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1.
Artigo em Inglês | MEDLINE | ID: mdl-32649793

RESUMO

Aluminium batteries constitute a safe and sustainable high-energy-density electrochemical energy-storage solution. Viable Al-ion batteries require suitable electrode materials that can readily intercalate high-charge Al3+ ions. Here, we investigate the Al3+ intercalation chemistry of anatase TiO2 and how chemical modifications influence the accommodation of Al3+ ions. We use fluoride- and hydroxide-doping to generate high concentrations of titanium vacancies. The coexistence of these hetero-anions and titanium vacancies leads to a complex insertion mechanism, attributed to three distinct types of host sites: native interstitial sites, single vacancy sites, and paired vacancy sites. We demonstrate that Al3+ induces a strong local distortion within the modified TiO2 structure, which affects the insertion properties of the neighbouring host sites. Overall, specific structural features induced by the intercalation of highly polarising Al3+ ions should be considered when designing new electrode materials for polyvalent batteries.

2.
Sci Rep ; 10(1): 9516, 2020 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-32528106

RESUMO

Drosophila flies are versatile animal models for the study of gene mutations in neuronal pathologies. Their small size allows performing in vivo Magic Angle Spinning (MAS) experiments to obtain high-resolution 1H nuclear magnetic resonance (NMR) spectra. Here, we use spatially-resolved 1H high-resolution MAS NMR to investigate in vivo metabolite contents in different segments of the fly body. A comparative study of metabolic changes was performed for three neurodegenerative disorders: two cell-specific neuronal and glial models of Huntington disease (HD) and a model of glutamate excitotoxicity. It is shown that these pathologies are characterized by specific and sometimes anatomically localized variations in metabolite concentrations. In two cases, the modifications of 1H MAS NMR spectra localized in fly heads were significant enough to allow the creation of a predictive model.

3.
Inorg Chem ; 2020 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-32286067

RESUMO

A crystallographic approach incorporating multinuclear high field solid state NMR (SSNMR), X-ray structure determinations, TEM observation, and density functional theory (DFT) was used to characterize two polymorphs of rubidium cryolite, Rb3AlF6. The room temperature phase was found to be ordered and crystallizes in the Fddd (no. 70) space group with a = 37.26491(1) Å, b = 12.45405(4) Å, and c = 17.68341(6) Å. Comparison of NMR measurements and computational results revealed the dynamic rotations of the AlF6 octahedra. Using in situ variable temperature MAS NMR measurements, the chemical exchange between rubidium sites was observed. The ß-phase, i.e., high temperature polymorph, adopts the ideal cubic double-perovskite structure, space group Fm3m, with a = 8.9930(2) Å at 600 °C. Additionally, a series of polymorphs of K3AlF6 has been further characterized by high field high temperature SSNMR and DFT computation.

4.
Inorg Chem ; 58(24): 16387-16401, 2019 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-31790218

RESUMO

Crystallization from glass can lead to the stabilization of metastable crystalline phases, which offers an interesting way to unveil novel compounds and control the optical properties of resulting glass-ceramics. Here, we report on a crystallization study of the ZrF4-TeO2 glass system and show that under specific synthesis conditions, a previously unreported Te0.47Zr0.53OxFy zirconium oxyfluorotellurite antiglass phase can be selectively crystallized at the nanometric scale within the 65TeO2-35ZrF4 amorphous matrix. This leads to highly transparent glass-ceramics in both the visible and near-infrared ranges. Under longer heat treatment, the stable cubic ZrTe3O8 phase crystallizes in addition to the previous unreported antiglass phase. The structure, microstructure, and optical properties of 65TeO2-35ZrF4Tm3+-doped glass-ceramics, were investigated in detail by means of X-ray diffraction, scanning and transmission electron microscopies, and 19F, 91Zr, and 125Te NMR, Raman, and photoluminescence spectroscopies. The crystal chemistry study of several single crystals samples by X-ray diffraction evidence that the novel phase, derived from α-UO3 type, corresponds in terms of long-range ordering inside this basic hexagonal/trigonal disordered phase (antiglass) to a complex series of modulated microphases rather than a stoichiometric compound with various superstructures analogous to those observed in the UO3-U3O8 subsystem. These results highlight the peculiar disorder-order phenomenon occurring in tellurite materials.

