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Pussacq T.,CNRS Laboratory of Catalysis and Solid State Chemistry | Kabbour H.,CNRS Laboratory of Catalysis and Solid State Chemistry | Colis S.,IPCMS | Vezin H.,CNRS Laboratory of Infrared and Raman Spectrochemistry | And 6 more authors.
Chemistry of Materials | Year: 2017

The reduction of the layered perovskites Ln2Ti2O7 (LnTO, with lanthanide Ln = La, Pr, or Nd) was studied with the aim of shifting the ultraviolet (UV) photocalytic activity for water splitting in the visible range by Ti3+ donor doping. For all phases, after reduction by CaH2, the absorbance is extended beyond the UV-visible region, giving rise to a gaplike edge in the mid-infrared at ∼0.4 eV with a dark coloration of the samples. When the precursor with Ln = La was reduced under a high-temperature H2 flow, we found a progressive nanotexturation down to 300 nm, which is responsible for a degree of Ti3+ segregation at the surface. Magnetic measurements, thermal analysis, and powder neutron diffraction reveal that the samples reduced by both routes have a similar amount of anion vacancy with δ = 0.27 (in La2Ti2O7−δ). It represents a limited topotactic reduction stage, prior to the reconstructive reduction into La5Ti3.8+ 5O17 observed under more severe reducing conditions. For the sample reduced by CaH2, a minor amount of hydride appears to be incorporated (∼0.02 H per FU), with Ti3+···H- bonding observed by hyperfine sublevel correlation spectroscopy electron paramagnetic resonance and density functional theory calculations. Preliminary electrocatalysis tests show a promising anodic activity for water splitting hydrogen evolution with a voltage onset as low as 0.6 V versus the reversible hydrogen electrode. © 2017 American Chemical Society.

Cabanetos C.,University of Nantes | Bentoumi W.,Ecole Normale Superieure de Lyon | Silvestre V.,University of Nantes | Blart E.,University of Nantes | And 9 more authors.
Chemistry of Materials | Year: 2012

We report herein the synthesis, the functionalization, and the successful radical polymerization of very nonlinear optical (NLO) active push-pull polyene chromophores (CPO). Second, the thermal Huisgen cyclo-addition cross-linking reaction was implemented, and it proved to be fully compatible with a polyene-based push-pull chromophore. Toward this goal, PMMA-co-CPO-3 and two cross-linkable polymers (PCC1-CPO-3 and PCC2-CPO-3) were first prepared and characterized by a modified Teng and Man technique performed in transmission. These first series of polymers were not compatible with the applied poling conditions because an irreversible film degradation was systematically observed at a temperature significantly lower than the cross-linking temperature. Consequently, a second series of polymers was prepared, in which the cross-linking temperature was decreased by functionalizing acetylenic moieties with ester electron withdrawing groups, which decrease the activation energy of the thermal Huisgen cyclo-addition. These new polymers were stable until the cross-linking reaction, and they exhibit bulk electro-optic coefficients (r 33) until 41 pm/V at 1.5 μm. Furthermore, it was shown that the Huisgen cross-linking reaction is compatible with such push-pull polyene-based chromophores, and it systematically enhances the stability of the electro-optic activity because chromophore orientation was maintained up to 96 °C against 70 °C for the same uncross-linked polymer. © 2012 American Chemical Society.

PubMed | University of Strasbourg and IPCMS
Type: | Journal: Langmuir : the ACS journal of surfaces and colloids | Year: 2016

Following our previous contribution ( Gromer, A. et al. Langmuir 2015 , 31 , 10983 - 10994 ) presenting a new simulation tool devoted to particle distributions in drying latex films, this Article describes the prediction of surfactant concentration profiles in the vertical direction during the complete film formation process. The simulation is inspired by cellular automata and equations by Routh and co-workers. It includes effects that were not considered before: surfactant convection by water and surfactant desorption upon particle deformation. It is based on five parameters describing the nature of the polymer/surfactant system and on film formation conditions. In particular, the viscoelastic properties of the polymer were taken into account through the parameter introduced by Routh and Russel. Results show the importance of convection by water and the influence of the particular deformation mechanism on the final surfactant distribution. Excesses or depletions can be predicted either on the surface or on the substrate sides, in qualitative agreement with the numerous existing experimental studies. The complex interplay between parameters governing surfactant distributions makes the results unpredictable without the help of such a simulation tool. Therefore, it should be of interest to both industrial and academic scientists.

