Jean-Paul Amoureux

French National Centre for Scientific Research, Lutetia Parisorum, Île-de-France, France

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Publications (85)319.04 Total impact

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    ABSTRACT: Bioinorganic vanadium(V) solids are often challenging for structural analysis. Here, we explore an NMR crystallography approach involving multinuclear (13) C/(51) V solid-state NMR spectroscopy, density functional theory (DFT), and spin dynamics numerical simulations, for the spectral assignment and the 3D structural analysis of an isotopically unmodified oxovanadium(V) complex, containing 17 crystallographically inequivalent (13) C sites. In particular, we report the first NMR determination of C-V distances. So far, the NMR observation of (13) C-(51) V proximities has been precluded by the specification of commercial NMR probes, which cannot be tuned simultaneously to the close Larmor frequencies of these isotopes (100.6 and 105.2 MHz for (13) C and (51) V, respectively, at 9.4 T). By combining DFT calculations and (13) C-(51) V NMR experiments, we propose a complete assignment of the (13) C spectrum of this oxovanadium(V) complex. Furthermore, we show how (13) C-(51) V distances can be quantitatively estimated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    ChemPhysChem 03/2015; 16(8). DOI:10.1002/cphc.201500033 · 3.36 Impact Factor
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    ABSTRACT: This work presents a detailed analysis of a recently proposed nuclear magnetic resonance method [Wang et al., Chem. Commun. 49(59), 6653-6655 (2013)] for accelerating heteronuclear coherence transfers involving half-integer spin quadrupolar nuclei by manipulating their satellite transitions. This method, called Population Transfer Heteronuclear Multiple Quantum Correlation (PT-HMQC), is investigated in details by combining theoretical analyses, numerical simulations, and experimental investigations. We find that compared to instant inversion or instant saturation, continuous saturation is the most practical strategy to accelerate coherence transfers on half-integer quadrupolar nuclei. We further demonstrate that this strategy is efficient to enhance the sensitivity of J-mediated heteronuclear correlation experiments between two half-integer quadrupolar isotopes (e.g., (27)Al-(17)O). In this case, the build-up is strongly affected by relaxation for small T2' and J coupling values, and shortening the mixing time makes a huge signal enhancement. Moreover, this concept of population transfer can also be applied to dipolar-mediated HMQC experiments. Indeed, on the AlPO4-14 sample, one still observes experimentally a 2-fold shortening of the optimum mixing time albeit with no significant signal gain in the (31)P-{(27)Al} experiments.
    The Journal of Chemical Physics 03/2015; 142(9):094201. DOI:10.1063/1.4913683 · 3.12 Impact Factor
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    ABSTRACT: Quadrupolar echo NMR spectroscopy of static solids often requires RF excitation that covers spectral widths exceeding 100 kHz, which is difficult to obtain due to instrumental limitations. In this work we revisit four well-known composite pulses (COM-I, II, III and IV) for broadband excitation in deuterium quadrupolar echo spectroscopy. These composite pulses are combined with several phase cycling schemes that were previously shown to decrease finite pulse width distortions in deuterium solid-echo experiments performed with two single pulses. The simulations and experiments show that COM-II and IV composite pulses combined with an 8-step phase cycling aid in achieving broadband excitation with limited pulse width distortions.
    Solid State Nuclear Magnetic Resonance 12/2014; 66-67. DOI:10.1016/j.ssnmr.2014.12.004 · 2.86 Impact Factor
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    ABSTRACT: The assignment of NMR signals in paramagnetic solids is often challenging since: (i) the large paramagnetic shifts often mask the diamagnetic shifts specific to the local chemical environment, and (ii) the hyperfine interactions with unpaired electrons broaden the NMR spectra and decrease the coherence lifetime, thus reducing the efficiency of usual homo- and hetero-nuclear NMR correlation experiments. Here we show that the assignment of (1)H and (13)C signals in isotopically unmodified paramagnetic compounds with moderate hyperfine interactions can be facilitated by the use of two two-dimensional (2D) experiments: (i) (1)H-(13)C correlations with (1)H detection and (ii) (1)H-(1)H double-quantum↔single-quantum correlations. These methods are experimentally demonstrated on isotopically unmodified copper (II) complex of l-alanine at high magnetic field (18.8T) and ultra-fast Magic Angle Spinning (MAS) frequency of 62.5kHz. Compared to (13)C detection, we show that (1)H detection leads to a 3-fold enhancement in sensitivity for (1)H-(13)C 2D correlation experiments. By combining (1)H-(13)C and (1)H-(1)H 2D correlation experiments with the analysis of (13)C longitudinal relaxation times, we have been able to assign the (1)H and (13)C signals of each l-alanine ligand. Copyright © 2014 Elsevier Inc. All rights reserved.
