Gérald Lelong

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• Ph-D in Material Sciences
• Maître de Conférences at Sorbonne University

Using a simple route for preparing uniform spherical mesoporous MCM-41 materials based on a one-step synthesis in an all-water medium, we have investigated the effects of changes of the surfactant composition. The morphology, texture and structure of five samples with different compositions reveal that both, the external organization and internal p...

Elucidating pressure-induced structural transitions in glasses at a microscopic level is a formidable challenge. Here, the local environment of amorphous germania (a-GeO2) is investigated, from room pressure up to 18 GPa, using in situ inelastic x-ray-scattering measurements at the oxygen K-edge. The appearance of GeO5 units at intermediate pressur...

The crystal structures of two members of the Li2O–B2O3 phase diagram, Li6B4O9 and Li3B11O18, have been solved from single-crystal X-ray diffraction, and their structure has been further confirmed by Rietveld refinement on powder samples. Li6B4O9 crystallizes in the P21/n space group with a = 3.31913(15) Å, b = 23.361(2) Å, c = 9.1582(4) Å, and β =...

Probing the local environment of low-Z elements such as oxygen is of great interest for understanding the atomic scale behavior in materials, but it requires experimental techniques allowing to work with versatile sample environments. In this paper, the local environment of lithium borate crystals is investigated using non-resonant inelastic X-ray...

Transmission optical absorption spectra of ion-irradiated 3C-SiC epitaxial films on a silicon substrate are measured in the visible-near infrared range from room temperature down to about 10 K. These data show strong interference fringe patterns on top of the silicon absorption edge at about 10,460 cm¹ which limits the transmittance of the samples....

The FTIR absorption bands of virgin and electron-irradiated CeO2 single crystals were measured from 20 K to 500 K between 4000 cm−1 and 12,000 cm−1 (~830 nm to 2500 nm). Three broad bands centered at about 6100 cm−1 (~0.75 eV), 7000 cm−1 (~0.87 eV), and 10,500 cm−1 (~1.3 eV) were recorded above 100 K for the 2.5 MeV electron energy. Two smaller ban...

Cable bacteria embed a network of conductive protein fibers in their cell envelope that efficiently guides electron transport over distances spanning up to several centimeters. This form of long-distance electron transport is unique in biology and is mediated by a metalloprotein with a sulfur-coordinated nickel (Ni) cofactor. However, the molecular...

Epitaxial cubic (100) 3C-SiC films on a (100) silicon wafer were irradiated at room temperature with 2.3-MeV Si+ or 3.0-MeV Kr+ ions up to a fluence of 1 × 1016 cm−2. The evolutions of the epilayer and the substrate were followed as a function of ion fluence by using micro-Raman spectroscopy, optical absorption, and diffuse reflectance spectroscopy...

Des billes de notre enfance aux vitraux des cathédrales, le verre coloré exerce sur nous une grande fascination. La coloration du verre, souvent voulue pour donner un aspect esthétique ou protéger le contenu, est aussi parfois subie du fait de la présence d’impuretés comme le fer. Même à très faible concentration, le fer peut colorer le verre du ve...

Au sein de l’industrie verrière, connaître la composition et l’état structural des verres est un enjeu important pour le contrôle qualité sur les sites de production ou encore la recherche et le développement de nouveaux produits. Dans ce chapitre, nous décrirons brièvement différentes méthodes pouvant être utilisées par l’industrie verrière pour o...

Aggregates of charged metal particles obtained by electrostatic coupling with a compound of opposite charge in the vicinity of the net zero charge ratio are of interest in the field of plasmonics because the inter-particle distance is minimal, which favours plasmonic coupling. However, these structures present a low colloidal stability limiting the...

Raman scattering is applied to probe the radiation damage in swift heavy ion‐irradiated ceramics, namely zirconium nitride (ZrN), ceria (CeO2), and yttria‐stabilized zirconia (ZrO2: Y, or YSZ) for about the same high electronic stopping power of heavy ions. Raman spectra show that those ceramics are radiation‐resistant materials which are not amorp...

The assembly and stabilization of a finite number of nanocrystals in contact in water could maximize the optical absorption per unit of the material. Some local plasmonic properties exploited in applications, such as photothermia and optical signal amplification, would also be maximized which is important in the perspective of mass producing nanost...

