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Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

This article focuses on the Na2O-Ga2O3-TiO2 system, which is barely explored in the study of transparent conductive oxides (TCOs). NaxGa4+xTin−4−xO2n−2 (n = 5, 6, and 7 and x ≈ 0.7–0.8) materials were characterized using neutron powder diffraction and aberration-corrected scanning transmission electron microscopy. Activation energy, as a function of different structures depending on tunnel size, shows a significant improvement in Na+ ion conduction from hexagonal to octagonal tunnels. New insights into the relationship between the crystal structure and the transport properties of TCOs, which are crucial for the design and development of new optoelectronic devices, are provided., Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

Contrary to molecular species, only very few solids are reported to host manganese (V) species. Herein, we report three new compounds with a hydroxyapatite structural backbone built on the MnVO4 3− anion: Sr5[(Mn1−xSix)O4]3(OH)1−3x (x = 0 and 0.053), Sr5(MnO4)3(OH)1−yFy (y = 0.90), and Sr5[(Mn1−xSix)- O4]3F1−3x (x = 0.058). These solids are fully characterized using powder X-ray and neutron powder diffraction, scanning transmission electron microscopy, electron energy loss spectroscopy (EELS), thermogravimetric analysis, and magnetic measurements. Especially, we report for the first time EELS Mn−L2,3 spectra of manganese with the oxidation state (V). Contrary to other Mn(V) oxides, these solids and the nominal compound Sr5(MnO4)3OH do not comprise Ba2+ cations but rely only on Sr2+ cations, showing that barium is not a required element to stabilize Mn(V) species in inorganic solids. We show that by tuning soft chemistry conditions on the one hand and post-treatment topological transformation conditions on the other hand, Mn(V) and hydroxyl groups can be substituted by Si(IV) and fluoride ions, respectively. Hence, we deliver solids with a potentially wide composition range. These compounds show significant oxygen anionic conduction, thus suggesting the emergence of new functional materials built from high-oxidation state manganese cations., Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

Contrary to molecular species, only very few solids are reported to host manganese (V) species. Herein, we report three new compounds with a hydroxyapatite structural backbone built on the MnVO43– anion: Sr5[(Mn1–xSix)O4]3(OH)1–3x (x = 0 and 0.053), Sr5(MnO4)3(OH)1–yFy (y = 0.90), and Sr5[(Mn1–xSix)O4]3F1–3x (x = 0.058). These solids are fully characterized using powder X-ray and neutron powder diffraction, scanning transmission electron microscopy, electron energy loss spectroscopy (EELS), thermogravimetric analysis, and magnetic measurements. Especially, we report for the first time EELS Mn–L2,3 spectra of manganese with the oxidation state (V). Contrary to other Mn(V) oxides, these solids and the nominal compound Sr5(MnO4)3OH do not comprise Ba2+ cations but rely only on Sr2+ cations, showing that barium is not a required element to stabilize Mn(V) species in inorganic solids. We show that by tuning soft chemistry conditions on the one hand and post-treatment topological transformation conditions on the other hand, Mn(V) and hydroxyl groups can be substituted by Si(IV) and fluoride ions, respectively. Hence, we deliver solids with a potentially wide composition range. These compounds show significant oxygen anionic conduction, thus suggesting the emergence of new functional materials built from high-oxidation state manganese cations., Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

Este proyecto complementa el proyecto docente anterior (PIMCD 155) en el que se presentaron un conjunto de ejercicios que ayudan a extraer conclusiones a partir de los datos aportados por diferentes técnicas instrumentales de caracterización de sólidos inorgánicos. Así, en principio se elabora de material docente que implique la interpretación de los datos aportados por cada Técnicas que hemos considerado que todo estudiante de grado debe conocer. Se enfatiza la relevancia de estos resultados en la comprensión de los compuestos inorgánicos. Y en la parte final, hemos elaborado una práctica en la que se manejan los datos aportados por las técnicas y se presenta la complementariedad de todas ellas, y el tipo de información relevante que podemos obtener.