    Journal of magnetic resonance (San Diego, Calif.: 1997) 12/2014; 251C:36-42. DOI:10.1016/j.jmr.2014.11.013
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    ABSTRACT: Host-guest interactions in dealuminated HY zeolite have been investigated by advanced C-13-Al-27 solid-state NMR experiments. This analysis allows us to report new insights into the adsorption geometry of acetone and its interaction with acid sites in the zeolite channels.
    Journal of Physical Chemistry Letters 09/2014; 5(17):3068-3072. DOI:10.1021/jz501389z · 6.69 Impact Factor
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    ABSTRACT: We introduce a magic-angle spinning NMR experiment to estimate specific distances in a solid material between a given site occupied by a quadrupolar nucleus and the nearby spin-1/2 nuclei. The new sequence, called DANTE-S-REDOR, consists of a frequency-selective dephasing experiment where heteronuclear dipolar couplings are reintroduced by applying a symmetry-based sequence (S-REDOR). The selectivity is achieved by applying a pulse train, such as Delays Alternating with Nutations for Tailored Excitation (DANTE), to the quadrupolar nucleus. This new method allows quantitative analysis of proximities in the 3-4 angstrom range of protons in OH ligands and one of the V-51 sites in a complex decavanadate cluster, namely Cs-4[H(2)V(10)O(28]center dot)4H(2)O. The high selectivity of the DANTE-S-REDOR sequence offers the possibility to investigate a wide range of materials with different quadrupolar nuclei, including polyoxometalates, oxides, zeolites, and aluminophosphates.
    The Journal of Physical Chemistry C 08/2014; 118(32):18580-18588. DOI:10.1021/jp505194q · 4.84 Impact Factor
  • Yi Qian, Ming Shen, Jean-Paul Amoureux, Isao Noda, Bingwen Hu
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    ABSTRACT: The dependence of SNR on number-of-scans relationship in COV2D is analyzed for the first time, and we found SNRcov∝n/2 while SNRFT∝n.
    Solid State Nuclear Magnetic Resonance 05/2014; 59-60. DOI:10.1016/j.ssnmr.2014.02.002 · 2.86 Impact Factor
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    ABSTRACT: We show how (27)Al-(13)C proximities in the microporous metal-organic framework MIL-100(Al) can be probed using advanced (27)Al-(13)C NMR methods boosted by Dynamic Nuclear Polarization.
