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1.
Acta Crystallogr B Struct Sci Cryst Eng Mater ; 78(Pt 3 Pt 2): 425-435, 2022 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-35702960

RESUMO

The crystal structures of (CH3NH3)2Cu(Cl1-xBrx)4 compounds have been investigated by means of synchrotron powder X-ray diffraction and pair distribution function analysis at room temperature. As a result, new insights are gained about the structural properties of these compounds, suggesting a monoclinic symmetry (space group No. 14: P21/c - C_{2h}^{5}) induced by the co-operative orbital ordering produced by the Jahn-Teller distortion characterizing the 3d9 Cu2+ ion. In contrast to previous studies, a significant amount of vacancies is found at halogen positions, a feature that can be likely ascribed to the synthesis technique adopted in the present study. Br atoms preferentially occupy axial positions, likely on account of reduced steric hindrance at these sites.

2.
Front Cardiovasc Med ; 8: 747858, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34746263

RESUMO

Background: Catheter ablation is a treatment option for sustained ventricular tachycardias (VTs) that are refractory to pharmacological treatment; however, patients with fast VT and electrical storm (ES) are at risk for cardiogenic shock. We report our experience using cardiopulmonary support with extracorporeal membrane oxygenation (ECMO) during catheter ablation of VT. Methods: Sixty-two patients (mean age 68 ± 9 years; 94% male) were referred to our center for catheter ablation of repeated episodes of hemodynamically unstable ventricular arrhythmias. ES was defined as the occurrence of three or more VT/ventricular fibrillation episodes requiring electrical cardioversion or defibrillation in a 24-h period. All patients had hemodynamically unstable VTs. Results: Thirty-one patients (group 1) performed catheter ablation without ECMO support and 31 patients (group 2) with ECMO support. At the end of the procedure, ventricular inducibility was not performed in 16 patients of group 1 (52%) due to significant hemodynamic instability. Ventricular inducibility was performed in the other 15 patients (48%); polymorphic VTs were inducible in eight patients. In group 2, VTs were not inducible in 29 patients (93%); polymorphic VTs were inducible in two patients. The median follow-up duration was 24 months. Four patients of group 1 (13%) and five patients of group 2 (16%) died due to refractory heart failure. An implantable cardioverter-defibrillator intervention (shock or antitachycardia pacing) was documented in 13 patients of group 1 (42%) and six patients of group 2 (19%). Conclusions: Extracorporeal membrane oxygenation support during catheter ablation for hemodynamically unstable VTs is a useful tool to prevent acute procedural heart failure and to reduce arrhythmic burden.

3.
ACS Nano ; 2021 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-34668701

RESUMO

Metal halide perovskites are one of the most investigated materials in optoelectronics, with their lead-based counterparts being renowned for their enhanced optoelectronic performance. The 3D CsPbX3 structure has set the standard with many studies currently attempting to substitute lead with other metals while retaining the properties of this material. This effort has led to the fabrication of metal halides with lower dimensionality, wherein particular 2D layered perovskite structures have captured attention as inspiration for the next generation of colloidal semiconductors. Here we report the synthesis of the Ruddlesden-Popper Cs2CdCl4:Sb3+ phase as colloidal nanoplatelets (NPs) using a facile hot injection approach under atmospheric conditions. Through strict adjustment of the synthesis parameters with emphasis on the ligand ratio, we obtained NPs with a relatively uniform size and good morphological control. The particles were characterized through transmission electron microscopy, synchrotron X-ray diffraction, and pair distribution function analysis. The spectroscopic characterization revealed most strikingly an intense cyan emission under UV excitation with a measured PLQY of ∼20%. The emission was attributed to the Sb3+-doping within the structure.

4.
Artigo em Inglês | MEDLINE | ID: mdl-33237883

RESUMO

The local structure of La(Fe1-xMnx)AsO has been investigated using temperature dependent Fe K-edge extended x-ray absorption fine structure (EXAFS) measurements. The EXAFS data reveal distinct behavior of Fe-As and Fe-Fe atomic displacements with a clear boundary between x≦0.02 and x>0.02. The Fe-As bondlength shows a gradual thermal expansion while the Fe-Fe bond manifests a temperature dependent anomaly at ∼180 K for x>0.02. It is interesting to find characteristically different nature of Fe-As and Fe-Fe bondlengths shown by the temperature dependent mean square relative displacements. Indeed, the Fe-As bond, stiffer than that of the Fe-Fe, gets softer for x$\le$0.02 and hardly shows any change for x>0.02. On the other hand, Fe-Fe bond tends to be stiffer for x≦0.02 followed by a substantial softening for x>0.02. Such a distinction has been seen also in the As K-edge x-ray absorption near edge structure (XANES), probing local geometry around As atom together with the valence electronic structure. The results suggest that local atomic displacements by Mn substitution inducing increased iron local magnetic moment that should be the main reason for its dramatic effect in iron-based superconductors.