Se han elaborado una coleccón de ejercicios utilizando las técnicas de caracterizacion de materiales inorgánicos Además se incluyen un tutorial en el que se dirige al estudiante como es la manera de identificar las bandas caracteristicas de los compuestos, y tambien hay conocimientos generales de EDS. Los ejercicios propuestos tambien se presentan resueltos paso a paso para que se puedan seguir de manera sencilla su desarrollo.

Se han elaborado una coleccón de ejercicios utilizando las técnicas de caracterizacion de materiales inorgánicos Además se incluyen un tutorial en el que se dirige al estudiante como es la manera de identificar las bandas caracteristicas de los compuestos, y tambien hay conocimientos generales de EDS. Los ejercicios propuestos tambien se presentan resueltos paso a paso para que se puedan seguir de manera sencilla su desarrollo.

For the last 20 years, silica-based mesoporous materials have provided a sound platform for the development of biomedical technology applied to tissue engineering and drug delivery. Their unique structural and textural characteristics, chiefly, the ordered distribution of homogeneous and tunable pores with high surface areas and large pore volume, and their excellent biocompatibility provide an excellent starting point for bone tissue regeneration on the mesoporous surface, and also to load species of interest inside the pores. Adequate control of the synthesis conditions and functionalization of the mesoporous surface are critical factors in the design of new systems that are suitable for use in specific medical applications. Simultaneously, the use of appropriate characterization techniques in the several stages of design and manufacture of mesoporous particles allows us to ascertain the textural, structural and compositional modifications induced during the synthesis, functionalization and post-in vitro assays processes. In this scenario, the present paper shows, through several examples, the role of transmission electron microscopy and associated spectroscopic techniques in the search for useful information in the early design stages of mesoporous systems, with application in the fields of tissue regeneration and drug delivery systems., Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

The optimization of novel transparent conductive oxides (TCOs) implies a better understanding of the role that the dopant plays on the optoelectronic properties of these materials. In this work, we perform a systematic study of the homologous series ZnkIn2Ok+3 (IZO) by characterizing the specific location of indium in the structure that leads to a nanodomain framework to release structural strain. Through a systematic study of different terms of the series, we have been able to observe the influence of the k value in the nano-structural features of this homologous series. The stabilization and visualization of the structural modulation as a function of k is discussed, even in the lowest term of the series (k = 3). The strain fields and atomic displacements in the wurtzite structure as a consequence of the introduction of In3+ are evaluated., Ministerio de Ciencia, Innovación y Tecnología /Ministerio de Economía, Comunidad de Madrid, Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

©2020 American Chemical Society This work was supported by the Spanish Ministry of Innovation, Science and Technology and Spanish Ministry of Economy through Research Projects MAT2014-54372-R, MAT2017-82252-R, RTI2018-097195-B-I00 and PCIN-2017-106. This work is partially supported by ShanghaiTech ChEM under the grant number EM02161943. We thank the National Facility ELECMI ICTS and CAI for nuclear magnetic resonance (UCM) and XRD (UCM) facilities. J.B. and A.T.P. acknowledge financial support from the Comunidad de Madrid through the Talento fellowship 2017-T2/IND-5617 and PR65/19 Research Project, respectively., The effect of In^(3+) substitution by Ga^(3+) or Al^(3+) on the structure and luminescent properties of Zn_7In_(2-x)M_xO_10 (M = Ga or Al; 0 <= x <= 1) oxides has been investigated by means of high spatial resolution X-ray spectroscopy and high-angle annular dark-field images, combined with magic angle spinning nuclear magnetic resonance spectroscopy. Local structural variations have been identified for the Al- and Ga-doped samples through the analysis of atomically resolved chemical maps and the identification of their structural environment within the wurtzite lattice. In3+ is distributed in a zig-zag modulation, while Al^(3+) and Ga^(3+) are located in a flat distribution at the center of the wurtzite block. Density functional theory calculations provide unambiguous evidence for the preferential flat location of Ga^(3+) and Al^(3+) associated with the different strains introduced in the structure as a result of their ionic radii. The characterization of the photoluminescence response reveals the appearance of new radiative recombination pathways for the doped materials because of the presence of new defect levels in the band gap of the Zn_7In_2O_10 structure., Ministerio de Economía y Competitividad (MINECO), Ministerio de Ciencia e Innovación (MICINN), Comunidad de Madrid, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