    Chemical Communications 12/2013; 50(8). DOI:10.1039/c3cc47208f · 6.72 Impact Factor
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    ABSTRACT: We analyze the direct excitation of wide one-dimensional spectra of nuclei with spin I=1/2 or 1 in rotating solids submitted to pulse trains in the manner of Delays Alternating with Nutations for Tailored Excitation (DANTE), either with one short rotor-synchronized pulse of duration τp in each of K rotor periods (D1(K)) or with N interleaved equally spaced pulses τp in each rotor period, globally also extending over K rotor periods (DN(K)). The excitation profile of DN(K) scheme is a comb of rf-spikelets with NνR=N/TR spacing from the carrier frequency, and a width of each spikelet inversely proportional to the length, KTR, of DN(K) scheme. Since the individual pulse lengths, τp, are typically of a few hundreds of ns, DN(K) scheme can readily excite spinning sidebands families covering several MHz, provided the rf carrier frequency is close enough to the resonance frequency of one the spinning sidebands. If the difference of isotropic chemical shifts between distinct chemical sites is less than about 1.35/(KTR), DN(K) scheme can excite the spinning sidebands families of several sites. For nuclei with I=1/2, if the homogeneous and inhomogeneous decays of coherences during the DANTE sequence are neglected, the K pulses of a D1(K) train have a linearly cumulative effect, so that the total nutation angle is θtot=K2πν1τp, where ν1 is the rf-field amplitude. This allows obtaining nearly ideal 90° pulses for excitation or 180° rotations for inversion and refocusing across wide MAS spectra comprising many spinning sidebands. If one uses interleaved DANTE trains DN(K) with N>1, only spinning sidebands separated by intervals of NνR with respect to the carrier frequency are observed as if the effective spinning speed was NνR. The other sidebands have vanishing intensities because of the cancellation of the N contributions with opposite signs. However, the intensities of the remaining sidebands obey the same rules as in spectra obtained with νR. With increasing N, the intensities of the non-vanishing sidebands increase, but the total intensity integrated over all sidebands decreases. Furthermore, the NK pulses in a DN(K) train do not have a simple cumulative effect and the optimal cumulated flip angle for optimal excitation, θtot(opt)=NK2πν1τp, exceeds 90°. Such DN(K) pulse trains allow achieving efficient broadband excitation, but they are not recommended for broadband inversion or refocusing as they cannot provide proper 180° rotations. Since DN(K) pulse trains with N>1 are shorter than basic D1(K) sequences, they are useful for broadband excitation in samples with rapid homogeneous or inhomogeneous decay. For nuclei with I=1 (e.g., for (14)N), the response to basic D1(K) pulse train is moreover affected by inhomogeneous decay due to 2nd-order quadrupole interactions, since these are not of rank 2 and therefore cannot be eliminated by spinning about the magic angle. For large quadrupole interactions, the signal decay produced by second-order quadrupole interaction can be minimized by (i) reducing the length of DN(K) pulse trains using N>1, (ii) fast spinning, (iii) large rf-field, and (iv) using high magnetic fields to reduce the 2nd-order quadrupole interaction.
    Journal of Magnetic Resonance 09/2013; 236C:105-116. DOI:10.1016/j.jmr.2013.09.003 · 2.32 Impact Factor
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    ABSTRACT: A series of transition-metal organometallic complexes with commonly occurring metalchlorine bonding motifs were characterized using (35) Cl solid-state NMR (SSNMR) spectroscopy, (35) Cl nuclear quadrupole resonance (NQR) spectroscopy, and first-principles density functional theory (DFT) calculations of NMR interaction tensors. Static (35) Cl ultra-wideline NMR spectra were acquired in a piecewise manner at standard (9.4 T) and high (21.1 T) magnetic field strengths using the WURST-QCPMG pulse sequence. The (35) Cl electric field gradient (EFG) and chemical shielding (CS) tensor parameters were readily extracted from analytical simulations of the spectra; in particular, the quadrupolar parameters are shown to be very sensitive to structural differences, and can easily differentiate between chlorine atoms in bridging and terminal bonding environments. (35) Cl NQR spectra were acquired for many of the complexes, which aided in resolving structurally similar, yet crystallographically distinct and magnetically inequivalent chlorine sites, and with the interpretation and assignment of (35) Cl SSNMR spectra. (35) Cl EFG tensors obtained from first-principles DFT calculations are consistently in good agreement with experiment, highlighting the importance of using a combined approach of theoretical and experimental methods for structural characterization. Finally, a preliminary example of a (35) Cl SSNMR spectrum of a transition-metal species (TiCl4 ) diluted and supported on non-porous silica is presented. The combination of (35) Cl SSNMR and (35) Cl NQR spectroscopy and DFT calculations is shown to be a promising and simple methodology for the characterization of all manner of chlorine-containing transition-metal complexes, in pure, impure bulk and supported forms.
