidation at low potentials (0.400 V). A linear relationship between current and hydrogen peroxide concentration was obtained with a sensitivity of 0.43 μAmM −1 cm −2 and a detection limit of 0.31 μM.

9 pags., 6 figs., 2 tabs., Pyrolyzed non-precious metal catalysts (NPMCs) are promising materials to replace platinum-based catalysts in the cathode of the fuel cells. These catalysts present high catalytic activity both in alkaline and acid media for the oxygen reduction reaction (ORR). These catalysts are essentially heterogeneous as they can present different types of active sites. MNx structures have been proposed as the most active for the ORR, similar to those of the MN4 structures of metal porphyrins and phthalocyanines. Several parameters have been proposed as reactivity descriptors to correlate the structure of these materials with their catalytic activity, such as the amount of MNx and of pyridinic nitrogens in the graphitic structure. In this study, we have explored the metal center redox potential of the catalyst as an overall reactivity descriptor. We have investigated this descriptor for pyrolyzed and intact catalysts for the ORR in acid and basic media. We have found that for all catalysts tested, there is a linear correlation between the redox potential of the catalyst and the catalytic activity expressed as (log i)). The activity increases as the redox potential becomes more positive. The correlation gives a straight line of slope close to +0.12 V/decade which agrees with the theoretical slope proposed in a previous publication assuming the adsorbed M − O follows a Langmuir isotherm and that the redox potential is directly linked to the M − O binding energy. The Tafel plots present two slopes, at low and high overpotentials. Based on these results, we proposed two different mechanisms. The low Tafel slopes of −60 mV appear at potentials where the surface concentration of M(II) active sites is potential dependent (close to the onset potential). At higher overpotentials the surface coverage of M(II) becomes constant and the slope changes to −0.120 V/decade., This work was supported by Fondecyt Regular Projects 1161117,1181037, Fondecyt Postdoctoral Projects 3170330 and 3180509, andConicyt Scholarship 21160955.

© The Author(s)., For the first time, the synthesis, characterization, and analytical application for hydrogen peroxide quantification of the hybrid materials of Co2TiO4 (CTO) and reduced graphene oxide (RGO) is reported, using in situ (CTO/RGO) and ex situ (CTO+RGO) preparations. This synthesis for obtaining nanostructured CTO is based on a one-step hydrothermal synthesis, with new precursors and low temperatures. The morphology, structure, and composition of the synthesized materials were examined using scanning electron microscopy, X-ray diffraction (XRD), neutron powder diffraction (NPD), and X-ray photoelectron spectroscopy (XPS). Rietveld refinements using neutron diffraction data were conducted to determine the cation distributions in CTO. Hybrid materials were also characterized by Brunauer–Emmett–Teller adsorption isotherms, Scanning Electron microscopy, and scanning electrochemical microscopy. From an analytical point of view, we evaluated the electrochemical reduction of hydrogen peroxide on glassy carbon electrodes modified with hybrid materials. The analytical detection of hydrogen peroxide using CTO/RGO showed 11 and 5 times greater sensitivity in the detection of hydrogen peroxide compared with that of pristine CTO and RGO, respectively, and a two-fold increase compared with that of the RGO+CTO modified electrode. These results demonstrate that there is a synergistic effect between CTO and RGO that is more significant when the hybrid is synthetized through in situ methodology., Funding was provided by Conicyt-Fondecyt Chile (Grant N°1161225), Conicyt-FONDEQUIP Chile (Grant N° EQM170111), and Redes de Investigación 021842SG_RED: RCNM-USACH “Red de Caracterización de NanoMateriales—Universidad de Santiago de Chile”. Additional funding was provided by Ministerio de Economia (MINECO, Spain) under project RTI2018-095303-B-C51.

Iron macrocyclic complexes (MN4) are promising catalysts for replacing platinum (the industrial standard) in electrocatalysis. In particular, FeN4 complexes have shown lower overpotential than Pt for the oxygen reduction reaction (ORR) in alkaline media. To predict the electrochemical activity of metal electrodes and molecular catalysts towards the ORR, reactivity descriptors with typical volcano correlation have been demonstrated. The most important are M–O2 binding energy and M(n)+/M(n−1)+ redox potentials for the complexes. We studied a new Fe complex, which possesses powerful electron-withdrawing fluorine residues at the periphery of the phthalocyanine ring. Fe hexadecafluorophthalocyanine (16(F)FePc) was characterized by electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy (XPS) in the presence and in absence of O2. Experimental and calculated O2–Fe binding energies, as well as electrochemical characterization confirms the excellent activity of this complex for the ORR placing this complex at the top of the MN4 volcano correlation.