©2020 Royal Society of Chemistry This work was supported by the Spanish Ministry of Innovation, Science and Technology and Spanish Ministry of Economy through Research Projects MAT2014-54372-R, MAT-2015-65274-R/FEDER, MAT2016-81720-REDC, MAT2017-82252-R, RTI2018-097195-B-I00 and M-ERA.NET PCIN-2017-106. We thank the National Center of Electron Microscopy (UCM) for facilities., Herein, we achieve the synthesis and structural study of a luminescent Na-stabilized Ga-Ti oxide homologous series by atomically resolved electron microscopy. Relevant optical properties as a function of the titanium content have been revealed. In particular, the excitation and emission bands change with the series term, showing wide tunability of the luminescence bands, ranging from the ultraviolet to the infrared. First principles studies of these structures have been done in the framework of density functional theory (DFT) to understand the optical properties. Good agreement with the experimental measurements for the three synthesized terms has been obtained from the perspective of the composition and occupancy of the crystallographic sites, as well as from the energy band structure point of view. This work paves the way to explore further the capabilities of tuning the electronic and optical properties in a variety of application fields., Ministerio de Ciencia e Innovación (MICINN)/M-ERA.Net, Ministerio de Ciencia e Innovación (MICINN), Ministerio de Economía y Competitividad (MINECO)/FEDER, Ministerio de Economía y Competitividad (MINECO), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

We fabricated large-area atomically thin MoS2 layers through the direct transformation of crystalline molybdenum trioxide (MoO3) by sulfurization at relatively low temperatures. The obtained MoS2 sheets are polycrystalline (~10–20 nm single-crystal domain size) with areas of up to 300 × 300 µm2, 2–4 layers in thickness and show a marked p-type behavior. The synthesized films are characterized by a combination of complementary techniques: Raman spectroscopy, X-ray diffraction, transmission electron microscopy and electronic transport measurements., Unión Europea. Horizonte 2020, EU Graphene Flagship, Ministerio de Economía y Competitividad (MINECO), Ministerio de Economía y Competitividad (MINECO)/Programa Juan de la Cierva, Depto. de Física de Materiales, Depto. de Química Inorgánica, Fac. de Ciencias Físicas, Fac. de Ciencias Químicas, TRUE, pub

We fabricated large-area atomically thin MoS2 layers through the direct transformation of crystalline molybdenum trioxide (MoO3) by sulfurization at relatively low temperatures. The obtained MoS2 sheets are polycrystalline (~10-20 nm single-crystal domain size) with areas of up to 300 × 300 μm2, 2-4 layers in thickness and show a marked p-type behavior. The synthesized films are characterized by a combination of complementary techniques: Raman spectroscopy, X-ray diffraction, transmission electron microscopy and electronic transport measurements., QN/van der Zant Lab

[EN] Silicon-based materials are needed in cutting-edge technological fields, for which hierarchical porosity and photonic properties help improve performance. In this work, the versatility of several fabrication routes that combine silicon infiltration by chemical vapor deposition (CVD), reactive ion etching (RIE), and carbon calcination, which produce a palette of novel silicon-based material architectures, is demonstrated. Design strategies are discussed and the main features of the processing steps are addressed to provide a variety of new silicon-based materials with high morphological versatility and photonic quality. Three-dimensional hollow carbon opals (HCO) permit control of the porosity of subsequent architectures through the initial silicon infiltration, while open or closed surfaces are achieved primarily as a function of RIE conditions. The composition of derived structures depends on the sequence in which the processes are applied. As a result, pure Si and hybrid C–Si inverse structures can be produced with open or closed spheres in the top layer and with an optional passivation layer. Remarkably, by properly choosing the Si infiltration parameters and the calcination/RIE procedure, final structures are achieved with double-shell spheres.

We fabricated large-area atomically thin MoS2 layers through the direct transformation of crystalline molybdenum trioxide (MoO3) by sulfurization at relatively low temperatures. The obtained MoS2 sheets are polycrystalline (~10–20 nm single-crystal domain size) with areas of up to 300 × 300 µm2, 2–4 layers in thickness and show a marked p-type behavior. The synthesized films are characterized by a combination of complementary techniques: Raman spectroscopy, X-ray diffraction, transmission electron microscopy and electronic transport measurements.