The assembly and stabilization of a finite number of nanocrystals in contact in water could maximize the optical absorption per unit of material. Some local plasmonic properties exploited in applications, such as photothermia and optical signal amplification, would also be maximized which is important in the perspective of mass producing nanostruct...

Glass and melt structures are inherently complex and disordered with significant changes expected to occur with temperature. In the present paper, a comparison of the structure of glasses and liquids along the MgSiO3–CaSiO3 join is carried out using neutron and X-ray diffraction (XRD). Empirical Potential Structure Refinement (EPSR) simulations wer...

The radiation damage induced in cerium dioxide CeO2 and cerium-gadolinium mixed oxides (Ce, Gd)O2-x was studied by micro-Raman spectroscopy and diffuse UV-visible reflectance spectroscopy. Sintered samples of undoped CeO2 and (Ce, Gd)O2-x for 1 mol% and 5 mol% of Gd2O3 were irradiated at room temperature with 2.5-MeV Ar2+ and 12-MeV Ar4+ ions up to...

The damage recovery of an electron-irradiated CeO2 single crystal was studied by in situ UV-visible absorption spectroscopy during isochronal thermal annealing up to 873 K. The spectrum of the as-irradiated crystal shows band tailing below the fundamental absorption edge for photon energy near 3.2 eV. Two broad Gaussian bands centered at about 0.9...

A multi-edge study of the local structure of lithium borate glasses and melts has been carried out using X-ray Raman scattering (XRS) as a function of temperature. Thanks to a wide range of compositions, from pure B2O3 up to the metaborate composition, we are able to finely interpret in detail the modifications of the local environment of both the...

We use Ni ions as a structural probe to investigate the influence of modifier cations (Na, K, Mg, Ca, and Ba) on the structure of aluminosilicate glasses. The color of these glasses varies with the nature of the cations present in glass. Structural origin of this change is investigated by optical absorption and X-ray absorption spectroscopies. Our...

Gold nanoparticles are used in an expanding spectrum of biomedical applications. However little is known about their long term fate in the organism as it is generally admitted that gold nanoparticles inertness prevents their biodegradation. In this work, the biotransformations of gold nanoparticles captured by primary fibroblasts were monitored dur...

Reflection spectra of cerium dioxide sintered samples were measured in the UV-visible range after irradiation with various heavy ions (2.4-MeV Cu, 5-MeV W, 10-MeV W, 36-MeV W, 100-MeV Kr, and 200-MeV Xe). Differential reflectance spectra of irradiated samples after subtraction of the reference sample spectrum are fit with six broad Gaussian bands c...

Detecting and quantifying non-bridging oxygen (NBO) atoms is of particular interest for understanding the physical properties of melts or compressed materials, and requires an unequivocal spectral signature usable during in-situ measurements. In this paper, we evidence a low-energy feature of NBO in lithium silicate crystals using X-ray Raman scatt...

The quest for a possible liquid-liquid coexistence line in supercooled water below its homoge- neous nucleation line is faced by confining water within a porous silica substrate (MCM-41). This system is investigated by synchrotrone radiation Infra-Red spectroscopy, exploring both the intra- molecular and the inter-molecular vibrational dynamics, in...

Determining the uranyl(VI) UO22+ reactivity in crystalline and amorphous oxides is necessary to control its mobility. The intrinsic versatility of borate structural units containing both triangular BO3 and tetrahedral BO4 makes them original and rich hosts for uranyl. As part of the effort to determine the uranium stability in borate oxide glasses,...

Our understanding of the deep carbon cycle has witnessed amazing advances in the last decade, including the discovery of tetrahedrally coordinated high pressure (P) carbonate phases. However, little is known about the physical properties of their molten counterpart at moderate depths, while their properties at lower mantle conditions remain unexplo...

Ni:MgAl2O4 spinel demonstrates a reversible random Ni2+ site redistribution with increasing temperature. To determine the influence of the heat-treatment induced structure evolution on the nature of luminescence centers in NiO-doped spinel-based magnesium aluminosilicate glass-ceramics nucleated by a mixture of TiO2 and ZrO2, the detailed spectrosc...

