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101.
We performed molecular dynamics simulations of the atomic structure of silicon nanocrystals embedded in a stoichiometric amorphous silica matrix. The atom–atom interactions are described by a combination of well-assessed potentials for bulk silicon and SiO2, plus a mixing term to allow adjusting the charge transfer at the interface between Si and silica. For the free-standing Si nanocrystals, we find that the spherical structure is favoured with respect to the faceted one, up to at least a diameter of 6 nm. Correspondingly, the surface layer shows a higher diffusivity than the bulk. When embedded in the silica matrix, nanocrystals are under severe mechanical stress which is released by the combined formation of porosity at the interface and of bridging Si–O–Si bonds, whose density increases with the nanocrystal size. Vibrational frequencies specific to the interface bonding are identified and discussed. 相似文献
102.
[reaction: see text] Tetrazoles frequently replace carboxylic acids in pharmaceutical drugs. However, while the binding modes of tetrazolate and carboxylate anions in amidinium complexes turns out to be similar, the association constant of the former is 2-3 orders of magnitude smaller in DMSO. Crystal structures revealed that the N...H-N hydrogen bonds in amidinium tetrazolates are bent (162 degrees and 169 degrees ) and noticeably longer (N...N 2.96 A) than corresponding hydrogen bonds in both amidinium carboxylates and ammonium tetrazolates. 相似文献
103.
Inside Back Cover: Synthesis of Polysubstituted γ‐Butenolides via a Radical Pathway: Cyclization of α‐Bromo Aluminium Acetals and Comparison with the Cyclization of α‐Bromoesters at High Temperature (Chem. Eur. J. 32/2015) 下载免费PDF全文
104.
Hailong Yuan Dr. Florian Massuyeau Nicolas Gautier Dr. Antoine Blaise Kama Dr. Eric Faulques Dr. Fei Chen Dr. Qiang Shen Dr. Lianmeng Zhang Dr. Michael Paris Dr. Romain Gautier 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(7):2824-2829
Near-UV-pumped white-light-emitting diodes with ultra-high color rendering and decreased blue-light emission is highly desirable. However, discovering a single-phase white light emitter with such characteristics remains challenging. Herein, we demonstrate that Mn doping as low as 0.027 % in the hybrid post-perovskite type (TDMP)PbBr4 (TDMP=trans-2,5-dimethylpiperaziniium) enables to achieve a bright pure white emission replicating the spectrum of the sun's rays. Thus, a white phosphor exhibiting an emission with CIE coordinates (0.330, 0.365), a high photoluminescence quantum yield of 60 % (new record for white light emission of hybrid lead halides), and an ultra-high color rendering index (CRI=96, R9=91.8), corresponding to the record value for a single phase emitter was obtained. The investigation of the photoluminescence properties revealed how free excitons, self-trapped excitons, and low amount of Mn dopants are coupled to give rise to such pure white emission. 相似文献
105.
Dr. Romain Plais Guy Gouarin Amélie Bournier Olfa Zayene Vanessa Mussard Flavien Bourdreux Dr. Jérome Marrot Arnaud Brosseau Dr. Anne Gaucher Dr. Gilles Clavier Dr. Jean-Yves Salpin Prof. Dr. Damien Prim 《Chemphyschem》2023,24(2):e202200524
Modulation and fine-tuning of the strength of weak interactions to bind anions are described in a series of synthetic receptors. The general design of the receptors includes both a urea motif and a tetrazine motif. The synthetic sequence towards three receptors is detailed. Impacts of H-bond strength and linker length between urea and tetrazine on chloride complexation are studied. Binding properties of the chloride anion are examined in both the ground and excited states using a panel of analytical methods (NMR spectroscopy, mass spectrometry, UV/Visible spectroscopies, and fluorescence). A ranking of the receptors by complexation strength has been determined, allowing a better understanding of the structure-properties relationship on these compounds. 相似文献
106.
A small library of squamocin analogues has been prepared and screened biologically (cytotoxicity, inhibition of mitochondrial complex I and complex III). To centre diversity on a crucial part of the molecule (i.e., the α,β-unsaturated lactone), an original and reliable lactone opening reaction has been discovered and exploited among other efficient reactions. 相似文献
107.
Sol-gel porous materials with tailored or nanostructured cavities have been increasingly used as nanoreactors for the enhancement of reactions between entrapped chemical reactants. The domains of applications issued from these designs and engineering are extremely wide. This tutorial review will focus on one of these domains, in particular on optical chemical sensors, which are the subject of extensive research and development in environment, industry and health. 相似文献
108.
109.
Romain Joly Genevive Raugel 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2010,27(6):539-1440
In this paper, we show that, for scalar reaction–diffusion equations ut=uxx+f(x,u,ux) on the circle S1, the Morse–Smale property is generic with respect to the non-linearity f. In Czaja and Rocha (2008) [13], Czaja and Rocha have proved that any connecting orbit, which connects two hyperbolic periodic orbits, is transverse and that there does not exist any homoclinic orbit, connecting a hyperbolic periodic orbit to itself. In Joly and Raugel (2010) [31], we have shown that, generically with respect to the non-linearity f, all the equilibria and periodic orbits are hyperbolic. Here we complete these results by showing that any connecting orbit between two hyperbolic equilibria with distinct Morse indices or between a hyperbolic equilibrium and a hyperbolic periodic orbit is automatically transverse. We also show that, generically with respect to f, there does not exist any connection between equilibria with the same Morse index. The above properties, together with the existence of a compact global attractor and the Poincaré–Bendixson property, allow us to deduce that, generically with respect to f, the non-wandering set consists in a finite number of hyperbolic equilibria and periodic orbits. The main tools in the proofs include the lap number property, exponential dichotomies and the Sard–Smale theorem. The proofs also require a careful analysis of the asymptotic behavior of solutions of the linearized equations along the connecting orbits. 相似文献
110.
Let (ρ λ ) λ∈Λ be a holomorphic family of representations of a finitely generated group G into PSL(2,ℂ), parameterized by a complex manifold Λ. We define a notion of bifurcation current in this context, that is, a positive closed current on Λ describing the bifurcations of this family of representations in a quantitative sense. It is the analogue of the bifurcation current introduced by DeMarco for holomorphic families of rational mappings on ℙ1. Our definition relies on the theory of random products of matrices, so it depends on the choice of a probability measure μ on G. 相似文献