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Several types of Quantum Dots (QDs) (CdS, CdSe and InP, as well as core-shell QDs such as type I InP-ZnS, quasi type-II CdSe-CdS and inverse type-I CdS-CdSe) were considered for generating α-aminoalkyl free radicals. The feasibility of the oxidation of the N-aryl amines and the generation of the desired radical was evidenced experimentally by quenching of the photoluminescence of the QDs and by testing a vinylation reaction using an alkenylsulfone radical trap. The QDs were tested in a radical [3+3]-annulation reaction giving access to tropane skeletons and that requires the completion of two consecutive catalytic cycles. Several QDs such as CdS core, CdSe core and inverted type I CdS-CdSe core-shell proved to be efficient photocatalysts for this reaction. Interestingly, the addition of a second shorter chain ligand to the QDs appeared to be essential to complete the second catalytic cycle and to obtain the desired bicyclic tropane derivatives. Finally, the scope of the [3+3]-annulation reaction was explored for the best performing QDs and isolated yields that compares well with classical iridium photocatalysis were obtained.

In piezoelectric inertia motors, friction is not a synonymous of energy loss but is the source of motion. Their performances are thus prone to wear and friction coefficient variation. To address these issues, this paper first aims at improving the understanding of tribological solicitations by means of a dedicated in situ tribotesting while exploiting the 3rd body flow framework. Beyond the introduction of transparent glass pins to see inside the contact in operation, the key of this work is to consider both the mechanism effect and the friction couple. As a result, a solution has been proposed to multiply the motor lifetime by more than ten while keeping stable speed performances, and, above all, without multiplying tests with numerous friction materials.

The discrete circle map is the archetypical example of a driven periodic system, showing a complex resonance structure under a change of the forcing frequency known as the devil's staircase. Adler's equation can be seen as the direct continuous equivalent of the circle map, describing locking effects in periodic systems with continuous forcing. This type of locking produces a single fundamental resonance tongue without higher-order resonances, and a devil's staircase is not observed. We show that, with harmonically modulated forcing, nonlinear oscillations close to a Hopf bifurcation generically reproduce the devil's staircase even in the continuous case. Experimental results on a semiconductor laser driven by a modulated optical signal show excellent agreement with our theoretical predictions. The locking appears as a modulation of the oscillation amplitude as well as the angular oscillation frequency. Our results show that by proper implementation of an external drive, additional regions of stable frequency locking can be introduced in systems which originally show only a single Adler-type resonance tongue. The induced resonances can be precisely controlled via the modulation parameters.

International audience; Herein, we demonstrate the potential of ultrabright fluorescent silica-coated organic nanocrystals for two-photon in vivo imaging. These unique nanoparticles (NPs) containing a crystalline core of small push-pull dipolar dye are specifically designed to exhibit two-photon absorption for 2 fluorescence imaging. The NPs can be easily functionalized using click chemistry in pure water, with preservation of the organic core. A novel small-volume DLS technique was used to evaluate the effect of PEGylation on the colloidal stability of the NPs in complex media containing salts and proteins, mimicking the composition of blood serum. The potential of these bright red-emitting NPs for two-photon fluorescence imaging is demonstrated both in vitro and in vivo.

Background French Guiana, a French overseas department located in South America between Brazil and Surinam, is the only European territory geographically located in the Amazonian forest complex and is considered endemic for yellow fever (YF). In the context of the emergent threat of YF in Latin America, we conducted a large household cross-sectional survey from June to October 2017 to estimate vaccination coverage in the population and to determine associations with sociodemographic and geographical characteristics. Methodology/Principal findings In total, 1,415 households and 2,697 individuals were included from the 22 municipalities of French Guiana. YF vaccination coverage was estimated at 95.0% (95% CI: 93.4–96.2) in the entire territory but was spatially heterogeneous, with the lowest levels estimated in the western part of the territory along the Surinamese cross-border region, particularly in children under 16 years who were not enrolled in school, immigrant adults and disadvantaged populations with low socioeconomic indexes. Conclusions/Significance Despite the good vaccination coverage against YF in the general population of French Guiana resulting from the compulsory nature of YF vaccination for residents and travelers, there is an urgent need to improve vaccination coverage in vulnerable populations living in the northwestern part of the territory to limit the risk of transmission in the context of the emerging YF threat in South America. Despite the relative rarity of YF and the significant number of infectious and tropical diseases in French Guiana, clinicians should adopt a high index of suspicion for YF, particularly in vulnerable and at-risk populations., Author summary Yellow fever (YF) is the most severe arbovirus to circulate in the Americas. French Guiana, a French overseas department located in South America between Brazil and Surinam, is the only European territory geographically located in the Amazonian forest complex and is considered endemic for YF. We conducted a large general population survey from June to October 2017 to estimate vaccination coverage in the population and to identify target vulnerable populations for catch-up vaccination strategies. In total, 1,415 households and 2,697 individuals were included from the 22 municipalities of French Guiana. YF vaccination coverage was estimated at 95.0% (95% CI: 93.4–96.2) in the entire territory but was spatially heterogeneous, with the lowest levels estimated in the western part of the territory along the Surinamese cross-border region, particularly in children under 16 years who were not enrolled in school, immigrant adults and disadvantaged groups of populations with low socioeconomic indexes. Our findings showed that vaccination campaigns should be prioritized and adapted to improve vaccination coverage among vulnerable populations living in the northwestern part of the territory to limit the risk of transmission in the context of the emerging YF threat in South America. Despite the relative rarity of YF and the significant number of infectious and tropical diseases in French Guiana, clinicians should adopt a high index of suspicion for YF, particularly in vulnerable and at-risk populations.

