Person: González Calbet, José María
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First Name
José María
Last Name
González Calbet
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Química Inorgánica
Area
Química Inorgánica
Identifiers
18 results
Search Results
Now showing 1 - 10 of 18
Item Textura porosa de la akageneita sintética(2015) González Calbet, José MaríaItem New insights into the luminescence properties of a Na stabilized Ga-Ti oxide homologous series(Journal of materials chemistry C, 2020) García Fernández, Javier; García Carrión, Marina; Torres Pardo, Almudena; Martínez Casado, Ruth; Ramírez Castellanos, Julio; Nogales Díaz, Emilio; González Calbet, José María; Méndez Martín, BianchiHerein, 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.Item Evaluation of the Nanodomain Structure in In-Zn-O Transparent Conductors(Nanomaterials, 2021) García-Fernández, Javier; Torres-Pardo, Almudena; Ramírez Castellanos, Julio; Rossell, Marta D.; González Calbet, José MaríaThe 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.Item Hydroxyapatites as Versatile Inorganic Hosts of Unusual Pentavalent Manganese Cations(Chemistry of Materials, 2020) Varela Losada, María Áurea; Gómez Recio, Isabel; Serrador, Laura; Hernando González, María; Matesanz, Emilio; Torres Pardo, María De La Almudena; Fernández-Díaz, María Teresa; Martínez, Jose L.; Gonell, Francisco; Rousse, Gwenaelle; Sanchez, Clément; Laberty-Robert, Christel; Portehault, David; González Calbet, José María; Parras Vázquez, Marina MartaContrary 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.- Project number: PIMCD16/23-24
Item Elaboración de material audiovisual sobre síntesis de materiales inorgánicos(2023) Tinoco Rivas, Miguel; González Calbet, José María; Ruiz González, María Luisa; Muñoz Gil, Daniel; Gómez Recio, Isabel; Patricia Delgado Martínez Item Influence of cation substitution on the complex structure and luminescent properties of the Zn_kIn_2O_(k+3) system(Chemistry of materials, 2020) García Fernández, Javier; Torres Pardo, Almudena; Bartolomé Vílchez, Javier; Martínez Casado, Ruth; Zhang, Qing; Ramírez Castellanos, Julio; Terasaki, Osamu; Cremades Rodríguez, Ana Isabel; González Calbet, José MaríaThe 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.Item Complex structural ordering of the oxygen deficiency in La_-0.5 Ca_2.5Mn_2O_7-delta Ruddlesden-Popper phases(Acta crystallographica a-foundation and advances, 2019) González Merchante, Daniel; Cortés Gil, Raquel; Alonso Rodríguez, José María; Matesanz Sáez, Emilio; Rivera Calzada, Alberto Carlos; Santamaría Sánchez-Barriga, Jacobo; Ruiz González, María Luisa; González Calbet, José MaríaRuddlesden-Popper oxides, (AO)(ABO_3))_n, occupy a prominent place in the landscape of materials research because of their intriguing potential applications. Compositional modifications to the cation sublattices, A or B, have been explored in order to achieve enhanced functionalities. However, changes to the anionic sublattice have been much less explored. In this work, new oxygen-deficient manganese Ruddlesden-Popper-related phases, La_0.5Ca_2.5Mn_2O_6.5, and La_0.5Ca_2.5Mn_2O_6.25, have been synthesized by controlled reduction of the fully oxidized n = 2 term La_0.5Ca_2.5Mn_2O_7. A complete structural and compositional characterization, by means of neutron diffraction, electron diffraction and atomically resolved scanning transmission electron microscopy and electron energy-loss spectroscopy techniques, allows the proposition of a topotactic reduction pathway through preferential oxygen removal in the [MnO_2] layers along [031] and [013] directions. The gradual decrease of the Mn oxidation state, accommodated by short-range ordering of anionic vacancies, reasonably explains the breaking of ferromagnetic interactions reinforcing the emergence of antiferromagnetic ones. Additional short-range order-disorder phenomena of La and Ca cations have been detected in the reduced La_0.5Ca_2.5Mn_2º_7-delta, as previously reported in the parent compound.Item Effect of the synthesis method on the properties of lithium doped graphene oxide composites with tin oxide nanoparticles: Towards white luminescence(Journal of physics and chemistry of solids, 2019) Prado Hurtado, Félix del; Taeño