UV-visible absorption spectroscopy and Raman spectroscopy were used to study damage production in cerium dioxide epitaxial films and polycrystalline sintered samples after irradiation with electrons for three energies to span the threshold displacement energies of cerium and oxygen atoms, and 2.4-MeV Cu ions. Neither amorphization nor specific colo...

UV-visible absorption spectroscopy and Raman spectroscopy were used to study damage production in cerium dioxide epitaxial films and polycrystalline sintered samples after irradiation with electrons for three energies to span the threshold displacement energies of cerium and oxygen atoms, and 2.4-MeV Cu ions. Neither amorphization nor specific colo...

Supporting Information S1

Plain Language Summary Iron oxides are important end‐members of the complex materials that constitute the Earth's interior. Among them, FeO and Fe2O3 have long been considered as the main end‐members of the ferrous (Fe²⁺) and ferric (Fe³⁺) states of iron, respectively. All geochemical models assume that high oxygen concentrations are systematically...

We investigate the state of water confined in the cylindrical pores of MCM-41 type mesoporous silica, with pore diameters of 2.8 nm and 4.5 nm, over the temperature range 160 - 290 K by combining small angle neutron scattering and wide angle diffraction. This allows us to observe simultaneously the intermolecular correlations in the local water str...

We investigate the state of water confined in the cylindrical pores of MCM-41 type mesoporous silica, with pore diameters of 2.8 nm and 4.5 nm, over the temperature range 160 - 290 K by combining small angle neutron scattering and wide angle diffraction. This allows us to observe simultaneously the intermolecular correlations in the local water str...

We have studied the formation of color centers in magnesium aluminate spinel (MgAl2O4) by X-ray and electron irradiations near room temperature (RT). For this purpose, Cu K radiation and three electron energies (1.0, 1.4, and 2.5 MeV) were used for variable fluences (up to 4.2x1018 cm-2). Off-line UV-visible optical absorption spectra were recorde...

An efficient technique for calculating K edges in X-ray Raman Spectroscopy in the framework of a single-particle theory is presented. It is based on a recursive method to compute the dynamic structure factor as a continued fraction, without requiring the explicit calculation of high-lying unoccupied electronic states. Multipole transitions are calc...

The functional importance of lithium in many types of materials requires reliable methods to study its local structure and dynamics. Nuclear magnetic resonance (NMR) spectroscopy should be ideal for this purpose, but suffers from poor resolution due to intrinsic dipolar broadening. We overcome this problem by diluting the 7Li spins with 6Li, produc...

The photo-annealing of colour centres in yttria-stabilised zirconia (YSZ) was studied by electron paramagnetic resonance spectroscopy upon UV-ray or laser light illumination, and compared to thermal annealing. Stable hole centres (HCs) were produced in as-grown YSZ single crystals by UV-ray irradiation at room temperature (RT). The HCs produced by...

Micro-Raman spectroscopy, X-band electron paramagnetic resonance (EPR) spectroscopy, and UV-visible optical absorption spectroscopy were used to study the damage production in cerium dioxide (CeO2) single crystals by electron irradiation for three energies (1.0, 1.4, and 2.5 MeV). The Raman-active T2g peak was left unchanged after 2.5-MeV electron...

The damage induced by heavy-ion irradiation has been studied in yttrium iron garnet (Y3Fe5O12 or YIG) films, doped with Ca, Tb and Tm, grown by liquid-phase epitaxy on gadolinium gallium garnet (Gd3Ga5O12 or GGG) substrates. Irradiations of doped-YIG epitaxial films and GGG substrates with 36-MeV 183W and 12-MeV 197Au ions were applied for fluences...

Advanced semi-empirical calculations have been performed to compute simultaneously optical absorption and K pre-edge X-ray Absorption spectra of Fe2+ in four distinct site symmetries found in minerals. The four symmetries, i.e. a distorted octahedron, a distorted tetrahedron, a square planar site, and a trigonal bipyramidal site, are representative...

