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Chettibi S.,University of Mentouri Constantine | Keghouche N.,University of Mentouri Constantine | Benguedouar Y.,University of Mentouri Constantine | Bettahar M.M.,French National Center for Scientific Research | Belloni J.,Laboratoire Of Chimie Physique
Catalysis Letters | Year: 2013

The radiolysis route is applied to synthesize nickel catalysts deposited on titanium dioxide. The TPR profile of radiation-induced Ni/TiO2 catalyst indicates a more complete reduction of the irradiated catalysts compared to the conventionally H2-reduced one. When tested in the benzene hydrogenation, the radiolytic Ni/TiO2 exhibits catalytic properties with higher efficiency than the H2-reduced catalyst. This observation is assigned to the presence of intermetallic Ni-Ti compounds (Ni2.66Ti1.33 and Ni3Ti) evidenced by XRD. In contrast, the calcined and H2-reduced catalyst contains predominantly the oxidized Ni5TiO7 phase, where the nickel is in strong interaction with the support. The TEM observations show highly dispersed nickel. Graphical Abstract: When tested in the benzene hydrogenation reaction, the catalyst Ni/TiO2 prepared by gamma-irradiation exhibits catalytic properties (the turn-over frequency at total conversion is 33.5 molecules Bz Ni at -1 s-1 at 140 C) with higher efficiency and at lower temperature than the H2-reduced catalyst. This observation is assigned to extremely dispersed nickel nanoparticles and to intermetallic Ni2.66Ti1.33 and Ni3Ti compounds evidenced by XRD. [Figure not available: see fulltext.] © 2013 Springer Science+Business Media New York. Source

Bernardi F.,Federal University of Rio Grande do Sul | Traverse A.,Laboratoire Of Chimie Physique | Olivi L.,Elettra - Sincrotrone Trieste | Alves M.C.M.,Federal University of Rio Grande do Sul | Morais J.,Federal University of Rio Grande do Sul
Journal of Physical Chemistry C | Year: 2011

PtxPd1-x (x = 0.5, 0.3, or 0) nanoparticles submitted to hydrogen reduction and posterior H2S sulfidation at 300 °C were characterized by in situ and ex situ X-ray absorption spectroscopy (XAS). The XAS measurements allowed monitoring short-range order changes around the Pt and Pd atoms induced by the thermal processes. Using the structural parameters obtained from the fitting procedure of the extended X-ray absorption fine structure (EXAFS) data, it was observed that the number of chemisorbed sulfur atoms is proportional to the quantity of Pd in the vicinity of Pt. A correlation between the sulfur reactivity of the nanoparticles and the bimetallic interaction effect is then evidenced. © 2011 American Chemical Society. Source

Kulesza J.,Technical University of Gdansk | Kulesza J.,Laboratoire Of Chimie Physique | Bochenska M.,Technical University of Gdansk
European Journal of Inorganic Chemistry | Year: 2011

There is an increasing interest in applying p-tert-butylcalix[4]arenes as sensing materials in ion-selective electrodes (ISEs). Considerable efforts were made to design calixarenes that are selective for some heavy- or transition-metal ions to be used in ISEs for controlling and monitoring the level of such pollutants in the environment. It has been reported that introduction of softer sulfur atoms instead of oxygen atoms in calix[4]arene substituents promotes their complexing ability towards transition- and heavy-metal ions, which are toxic for human beings and pollute the environment. In this microreview, we present sulfur-containing calix[4]arenes acting as sensing materials for metal cations such as Ag+, Pb2+, Cu2+, Cd2+ but also as efficient extractants for Pd 2+, Au3+ and Hg2+. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Belloni J.,Laboratoire Of Chimie Physique | Mostafavi M.,Laboratoire Of Chimie Physique
Actualite Chimique | Year: 2011

Aggregates are compounds constituted of a small number (or nuclearity)n of atoms or molecules. They represent an intermediate state of matter, also named mesoscopic, between both stable states of single atoms (or molecules) and the bulky condensed phase. The aggregates were for long out of reach to experimental observation due to their extremely small size and also totheir short life-time. They tend indeed, depending on the thermodynamicalconditions, to evaporate, sublimate or dissolve, or on the contrary to growtoward the bulky condensed phase. Likewise, theory could not for long describe the aggregates and the complexity of these multi-atomic supra-molecules. However, the very specific properties of aggregates, which are distinct from the bulk, precisely appear for the smallest sizes, between a few tenths of nanometers and a few nanometers. The present knowledge of their behavior is crucial since it governsthe shape, structure, reactivity or stability ofnanoparticles that they form as precursors and that have an increasing rolein nanotechnologies. Source

Loreau J.,Roosevelt University | Sodoga K.,Laboratoire Of Chimie Physique | Sodoga K.,University of Lome | Lauvergnat D.,Laboratoire Of Chimie Physique | And 3 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

The charge-transfer in low-energy (0.25 to 150eV/amu) H(nl)+He +(1s) collisions is investigated using a quasimolecular approach for the n=2,3 as well as the first two n=4 singlet states. The diabatic potential energy curves of the HeH+ molecular ion are obtained from the adiabatic potential energy curves and the nonadiabatic radial coupling matrix elements using a two-by-two diabatization method, and a time-dependent wave-packet approach is used to calculate the state-to-state cross sections. We find a strong dependence of the charge-transfer cross section on the principal and orbital quantum numbers n and l of the initial or final state. We estimate the effect of the nonadiabatic rotational couplings, which is found to be important even at energies below 1eV/amu. However, the effect is small on the total cross sections at energies below 10eV/amu. We observe that to calculate charge-transfer cross sections in an n manifold, it is only necessary to include states with n′≤n, and we discuss the limitations of our approach as the number of states increases. © 2010 The American Physical Society. Source

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