7 pags., 10 figs. -- Open Access funded by Creative Commons Atribution Licence 4.0, In the present work, the application of the amine electrooxidation method to achieve the grafting of amino β-cyclodextrins (CD-amines) on glassy carbon electrodes (GCE) in aqueous media has been investigated. The results indicate that the electrooxidation procedure of CD-amines on GCE effects their covalent immobilization without the need of additional linkers or intermediates. Cyclic voltammograms of ferricyanide proved that the immobilized CDs cover at a large extent the GCE surface. This immobilization is due to real grafting and not the result of a weak physisorption interaction. Indeed, the presence of contributions characteristic of amide groups and the absence of peaks typical of amine groups in the XPS N 1s spectra of the modified GCE, support the evidence of the covalent bonding of the CDs to the glassy carbon surface through amide bond formation. Electrochemical experiments demonstrated that ferrocenemethanol and bentazon can be encapsulated within the cavity of the CDs immobilized on GCEs via the formation of inclusion compounds. Overall, the results of the present work show that this simple amine-electrooxidation strategy is suitable to immobilize CDs on glassy carbon surfaces while maintaining their inclusion abilities and, therefore, open the door to design cheap and simple electrochemical sensors for environmental applications., The authors acknowledge financial support from FONDECYT (Grant. N. 1151329) and MINECO, Spain (Project MAT2015-64110- C2-1-P).

12 pags., 12 figs., 2 tabs., We have evaluated the electrocatalytic activity of hybrid electrodes containing Fe(II) phthalocyanine and tested these electrodes for L-cysteine oxidation and L-cystine reduction. The hybrid electrodes consisted of pristine multi-walled carbon nanotubes and functionalized with [sbnd]COOH, [sbnd]NH groups (MWCNT-p, MWCNT-c and MWCNT-a). These MWCNTs were modified with iron (II) phthalocyanine (FePc). The characterization of the hybrid systems was performed using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and AFM with the purpose of elucidating the type of interaction between FePc and MWCNTs. The Fe(II)/(I) and Fe(III)/(II) redox potentials associated with the metal center where evaluated using cycling voltammetry. The redox processes are slightly affected by the presence of MWCNTs. The activity for both reactions increases substantially by the presence of modified MWCNTs essentially by an area effect. However, when the currents are normalized by the amount of active sites estimated from the surface coverages of FePc, the activities are still higher for FePc attached to MWCNTs. The data for L-cysteine oxidation fits well on a volcano correlation published previously for several metal phthalocyanines and metalporphyrins., The authors are grateful to Fondecyt Projects 1140199, 1181037,Nucleo Milenio RC 120001, Anillo ACT-1412, Fondecyt PostdoctoralProject 3150271 and Conicyt Scholarships M.P.O. 21130168. Fon-dequip EQM 130149&Fondequip EQM 160036

Mine wastes from abandoned exploitations are sources of high concentrations of hazardous metal(oid)s. Although these contaminants can be attenuated by sorbing to secondary minerals, in this work we identified a mechanism for long-distance dispersion of arsenic and metals through their association to mobile colloids. We characterize the colloids and their sorbed contaminants using spectrometric and physicochemical fractionation techniques. Mechanical action through erosion may release and transport high concentrations of colloid-associated metal(oid)s towards nearby stream waters, promoting their dispersion from the contamination source. Poorly crystalline ferrihydrite acts as the principal As-sorbing mineral, but in this study we find that this nanomineral does not mobilize As independently, rather, it is transported as surface coatings bound to mineral particles, perhaps through electrostatic biding interactions due to opposing surface charges at acidic to circumneutral pH values. This association is very stable and effective in carrying along metal(oid)s in concentrations above regulatory levels. The unlimited source of toxic elements in mine residues causes ongoing, decades-long mobilization of toxic elements into stream waters. The ferrihydrite-clay colloidal composites and their high mobility limit the attenuating role that iron oxides alone show through adsorption of metal(oid)s and their immobilization in situ. This may have important implications for the potential bioavailability of these contaminants, as well as for the use of this water for human consumption., The Spanish Ministry of Economy and Competitiveness supported this study (CGL2010-17434).

Perovskite type and related materials have attracted considerable interest as both electrolyte and electrodes within Solid Oxide Fuel Cells. Traditionally, doping with aliovalent cations of similar size on either site has been used to alter materials properties to enhance performance of the materials in these cells. However, recent literature has shown that anion incorporation strategies have also been successful in optimising electrical and ionic properties of perovskites and related structures. The two most successful anion doping strategies, are fluorine doping and oxyanion doping, the latter which is the focus of our work. In particular, our recent work has focused on doping with various oxyanions (Carbonate. Borate, Phosphate, Silicate, Sulphate) in perovskite and related structures. [1-3] In previous work, we showed how small amounts of silicate doping can cause structural changes that lead to large increases in conductivity such as in the case of (Ca/Sr)2MnFeO6- δ.[4] In view of this, we have extended these studies to examine the structural modifications caused by PO4 3- doping and the consequent effect on electrical conductivity. [1] C A Hancock, J M Porras-Vazquez, P J Keenan, P R Slater, Dalton Trans, 2015, 44, 10559-10569 [2] J Deakin, P Slater, J. Solid State Chem 2021, 294, 121870 [3] A. Jarvis, P R Slater Crystals 2017, 7(6), 169 [4] A D Smith, M S James, P R Slater, ECS Trans. 2019 91(1) 1425-1436