    Chemistry - A European Journal 09/2013; 19(37). DOI:10.1002/chem.201301268 · 5.70 Impact Factor
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    ABSTRACT: Advanced multinuclear solid state NMR experiments were developed to probe the structure of two organometallic aluminum derivatives, Li[Al(CH3)3CH2Si(CH3)3] (1) and Li[Al(CH3)4] (2), which are relevant to olefin polymerization processes. For the first time, NMR observation of 27Al–13C covalent bonds in solids is performed with the natural abundance material 1. Unprecedented triple-resonance (1H–13C–27Al) and quadruple-resonance (1H–7Li–13C–27Al) heteronuclear correlation two-dimensional NMR experiments are also introduced to probe 27Al–13C and 13C–7Li proximities for 2. High-resolution solid-state NMR spectra thus obtained provide information on the local structure of these representative organometallic derivatives that proved to be most complementary and in full agreement with the structures obtained by X-ray diffraction.
    The Journal of Physical Chemistry C 08/2013; 117(35):18091–18099. DOI:10.1021/jp4055044 · 4.84 Impact Factor
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    ABSTRACT: We explore modulation-sideband recoupling conditions of the (13)C-(13)C Second-order Hamiltonian among Analogous nuclei plus pulse sequence (SHA+), and found that this sequence can be used in two different recoupling regimes. The first regime, νR>Δνiso(max), is recommended for broad-band recoupling to avoid any rotational resonance broadening. In this regime, the spinning speed should be only slightly larger than Δνiso(max), to obtain the best transfer efficiency. The second regime, νR<Δνiso(max), can be used to observe long-range constraints with lower spinning speed, which increases the transfer efficiency, and may allow using bigger rotors to increase the S/N ratio.
    Solid State Nuclear Magnetic Resonance 08/2013; 55-56. DOI:10.1016/j.ssnmr.2013.07.001 · 2.86 Impact Factor
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    ABSTRACT: We show that for half-integer quadrupolar nuclei, the manipulation of the satellite transitions can accelerate and enhance coherence transfer to other isotopes. This novel strategy is demonstrated to improve the sensitivity of (31)P-{(27)Al} J-HMQC experiments for a layered aluminophosphate Mu-4.
    Chemical Communications 06/2013; 49(59). DOI:10.1039/c3cc42961j · 6.72 Impact Factor
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    ABSTRACT: We demonstrate that a very simple experiment, Cross-Polarization with Variable Contact-time (CP-VC), is very efficient at ultra-fast MAS (νR⩾60kHz) to measure accurately the C-H and N-H distances, and to analyze the dynamics of bio-molecules. This experiment can be performed with samples that are either (13)C or (15)N labeled or without any labeling. The method is very robust experimentally with respect to imperfect Hartman-Hahn setting, and presents a large scaling factor allowing a better dipolar determination, especially for long C-H or N-H distances, or for CH3 or NH3 moieties with three-site hopping. At ultra-fast MAS, it can be used quantitatively in a 2D way, because its scaling factor is then little dependent on the offsets. This robustness with respect to offset is related to the ultra-fast spinning speed, and hence to the related small rotor diameter. Indeed, these two specifications lead to efficient n=±1 zero-quantum Hartman-Hahn CP-transfers with large RF-fields on proton and carbon or nitrogen channels, and large dipolar scaling factor.
    Journal of Magnetic Resonance 05/2013; 233C:56-63. DOI:10.1016/j.jmr.2013.05.005 · 2.32 Impact Factor
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    ABSTRACT: Nuclear spins as spies to explore the structure of materials This article illustrates how solid state NMR, which is by nature a local spectroscopic technique, is also able to establish dialogs between nuclear spins over distances up to few nanometers. Access to such length scales is possible through one-dimensional and multidimensional experiments that give chemical signatures not only from one unique atom in relation with its environment, but from groups of atoms chemically bonded or spatially close. In that sense, solid state NMR appears as a perfect investigation tool for materials with more and more complex compositions and structures. The selected examples belong to families of materials that have been developed for applications in the fields of energy (glasses for nuclear waste management), health (hybrid materials for controlled release of drugs) and sustainable development (heterogeneous catalysts).
