Search results for "doping"

Dielectric properties of lithium niobate single crystals doped with gadolinium

2013

In this paper dielectric properties of LiNbO3:Gd single crystals at temperatures ~ 290–490 K at narrow frequency range (0.5–106 Hz) are presented. The influence of growth conditions was also investigated. The anomalies on dielectric plots depend on the development of the micro- and nano-domain structure.

Chiral Inversion of Thiolate-Protected Gold Nanoclusters via Core Reconstruction without Breaking an Au-S Bond

2019

On the basis of density functional theory computations of the well-known chiral Au38(SR)24 nanocluster and its Pd- and Ag-doped derivatives, we propose here a mechanism for chiral inversion that does not require the breaking of a metal-sulfur bond at the metal-ligand interface but features a collective rotation of the gold core. The calculated energy barriers for this mechanism for Au38 and Pd-doped Au38 are in the range of 1-1.5 eV, significantly lower than barriers involving the breakage of Au-S bonds (2.5 eV). For Ag-doped Au38, barriers for both mechanisms are similar (1.3-1.5 eV). Inversion barriers for a larger chiral Au144(SR)60 are much higher (2.5-2.8 eV). Our computed barriers are…

Phases transitions in complexe oxides with perovskite structure : case system (1-x)Na0,5Bi0,5TiO3 - xCaTiO3

2015

The solid solutions (1-x)Na0,5Bi0,5TiO3 (NBT) – xCaTiO3 (CT) were studied by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, impedance spectroscopy and DSC. These materials have a perovskite crystalline structure. This study reveals not only the complexity but also the richness of physical phenomena in these compounds: phases transitions sequences, the Ca2+ effect on the physical-chemistry properties and the relation between dielectric properties and crystalline structure. Thereby, (1-x)NBT – xCT solid solutions (0 ≤ x ≤ 1.00) were synthesized by chemical solid route, then they were sintered by a particular procedure in order to avoid sodium and bismuth volatilization. …

Efficient vacuum deposited p-i-n and n-i-p perovskite solar cells employing doped charge transport layers

2016

Methylammonium lead halide perovskites have emerged as high performance photovoltaic materials. Most of these solar cells are prepared via solution-processing and record efficiencies (>20%) have been obtained employing perovskites with mixed halides and organic cations on (mesoscopic) metal oxides. Here, we demonstrate fully vacuum deposited planar perovskite solar cells by depositing methylammonium lead iodide in between intrinsic and doped organic charge transport molecules. Two configurations, one inverted with respect to the other, p-i-n and n-i-p, are prepared and optimized leading to planar solar cells without hysteresis and very high efficiencies, 16.5% and 20%, respectively. It is t…

2014

Somatic gene therapy is a promising tool for the treatment of severe diseases. Because of its abuse potential for performance enhancement in sports, the World Anti-Doping Agency (WADA) included the term 'gene doping' in the official list of banned substances and methods in 2004. Several nested PCR or qPCR-based strategies have been proposed that aim at detecting long-term presence of transgene in blood, but these strategies are hampered by technical limitations. We developed a digital droplet PCR (ddPCR) protocol for Insulin-Like Growth Factor 1 (IGF1) detection and demonstrated its applicability monitoring 6 mice injected into skeletal muscle with AAV9-IGF1 elements and 2 controls over a 3…

Highly textured boron/nitrogen co-doped TiO2 with honeycomb structure showing enhanced visible-light photoelectrocatalytic activity

2020

International audience; In this work, we report a novel photocatalyst based on boron and nitrogen co-doped TiO2 rutile (1 1 0) honeycomb structures. The photocatalyst has been prepared by simultaneously oxidizing and doping a Ti-foil substrate at 750 degrees C. The unit cell volume and the crystallite size of grown TiO2 films were measured by Rietveld refinement analysis. The co-doping by boron and nitrogen was achieved simultaneously with the oxidation of the titanium, resulting in a rutile (1 1 0) textured TiO2 film. X-ray photoelectron spectroscopy analysis revealed the presence of Ti-O-N and Ti-O-B-N bonds, and the presence of crystal defects in the lattice was detected and displayed by…

A simple analysis of the HA centre destruction temperatures for doped alkali halides

1998

Abstract A simple relation for the destruction temperatures Td of the HA centres (H centres trapped by an impurity cation) as a function of the difference in the radii for a host cation and impurity in alkali halide crystals is presented and theoretically justified. This relation allows to predict Td for H centres trapped by other monovalent cation impurities.

Luminescence spectra and decay kinetics in ZnWO4 and CdWO4 crystals

2004

The luminescence spectra and luminescence decay kinetics in ZnWO4 (nominal pure and doped with Fe and Mo) under pulsed electron beam and pulsed nitrogen laser excitation have been investigated. It is suggested that the two-stage intrinsic luminescence decay observed under ionizing radiation excitation in ZnWO4 and CdWO4 was due to two different self-trapped exciton (STE) configurations in these crystals. The role of Fe and Mo impurities for scintillation efficiency in ZnWO4 and CdWO4 has been discussed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Intrinsic Organic Semiconductors as Hole Transport Layers in p–i–n Perovskite Solar Cells

2021

Thin polymeric and small-molecular-weight organic semiconductors are widely employed as hole transport layers (HTLs) in perovskite solar cells. To ensure ohmic contact with the electrodes, the use of doping or additional high work function (WF) interlayer is common. In some cases, however, intrinsic organic semiconductors can be used without any additive or buffer layers, although their thickness must be tuned to ensure selective and ohmic hole transport. Herein, the characteristics of thin HTLs in vacuum-deposited perovskite solar cells are studied, and it is found that only very thin (<5 nm) HTLs readily result inhigh-performing devices, as the HTL acts as a WF enhancer while still ens…

Rilevazione statistica della diffusione e della conoscenza di sostanze dopanti, integratori e dell' Exercise Addiction

2014

I benefici derivanti dalla pratica dell'esercizio fisico sono stati ampiamente documentati. Tuttavia, l’eccessivo ricorso alla attività fisica può condurre alla messa in atto di pattern compulsivi di allenamento che possono evolversi in una vera e propria patologia: l' exercise addiction. Studi recenti suggeriscono l'espansione di due fenomeni: il doping amatoriale e l'abuso di integratori per lo sport. Sono stati somministrati 686 test. I partecipanti allo studio sono stati scelti tra studenti di scuola media superiore, studenti universitari e frequentatori di ambienti sportivi. Il 42,5% degli intervistati dichiara di assumere sostanze per migliorare le prestazioni sportive e quindi di dop…