15 pags., 7 figs., 5 tabs., The control of chemical, morphological, textural and magnetic properties developed in magnetic activated carbons (MACs) from industrial food waste, was achieved. The process parameters involved in a sustainable and optimized one-step activation route, based on the circular economy model, played an important role and its influence was studied, offering interesting and outstanding results. Magnetite crystals were formed on the MACs surface obtained from 400 °C to 800 °C while other iron species, such as metallic iron and iron carbides, were formed only at 800° C. Acid washing favored the mineral matter removal and the presence of iron species was drastically reduced in acid-washed MACs, mainly the iron species originated at 800 °C. Water-washed MACs presented better magnetic response at high temperatures (confirmed by XRD, FTIR, Raman, Mössbauer spectroscopy and VSM characterization techniques). High BET surface area (≈ 822 m/g) and a large micropore volume (≈ 0.30 cm/g), were reached by acid washed MACs at 800 °C. The obtained MACs were fundamentally microporous, but some mesoporosity was also observed when activating agent/precursor mass ratio (1:1) is used. It can be concluded that a MACs strategic design was reached with the objective of removing specific pollutants in multiple environmental applications., This work was supported by the Plan Nacional, Ministerio de Economía y Competitividad of Spain: PN (MINECO), under the Project CTM2014-58435-C2-1-R.

We studied the effect of laser fluence on the morphology, composition, structure and electric conductivity of deposits generated by pulsed laser ablation of a metallic aluminium target in vacuum using a Q-switched Nd:YAG laser (1064 nm, 15 ns). Upon irradiation for one hour at a repetition rate of 10 Hz, a smooth layer of several tens of nanometres, as revealed by atomic force microscopy (AFM) was deposited on glass. Surface chemical composition was determined by X-ray photoelectron spectroscopy, and to study the conductivity of deposits both I–V curves and conductive-AFM measurements were performed. Irradiation at fluences around 2.7 J/cm resulted in deposition of amorphous aluminium oxide films. Differently, at higher fluences above 7 J/cm, the films are constituted by metallic aluminium. Optical emission spectroscopy revealed that highly ionized species are more abundant in the ablation plumes generated at higher fluences. The results demonstrate the possibility to control by PLD the metal or dielectric character of the films., This research was supported by the Spanish Ministry of Economy and Competitiveness (MINECO, projects CTQ2013-43086-P, MAT2015-66443-C2-1-R and a Ramon y Cajal contract awarded to E.R. (RYC-2011-08069)). MO thanks CSIC for a contract.

5 pags., 3 figs., We have studied the adsorption and electrooxidation of CO on PtAu nanoalloys, aiming at providing further insight about the correlation between atomic structure and catalytic properties. The multiplicity of adsorption sites with different geometry and composition on the nanoparticles surface is demonstrated by a combination of electrochemical and infrared experiments. Specifically, the occurrence of low- and high-coordinated Pt atoms was confirmed by the splitting of the linearly-bonded CO band after removing CO from the electrolyte. Despite the low activity for the electrooxidation of CO of our PtAu nanoparticles, the combination of small Pt(111) terraces and small Pt atomic ensembles on their surfaces revealed by our experiments is connected with the negligible CO poisoning and the resulting high catalytic activity of our PtAu NPs for the formic acid oxidation reaction [Electrochim. Acta 2017, 224, 56–63]., Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)is gratefully acknowledged forfinancial support (grant #3039/2010).

Ruddlesden-Popper type compounds have the general formula, An+1MnO3n+1±x (typically A is a rare earth, alkaline earth, M is a transition metal), and are constructed of perovskite-type layers separated by rock salt type blocks. While n ​= ​1, 2 phases are typically straightforward to prepare, the synthesis of higher order (n ​> ​2) systems is difficult. In this paper we show that chromate (CrO42−) doping can be exploited to stabilise new n ​= ​3 Ruddlesden-Popper systems, Sr4Fe3-xCrxO10-δ: without chromate doping, a mixture of the n ​= ​2 phase Sr3Fe2O7-x and perovskite-type SrFeO3-x is obtained. This can be explained by the stabilisation of the central perovskite building block by chromate incorporation, similar to prior work on sulfate and carbonate doping in this system. The structure, and Fe/Cr oxidation states were evaluated by X-ray diffraction, 57Fe Mossbauer spectroscopy and X-ray absorption spectroscopy supporting the incorporation of Cr as CrO42−. In order to examine the potential of these new systems for use as a SOFC cathode material, conductivity studies were carried out, which showed semiconducting behaviour with slightly higher conductivities than the sulfate doped counterparts.

13 pags., 14 figs., 4 tabs., The aim of this work is to produce a superparamagnetic core-shell adsorbent material composed of magnetite nanoparticles coated with a silica layer and functionalized with betaine for applications associated with the recovery of molybdenum and rhenium anions from highly acidic aqueous solutions. The resulting nanoparticles with a quaternary amine surface were predominantly spherical with average diameters of 14.3 ± 1.7 nm. Adsorption experiments at pH values of 1-2 confirmed that it was possible to uptake molybdate and perrhenate species using this adsorbent nanomaterial, achieving maximum loading capacities of 15 mg/g for Mo and 19 mg/g for Re., The authors are grateful for the financial assistance provided bythe PTID project, Facultad de Ciencias Químicas y Farmacéuticas,Universidad de Chile, and Fondecyt Project N1140331. Laboratorio de Magnetismo Molecular, Universidad Andrés Bello, Chile, CONICYTFONDEQUIP/PPMS/EQM130086 forthe magnetic measurements and corresponding discussion.