RESEARCH ID L-2854-2014 (Rafael Castillo Romero) ORCID 0000-0003-1957-3098 (Rafael Castillo Romero) RESEARCH ID K-8193-2014 (Alejandro Baeza García) ORCID 0000-0002-9042-8865 (Alejandro Baeza García) RESEARCH ID M-3378-2014 (María Vallet Regí) ORCID 0000-0002-6104-4889 (María Vallet Regí), The use of nanoparticles able to transport drugs, in a selective and controlable manner, directly to diseased tissues and cells have improved the therapeutic arsenal for addressing unmet clinical situations. In the recent years, a vast number of nanocarriers with inorganic, organic, hybrid and even biological nature have been developed, expecially for their application in oncology fied. The exponential growing in the nanomedicine field would not have been possible without the also rapid expansion of electron microscopy techniques, which allow a more precise observation of nanometric objects. The use of these techniques provides a better understanding of the key parameters which rule their synthesis and behavior. In this review, the recent advances performed in the application of inorganic nanoparticles for clinical uses and the role which has played electron microscopy will be presented., Unión Europea. H2020, European Research Council, Ministerio de Ciencia e Innovación (MICINN), Depto. de Química en Ciencias Farmacéuticas, Fac. de Farmacia, TRUE, inpress

The application of mesoporous bioactive glasses (MBGs)containing controllable amount of different ions, with the aim to impart antibacterial activity, as well as stimulation of osteogenesis and angiogenesis, is attracting an increasing interest. In this contribution, in order to endow nano-sized MBG with additional biological functions, the framework of a binary SiO2-CaO mesoporous glass was modified with different concentrations of copper ions (2 and 5% mol.), through a one-pot ultrasound-assisted sol-gel procedure. The Cucontaining MBG (2% mol.) showed high exposed surface area (550 m2 g-1), uniform mesoporous channels (2.6 nm), remarkable in vitro bioactive behaviour and sustained release of Cu2+ ions. Cu-MBG nanoparticles and their ionic dissolution extracts exhibited antibacterial effect against three different bacteria strains, E. coli, S. aureus, S. epidermidis, and the ability to inhibit and disperse the biofilm produced by S. epidermidis. The obtained results suggest that the developed material, which combines in single multifunctional agent excellent bioactivity and antimicrobial ability, offers promising opportunities for the prevention of infectious diseases and the effective treatment of bone defects., Unión Europea. H2020, European Research Council (ERC), Depto. de Química en Ciencias Farmacéuticas, Fac. de Farmacia, TRUE, pub

The elucidation of the reaction mechanisms involving redox processes in functional transition-metal oxides, which usually start in areas of very few nanometers in size, is yet a challenge to be satisfactorily achieved. Atomically resolved HAADF and EELS have provided both chemical and structural information at the nanoscale, which reveal the preservation of short-range cationic order in areas of 2–3 nm length as the driving force behind the reversibility of the Ca2Mn3O8–Ca2Mn3O5 redox process. Oxygen evolution is accommodated by cationic diffusion along the Ca and Mn layers of the cation-deficient Ca2Mn3O8 delafossite related structure, whereas Mn remains octahedrally coordinated.

The influence of particle size in both the structure and thermochromic behavior of 4H-SrMnO related perovskite is described. Microsized SrMnO suffers a structural transition from hexagonal (P6/mmc) to orthorhombic (C222) symmetry at temperature close to 340 K. The orthorhombic distortion is due to the tilting of the corner-sharing MnO units building the 4H structural type. When temperature decreases, the distortion becomes sharper reaching its maximal degree at ∼125 K. These structural changes promote the modification of the electronic structure of orthorhombic SrMnO phase originating the observed color change. nano-SrMnO adopts the ideal 4H hexagonal structure at room temperature, the orthorhombic distortion being only detected at temperature below 170 K. A decrease in the orthorhombic distortion degree, compared to that observed in the microsample, may be the reason why a color change is not observed at low temperature (77 K).

