Search results for "EXAFS"
showing 10 items of 88 documents
Palladium local structure of La1-xSrxCo1-yFey-0.03Pd0.03O3-δperovskites synthesized using a one pot citrate method
2014
Nanostructured La1-xSrxCo1-yFey-0.03Pd0.03O3-δ(LSCF-Pd) perovskites with fixed La-Sr composition (x = 0.4) and two different Fe contents (y = 0.2 and 0.8) were successfully synthesized using a one pot citrate method starting from nitrates of the metal cations. Pd-free La1-xSrxCo1-yFeyO3-δ(LSCF) systems were prepared for comparison. LSCF powders were calcined at 1300 °C and characterized by XRD and Rietveld refinement, EXAFS, XPS, TPR analyses. Promotion of La0.6Sr0.4Co0.8Fe0.2O3-δand of La0.6Sr0.4Co0.2Fe0.8O3-δby incorporation of palladium was evidenced by solving the local environment of Pd using EXAFS spectroscopy. XPS analyses, in agreement with TPR measurements, demonstrated an inc…
Grafting, self-organization and reactivity of double-decker rare-earth phthalocyanine
2019
Unveiling the interplay of semiconducting organic molecules with their environment, such as inorganic materials or atmospheric gas, is the first step to designing hybrid devices with tailored optical, electronic or magnetic properties. The present article focuses on a double-decker lutetium phthalocyanine known as an intrinsic semiconducting molecule, holding a Lu ion in its center, sandwiched between two phthalocyanine rings. Carrying out experimental investigations by means of electron spectroscopies, X-ray diffraction and scanning probe microscopies together with advanced ab initio computations, allows us to unveil how this molecule interacts with weakly or highly reactive surfaces. Our…
Molekulārās dinamikas metodes pielietošana Y2O3 un FeF3 rentgenabsorbcijas spektru interpretācijai
2015
Rentgenabsorbcijas spektroskopija ir viena no eksperimentālajām metodēm, kas spēj sniegt informāciju par parauga lokālo struktūru. No otras puses, informāciju par lokālo struktūru iespējams iegūt no molekulārās dinamikas simulācijām. Šajā darbā eksperimentālie rentgenabsrobcijas spektri tiek izmantoti, lai novērtētu FeF3 un Y2O3 klasiskās molekulārās dinamikas spēka lauka modeļu kvalitāti. Labākos spēka lauka modeļus iespējams izmantot eksperimentālo rentgenabsorbcijas spektru analīzē un interpretācijā.
Synthesis, Structural characterization and Exafs investigations of new ruthenium(III) complexes.
2008
Two new complexs of Ru(III) with glucosaminic acid and 1-Methyluracil, [RuCl2(Glun-N,O)2]H (I), (Glun-= glucosaminate); [RuCl4(1-MeU-N3)(DMSO)]H2.H2O (II), (1-MeU-= 1-Methyluracilate) were prepared from the same Ru(III) precursors, RuCl3•3H2O and [(DMSO)2H][trans-RuCl4(DMSO)2]. The characterization of the complexes have been carried out by elemental analysis, FT-IR, ES-MS, NMR and EXAFS.
A spin transition molecular material with a wide bistability domain.
2002
International audience; [Fe(hyptrz)3](4-chloro-3-nitrophenylsulfonate)22 H2O (1; hyptrz=4-(3-hydroxypropyl)-1,2,4-triazole) has been synthesized and its physical properties have been investigated by several physical techniques including magnetic susceptibility measurements, calorimetry, and Mössbauer, optical, and EXAFS spectroscopy. Compound 1 exhibits a spin transition below room temperature, together with a very wide thermal hysteresis of about 50 K. This represents the widest hysteresis loop ever observed for an FeII-1,2,4-triazole spin transition material. The cooperativity is discussed on the basis of temperature-dependent EXAFS studies and of the structural features of a CuII analogu…
Photocontrolled On-Surface Pseudorotaxane Formation with Well-Ordered Macrocycle Multilayers.
2016
The photoinduced pseudorotaxane formation between a photoresponsive axle and a tetralactam macrocycle was investigated in solution and on glass surfaces with immobilized multilayers of macrocycles. In the course of this reaction, a novel photoswitchable binding station with azobenzene as the photoswitchable unit and diketopiperazine as the binding station was synthesized and studied by NMR and UV/Vis spectroscopy. Glass surfaces have been functionalized with pyridine-terminated SAMs and subsequently with multilayers of macrocycles through layer-by-layer self assembly. A preferred orientation of the macrocycles could be confirmed by NEXAFS spectroscopy. The photocontrolled deposition of the …
Structure et croissance de nanophases supportées d'oxyde de tungstène
2010
Tungsten trioxide nanorods can be elaborated on muscovite mica substrate through simple vapor deposition method. Growth of rods seems to follow a Stranski-Krastanov model. Their crystallography was investigated by TEM and reveals the presence of hexagonal phase. Such a metastable structure occurs from an interfacial hexagonal tungsten bronze which grows epitaxially on the substrate. This bronze phase contains potassium atoms coming from mica. Concerning the thickest rods, a monoclinic phase grows on the top of the hexagonal one. The hexagonal structure is thermally very stable: after annealing at 600°C, this phase is still detected whereas the rod morphology is destroyed. This point seems t…
X-ray absorption spectroscopy study of local dynamics and thermal expansion in ReO3
2015
The thermal expansion of polycrystalline ${\mathrm{ReO}}_{3}$ is studied in vacuum by x-ray diffraction from 300 to 600 K and by extended x-ray absorption fine structure (EXAFS) at the Re ${L}_{3}$ edge from 30 to 600 K. A detailed EXAFS analysis is presented up to the sixth coordination shell around Re. The crystal thermal expansion is weak throughout the explored range, negative below 100 K, positive from 150 to 500 K, and negative again above 500 K. The analysis of mean square relative displacements obtained by EXAFS and of mean square displacements available from x-ray and neutron diffraction measurements confirms the presence of significant static disorder in the investigated samples. …
Support effects on NiO-based catalysts for the oxidative dehydrogenation (ODH) of ethane
2019
[EN] We report on the effect of NiO-support interactions on the chemical nature of Ni species in a series of supported NiO catalysts for the ODH of ethane. SiO2, TiO2-anatase, a high surface area TiO2 and a porous clay hetero-structure (PCH) with TiO2 and SiO2 pillars were used as supports, which led to a selectivity to ethylene in the range 30-90% over supported NiO catalysts. The catalysts were characterized by means of XRD, N-2-Adsorption, H-2-TPR, XPS and in situ (under H-2 reductive atmosphere) and ex situ XAS spectroscopy. The catalytic performance of supported materials is discussed in terms of their reducibility and specific reduction kinetics, but also taking into account the speci…
Proton Dynamics in In:BaZrO3: Insights on the Atomic and Electronic Structure from X-ray Absorption Spectroscopy
2009
The local structure of Ba2+, Zr4+, and In3+ in In:BaZrO3 is investigated with EXAFS for samples having 0 to 75% In3+ content. It is found that indium can be inserted in any ratio in the host matrix oxide and that the oxygen coordination shell displays an In-O distance very similar to the Zr-O length. In the Zr-rich compositions, there is a preferred dopant-vacancy association that, however, does not give rise to dopant-proton interaction in the hydrated samples. The tendency of Ba2+ to be attracted toward the dopant site is attributed to the electrostatic interaction with the dopant and to the structural rearrangement around the In3+ site. Third cumulant analysis at high temperatures (up to…