5.
Dalton Trans ; 48(2): 587-601, 2019 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-30534767

RESUMO

Solid state NMR signals are very sensitive to the local environment of the observed nucleus; however, their interpretation is not straightforward. On the other hand, first-principles DFT calculations of NMR parameters can now be applied to periodic compounds to predict NMR parameters. Thus, ab initio calculations can help to interpret the NMR spectra exhibited by complex materials, to assign NMR lines to structural environments, and even to enlighten the environmental factors influencing the NMR parameters for a given nucleus. Both techniques have been applied to crystalline compounds of the KF-YF3 binary system, γ-K3YF6, K2YF5, KYF4, ß-KY2F7 and α-KY3F10, which present a variety of YFn and KFm polyhedra. First, the structure of K2YF5 was refined in the Pnma space group and, for all compounds, atomic positions were optimized by DFT. The 19F, 89Y and 39K NMR spectra have been recorded and the measured NMR parameters are compared to those calculated from the first-principles DFT method, allowing unambiguous assignments of NMR lines to crystallographic sites. Linear correlations between the experimental δiso and calculated σiso values for the three nuclei are used to predict the theoretical 19F spectra of KYF4 (24 F sites) and ß-KY2F7 (19 F sites) as well as the 39K spectrum of KYF4 (6 K sites). For 89Y and 39K, both computational and experimental results show a decrease of the isotropic chemical shift values when the cation coordination number increases. Above all, 89Y isotropic chemical shift values correlate with the number of K atoms present in the Y second coordination sphere. For 19F, the combination of isotropic chemical shift and chemical shift anisotropy allows for distinguishing four kinds of F environments.

6.
Nat Commun ; 9(1): 4484, 2018 10 26.
Artigo em Inglês | MEDLINE | ID: mdl-30367043

RESUMO

Tetrahedral units can transport oxide anions via interstitial or vacancy defects owing to their great deformation and rotation flexibility. Compared with interstitial defects, vacancy-mediated oxide-ion conduction in tetrahedra-based structures is more difficult and occurs rarely. The isolated tetrahedral anion Scheelite structure has showed the advantage of conducting oxygen interstitials but oxygen vacancies can hardly be introduced into Scheelite to promote the oxide ion migration. Here we demonstrate that oxygen vacancies can be stabilized in the BiVO4 Scheelite structure through Sr2+ for Bi3+ substitution, leading to corner-sharing V2O7 tetrahedral dimers, and migrate via a cooperative mechanism involving V2O7-dimer breaking and reforming assisted by synergic rotation and deformation of neighboring VO4 tetrahedra. This finding reveals the ability of Scheelite structure to transport oxide ion through vacancies or interstitials, emphasizing the possibility to develop oxide-ion conductors with parallel vacancy and interstitial doping strategies within the same tetrahedra-based structure type.

7.
Inorg Chem ; 57(8): 4328-4339, 2018 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-29620359

RESUMO

Luminescent materials based on copper complexes are currently receiving increasing attention because of their rich photophysical properties, opening a wide field of applications. The copper iodide clusters formulated [Cu4I4L4] (L = ligand), are particularly relevant for the development of multifunctional materials based on their luminescence stimuli-responsive properties. In this context, controlling and modulating their photophysical properties is crucial and this can only be achieved by thorough understanding of the origin of the optical properties. We thus report here, the comparative study of a series of cubane copper iodide clusters coordinated by different phosphine ligands, with the goal of analyzing the effect of the ligands nature on the photoluminescence properties. The synthesis, structural, and photophysical characterizations along with theoretical investigations of copper iodide clusters with ligands presenting different electronic properties, are described. A method to simplify the analysis of the 31P solid-state NMR spectra is also reported. While clusters with electron-donating groups present classical luminescence properties, the cluster bearing strong electron-withdrawing substituents exhibits original behavior demonstrating a clear influence of the ligands properties. In particular, the electron-withdrawing character induces a decrease in energy of the unoccupied molecular orbitals, that consequently impacts the emission properties. The modification of the luminescence thermochromic properties of the clusters are supported by density functional theory (DFT) calculations. This study demonstrates that the control of the luminescence properties of these compounds can be achieved through modification of the coordinated ligands, nevertheless the role of the crystal packing should not be underestimated.

