Search

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.

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., 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.

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).