    L'Actualité chimique 05/2013; 44(19-364):73-81. DOI:10.1002/chin.201319230 · 0.09 Impact Factor
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    ABSTRACT: We recently described a family of experiments for R2n(v) Driven Spin Diffusion (RDSD) spectroscopy suitable for homonuclear correlation experiments under fast MAS conditions [G. Hou, S. Yan, S.J. Sun, Y. Han, I.J. Byeon, J. Ahn, J. Concel, A. Samoson, A.M. Gronenborn, T. Polenova, Spin diffusion drive by R-symmetry sequencs: applications to homonuclear correlation spectroscopy in MAS NMR of biological and organic solids, J. Am. Chem. Soc. 133 (2011) 3943-3953]. In these RDSD experiments, since the broadened second-order rotational resonance conditions are dominated by the radio frequency field strength and the phase shifts, as well as the size of reintroduced dipolar couplings, the different R2n(v) sequences display unique polarization transfer behaviors and different recoupling frequency bandwidths. Herein, we present a series of modified R2n(v) sequences, dubbed COmbined R2n(v)-Driven (CORD), that yield broadband homonuclear dipolar recoupling and give rise to uniform distribution of cross peak intensities across the entire correlation spectrum. We report NMR experiments and numerical simulations demonstrating that these CORD spin diffusion sequences are suitable for broadband recoupling at a wide range of magnetic fields and MAS frequencies, including fast-MAS conditions (νr=40kHz and above). Since these CORD sequences are largely insensitive to dipolar truncation, they are well suited for the determination of long-range distance constraints, which are indispensable for the structural characterization of a broad range of systems. Using U-(13)C,(15)N-alanine and U-(13)C,(15)N-histidine, we show that under fast-MAS conditions, the CORD sequences display polarization transfer efficiencies within broadband frequency regions that are generally higher than those offered by other existing spin diffusion pulse schemes. A 89-residue U-(13)C,(15)N-dynein light chain (LC8) protein has also been used to demonstrate that the CORD sequences exhibit uniformly high cross peak intensities across the entire chemical shift range.
    Journal of Magnetic Resonance 04/2013; 232C:18-30. DOI:10.1016/j.jmr.2013.04.009 · 2.32 Impact Factor
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    ABSTRACT: Just in time: An NMR-driven structure resolution that allows structure determination from the powder diffraction data of a highly complex layered aluminophosphate, and was otherwise not possible despite the high quality of the synchrotron diffraction data, is proposed. This study shows that the strategy is general and allows reduction of the number of free parameters to search for a structure and converge under the limit of the combinatorial explosion of computing time.
    Chemistry - A European Journal 04/2013; 19(16). DOI:10.1002/chem.201203767 · 5.70 Impact Factor
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    ABSTRACT: Two-dimensional covariance (COV2D) spectroscopy offers an alternative approach to 2D Fourier transformation (FT2D) to obtain homo-nuclear correlation NMR spectra. Considerable saving in experimental time, without loss of resolution, can be achieved by incorporating COV2D with: (i) uniform sampling with a t1 cut-off (CUO) or non-uniform sampling (NUS), and (ii) constant or Gaussian accumulation profiles. We find that covariance treatment, combined with the CUO sampling and Gaussian accumulation profile provides better gain in experimental time, with respect to that required with FT2D NMR. This is in contrast with the maximum entropy (MaxEnt) reconstruction for 2D spectra, which works better with the NUS scheme rather than with the CUO scheme. We further discuss the experimental conditions that define this optimum acquisition, and explain how these parameters can easily be optimized 'on the fly' according to the desired resolution, which is quite sample-dependent.
