Multinuclear NMR as a tool for studying local order and dynamics in CH3NH3PbX3 (X = Cl, Br, I) hybrid perovskites

International audienceWe report on Pb, Br, N, H, C and H NMR experiments for studying the local order and dynamics in hybrid perovskite lattices. Pb NMR experiments conducted at room temperature on a series of MAPbX compounds (MA = CHNH; X = Cl, Br and I) showed that the isotropic Pb NMR shift is strongly dependent on the nature of the halogen ions. Therefore Pb NMR appears to be a very promising tool for the characterisation of local order in mixed halogen hybrid perovskites. Pb NMR on MAPbBrI served as a proof of concept. Proton, C and N NMR experiments confirmed the results previously reported in the literature. Low temperature deuterium NMR measurements, down to 25 K, were carried out to investigate the structural phase transitions of MAPbBr. Spectral lineshapes allow following the successive phase transitions of MAPbBr. Finally, quadrupolar NMR lineshapes recorded in the orthorhombic phase were compared with simulated spectra, using DFT calculated electric field gradients (EFG). Computed data do not take into account any temperature effect. Thus, the discrepancy between the calculated and experimental EFG evidences the fact that MA cations are still subject to significant dynamics, even at 25 K

NQR of spins I=3/2 : Liouville spaces and Ernst angle.Ultraslow critical behavior of chloranil by 35Cl NQR

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Local structure and dynamics of an icosahedral quasicrystal and its 1/1 approximant from Solid-State NMR

International audienceIn contrast to X-rays/Coherent neutron techniques that mainly measure space-time correlation functions of all atoms in the reciprocal space, solid-state NMR is a local probe that is very sensitive to short-ranged structural patterns and dynamics, with atomic selectivity. Moreover, it is recognized that both techniques are complementary to understand structure and dynamics at different time-scales. Both benefit from Large Scale Facilities (synchrotron, high field NMR, neutron reactors …) allowing unprecedented space-time resolution.In this presentation, we discuss how solid-state NMR experiments can shed light on structural organization, instabilities and dynamics in complex molecular systems. In particular, 45Sc solid state NMR experiments on the 1/1 approximant Zn6Sc and quasicrystal ZnScAg at different fields and temperatures are reported, and discussed in complementarity to available structural studies

Self-Organization of Quantum Rods Induced by Lipid Membrane Corrugations

International audienceSelf-organization of fluorescent nanoparticles, using biological molecules such as phospholipids to control assembly distances, is a promising method for creating hybrid nanostructures. We report here the formation of hybrid condensed phases made of anisotropic nanoparticles and phospholipids. Such structure formation is driven by electrostatic interaction between the nanoparticles and the phospholipids, and results in the formation of a 2D rectangular liquid crystal, as confirmed by high-resolution Small-Angle X-ray Scattering (SAXS). Moreover, we show that the fluorescent properties of the NPs are not modified by the self-assembly proces

Metabolic profiling of deschloro-N-ethyl-ketamine and identification of new target metabolites in urine and hair using human liver microsomes and high-resolution accurate mass spectrometry

International audienceThe aim of this study was to identify new markers of deschloro-N-ethyl-ketamine (O-PCE), a ketamine analogue that has been involved in acute intoxications with severe outcomes including death and whose metabolism has never been studied before. In vitro study after 2-h incubation with pooled human liver microsomes (HLMs) cross-checked by the analysis of urine and hair from a 43-year-old O-PCE user (male) were performed by liquid chromatography–high resolution mass spectrometry (LC-HRMS). Acquired data were processed by the Compound Discoverer® software, and a full metabolic profile of O-PCE was proposed. In total, 15 metabolites were identified, 10 were detected in vitro (HLMs) and confirmed in vivo (urine and/or hair), two were present only in HLMs, and the remaining three metabolites were identified only in biological specimens. While O-PCE was no longer detected in urine, nine metabolites were identified allowing to increase its detection window. In descending order of metabolites abundance, we suggest using 2-en-PCA-N-Glu (34%, first), M3 (16%, second), O-PCA-N-Glu (15.4%, third), OH-O-PCE (15%, fourth) and OH-PCE (11.9%, fifth) as target metabolites to increase the detection window of O-PCE in urine. In hair, nine metabolites were identified. OH-PCA was the major compound (78%) with a relevant metabolite to parent drug ratio (=6) showing its good integration into hair and making it the best marker for long-term monitoring of O-PCE exposure

La prise de responsabilité des jeunes et les associations: Courcelles, une pédagogie de l'engagement