8.
Chemistry ; 24(10): 2457-2465, 2018 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-29178609

RESUMO

RhL2 complexes of phosphonate-derivatized 2,2'-bipyridine (bpy) ligands L were immobilized on titanium oxide particles generated in situ. Depending on the structure of the bipy ligand-number of tethers (1 or 2) to which the phosphonate end groups are attached and their location on the 2,2'-bipyridine backbone (4,4'-, 5,5'-, or 6,6'-positions)-the resulting supported catalysts showed comparable chemoselectivity but different kinetics for the hydrogenation of 6-methyl-5-hepten-2-one under hydrogen pressure. Characterization of the six supported catalysts suggested that the intrinsic geometry of each of the phosphonate-derivatized 2,2'-bipyridines leads to supported catalysts with different microstructures and different arrangements of the RhL2 species at the surface of the solid, which thereby affect their reactivity.

9.
J Phys Chem Lett ; 9(1): 19-24, 2018 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-29232141

RESUMO

Al site distribution in the structurally complex and industrially important ZSM-5 zeolite is determined by studying the spectroscopic response of Al(OSi)4 units and using a self-consistent combination of up-to-date solid-state NMR correlations (29Si-27Al and 1H-27Al D-HMQC) and quantum chemistry methods (DFT-D). To unravel the driving forces behind specific Al sitting positions, our approach focuses on ZSM-5 containing its more efficient OSDA, tetrapropylammonium.

10.
J Biomed Mater Res B Appl Biomater ; 106(8): 2786-2795, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-29226553

RESUMO

An injectable purely apatitic calcium phosphate cement (CPC) was successfully combined to a water-soluble radiopaque agent (i.e., Xenetix® ), to result in an optimized composition that was found to be as satisfactory as poly(methyl methacrylate) (PMMA) formulations used for vertebroplasty, in terms of radiopacity, texture and injectability. For that purpose, the Xenetix dosage in the cement paste was optimized by injection of the radiopaque CPC in human cadaveric vertebrae under classical PMMA vertebroplasty conditions, performed by interventional radiologists familiar with this surgical procedure. When present in the cement paste up to 70 mg I mL-1 , Xenetix did not influence the injectability, cohesion, and setting time of the resulting composite. After hardening of the material, the same observation was made regarding the microstructure, mechanical strength and alpha-tricalcium phosphate to calcium deficient apatite transformation rate. Upon implantation in bone in a small animal model (rat), the biocompatibility of the Xenetix-containing CPC was evidenced. Moreover, an almost quantitative release of the contrast agent was found to occur rapidly, on the basis of in vitro static and dynamic quantitative studies simulating in vivo implantation. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2786-2795, 2018.


Assuntos
Apatitas , Cimentos para Ossos , Meios de Contraste , Teste de Materiais , Coluna Vertebral , Vertebroplastia/métodos , Animais , Apatitas/química , Apatitas/farmacologia , Cimentos para Ossos/química , Cimentos para Ossos/farmacologia , Meios de Contraste/química , Meios de Contraste/farmacologia , Humanos , Masculino , Polimetil Metacrilato/química , Polimetil Metacrilato/farmacologia , Ratos , Ratos Endogâmicos Lew , Coluna Vertebral/diagnóstico por imagem , Coluna Vertebral/cirurgia
11.
Inorg Chem ; 56(23): 14446-14458, 2017 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-29152977