González, María; Maestre Varea, David; Ramírez Castellanos, Julio; González Calbet, José María; Cremades Rodríguez, Ana IsabelGraphene oxide (GO) based composites functionalized with nanoparticles are emerging as potential candidates for multifunctional devices. As the synthesis route can strongly influence the way in which the nanoparticles are anchored to GO and the resulting properties, different routes have been employed and evaluated in this work for the preparation of composites formed by GO and undoped or Li doped SnO_2 nanoparticles. Promotion of synergetic effects, as well as changes in the structural and luminescent properties of the composites have been also analyzed. In comparison with GO, composite samples synthesized in this work involve enhanced luminescence while retaining nearly white emission, which could lead to wider applicability of GO based composites in free standing and emitting and sensing devices. Aspects, such as GO reduction, stabilization of different Sn-based oxides, variation in the concentration of oxygen related functional groups, changes in the sp^2 domain sizes, incorporation of lithium and enhancement of the luminescence, have been analyzed in this work by means of xray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), energy dispersive x-ray spectroscopy (EDS), Raman spectroscopy, x-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) characterizations.Item Exceptional Low-Temperature CO Oxidation over Noble-Metal-Free Iron-Doped Hollandites: An In-Depth Analysis of the Influence of the Defect Structure on Catalytic Performance(ACS Catalysis, 2021) Gómez Recio, Isabel; Pan, Huiyan; Azor Lafarga, Alberto Eduardo; Ruiz González, María Luisa; Hernando González, María; Parras Vázquez, Marina Marta; Fernández-Díaz, María Teresa; Delgado, Juan J.; Chen, Xiaowei; Goma Jiménez, Daniel; Portehault, David; Sanchez, Clément; Cabero Piris, Mariona; Martínez-Arias, Arturo; González Calbet, José María; Calvino, José J.A family of iron-doped manganese-related hollandites, KxMn1–yFeyO2−δ (0 ≤ y ≤ 0.15), with high performance in CO oxidation have been prepared. Among them, the most active catalyst, K0.11Mn0.876Fe0.123O1.80(OH)0.09, is able to oxidize more than 50% of CO at room temperature. Detailed compositional and structural characterization studies, using a wide battery of thermogravimetric, spectroscopic, and diffractometric techniques, both at macroscopic and microscopic levels, have provided essential information about this never-reported behavior, which relates to the oxidation state of manganese. Neutron diffraction studies evidence that the above compound stabilizes hydroxyl groups at the midpoints of the tunnel edges as in isostructural β-FeOOH. The presence of oxygen and hydroxyl species at the anion sublattice and Mn3+, confirmed by electron energy loss spectroscopy, appears to play a key role in the catalytic activity of this doped hollandite oxide. The analysis of these detailed structural features has allowed us to point out the key role of both OH groups and Mn3+ content in these materials, which are able to effectively transform CO without involving any critical, noble metal in the catalyst formulation.Item Tuning magnetoconductivity in LaMnO3 NPs through cationic vacancy control(Nanomaterials, 2023) Hernando Grande, Antonio; Ruiz González, María Luisa; Díaz, Omar; Alonso Gómez, José Miguel; Martínez, José L.; Ayuela, Andrés; González Calbet, José María; Cortés Gil, RaquelThe inclusion of La-Mn vacancies in LaMnO3 nanoparticles leads to a noticeable change in conductivity behavior. The sample retains its overall insulator characteristic, with a typical thermal activation mechanism at high temperatures, but it presents high magnetoconductivity below 200 K. The activation energy decreases linearly with the square of the reduced magnetization and vanishes when the sample is magnetized at saturation. Therefore, it turns out that electron hopping between Mn3+ and Mn4+ largely contributes to the conductivity below the Curie temperature. The influence of the applied magnetic field on conductivity also supports the hypothesis of hopping contribution, and the electric behavior can be explained as being due to an increase in the hopping probability via spin alignment.