Single crystals of magnesium aluminate spinel (MgAl2O4) with (1 0 0) or (1 1 0) orientations and cerium dioxide or ceria (CeO2) were irradiated by 1.0 MeV and 2.5 MeV electrons in a high-fluence range. Point-defect production was studied by off-line UV-visible optical spectroscopy after irradiation. For spinel, regardless of both crystal orientatio...

A new low-cost experimental setup based on two compact dispersive optical spectrometers and a specific sample stage has been developed to measure optical absorption transmission spectra overin the 350-2500 nm energy range on stained glass panels. We demonstrate how near-infrared data are essential to identify the coloring species in addition to UV-...

Three glasses in the Li2O–Al2O3–SiO2 (LAS), MgO–Al2O3–SiO2 (MAS) and ZnO–Al2O3–SiO2 (ZAS) systems were investigated to obtain spinel-based transparent glass-ceramics doped with TiO2 to induce internal nucleation and with NiO to provide optically active ion. The sequence of phase transformations of initial glasses during heat-treatments was studied...

The evolution of Ni2+ environment has been systematically investigated using optical and in situ X-ray absorption spectroscopy (XAS) to determine the influence of nucleating agents (TiO2 and/or ZrO2) during the formation of spinel in magnesium aluminosilicate glass–ceramics. The results were complemented by in situ X-ray diffraction data. According...

The structure of nuclear glasses and of simplified surrogates has been investigated using complementary diffraction and spectroscopic methods, together with numerical modeling. The diversity of structural surroundings of cations in glasses is reviewed at various scales. Cations usually occur in smaller sites in glasses than in crystals, with unusua...

A new experimental setup, combining a custom-designed Schwarzschild-type Cassegrain-based microscope and an ultraviolet‐visible-near infrared (UV-Vis-NIR) spectrophotometer, has been developed, focusing the light beam down to 20 μm diameter. Optical absorption spectra (in the 300‐2500 nm range) have been measured on micrometer-sized natural glass i...

Fe has long been known to play an important role in determining the properties of natural magmatic liquids and glasses [1]. The determination of the sites occupied by ferrous and ferric cations in volcanic glasses may provide information on the physico-chemical conditions prevailing at the magmatic stage as well as on the cooling conditions during...

Fe has long been known to play an important role in determining the properties of natural magmatic liquids and glasses [1]. The determination of the sites occupied by ferrous and ferric cations in volcanic glasses may provide information on the physico-chemical conditions prevailing at the magmatic stage as well as on the cooling conditions during...

The crystal structures of the title compounds are determined by single crystal XRD and Rietveld refinement of powder XRD data.

An original setting, combining a Cassegrain microscope and a UV-visible-near IR spectrophotometer, focusing the beam down to 50 µm diameter, has been used to get optical absorption spectra (OAS) of glass inclusions in minerals in the 330-2500 nm range. OAS of trachyandesite glass inclusions trapped in olivine, from the Yasur vulcano (Vanuatu arc) [...

An original setting, combining a Cassegrain microscope and a UV-visible-near IR spectrophotometer, focusing the beam down to 50 µm diameter, has been used to get optical absorption spectra (OAS) of glass inclusions in minerals in the 330 - 2500 nm range. OAS of trachyandesite glass inclusions trapped in olivine, from the Yasur vulcano (Vanuatu arc)...

Probing the local environment of low-Z elements such as oxygen is of great interest for understanding the atomic scale behavior in materials, but it requires experimental techniques allowing to work with versatile sample environments. In this paper, the local environment of lithium borate crystals is investigated using non-resonant inelastic X-ray...

Alkali lime silicate glasses containing 5 wt% of CoO were investigated by Co K-edge XANES and EXAFS and optical absorption spectroscopy. Our results reveal the presence of tetrahedral Co2+ connected with the glass network, with a IVCo–O–Si angle of 134°. Changing the alkali from K+ to Na+ induces an increase of the local disorder around Co2+, as sh...

Glasses can be formed through geological phenomena such as natural obsidians and tektites. Obsidians are iron bearing aluminosilicate glasses formed during volcanic events, mainly in the American Cordilleras ranges and in the Mediterranean basin. Tektites differ by the absence of OH/H2O and contain different alkaline and alkaline earth contents. Th...