RESUMO

Eu-doped Sr1-x/2Al2-xSixO4 (x = 0.2, 0.4, and 0.5) transparent ceramics have been synthesized by full and congruent crystallization from glasses prepared by aerodynamic levitation and laser-heating method. Structural refinements from synchrotron and neutron powder diffraction data show that the ceramics adopt a 1 × 1 × 2 superstructure compared to the SrAl2O4 hexagonal polymorph. While the observed superstructure reflections indicate a long-range ordering of the Sr vacancies in the structure, 29Si and 27Al solid-state NMR measurements associated with DFT computations reveal a significant degree of disorder in the fully polymerized tetrahedral network. This is evidenced through the presence of Si-O-Si bonds, as well as Si(OAl)4 units at remote distances of the Sr vacancies and Al(OAl)4 units in the close vicinity of Sr vacancies departing from local charge compensation in the network. The transparent ceramics can be doped by europium to induce light emission arising from the volume under UV excitation. Luminescence measurements then reveal the coexistence of Eu2+ and Eu3+ in the samples, thereby allowing tuning the emission color depending on the excitation wavelength and suggesting possible applications such as solid state lighting.

12.
J Chem Phys ; 147(13): 134902, 2017 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-28987098

RESUMO

The intrinsic ionic conductivity of polyethylene oxide (PEO)-based block copolymer electrolytes is often assumed to be identical to the conductivity of the PEO homopolymer. Here, we use high-field 7Li nuclear magnetic resonance (NMR) relaxation and pulsed-field-gradient (PFG) NMR diffusion measurements to probe lithium ion dynamics over nanosecond and millisecond time scales in PEO and polystyrene (PS)-b-PEO-b-PS electrolytes containing the lithium salt LiTFSI. Variable-temperature longitudinal (T1) and transverse (T2) 7Li NMR relaxation rates were acquired at three magnetic field strengths and quantitatively analyzed for the first time at such fields, enabling us to distinguish two characteristic time scales that describe fluctuations of the 7Li nuclear electric quadrupolar interaction. Fast lithium motions [up to O(ns)] are essentially identical between the two polymer electrolytes, including sub-nanosecond vibrations and local fluctuations of the coordination polyhedra between lithium and nearby oxygen atoms. However, lithium dynamics over longer time scales [O(10 ns) and greater] are slower in the block copolymer compared to the homopolymer, as manifested experimentally by their different transverse 7Li NMR relaxation rates. Restricted dynamics and altered thermodynamic behavior of PEO chains anchored near PS domains likely explain these results.

13.
Acta Biomater ; 62: 328-339, 2017 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-28864250

RESUMO

Two commercial formulations of apatitic calcium phosphate cements (CPCs), Graftys® Quickset (QS) and Graftys® HBS (HBS), similar in composition but with different initial setting time (7 and 15min, respectively), were combined to ovine whole blood. Surprisingly, although a very cohesive paste was obtained after a few minutes, the setting time of the HBS/blood composite dramatically delayed when compared to its QS analogue and the two blood-free references. Using solid state NMR, scanning electron microscopy and high frequency impedance measurements, it was shown that, in the particular case of the HBS/blood composite, formation of a reticulated and porous organic network occurred in the intergranular space, prior to the precipitation of apatite crystals driven by the cement setting process. The resulting microstructure conferred unique biological properties to this material upon implantation in bone defects, since its degradation rate after 4 and 12weeks was more than twice that for the three other CPCs, with a significant replacement by newly formed bone. STATEMENT OF SIGNIFICANCE: A major challenge in the design of bone graft substitutes is the development of injectable, cohesive, resorbable and self-setting calcium phosphate cement (CPC) that enables rapid cell invasion with initial mechanical properties as close as bone ones. Thus, we describe specific conditions in CPC-blood composites where the formation of a 3D clot-like network can interact with the precipitated apatite crystals formed during the cement setting process. The resulting microstructure appears more ductile at short-term and more sensitive to biological degradation which finally promotes new bone formation. This important and original paper reports the design and in-depth chemical and physical characterization of this groundbreaking technology.