A novel thermochemical process based on a single step was optimized to obtain magnetic activated carbons from an industrial biomass waste. Anhydrous iron chloride was used as an activating agent and mixed directly with the chestnut shell waste. The effect of the activation temperature (220-800 °C) on the chemical, morphological, textural, and magnetic properties of the materials was studied. The results demonstrated the presence of different iron compounds depending on the activation temperature set as well as their influence on morphological and textural development of the magnetic activated carbons (BET specific surface area, S up to 568 m g, total pore volume, V, up to 0.294 cm g vs 1 m g and 0.007 cm g, respectively, for the raw biomass waste). The techniques employed, especially Mössbauer spectroscopy, showed relative contributions of the different iron compounds (magnetite, maghemite, metallic iron, and so on) in the materials. The higher activation temperature (800 °C) favored the formation of metal Fe and iron carbide. Additionally, the magnetic properties measured by vibrating sample magnetometry confirmed the coexistence of different ferromagnetic phases with the remanent magnetization, M, (up to 3.88 emu/g) and coercivity, H, (up to 140 Oe), being larger as the activation temperature increases. A higher activation temperature favored the development and evolution toward other iron compounds, while at low temperature, 220 °C, the presence of these compounds were null, and their behavior resembled the results obtained for the original biomass waste.

17 pags., 11 figs., 6 tabs., With the purpose of obtaining inexpensive electrodes for the degradation of organic pesticides by the electro-Fenton reaction, the required HO being obtained by the 2-electron reduction of dissolved O, we have prepared glassy carbon electrodes coated with a mixture of graphite with Mo- and/or Co-modified zeolites. Three zeolites were used, Linde type A (ZA), Faujasite (ZY), and MFI (ZSM5), whose maximum possible cation exchange, directly given by the Al/Si ratio, and their hydrophilicity increases in the order ZSM5 < ZY < ZA. The zeolites were modified with Mo and/or Co by the wet impregnation method and characterized by different techniques. The outer surfaces of the three Mo-modified zeolites showed Mo-containing grains (in ZA) or needles (in ZY and ZSM5), which could be largely washed away with hot water. Electrodes were made by depositing on a disc of glassy carbon (GC) a mixture of graphite, zeolite, and a binder. Quite unexpectedly, the cyclic voltammograms (CVs) of the three Mo-modified zeolites showed at least five pairs of anodic–cathodic peaks, which we assume are due to the presence of the MoO isopolyoxomolybdate anion, proceeding from the impregnating solution, and anchored on the zeolites’ surface. With a rotating ring-disc electrode, the highest efficiency for HO production at − 0.2 V, namely, 12.7%, was obtained with the GC/graphite-(CoMo-exchanged ZA) electrode, but this efficiency decreased with time. On the contrary, the three zeolites modified only with Mo were stable in 4-h electrolyses at − 0.2 V and yielded the highest HO concentrations, which we attribute to the MoO isopolyoxomolybdate anchored on the zeolites. The HO yield was the same for the three Mo-modified zeolites, irrespective of their exchange capacity and hydrophobic/hydrophilic character. [Figure not available: see fulltext.]., This work was supported by CONICYT Chile under Grant FONDECYT-1140207 and FONDEQUIP-EQM 160070 and DICYT-USACH grant 021841UZ. FF acknowledges a MECESUP USA 1555 Grant.

Magnesium- and cobalt- substituted FeSb2O4, of composition Fe1−xMgxSb2O4 (x = 0.25, 0.50, 0.75) and Fe0.25Co0.75Sb2O4 have been examined by 57Fe Mossbauer spectroscopy. The complex spectra recorded from the magnetically ordered materials are interpreted in terms of models in which the dominant magnetic interactions occur along the rutile-related chains of FeO6 octahedra in the magnetic structure of FeSb2O4. In materials of the type Fe1−xMgxSb2O4, the diamagnetic Mg2+ ions have no magnetic moment and behave as non-magnetic blocks which disrupt the magnetic interactions in the chains along the c-axis forming segments of iron-containing chains separated by Mg2+ ions. In Fe0.25Co0.75Sb2O4 the spectra are composed of components from different configurations of neighbouring Fe2+ and Co2+ ions.

Highly oriented magnetite thin films showing well-defined fourfold in-plane magnetic anisotropy have been grown on TiN buffered Si(001) substrates by ion beam sputtering assisted by a second ion beam containing a controlled mixture of Ar and O ions. The structure and composition of stoichiometric FeO and non-stoichiometric FeO magnetite thin films have been characterized by X-ray diffraction, Rutherford backscattering spectroscopy and Mössbauer spectroscopy. Magneto-optical Kerr effect measurements show that the maxima of the remanence and coercivity of all these films lie along the Si[010] and [100] directions. The introduction of Fe vacancies in magnetite does not alter the well-defined fourfold in-plane anisotropy but induces a decrease of the coercive field as the number of vacancies increases. Furthermore, the results indicate that a 5 nm TiN thick buffer layer is enough to maintain the FeO[100]/TiN[100]/Si[100] epitaxial relationship.