National audienceLes acteurs associatifs se plaignent souvent, et de façon récurrente, de l’absence de jeunes ou de militants, sans pour autant, basculer vers une analyse des mécanismes qui permettraient, à des jeunes, de devenir des membres de l’association, engagés et porteurs du projet.Le propos est ici différent. Parler de la prise de responsabilité comme d’un processus, envisager la prise de responsabilité en tant que telle, consiste à passer dans un autre registre, celui d’un processus dans lequel l’individu prend à sa charge et se voit confié, une responsabilité, c’est-à-dire quelque chose qu’il assumera mais aussi quelque chose qu’on choisit de lui confier à la hauteur des capacités qu’on lui prête.En passant par différentes phases, plus ou moins réfléchies avant ce travail, les personnes expérimentent à l’occasion de différentes situations leur capacité à prendre en charge des tâches, des réalisations, face aux autres. Amener les personnes à entrer dans ces situations, à y éprouver la possibilité d’y faire ce qui est attendu, sont différentes modalités permettant que progressivement, avec des niveaux d’implication singuliers, le projet lui-même de l’association se trouve pris en considération.La prise de responsabilité comme processus se révèle être un chemin sur lequel les protagonistes prennent conscience des leviers à prendre en compte pour que le sens du projet de l’association puisse se poursuivre, et donc aussi, des choses qu’il ne faut pas modifier au risque sinon de voir l’ensemble du fonctionnement remis en cause. De nombreuses situations vécues, analysées, discutées, débattues sont nécessaires pour s’approprier les choses mais aussi pour les faire exister. Nous proposons dans cet ouvrage de raconter avec des vignettes et des réflexions théoriques les différentes étapes identifiées, leur contenu, les formes d’accompagnement mises en place, les voies de re-médiation et de recours, et finalement, comment l’association donne du pouvoir d’agir aux jeunes qui forment la force vive de ce projet

The kinetics features of a thermal spin transition characterized by optical microscopy on the example of [Fe(bbtr)3](ClO4)2 single crystals: Size effect and mechanical instability

We investigated by optical microscopy the thermal spin transition in single crystals of [Fe(bbtr)3](ClO4)2 (bbtr = 1,4-di(1,2,3-triazol-1-yl) butane). The growth of the low-spin phase was observed for different crystal orientations and sizes. The process always started from a corner of the crystal but its further development depended on the size, shape and thermal history of the crystal. In crystals of smaller size, under isothermal conditions, the low-spin phase developed in a continuous way, through the propagation of a rather well defined transformation front, with a higher propagation velocity inside the planes perpendicular to the c axis. In larger crystals the spontaneous occurrence of inhomogeneous stresses led to a stepwise propagation process

Structure of liquid films of an ordered foam confined in a narrow channel.

International audienceA bamboo foam is the simplest case of an ordered foam confined in a narrow channel. It is made of a regular film distribution, arranged perpendicularly to the channel. Our work consists of studying the structural properties of several films taken in a drained foam. X-ray experiments highlighted the equality of the equilibrium thickness for each film within a foam. The same thickness was found as by measurements of disjoining pressure isotherms, proving as well that films of a bamboo foam behave like isolated ones. The refinement of X-ray data by a simple model of specular reflectivity showed a significant variation of the electronic distribution of the surfactant layer for a common black film forwarding from one equilibrium state to another. A discussion on the organization of the surfactant molecules to the gas/liquid interface and film is proposed

Structure and Dynamics of a Tsai‐type quasicrystal and approximant from 45Sc and 67Zn NMR studies

International audienceNMR is a recognized complementary method to X-rays/Neutron diffusion for structure and dynamics understanding, dueto different space-time correlation function probe range, and atomic selectivity. Both benefit from Large Scale Facilities (synchrotron,high field NMR, neutron reactors …) allowing unprecedented space-time resolution. For instance, the family of icosahedralquasicrystals of Tsai type [1,2] contains binary stable i-QC with low chemical disorder that offer the opportunity of precise structuralanalysis [3] to reconstruct the atomic structure from a 6-dimensional superspace projection, using 1/1 and 2/1 approximant periodicstructures as starting models. However, the complexity of superspace crystallography requires assumptions and approximations inorder to answer to the question "where are the atoms". Thus, major questions about local structure, dynamics and possible phasetransition in the quasicrystal are still to be answered. To the best of our knowledge, no NMR studies have been performed on suchiQc.In this presentation, solid-state NMR experiments of 45Sc (I=7/2, 100%) and 67Zn (I=5/2, 4.1%) nuclei at different fields andtemperatures, in the 1/1 approximant Zn6Sc and quasicrystal ZnScAg are reported and discussed in the light of structural studies. Bothnuclei carry complementary information to probe intershell coupling and tetrahedron induced distorsions. Indeed, 12 scandium atomsconstitute the second shell of a Tsai cluster, composed of a tetrahedron (4Zn), dodecahedron (20Zn), Sc icosahedron and larger shellsof zinc( Fig.1). Another type of building brick is the double Friauf polyhedron, that exists only in the 2/1 approximant and iQc. Wewill discuss how our NMR results provide insight in the structure (double Friauf and icosahedral sites) and dynamics (frozen state inthe iQc), from comparison between the 1/1 approximant and iQc.References[1] A. P. Tsai, J. Q. Guo, E. Abe, H. Takakura, T. J. Sato, Nature, 2000, 408, 537[2] A.P. Tsai, Chem. Soc. Rev., 2013, 42, 5352.[3] H. Takakura, C. Pay Gomez, A. Yamamoto, M. de Boissieu, A. P. Tsai, Nat. Mater.,2007, 6,58Acknowledgements: We acknowledge IRRMN FR3050 CNRS for support of High Field NMR experiments in Lille. This researchreceived FEDER financial support (FEDER 34722-Prin2Tan) for funding NMR spectrometers in Rennes

Hybrid Perovskite: Solid-State NMR Investigation From Room To Very Low Temperatures

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