Assuntos
Apatitas , Cimentos para Ossos , Cerâmica , Teste de Materiais , Osteogênese/efeitos dos fármacos , Animais , Apatitas/química , Apatitas/farmacologia , Cimentos para Ossos/química , Cimentos para Ossos/farmacologia , Cerâmica/química , Cerâmica/farmacologia , Coelhos
14.
Sci Rep ; 7(1): 8224, 2017 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-28811630

RESUMO

In this work, we show that it is possible to overcome the limitations of solid-state MRI for rigid tissues due to large line broadening and short dephasing times by combining Magic Angle Spinning (MAS) with rotating pulsed field gradients. This allows recording ex vivo 31P 3D and 2D slice-selected images of rigid tissues and related biomaterials at very high magnetic field, with greatly improved signal to noise ratio and spatial resolution when compared to static conditions. Cross-polarization is employed to enhance contrast and to further depict spatially localized chemical variations in reduced experimental time. In these materials, very high magnetic field and moderate MAS spinning rate directly provide high spectral resolution and enable the use of frequency selective excitation schemes for chemically selective imaging. These new possibilities are exemplified with experiments probing selectively the 3D spatial distribution of apatitic hydroxyl protons inside a mouse tooth with attached jaw bone with a nominal isotropic resolution nearing 100 µm.


Assuntos
Campos Magnéticos , Imagem por Ressonância Magnética/métodos , Isótopos de Fósforo , Prótons , Materiais Biocompatíveis , Imageamento Tridimensional , Espectroscopia de Ressonância Magnética/métodos , Especificidade de Órgãos , Imagens de Fantasmas
15.
J Magn Reson ; 277: 30-35, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-28219822

RESUMO

We show that two widely used 2D solid-state NMR (ssNMR) pulse sequences can be implemented in an ultrafast (UF) manner, and yield 2D spectra of elastomers in a single scan, under magic-angle spinning. UF 2D ssNMR provides an acceleration of one to several orders of magnitude for classic experiments.

16.
Dalton Trans ; 45(39): 15565-15574, 2016 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-27722721

RESUMO

The room temperature structure of Ba5AlF13 has been investigated by coupling electron, synchrotron and neutron powder diffraction, solid-state high-resolution NMR (19F and 27Al) and first principles calculations. An initial structural model has been obtained from electron and synchrotron powder diffraction data, and its main features have been confirmed by one- and two-dimensional NMR measurements. However, DFT GIPAW calculations of the 19F isotropic shieldings revealed an inaccurate location of one fluorine site (F3, site 8a), which exhibited unusual long F-Ba distances. The atomic arrangement was reinvestigated using neutron powder diffraction data. Subsequent Fourier maps showed that this fluorine atom occupies a crystallographic site of lower symmetry (32e) with partial occupancy (25%). GIPAW computations of the NMR parameters validate the refined structural model, ruling out the presence of local static disorder and indicating that the partial occupancy of this F site reflects a local motional process. Visualisation of the dynamic process was then obtained from the Rietveld refinement of neutron diffraction data using an anharmonic description of the displacement parameters to account for the thermal motion of the mobile fluorine. The whole ensemble of powder diffraction and NMR data, coupled with first principles calculations, allowed drawing an accurate structural model of Ba5AlF13, including site-specific dynamical disorder in the fluorine sub-network.