We have grown mixed magnetite/cobalt ferrite epitaxial films on SrTiO3 by infrared pulsed-laser deposition. Diffraction experiments indicate epitaxial growth with a relaxed lattice spacing. The films are flat with two distinct island types: nanometric rectangular mounds in two perpendicular orientations, and larger square islands, attributed to the two main components of the film as determined by Mössbauer spectroscopy. The origin of the segregation is suggested to be the oxygen-deficiency during growth.

The exposure of carbon steel in marine atmospheres can lead in certain circumstances to the formation of thick rust layers (containing a number of compact laminas) that are easily detached (exfoliated) from the steel substrate, leaving it unprotected and considerably accelerating the corrosion process. This deterioration phenomenon is of particular concern in steel infrastructures located close to the sea (civil constructions, bridges, etc.), whose service lifetime can be extraordinarily limited. High times of wetness of the metallic surface and high chloride ion deposition rates play a decisive role in the formation of this type of rust. Research has been carried out for 1 year in eight pure marine atmospheres with annual average chloride deposition rates of 70–1906 mg Cl-/m2 day. The studied carbon steels consisted of one mild steel, one conventional weathering steel (Corten A), and one high nickel (~3 wt.%) advanced weathering steel (AWS). The paper describes the environmental conditions that lead to the formation of these thick multilaminar rust layers and presents a characterisation study of this singular type of rust using a variety of analysis techniques: scanning electron microscopy/energy-dispersive X-ray spectroscopy, X-ray diffraction, Mössbauer spectroscopy, and transmission electron microscopy/electron diffraction. The Ni-AWS shows greater resistance to the occurrence of rust exfoliation.

© 2015 Z. Published by Elsevier Ltd. In this paper we report the successful incorporation of germanium into Sr1-yCayFeO3-δ perovskite materials for potential applications as electrode materials for solid oxide fuel cells. It was observed that Ge doping leads to a change from a tetragonal cell (with partial ordering of oxygen vacancies) to a cubic one (with the oxygen vacancies disordered). Annealing experiments in 5%H2/95%N2 (up to 800 °C) also showed the stabilization of the cubic form in reducing conditions for the 15 mol% Ge-doped SrFeO3-δ sample, in contrast to the undoped systems which showed a transition to an oxygen vacancy ordered brownmillerite-type phase. In order to examine the potential of these systems as SOFC cathodes, composite electrodes comprising 50% Ce0.9Gd0.1O1.95 and 50% Sr1-yCay(Fe/Ge)O3-δ on dense Ce0.9Gd0.1O1.95 pellets were examined in air. The results showed an improvement in the area specific resistances (ASR) values for the Ge-doped samples with respect to the undoped ones, with the best performance for the Ge doped SrFeO3-δ system (0.24 and 0.06 Ω cm2 at 700 and 800 °C, respectively, for SrFe0.85Ge0.15O3-δ). Thus, the results show that germanium can be incorporated into Sr1-yCayFeO3-δbased materials leading to materials with potential for use as cathode materials in solid oxide fuel cells (SOFC).

The Enterococcus species is the third main cause of infective endocarditis (IE) worldwide, and it is gaining relevance, especially among healthcare-associated cases. Patients with enterococcal IE are older and have more comorbidities than other types of IE. Classical treatment options are limited due to the emergence of high-level aminoglycosides resistance (HLAR), vancomycin resistance and multidrug resistance in some cases. Besides, few new antimicrobial alternatives have shown real efficacy, despite some of them being recommended by major guidelines (including linezolid and daptomycin). Ampicillin plus ceftriaxone 2 g iv./12 h is a good option for Enterococcus faecalis IE caused by HLAR strains, but randomized clinical trials are essential to demonstrate its efficacy for non-HLAR EFIE and to compare it with ampicillin plus short-course gentamicin. The main mechanisms of resistance and treatment options are also reviewed for other enterococcal species.

17 pags, 18 figs, 1 tab . -- This article is part of the Topical Collection on Proceedings of the 4th Mediterranean Conference on the Applications of the Mössbauer Effect (MECAME 2018), Zadar, Croatia, 27–31 May 2018, We report on this paper on the Mössbauer characterisation of the family of synthetic helvite analogues, FeM[BeSiO]X (M = Fe, Mn, Zn; X = S, Se). The data show iron to be present as high spin Fe(II) in tetrahedral coordination. The room temperature Mössbauer spectra are composed either by singlets or doublets with small quadrupole splitting values suggesting a small valence contribution at that temperature. From the dependence of the quadrupole splitting with temperature the separation Δ between the two e orbitals has been estimated. The values of Δ range from 46.3 cm for the material Fe[BeSiO]S to 58.2 cm for the material FeZn[BeSiO]S. The lack of long-range magnetic order observed in the Mössbauer spectra was confirmed by neutron diffraction data which suggests that the MX units are largely magnetically isolated within their cages leading to a frustrated magnet with no long range interaction for the sulfide species.