A sepiolite from Grant County (USA) was studied with two objectives. First, from a purely methodological perspective, a comparative micromorphological study was conducted using two imaging techniques: high-resolution transmission electron microscopy (HR-TEM) and atomic-force microscopy (AFM). The second objective was to determine whether the structural change that occurred in sepiolite after heating over 500 ºC induced observable morphological changes. The fibrous morphology of epiolite was observed; furthermore, bundles and rods were observed in both the TEM and AFM imagery. However, individual laths were easily observed by TEM but could only be deduced from the irregularities of the rod surfaces by AFM. A good approximation of the lath widths (~21 nm) can be obtained from measurements using the two techniques, but AFM allows for the determination of the height of the rods (~31 nm) and shows that the mesocrystals are tabular. The folding of the structure after heating was followed by XRD and HR-TEM. The precise measurements performed by HR-TEM and AFM on the folded sepiolite show the micromorphological change in the particles, which decrease in width after folding (from ~21 nm to ~18 nm) in accord with the reduction of the unit cell., Ministerio de Economía y Competitividad (MINECO), Depto. de Mineralogía y Petrología, Fac. de Ciencias Geológicas, TRUE, pub

In this work, through a comparative study of self-assembled (SA) and selective area grown (SAG) (In)GaN nanocolumn (NC) ensembles, we first give a detailed insight into improved crystallographic uniformity (homogeneity of crystallographic tilts and twists) of the latter ones. The study, performed making use of: reflective high energy electron diffraction, X-ray diffraction and scanning electron microscopy, reveals that unlike their SA counterparts, the ensembles of SAG NCs show single epitaxial relationship to both sapphire(0001) and Si(111) underlying substrates. In the second part of the article, making use of X-ray diffraction, we directly show that the selective area growth leads to improved compositional uniformity of InGaN NC ensembles. This further leads to improved spectral purity of their luminescence, as confirmed by comparative macro-photoluminescence measurements performed on SA and SAG InGaN NC ensembles. An improved crystallographic uniformity of NC ensembles facilitates their integration into optoelectronic devices, whereas their improved compositional uniformity allows for their employment in single-color optoelectronic applications.

In this work, through a comparative study of self-assembled (SA) and selective area grown (SAG) (In)GaN nanocolumn (NC) ensembles, we first give a detailed insight into improved crystallographic uniformity (homogeneity of crystallographic tilts and twists) of the latter ones. The study, performed making use of: reflective high energy electron diffraction, X-ray diffraction and scanning electron microscopy, reveals that unlike their SA counterparts, the ensembles of SAG NCs show single epitaxial relationship to both sapphire(0001) and Si(111) underlying substrates. In the second part of the article, making use of X-ray diffraction, we directly show that the selective area growth leads to improved compositional uniformity of InGaN NC ensembles. This further leads to improved spectral purity of their luminescence, as confirmed by comparative macro-photoluminescence measurements performed on SA and SAG InGaN NC ensembles. An improved crystallographic uniformity of NC ensembles facilitates their integration into optoelectronic devices, whereas their improved compositional uniformity allows for their employment in single-color optoelectronic applications.

We have determined why hydrothermal synthesis is not an adequate method to obtain nanoparticles in the Sr-Mn-O system. At high KOH concentration, which is more appropriate for obtaining nanoparticles, Sr is partially incorporated inside an intermediate (K,Sr)xMnO2·nH2O layered phase that prevents the formation of 4H-nanoparticles. Numerous experiments have been performed, screening the parameters involved in such processes (precursors, pH, temperature, etc.) in order to understand their influence on the shape, size, and purity of the 4H-final product. On analyzing the experimental results obtained by XRD, TEM, TGA, and EDS, among others, some peculiarities of the synthetic procedure were detected, including the appearance of side phases, SrMn3O6–x nanoribbons or the above-mentioned birnessite-type (K,Sr)xMnO2·nH2O phase, and the insertion of K+ within the 4H-phase prepared at high KOH concentration. Magnetic features are also discussed.

© 2015 by De Gruyter 2015. 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.