17.
Langmuir ; 32(22): 5480-90, 2016 06 07.
Artigo em Inglês | MEDLINE | ID: mdl-27166821

RESUMO

Different routes for preparing zirconium phosphonate-modified surfaces for immobilizing biomolecular probes are compared. Two chemical-modification approaches were explored to form self-assembled monolayers on commercially available primary amine-functionalized slides, and the resulting surfaces were compared to well-characterized zirconium phosphonate monolayer-modified supports prepared using Langmuir-Blodgett methods. When using POCl3 as the amine phosphorylating agent followed by treatment with zirconyl chloride, the result was not a zirconium-phosphonate monolayer, as commonly assumed in the literature, but rather the process gives adsorbed zirconium oxide/hydroxide species and to a lower extent adsorbed zirconium phosphate and/or phosphonate. Reactions giving rise to these products were modeled in homogeneous-phase studies. Nevertheless, each of the three modified surfaces effectively immobilized phosphopeptides and phosphopeptide tags fused to an affinity protein. Unexpectedly, the zirconium oxide/hydroxide modified surface, formed by treating the amine-coated slides with POCl3/Zr(4+), afforded better immobilization of the peptides and proteins and efficient capture of their targets.


Assuntos
Proteínas Arqueais/química , Proteínas de Ligação a DNA/química , Organofosfonatos/química , Fosfopeptídeos/química , Fosfoproteínas/química , Sulfolobus acidocaldarius/química , Zircônio/química , Propriedades de Superfície
18.
Dalton Trans ; 44(47): 20675-84, 2015 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-26565802

RESUMO

The structures of the ß- and t-LaOF phases have been refined from XRPD patterns. For both phases, (19)F and (139)La solid-state NMR spectra recorded at high magnetic fields show the presence of a single F and a single La local environment, indicating a full anionic ordering in these oxyfluoride compounds. DFT calculations of the (19)F and (139)La chemical shielding tensors and of the (139)La EFG tensor have been performed for the proposed structural models. The observed good agreement between experimental and calculated NMR parameters for both phases highlights the accuracy of the structural data.

19.
Acta Biomater ; 24: 322-32, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26074157

RESUMO

UNLABELLED: Different possible options were investigated to combine an apatitic calcium phosphate cement with gallium ions, known as bone resorption inhibitors. Gallium can be either chemisorbed onto calcium-deficient apatite or inserted in the structure of ß-tricalcium phosphate, and addition of these gallium-doped components into the cement formulation did not significantly affect the main properties of the biomaterial, in terms of injectability and setting time. Under in vitro conditions, the amount of gallium released from the resulting cement pellets was found to be low, but increased in the presence of osteoclastic cells. When implanted in rabbit bone critical defects, a remodeling process of the gallium-doped implant started and an excellent bone interface was observed. STATEMENT OF SIGNIFICANCE: The integration of drugs and materials is a growing force in the medical industry. The incorporation of pharmaceutical products not only promises to expand the therapeutic scope of biomaterials technology but to design a new generation of true combination products whose therapeutic value stem equally from both the structural attributes of the material and the intrinsic therapy of the drug. In this context, for the first time an injectable calcium phosphate cement containing gallium was designed with properties suitable for practical application as a local delivery system, implantable by minimally invasive surgery. This important and original paper reports the design and in-depth chemical and physical characterization of this groundbreaking technology.


Assuntos
Apatitas/farmacologia , Cimentos para Ossos/farmacologia , Reabsorção Óssea/prevenção & controle , Fosfatos de Cálcio/farmacologia , Gálio/farmacologia , Animais , Apatitas/química , Cimentos para Ossos/química , Reabsorção Óssea/metabolismo , Reabsorção Óssea/patologia , Fosfatos de Cálcio/química , Linhagem Celular , Gálio/química , Camundongos , Coelhos
20.
Sci Rep ; 5: 9872, 2015 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-25892587

RESUMO

We have developed new methods enabling in vivo localization and identification of metabolites through their (1)H NMR signatures, in a drosophila. Metabolic profiles in localized regions were obtained using HR-MAS Slice Localized Spectroscopy and Chemical Shift Imaging at high magnetic fields. These methods enabled measurement of metabolite contents in anatomic regions of the fly, demonstrated by a decrease in ß-alanine signals in the thorax of flies showing muscle degeneration.


Assuntos
Drosophila/metabolismo , Metaboloma , Espectroscopia de Prótons por Ressonância Magnética , Animais , Animais Geneticamente Modificados/metabolismo , Feminino , Masculino , Tórax/metabolismo
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