Epitaxial cobalt ferrite thin films with strong in-plane magnetic anisotropy have been grown on Si (001) substrates using a TiN buffer layer. The epitaxial films have been grown by ion beam sputtering using either metallic, CoFe, or ceramic, CoFeO, targets. X-ray diffraction (XRD) and Rutherford spectrometry (RBS) in random and channeling configuration have been used to determine the epitaxial relationship CoFeO [100]/TiN [100]/Si [100]. Mössbauer spectroscopy, in combination with XRD and RBS, has been used to determine the composition and structure of the cobalt ferrite thin films. The TiN buffer layer induces a compressive strain in the cobalt ferrite thin films giving rise to an in-plane magnetic anisotropy. The degree of in-plane anisotropy depends on the lattice mismatch between CoFeO and TiN, which is larger for CoFeO thin films grown on the reactive sputtering process with ceramic targets.

The analysis by intense radiation sources of painting materials used in artworks gives valuable information about their composition and state of conservation, but it can also induce undesired modifications on the studied substrates. Here we use X-ray photoelectron spectroscopy (XPS) to follow the surface chemical changes that prolonged irradiation with soft X-rays (with maximum doses ranging from ~ 1.2x1017 to ~ 3.4x1017 photons cm-2) produce on azurite, malachite and alizarin pigments and on two egg-yolk temperas containing azurite or alizarin. The effects following exposure to Argon ion irradiation have been also studied for malachite and azurite tempera. XPS spectra of the samples show that both types of radiation induce similar superficial alterations, although, at the selected experimental conditions, the modification rate is slower for exposure to soft X-rays. The highest radiation stability is shown for alizarin and, on the contrary, azurite and malachite experience a progressive chemical reduction of Cu2+ to Cu+. The reduction of copper takes also place in the azurite tempera, while the proteins and lipids of the egg-yolk binder of azurite and alizarin temperas are subjected to degradation by irradiation with photons and ions. By employing XPS, the cleavage of C-N, C-O(H) and C=O bonds has been identified in the egg-yolk temperas.

Manganese oxides of spinel structure, LiMnO, LiNiMnO (0.25 ≤ x≤ 0.75), and NiMnO, were studied by EDS, XRD, SEM, magnetic (M-H, M-T), and XPS measurements. The samples were synthesized by an ultrasound-assisted sol-gel method. EDS analysis showed good agreement with the formulations of the oxides. XRD and Rietveld refinement of X-ray data indicate that all samples crystallize in the Fd3m space group characteristic of the cubic spinel structure. The a-cell parameter ranges from a = 8.2276 Å (x = 0) to a = 8.3980 Å (x = 1). SEM results showed particle agglomerates ranging in size from 2.3 μm (x = 0) down to 0.8 μm (x = 1). Hysteresis magnetization vs. applied field curves in the 5–300K range was recorded. ZFC-FC measurements indicate the presence of two magnetic paramagnetic-ferrimagnetic transitions. The experimental Curie constant was found to vary from 5 to 7.1 cm K mol for the range of compositions studied (0 ≤ x ≤ 1). XPS studies of these oxides revealed the presence of Ni, Mn, and Mn. The experimental Ni/Mn atomic ratios obtained by XPS were in good agreement with the nominal values. A linear relationship of the average oxidation state of Mn with Ni content was observed. The oxide’s cation distributions as a function of Ni content from x = 0 Li[MnMn]O to x = 1 Ni0.352+Mn0.653+[Ni0.652+Mn1.353+]O4 were proposed.

CoN4 complexes like Co phthalocyanines (CoPc) have been extensively studied as electrocatalysts for the oxygen reduction reaction (ORR) but they only promote the 2-electron reduction of O to give peroxide. In contrast, vitamin B a Co macrocyclic naturally occurring molecule has attracted the attention of the scientific community because instead of catalysing the 2-electron reduction of O to HO like the other Co macrocycles it promotes the 4-electron reduction to HO. Vitamin B possesses an axial back ligand and this seems to be the reason for its higher activity and selectivity for the 4-electron reduction of O. To test this hypothesis, we synthetized a CoPc axially coordinated to pyridine anchored to carbon nano-tubes (CoPc-Py-CNT). The Co centre is therefore coordinated to 5 N as in vitamin B. The modified CoPc containing catalytic material was characterized by EPR and XPS spectroscopy. Ab initio calculations, Koutecky– Levich extrapolation and Tafel plots well describe the similarities between the 2 complexes and reveal insights into the mechanism of action of Co penta-coordinated complexes. According to our results the pyridine back ligand increases the Co-O binding energy and making it more similar to that of Vitamin B, favouring the splitting of the O-O bond. The back ligand then plays a crucial role in modifying Co-O binding energy which is a well know reactivity descriptor.

We review here some of our recent work on the synthesis and characterisation of new perovskite-related oxide fluorides. We demonstrate the use of low temperature fluorination methods for the preparation of new phases with high fluorine contents. We also show how fluorine can be accommodated in different sites according to the structural details of the initial oxide and the fluorine content. Importantly, we describe how Mössbauer spectroscopy is a powerful technique for monitoring changes in cation oxidation state as a result of fluorination and for examining the complex magnetic interactions which result from the accommodation of fluorine within the structures and how these can be related to structural properties and changes to the superexchange pathways.