    The Analyst 03/2013; 138(8). DOI:10.1039/c3an36375a · 3.91 Impact Factor
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    ABSTRACT: We systematically studied the enhancement factor (per scan) and the sensitivity enhancement (per unit time) in 13C and 29Si cross-polarization magic angle spinning (CP-MAS) NMR boosted by dynamic nuclear polarization (DNP) of functionalized mesoporous silica nanoparticles (MSNs). Specifically, we separated contributions due to: (i) microwave irradiation, (ii) quenching by paramagnetic effects, (iii) the presence of frozen solvent, (iv) the temperature, as well as changes in (v) relaxation and (vi) cross-polarization behaviour. No line-broadening effects were observed for MSNs when lowering the temperature from 300 to 100 K. Notwithstanding a significant signal reduction due to quenching by TOTAPOL radicals, DNP-CP-MAS at 100 K provided global sensitivity enhancements of 23 and 45 for 13C and 29Si, respectively, relative to standard CP-MAS measurements at room temperature. The effects of DNP were also ascertained by comparing with state-of-the-art two-dimensional heteronuclear 1H{13C} and 29Si{1H} correlation spectra, using, respectively, indirect detection or Carr-Purcell-Meiboom-Gill (CPMG) refocusing to boost signal acquisition. This study highlights opportunities for further improvements through the development of high-field DNP, better polarizing agents, and improved capabilities for low-temperature MAS.
    Physical Chemistry Chemical Physics 03/2013; DOI:10.1039/c3cp00039g · 4.20 Impact Factor
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    ABSTRACT: The origin of the exceptionally high activity of (B, Ag)-codoped TiO2 catalysts under solar-light irradiation has been investigated by XPS and 11B solid-state NMR spectroscopy in conjunction with density functional theory (DFT) calculations. XPS experimental results demonstrated that a portion of the dopant Ag (Ag3+) ions were implanted into the crystalline lattice of (B, Ag)-codoped TiO2 and were in close proximity to the interstitial B (Bint.) sites, forming [Bint.-O-Ag] structural units. In-situ XPS experiments were employed to follow the evolution of the chemical states of the B and Ag dopants during Uv-Vis irradiation. It was found that the [Bint.-O-Ag] units could trap the photoinduced electron to form an unique intermediate structure in the (B, Ag)-codoped TiO2 during the irradiation, which is responsible for the photoinduced shifts of the B 1s and Ag 3d peaks observed in the in-situ XPS spectra. Solid-state NMR experiments including 11B triple-quantum and double-quantum magic angle spinning (MAS) NMR revealed that up to six different boron species were present in the catalysts and only the tri-coordinated interstitial boron (T*) species was in close proximity to the substitutional Ag species, leading to formation of [T*-O-Ag] structural units. Furthermore, as demonstrated by DFT calculations, the [T*-O-Ag] structural units were responsible for trapping the photoinduced electrons, which prolongs the life of the photoinduced charge carriers and eventually leads to a remarkable enhancement in the photocatalytic activity. All these unprecedented findings are expected to be crucial for understanding the roles of B and Ag dopants and their synergy effect in numerous titania-mediated photocatalytic reactions.
    Journal of the American Chemical Society 01/2013; 135(4). DOI:10.1021/ja312205c · 11.44 Impact Factor

Publication Stats

1k Citations
319.04 Total Impact Points

Institutions

  • 2003–2015
    • French National Centre for Scientific Research
      • Institut des Matériaux Jean Rouxel
      Lutetia Parisorum, Île-de-France, France
  • 2013–2014
    • East China Normal University
      • Department of Physics
      Shanghai, Shanghai Shi, China
  • 2008–2013
    • University of Lille Nord de France
      Lille, Nord-Pas-de-Calais, France
  • 2011
    • University of Colorado Colorado Springs
      Colorado Springs, Colorado, United States
  • 1996–2008
    • Université des Sciences et Technologies de Lille 1
      • • Unité de Catalyse et Chimie du Solide (UCCS)
      • • Unité de Dynamique et de Structure de Matériaux Moléculaires (UDSMM)
      Lille, Nord-Pas-de-Calais, France
  • 2007
    • Lille Catholic University
      Lille, Nord-Pas-de-Calais, France
  • 2000
    • Universität Siegen
      Siegen, North Rhine-Westphalia, Germany