5.
J Nanosci Nanotechnol ; 19(8): 4994-4999, 2019 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-30913812

RESUMO

In the present work, the crystallization of anatase TiO2 nanoparticles (NPs), using different ferrite nanoparticles with different chemical composition, dimensions and shape as nucleation seeds, was investigated. In particular, CoFe2O4, NiFe2O4 and Fe3O4 NPs with a volume ratio equal to 1:1000 with respect of TiO2 amount, were used in order to investigate the synthesis of nanocrystalline tetragonal anatase TiO2 by a hydrothermal synthesis. In addition, Lu2O3 nanoparticles were also used to detect the effect of a non-magnetic nanoparticle on the synthesis and nanocrystallization of titania. For each sample, a deep physical characterization was performed by XRD (with a Rietveld refinement of the structural data), FE-SEM, STEM, HRTEM, DSC analysis and BET surface area measurement. Furthermore, for some samples, the photocatalytic activity was investigated by degradation of methylene blue in aqueous medium, in the framework of a standard ISO 10678:2010 protocol. The hydrothermal synthesis was performed with a 3 hours' thermal treatment, at a pressure of approximatively 9 bar and a temperature significantly lower (Tmax═150 °C) than the usual temperature necessary to obtain crystalline anatase TiO2 (Tcryst═350 °C). The results give evidence that the mere presence of a nucleation seeds in the hydrothermal reactor, without any particular need for the composition and morphology, leads to crystalline anatase TiO2 nanoparticles with high photocatalytic performances.

6.
Acta Crystallogr B Struct Sci Cryst Eng Mater ; 74(Pt 5): 405-415, 2018 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-30297546

RESUMO

The crystal structure of Cu5FeS4 (bornite) has been investigated using synchrotron X-ray powder diffraction at temperatures between 10 and 275 K. Diffraction data confirm that bornite crystallizes in the orthorhombic space group Pbca at 275 K. The unit-cell volume decreases continuously on cooling, but undergoes an abrupt contraction below ∼65 K, where a first-order Pbca→Pca21 structural transition takes place. The primary active mode yielding the observed ordered structure corresponds to the irreducible representation Γ2-, with wavevector (0,0,0). Pair distribution function analysis shows strong discrepancies between the local and the average structure. The average Fe-S bond length obtained through the EXAFS local probe is consistent with the values independently provided by X-ray powder diffraction data, strongly supporting the preferred location of Fe.

7.
Science ; 358(6366): 975, 2017 11 24.
Artigo em Inglês | MEDLINE | ID: mdl-29170207
8.
J Phys Condens Matter ; 29(48): 485002, 2017 12 06.
Artigo em Inglês | MEDLINE | ID: mdl-29120863

RESUMO

We investigate with scanning tunneling microscopy/spectroscopy (STM/STS) and density functional theory (DFT) calculations the surface structures and the electronic properties of Fe1+y Te thin films grown by pulsed laser deposition. Contrary to the regular arrangement of antiferromagnetic nanostripes previously reported on cleaved single-crystal samples, the surface of Fe1+y Te thin films displays a peculiar distribution of spatially inhomogeneous nanostripes. Both STM and DFT calculations show the bias-dependent nature of such features and support the interpretation of spin-polarized tunneling between the FeTe surface and an unintentionally magnetized tip. In addition, the spatial inhomogeneity is interpreted as a purely electronic effect related to changes in hybridization and Fe-Fe bond length driven by local variations in the concentration of excess interstitial Fe cations. Unexpectedly, the surface density of states measured by STS strongly evolves with temperature in close proximity to the antiferromagnetic-paramagnetic first-order transition, and reveals a large pseudogap of 180-250 meV at about 50-65 K. We believe that in this temperature range a phase transition takes place, and the system orders and locks into particular combinations of orbitals and spins because of the interplay between excess interstitial magnetic Fe and strongly correlated d-electrons.

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