RESEARCHER ID M-3378-2014 (María Vallet Regí) ORCID 0000-0002-6104-4889 (María Vallet Regí) ORCID 0000-0002-9042-8865 (Alejandro Baeza) Researcher ID K-8193-2014 (Alejandro Baeza) Researcher ID 0000-0002-2549-1745 (Eduardo Guisasola Cal) Researcher ID E-8300-2012 (Eduardo Guisasola Cal), A novel nanocarrier based on functionalized mesoporous silica nanoparticles able to transport a non-toxic pro-drug and the enzyme responsible for its activation is presented. This nanodevice is able to generate in situ cytotoxic species once accumulated in the tumoral cell. Enzymes are sensitive macromolecules which can suffer denaturalization in biological media due to the presence of proteases or other aggressive agents. Moreover, the direct attachment of enzymes to the silica surface can reduce their activity by conformational changes or active site blockage. For these reasons, in order to create a robust system able to work in living organisms, the enzymes are previously coated with a protective polymeric shell which allows the attachment on the silica surface preserving their activity. The efficacy of this hybrid nanodevice for antitumoral purposes is tested against several human tumoral cells as neuroblastoma and leukemia showing significant efficacy. It converts this device in a promising candidate for further in vivo studies for oncology therapy., Ministerio de Economía y Competitividad (MINECO), Comunidad de Madrid, CICYT, Depto. de Química en Ciencias Farmacéuticas, Fac. de Farmacia, TRUE, pub

The growth of ordered arrays of InGaN/GaN nanocolumnar light emitting diodes by molecular beam epitaxy, emitting in the blue (441 nm), green (502 nm), and yellow (568 nm) spectral range is reported. The device active region, consisting of a nanocolumnar InGaN section of nominally constant composition and 250 to 500 nm length, is free of extended defects, which is in strong contrast to InGaN layers (planar) of similar composition and thickness. The devices are driven under pulsed operation up to 1300 A/cm2 without traces of efficiency droop. Electroluminescence spectra show a very small blue shift with increasing current, (almost negligible in the yellow device) and line widths slightly broader than those of state-of-the-art InGaN quantum wells.

The growth of ordered arrays of InGaN/GaN nanocolumnar light emitting diodes by molecular beam epitaxy, emitting in the blue (441 nm), green (502 nm), and yellow (568 nm) spectral range is reported. The device active region, consisting of a nanocolumnar InGaN section of nominally constant composition and 250 to 500 nm length, is free of extended defects, which is in strong contrast to InGaN layers (planar) of similar composition and thickness. The devices are driven under pulsed operation up to 1300 A/cm2 without traces of efficiency droop. Electroluminescence spectra show a very small blue shift with increasing current, (almost negligible in the yellow device) and line widths slightly broader than those of state-of-the-art InGaN quantum wells.

A general approach to the structural and analytical characterization of complex bulk oxides that exploits the advantage of the atomic spatial resolution and the analytical capability of aberration-corrected microscopy is described. The combined use of imaging and spectroscopic techniques becomes necessary to the complete characterization of the oxygen-deficient colossal magnetoresistant La0.56Sr0.44MnO2.5-related perovskite. In this compound, the formation of isolated (La/Sr)O and MnO rock-salt-type planar defects are identified from atomically resolved High Angle Annular Dark Field (HAADF) images. The location of the oxygen atomic columns from Annular Bright Field (ABF) images indicates edge-sharing MnO6 octahedra in the MnO planes and the study performed by Electron Energy Loss Spectroscopy (EELS) reveals different Mn oxidation states derived from the corner-or edge-sharing MnO6 octahedra environment.

