Search results for "Rossi"
showing 10 items of 267 documents
PELLEGRINO ROSSI RAPPORTEUR DU PROJET DE LOI RELATIF A LA CONSTITUTION POLITIQUE DES COLONIES FRANÇAISES
2018
On 12 June 1840, the lawyer and economist Pellegrino Rossi, Peer of France, entered the Commission chaired by Duke Victor de Broglie and in charge of an investigation of issues related to the slavery and the political constitution of the French colonies. This article aims to examine the role played by Pellegrino Rossi in the debate on the abolition of slavery in the French colonies and the project of political constitution of French colonies of which Rossi was the speaker and editor of the same articles.
Pyrene-benzoylthiophene Bichromophores as Selective Triplet Photosensitizers.
2006
Combination of the pyrene and benzoylthiophene units constitutes an interesting approach to design bichromophoric photosensitizers with increased intersystem crossing quantum yield and enhanced selectivity. The potential of this strategy has been illustrated in the present work by using a model photoisomerization reaction.
Ultrafast Relaxation Dynamics of Osmium−Polypyridine Complexes in Solution
2013
We present steady-state absorption and emission spectroscopy and femtosecond broadband photoluminescence up-conversion spectroscopy studies of the electronic relaxation of Os(dmbp)(3) (Os1) and Os(bpy)(2)(dpp) (Os2) in ethanol, where dmbp is 4,4'-dimethyl-2,2'-biypridine, bpy is 2,2'-biypridine, and dpp is 2,3-dipyridyl pyrazine. In both cases, the steady-state phosphorescence is due to the lowest (MLCT)-M-3 state, whose quantum yield we estimate to be <= 5.0 x 10(-3). For Os1, the steady-state phosphorescence lifetime is 25 ns. In both complexes, the photoluminescence excitation spectra map the absorption spectrum, pointing to an excitation wavelength-independent quantum yield. The ultrafa…
A coumarin based gold(i)-alkynyl complex: a new class of supramolecular hydrogelators.
2014
A phosphine-gold(I)-alkynyl-coumarin complex, [Au{7-(prop-2-ine-1-yloxy)-1-benzopyran-2-one}(DAPTA)] (1), was synthesized and the formation of long luminescent fibers in solution was characterized via fluorescence microscopy and dynamic light scattering. The fibers presented strong blue and green luminescence, suggesting that the gold(I) in the complex increased intersystem crossing due to the heavy atom effect, resulting in a significant increase in triplet emission. The X-ray structure of the fibers indicates that both aurophilic, π–π interactions and hydrogen bonding contribute to their formation in aqueous solvents.
Conformational disorder and optical properties of point defects in vitreous silica
2004
Abstract Disordered systems are characterized by the presence of local conformational heterogeneity, which reflects the complex landscape of the potential energy of the vitreous state. Optical properties of defects embedded in a vitreous matrix are also determined by the interaction with the surrounding environment; so the conformational disorder of the system induces spectral inhomogeneity. As a consequence, detailed experimental investigation of absorption and photoluminescence bands can give information on configurational substates around the chromophore. We focused our attention on B-type optical activity in silica glasses, characterized by a singlet emission and a triplet emission, conne…
Luminescence activity of surface and interior Ge-oxygen deficient centers in silica
2005
We report a comparative study on the optical activity of surface and interior Ge–oxygen deficient centers in pressed porous and sol–gel Ge-doped silica, respectively. The experimental approach is based on the temperature dependence of the two photoluminescence bands at 4.2 (singlet–singlet emission, S1! S0) and 3.1 eV (triplet–singlet emission, T1! S0), excited within the absorption band at about 5 eV. Our data show that the phonon assisted intersystem crossing process, linking the two excited electronic states, more effective for surface than for interior centers in the temperature range 5–300 K. For both centers, a distribution of the activation energies of the process is found. Based on th…
Effect of Halogen Ions on the Photocycle of Fluorescent Carbon Nanodots
2019
Carbon dots (C-dots) are well-known for their strong sensitivity to the environment, which reflects on intensity and shape changes of their fluorescence, induced by various interacting ions and molecules in solution. Although these interactions have been extensively studied in the last few years, especially in view of their possible sensing applications, the existing works have mostly focused on the quenching of C-dot fluorescence induced by metal cations. In fact, these latter easily bind to C-dots surfaces, which are negatively charged in most cases, promoting an electron transfer from the surface to them. Much less is known from the literature on the effect induced on C-dots by prototypi…
Dibenzo[hi,st]ovalene as Highly Luminescent Nanographene: Efficient Synthesis via Photochemical Cyclodehydroiodination, Optoelectronic Properties, an…
2019
Dibenzo[hi,st]ovalene (DBOV), as a new nanographene, has demonstrated promising optical properties, such as red emission with a high fluorescence quantum yield of 79% and stimulated emission, as well as high thermal stability and photostability, which indicated its promise as a light-emitting and optical gain material. However, the previous synthetic routes required at least 12 steps. This obstructed access to different derivatives, e.g., to obtain crystals suitable for X-ray diffraction analysis and to tune the optoelectronic properties. Here, we report an efficient synthetic pathway to DBOV based on a sequential iodination-benzannulation of bi(naphthylphenyl)diyne, followed by photochemic…
Computational evidence in favor of a two-state, two-mode model of the retinal chromophore photoisomerization
2000
In this paper we use ab initio multiconfigurational second-order perturbation theory to establish the intrinsic photoisomerization path model of retinal chromophores. This is accomplished by computing the ground state ( S 0 ) and the first two singlet excited-state ( S 1 , S 2 ) energies along the rigorously determined photoisomerization coordinate of the rhodopsin chromophore model 4- cis -γ-methylnona-2,4,6,8-tetraeniminium cation and the bacteriorhodopsin chromophore model all- trans -hepta-2,4,6-trieniminium cation in isolated conditions. The computed S 2 and S 1 energy profiles do not show any avoided crossing feature along the S 1 reaction path and maintain an energy gap >20 kcal⋅…
Highly deformed bands in Nd nuclei: New results and consistent interpretation within the cranked Nilsson-Strutinsky formalism
2019
International audience; Three new highly-deformed (HD) bands are identified in Nd136 and the highly deformed band of Nd137 is extended at higher spin by four transitions, revealing a band crossing associated with the occupation of the second νi13/2 intruder orbital. Extended cranked Nilsson-Strutinsky calculations are performed for all HD bands observed in Nd134, Nd136, and Nd137, achieving for the first time a consistent interpretation of all HD bands in the Nd nuclei. The new interpretation has significant consequences, like the change of parity of the yrast HD bands of Nd134 and Nd136, and the involvement of two negative-parity neutron intruder orbitals in the configurations of most HD b…