Iron has long been known to play an important role in determining the properties of natural magmatic liquids. The determination of the sites occupied by ferrous and ferric cations in volcanic glasses may provide information on the physico-chemical conditions prevailing at the magmatic stage as well as on the cooling conditions of the magma. We disc...

Iron has long been known to play an important role in determining the properties of natural magmatic liquids. The determination of the sites occupied by ferrous and ferric cations in volcanic glasses may provide information on the physico-chemical conditions prevailing at the magmatic stage as well as on the cooling conditions of the magma. We disc...

The pathway for pyranose ring conformational transitions in both anomers of glucose has been studied using molecular mechanics calculations both in vacuum and in aqueous (SPC/E) solution. The pathway for the transition in vacuum from the 4C1 to the 1C4 chair conformations in α-D-glucopyranose was found to proceed over a low barrier between the 4E a...

The microstructure evolution of confined glucose solutions in silica gels can provide insights into the effect of sugars in protecting living organisms under extreme dehydration conditions. Aqueous silica gels with relatively small pore sizes capable of deforming under changes in environmental conditions are used here as a model system. In situ mon...

Molecular dynamics simulations of water confined in two hydrophilic cylindrical pores-PH and PL-that differ in their silanol surface concentration (7.6 and 3.0 nm(-2), respectively) have been performed at 300 K. A strong interaction of interfacial water molecules with the pore was systematically found and gives rise to a layering effect, a signific...

Glucose aqueous solutions confined in MCM-41 cylindrical pores of diameter 3.2 nm have been studied by molecular dynamics (MD) simulations and quasielastic neutron scattering (QENS). MD simulations reveal a strong preferential interaction of glucose molecules with the silica walls, which induces significant concentration gradients within the pore....

Mesoporous silica nanoparticles (MSN) were functionalised by aminofluorescein (AMF) with diethylenetriaminepentaacetic acid spacer molecules which provide free carboxylic groups for binding cell-specific ligands such as folate. AMF allowed the exploration of cellular uptake by HeLa cells using confocal microscopy and flow cytometry. The functionali...

Molecular dynamics computer simulations have been carried out on aqueous solutions of glucose at concentrations bracketing those previously measured with quasi-elastic neutron scattering (QENS), in order to investigate the motions and interactions of the sugar and water molecules. In addition, QENS measurements have been carried out on fructose sol...

The dynamics of trehalose molecules in aqueous solutions confined in silica gel have been studied by quasielastic neutron scattering (QENS). Small-angle neutron scattering measurements confirmed the absence of both sugar clustering and matrix deformation of the gels, indicating that the results obtained are representative of homogeneous trehalose s...

Even though the active role of sugar molecules is well known as stabilizer agent for cell membranes upon dehydration, the responsible process is still unidentified. Nevertheless, the great affinity existing between sugar and water molecules – evidenced by the important number of hydrogen bondings between these two species – seems to be the main...

Even though the active role of sugar molecules is well known as stabilizer agent for cell membranes upon dehydration, the responsible process is still unidentified. Nevertheless, the great affinity existing between sugar and water molecules – evidenced by the important number of hydrogen bondings between these two species – seems to be the main age...

Recent progress in the synthesis and applications of MCM-41 based mesoporous materials is reviewed. Since the independent discovery in the early 1990s by groups in the Japan and USA of the formation of mesostructured silica using surfactants as structure directing agents, a variety of alternative synthesis routes have been proposed. These include t...

Highly luminescent single colloidal silver nanoparticles under blue excitation were detected. The intense luminescence observed from the single particles is attributed to different emissive centers. Picosecond lifetimes of those single nano-objects have been measured. Comparison with colloidal particles emission formed in aqueous solution, using po...

Silica gels containing solutions of glucose in heavy water at different concentrations have been prepared by a sol-gel method. Dynamical studies with quasielastic neutron scattering, compared with previous results on bulk solutions, show that the dynamics of the glucose molecules are not appreciably affected by the confinement, even though the gels...

Nano-silver doped silica films were deposited on glass slides using a sol-gel process and heat-treated at different temperatures. The films were characterized by ultraviolet-visible spectroscopy, x-ray photoelectron spectroscopy XPS, atomic force microscopy AFM, Rutherford backscattering spectrometry RBS, and transmission electron microscopy for th...