Stoichiometric 4H-SrMnO3.0 nanoparticles have been synthesized from thermal decomposition of a new molecular heterometallic precursor [SrMn(edta)(H2O)5]·3/2H 2O whose crystal structure has been solved by single crystal X-ray diffraction. From this precursor, highly homogeneous 4H-SrMnO3.0 nanoparticles, with average particle size of 70 nm, are obtained. The agglomeration of these nanoparticles maintains the sheet-assembling morphology of the metal-organic compound. Local structural information, provided by atomically resolved microscopy techniques, shows that 4H-SrMnO3.0 nanoparticles exhibit the same general structural features as the bulk material, although structural disorder, due to edge dislocations, is observed. The nanometric particle size enables a topotactic reduction process at low temperature stabilizing a metastable 4H-SrMnO2.82 phase. The oxygen deficiency is accommodated through extra cubic layers breaking the...chch... 4H-sequence. These defect areas are Mn3+ rich, as evidenced by high energy resolution EELS data. Magnetic characterization of nano-SrMnO 3.0 shows significant variations with respect to the bulk material. Besides the dominant antiferromagnetic interactions, a weak ferromagnetic contribution as well as exchange bias and a glassy-like component are present. After the reduction process, the stabilization of Mn3+ in the 4H-structure gives rise to magnetic anomalies in the 40-60 K temperature range. The origin of such magnetic features is discussed. © 2014 American Chemical Society.

Spurred by the decreased availability of fossil fuels and global warming, the idea of converting solar energy into clean fuels has been widely recognized. Hydrogen produced by photoelectrochemical water splitting using sunlight could provide a carbon dioxide lean fuel as an alternative to fossil fuels. A major challenge in photoelectrochemical water splitting is to develop an efficient photoanode that can stably oxidize water into oxygen. Here we report an efficient and stable photoanode that couples an active barium-doped tantalum nitride nanostructure with a stable cobalt phosphate co-catalyst. The effect of barium doping on the photoelectrochemical activity of the photoanode is investigated. The photoanode yields a maximum solar energy conversion efficiency of 1.5%, which is more than three times higher than that of state-of-the-art single-photon photoanodes. Further, stoichiometric oxygen and hydrogen are stably produced on the photoanode and the counter electrode with Faraday efficiency of almost unity for 100 min., AuthorCount:14

Procedimiento para modular las propiedades eléctricas de óxidos con estructura tipo perovskita derivados del niobato de sodio mediante la creación de vacantes catiónicas. La presente invención se refiere a un procedimiento para modificar controladamente las propiedades eléctricas del óxido NaNbO3 mediante la creación de vacantes catiónicas en la subred A de la estructura tipo perovskita. La introducción progresiva de vacantes en la subred A al dopar con un ión alcalinotérreo como por ejemplo Sr2+ o con un ión de tierra rara como por ejemplo La3+ permite la estabilización de un material ferroeléctrico, y el cambio continuo de comportamiento ferroeléctrico a ferroeléctrico-relaxor característico de las disoluciones sólidas tipo perovskita sin plomo. La presente invención incluye el procedimiento para la obtención de los óxidos que, en función de sus propiedades, pueden ser usados en dispositivos electrónicos como materiales piezoeléctricos y piroeléctricos en sensores y actuadores.

[EN] The invention relates to a method for the controlled modification of the electrical properties of NaNb03 oxide through the creation of cation vacancies in subnetwork A of the perovskite-type structure. The gradual introduction of vacancies into subnetwork A by means of doping with an alkaline-earth ion, e.g. Sr2+, or with a rare-eaxth ion, e.g. La3+, enables the stabilisation of a ferroelectric material and continuous conversion from ferroelectric to ferroelectric relaxor behaviour characteristic of lead-ftee perovskite-type solid solutions. The invention relates to a method for obtaining oxides which, depending on the properties thereof, can be used in electronic devices and as piezoelectric and pyroelectric materials in sensors and actuators., [ES] La presente invención se refiere a un procedimiento para modificar controladamente las propiedades eléctricas del óxido NaNbO3 mediante la creación de vacantes catiónicas en la subred A de la estructura tipo perovskita. La introducción progresiva de vacantes en la subred A al dopar con un ion alcalinotérreo como por ejemplo Sr2+o con un ion de tierra rara como por ejemplo La3+ permite Ia estabilización de un material ferroeléctrico, y el cambio continuo de comportamiento ferroeléctrico a ferroeléctrico-relaxor característico de las disoluciones sólidas tipo perovskita sin plomo. La presente invención incluye el procedimiento para Ia obtención de los óxidos que, en función de sus propiedades, pueden ser usados en dispositivos electrónicos como materiales piezoeléctricos y piroeléctricos en sensores y actuadores.