For the first time a critical analysis of the influence that four different graphene oxide reduction methods have on the electrochemical properties of the resulting reduced graphene oxides (RGOs) is reported. Starting from the same graphene oxide, chemical (CRGO), hydrothermal (hTRGO), electrochemical (ERGO), and thermal (TRGO) reduced graphene oxide were produced. The materials were fully characterized and the topography and electroactivity of the resulting glassy carbon modified electrodes were also evaluated. An oligonucleotide molecule was used as a model of DNA electrochemical biosensing. The results allow for the conclusion that TRGO produced the RGOs with the best electrochemical performance for oligonucleotide electroanalysis. A clear shift in the guanine oxidation peak potential to lower values (~0.100 V) and an almost two-fold increase in the current intensity were observed compared with the other RGOs. The electrocatalytic effect has a multifactorial explanation because the TRGO was the material that presented a higher polydispersity and lower sheet size, thus exposing a larger quantity of defects to the electrode surface, which produces larger physical and electrochemical areas., Financial support from the National Fund for Scientific and Technological Development-CHILE FONDECYT 161225 (80%) and FONDAP 15130011 (20%) are gratefully acknowledged. Daniela F. Báez acknowledges Chile’s National Commission for Scientific and Technological Research (CONICYT) scholarships for her PhD studies in Chile. Financial support from MINECO (Spain) under project MAT2015-64110-C2-1-P is also acknowledged., We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).

The formation of cubic nitrides with stoichiometry close to FeN obtained by ion assisted sputter deposition has been studied as a function of deposition parameters. In particular, we have explored the influence of the energy deposited by the assistant beam per deposited Fe atom to understand changes in composition, phase formation and nanocrystallinity of the films. An optimum N2+ ion energy and a JN/JFe ratio (JN and JFe represent the current density of N2+ ions and Fe atoms respectively) have been determined in order to obtain only iron mononitride phases. X-ray diffraction and Mössbauer spectroscopy revealed a phase evolution from ¿-Fex(x ¿ 2)N to ¿¿ and ¿¿-FeN as the N2+ ion energy and the JN/JFe flux ratio increase. Pure nanocrystalline iron mononitride, with nitrogen content close to 50%, is obtained when JN/JFe ratio reaches 5.9 and the N2+ ion energy is 63.4 eV. Further increments of N2+ energies and JN/JFe values reverse this behavior and a phase evolution from ¿¿ and ¿¿-FeN to ¿-Fex(x ¿ 2)N is found. This behavior is attributed to energy damage and resputtering phenomena. It has also been found that ¿¿-FeN phase coexists with ¿¿-FeN phase when the deposition is performed at room temperature.

A carbon-neutral fuel is desired when it comes to solving the issues associated with climate change. A smart approach would be to develop new materials to produce such fuels, which could be integrated with renewables to improve the efficiency (e.g., solid oxide fuel cells (SOFCs) in smart grid and concentrated solar fuel technologies). In this study, we report the utilization of nonstoichiometric perovskite oxides, BaCaNbFeO (BCNF) (0 ≤ x ≤ 1), to split CO into carbon, carbon monoxide, and oxygen at elevated temperatures. Powder X-ray diffraction shows the chemical stability of double perovskite-type BCNF after being exposed to 2000 ppm CO in Ar at 700 °C. Furthermore, all x ≤ 0.66 BCNF members exhibit high chemical stability even under pure CO at 700 °C. Scanning electron microscopy coupled with energy dispersive X-ray, Raman spectroscopy, temperature programmed oxidation (TPO) and mass spectroscopy (MS), and DFT analyses confirm the formation of solid carbon upon CO exposure, which increases with increasing Fe in BCNF. Mössbauer spectroscopy of the as-prepared BCNF shows the presence of Fe, Fe and Fe. Upon Ar exposure, the higher valent Fe component is reduced to Fe and subsequent oxidation of Fe seems to promote the CO reduction. Overall, these promising results of BCNFs, displaying redox activity at significantly lower temperatures compared to state-of-the-art ceria for CO reduction, show great potential for their use in renewable-driven fuel technologies.

An efficient and inexpensive catalyst for the oxygen reduction reaction (ORR) is the key missing component for large-scale development of fuel cells. Bio-inspired tethered electrocatalysts could be the solution to this problematic reaction. Either unsubstituted Fe phthalocyanine (FePc) or Fe hexadecachloro-phthalocyanine (16(Cl)FePc) was anchored to carbon nanotubes (CNTs) via a pyridine axial ligand. The results show that the fifth coordination plays a major role in increasing the catalytic activity of FePc and 16(Cl)FePc for the ORR. The coordination also allows the decoupling of the metal centre from the carbon support, thus changing the geometrical and electronic structure and hindering the production of HO. The pentacoordinated catalysts were stable in acidic pH according to the rotating disk analysis, but the activity of the hexadecachloro compound was not higher than that of the unsubstituted phthalocyanine. Cl atoms reduced the coupling between O and Fe, mismatching the energy of the frontier orbitals and lowering the activity towards the reduction of O.