PubMed | University of Strasbourg and IPCMS
Type: Journal Article | Journal: Langmuir : the ACS journal of surfaces and colloids | Year: 2015

This paper presents a simulation tool applied to latex film formation by drying, a hybrid between a classical numerical resolution method using finite differences and cellular automata, and making use of object-oriented programming. It consists of dividing real space into cells and applying local physical laws to simulate the exchange of matter between neighboring cells. In a first step, the simulation was applied to the simple case of vertical drying of a latex containing only one population of monodisperse particles and water. Our results show how the distribution of latex particles evolves through the different drying stages due to a combination of diffusion, convection, and particle deformation. While repulsive interactions between the particles tend to favor homogeneous distributions in the first drying stage, concentration gradients that develop in opposite ways can be observed depending on the drying regime. The distributions, calculated in various cases, reproduce and extend several theoretical results and are in qualitative agreement with some experimental findings.

Dayen J.-F.,IPCMS | Faramarzi V.,IPCMS | Pauly M.,IPCMS | Kemp N.T.,IPCMS | And 5 more authors.
Nanotechnology | Year: 2010

We present a simple and versatile patterning procedure for the reliable and reproducible fabrication of high aspect ratio (104) electrical interconnects that have separation distances down to 20 nm and lengths of several hundreds of microns. The process uses standard optical lithography techniques and allows parallel processing of many junctions, making it easily scalable and industrially relevant. We demonstrate the suitability of these nanotrenches as electrical interconnects for addressing micro and nanoparticles by realizing several circuits with integrated species. Furthermore, low impedance metal-metal low contacts are shown to be obtained when trapping a single metal-coated microsphere in the gap, emphasizing the intrinsic good electrical conductivity of the interconnects, even though a wet process is used. Highly resistive magnetite-based nanoparticles networks also demonstrate the advantage of the high aspect ratio of the nanotrenches for providing access to electrical properties of highly resistive materials, with leakage current levels below 1 pA. © 2010 IOP Publishing Ltd.

Le Guyader L.,Paul Scherrer Institute | Kleibert A.,Paul Scherrer Institute | Nolting F.,Paul Scherrer Institute | Joly L.,IPCMS | And 5 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

Ultrafast control of a ferromagnet (FM) via exchange coupling with an antiferromagnet (AFM) is demonstrated in a Co/SmFeO3 heterostructure. Employing time-resolved photoemission electron microscopy combined with x-ray magnetic circular dichroism, a sub-100-ps change of the Co spins orientation by up to 10 driven by the ultrafast heating of the SmFeO3 orthoferrite substrate through its spin reorientation phase transition is revealed. Numerical modeling of the ultrafast-laser-induced heat profile in the heterostructure, and the subsequent coupled spins dynamics and equilibration of the spin systems suggest that the localized laser-induced spin reorientation is hindered compared with the static case. Moreover, numerical simulations show that a relatively small Co/SmFeO3 exchange interaction could be sufficient to induce a complete and fast spin reorientation transition (SRT). © 2013 American Physical Society.

Morandi O.,French Institute for Research in Computer Science and Automation | Hervieux P.-A.,IPCMS | Manfredi G.,IPCMS
Nuovo Cimento della Societa Italiana di Fisica C | Year: 2010

A straightforward limit procedure is developed for evaluating the expectation value of a generic many-particle operator defined in the Abrikosov Coleman's pseudo-fermion formalism. It can be useful for the study of nonequilib rium Kondo-type problems. © Società Italiana di Fisica.