We report the microwave-assisted hydrothermal synthesis of bimetallic Pt-Au nanoparticles with different Pt/Au mole ratio, and investigate their performance towards the electro-oxidation of formic acid. The as-synthesized Pt-Au sol was dispersed on a graphite electrode, without any binding agents, which allowed us to control the mass of alloy deposited. Pt-Au alloys showed better activity than bulk Pt and/or Pt nanoparticles towards the oxidation of formic acid, as evidenced by the decrease in the onset potential and the higher currents in the corresponding cyclic voltammograms. The higher activity is due both to atomic-ensemble effects, which lead the reaction through the so-called direct pathway with insignificant CO poisoning, and to electronic effects, which optimised the interaction between the catalyst surface and the reactive intermediate in the direct path. Further insight into the individual contributions of atomic-ensemble and electronic effects and their effect on the catalytic activity was provided by the analysis of galvanostatic potential oscillations.

8 pags., 9 figs. 2 tabs., Suspensions of poly(bisphenol A carbonate) (PBAC) nanoparticles of varying size and shape have been produced by ablation of a PBAC target in liquid media with the fourth harmonic of a Q-switched Nd:YAG laser (wavelength 266 nm, full width at half maximum 4 ns, repetition rate 10 Hz). The polymer target was placed at the bottom of a rotating glass vessel filled with around a 10 mm column of liquid. Laser ablation in water leads to spherical nanoparticles with diameters of several tens of nanometers for fluences close to 1 J/cm. Ablation at lower fluences, around 0.1 J/cm, results in the production of nanoparticles of smaller diameters and also of non-spherical nanoparticles. Additional irradiations at the fluence of 0.1 J/cm were performed in several liquid media with different properties, in terms of density, viscosity, thermal conductivity, boiling temperature, isothermal compressibility and polarity. The different size distributions observed were related to the thermal conductivity of the systems, while their viscosity seems to be responsible for the development of nanostructures with different morphologies., AcknowledgementsThe authors gratefully acknowledge financial support fromthe MINECO (CTQ 2013-43086-P, MAT2014-59187-R, MAT2015-66443-C02-1-R). D.E.M. thanks CSIC for the tenure of JAE-Prefellowship and Fondo Social Europeo (FSE) for cofinancing the JAEProgram. E.R. also thanks MINECO for a Ramón y Cajal contract(RYC-2011-08069).

Fe-57 transmission Mossbauer at temperatures between 18 and 298 K and magnetic measurements have been used to characterize Fe-filled carbon nanotubes which were prepared by pyrolisis of Ferrocene + C-60 at atmospheric pressure under an Ar atmosphere at 1050 degreesC. The Mossbauer data have shown that the Fe phases encapsulated within the carbon nanotubes are alpha-Fe, Fe3C and gamma-Fe. The magnetic results are compatible with the Mossbauer data. Taken together the results allow us to propose a simple picture of the distribution of iron phases within the carbon nanotubes which would consist of an alpha-Fe core surrounded by an gamma-Fe shell, finally covered by an Fe3C layer.

Fe Mössbauer spectra have been recorded from the hexagonal (6H)- and trigonal (15R)- modifications of BaFeOF and are compared with those previously recorded from the cubic form of BaFeOF. The spectra, recorded over a temperature range from 15 to 650 K show that all of the iron in all the compounds is in the Fe state. Spectra from the 6H- and 15R-modifications were successfully fitted with components that were related to the Fe(1) and Fe(2) structural sites in the 6H variant and to the Fe(1), Fe(2) and Fe(3) structural sites in the 15R form. The magnetic ordering temperatures were determined as 597 ± 3 K for 6H-BaFeOF and 636 ± 3 K for 15R-BaFeOF. These values are surprisingly close to the value of 645 ± 5 K determined for the cubic form. The magnetic interactions in the three forms are compared with a view to explaining this similarity of magnetic ordering temperature.

Samples of nominal composition Fe50Co50 were produced by mechanical alloying byusing a planetary ball mill and different milling times. The samples were studied via X-raydiffraction, Mössbauer spectroscopy, and X-ray photoelectron spectroscopy to characterize thephase distribution resulting from the milling process. The Mössbauer data indicated that Co startsdiffusing into Fe after 8 h of milling. Between t = 8h and t = 24 h the sample has a heterogeneouscomposition, presenting a bimodal hyperfine field distribution with maxima centred at 34.3 T and35.8 - 36.4 T, compatible with the presence of different Fe environments (richer in Co and richerin Fe, respectively). After 48 h of milling, the sample presents a more homogeneous compositionshowing an almost symmetric hyperfine magnetic field distribution centred at H=34.9 T,indicating that a disordered equiatomic FeCo solid solution has already been formed. The X-rayphotoelectron spectroscopy data indicate that the native oxide layer formed on the freshly milledsamples contains Co2+, Fe2+ and Fe3+ oxides. After complete removal of this native oxide layer byAr ion bombardment, X-ray photoelectron spectroscopy analysis yields the composition of thenominal equiatomic Fe50Co50 alloy.