Wezka K.,University of Bath | Bouzid A.,IPCMS | Pizzey K.J.,University of Bath | Salmon P.S.,University of Bath | And 9 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

The evolution in structure of the prototypical network-forming glass GeSe2 is investigated at pressures up to ∼16 GPa by using a combination of neutron diffraction and first-principles molecular dynamics. The neutron diffraction work at pressures ≤8.2 GPa employed the method of isotope substitution, and the molecular dynamics simulations were performed with two different exchange-correlation functionals, the Becke-Lee-Yang-Parr (BLYP) and the hybrid Heyd-Scuseria-Ernzerhof HSE06. The results show density-driven structural transformations that differ substantially from those observed in common oxide glasses such as SiO2 and GeO2. Edge-sharing tetrahedra persist as important structural motifs until a threshold pressure of ∼8.5 GPa is attained, whereupon a mediating role is found for homopolar bonds in the appearance of higher coordinated Ge-centered polyhedra. These mechanisms of network transformation are likely to be generic for the class of glass-forming materials where homopolar bonds and fragility-promoting edge-sharing motifs are prevalent in the ambient-pressure network. © 2014 American Physical Society.

Aye M.,Aix - Marseille University | Di Giorgio C.,Aix - Marseille University | Berque-Bestel I.,French Institute of Health and Medical Research | Aime A.,French Institute of Health and Medical Research | And 4 more authors.
Mutation Research - Genetic Toxicology and Environmental Mutagenesis | Year: 2013

We proposed to evaluate the genotoxicity and mutagenicity of a new quantum dots (QDs) nanoplatform (QDsN), consisting of CdSe/ZnS core-shell QDs encapsulated by a natural fusogenic lipid (1,2-di-oleoyl-sn-glycero-3-phosphocholine (DOPC)) and functionalized by a nucleolipid N-[5'-(2',3'-di-oleoyl) uridine]-N',N',N'-trimethylammoniumtosylate (DOTAU). This QDs nanoplatform may represent a new therapeutic tool for the diagnosis and treatment of human cancers. The genotoxic, mutagenic and clastogenic effects of QDsN were compared to those of cadmium chloride (CdCl2). Three assays were used: (1) the Salmonella/microsome assay with four tester strains, (2) the comet assay and (3) the micronucleus test on CHO cells. The contribution of simulated sunlight was studied in the three assays while oxidative events were only explored in the comet assay in aliquots pretreated with the antioxidant l-ergothioneine. We found that QDsN could enter CHO-K1 cells and accumulate in cytoplasmic vesicles. It was not mutagenic in the Salmonella/mutagenicity test whereas CdCl2 was weakly positive. In the dark, both the QDsN and CdCl2 similarly induced dose-dependent increases in single-strand breaks and micronuclei. Exposure to simulated sunlight significantly potentiated the genotoxic activities of both QDsN and CdCl2, but did not significantly increase micronucleus frequencies. l-Ergothioneine significantly reduced but did not completely suppress the DNA-damaging activity of QDsN and CdCl2. The present results clearly point to the genotoxic properties and the risk of long-term adverse effects of such a nanoplatform if used for human anticancer therapy and diagnosis in the future. © 2012.

PubMed | IPCMS
Type: Journal Article | Journal: Nanotechnology | Year: 2016

We observe, as a function of temperature, a second order magnetic phase transition in nanometric Cr2O3 clusters that are epitaxially embedded in an insulating MgO matrix. They are investigated through their tunnel magneto-resistance signature, the MgO layer being used as a tunnel barrier. We infer the small magnetic dipoles carried by the Cr2O3 clusters and provide evidence of a magnetic phase transition at low temperature in those clusters: they evolve from an anti ferromagnetic state, with zero net moment close to 0 K, to a weak ferromagnetic state that saturates above about 10 K. The influence of magneto-electric effects on the weak ferromagnetic phase is also striking: the second order transition temperature turns out to be linearly dependent on the applied electric field.

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