A deeply etched pit reflector is presented in this paper. The pit is not depth sensitive and has a comparable reflection and loss to a slot. Moreover, a two-section 750 ${\mu }{\text {m}}$ laser cavity based on the pits is demonstrated. The laser achieved a side-mode suppression ratio of 40 dB, a linewidth of 280 KHz, and tuning across 40 nm.

International audience; We have developed a bright optical setup especially optimized for surface enhanced Raman scattering correlation spectroscopy. We show that the brightness of the experiment combined with the correlation approach permits in situ access to the size and shape of the SERS-active aggregates in solution despite a very weak SERS signal of the adsorbed molecules. As a result we demonstrate that dimers and larger SERS-active aggregates can be identified through the temporal fluctuations of the SERS signal of only a few hundred of adsorbed molecules i.e at zeptomole adsorbate concentrations. Monomers covered by a monolayer of MBA were also identified. These results open a way for single nanoparticle sensing, for single molecule SERS-active aggregate characterization or for quantitative monitoring of functionalization processes on metallic objects.

Silicon carbide (SiC) power devices are the only commercialized components to run at high voltage and high temperature. Normally on junction field-effect transistors (JFETs) have lower on-state resistance and lower output capacitance than other SiC switches, which reduces conduction and switching losses. However, normally on power devices induce a short-circuit in voltage-fed inverters (VFI) when the gate driver is not powered prior to the bus supply. This is a power-up limitation that has not received much attention in the literature, especially for safety systems that can be used in an integrated circuit capable of running at elevated temperature. This paper describes an original solution based on SiC JFETs to secure the inverter operation at power-up without gate driver supply for the SiC JFETs. The reliability test of the protection circuit and his impact on the ageing of the JFET of the VFI are also presented. The safety system is capable of running in elevated ambient temperatures. Experimental results have been carried out in a 540 V, 10 A inverter and at ambient temperatures from 27 to 200 °C.

The preparation of a single phase LaNiO 2 by controlled H 2 reduction of the perovskite LaNiO 3 is reported. The different steps of the synthesis are detailed. The structural characterization is made by X-ray diffraction (XRD) and neutron powder diffraction (NPD) and discussed; the derived crystal structure is the infinite-layer CaCuO 2 . Both XRD and NPD patterns are characterized by anisotropic shape broadening originating from size effect linked to the reduction process. From NPD, the LaNiO 2 powder is composed of platelet-like crystallites having an average thickness equal to 20 nm along the [001] direction. A modulation of the neutron diffraction background is observed and discussed in connection to the reduction process.

International audience; The slow flocculation of silver nanoparticle (NP) aggregates obtained through p-mercaptobenzoic acid (MBA) linker molecules was analyzed by surface-enhanced Raman scattering (SERS) correlation spectroscopy. We demonstrate that our experimental setup, together with the quantitative exploitation of the SERS intensity autocorrelation functions (ACFs) measured from the MBA molecules, enables to determine quantitatively and in situ the size of the SERS active clusters. Moreover, we show that it is possible to characterize the different states of aggregation during cluster formation simply by measuring the size of such silver aggregates. This has been accurately performed for both larger-size aggregates down to very few NPs only. We finally show that our approach is also sensitive to detect and analyze the SERS signal obtained from MBA molecules sitting on nonaggregated NPs. These experiments pave the way to the in situ characterization of functionalized metal NPs as well as the in situ monitoring of NP aggregation, in conjunction with deriving the optical properties of the as-formed clusters.

En 2011, l’Université Joseph Fourier (UJF), s'appuyant sur la force de la recherche interdisciplinaire des laboratoires grenoblois dans les Nanosciences et Nanotechnologies, a ouvert deux majeures : un M1 « Physique fondamentale et Nanosciences » et un M1 « Chimie et Nanosciences ». Dans ce cadre, des Travaux Pratiques interdisciplinaires et interplateformes ont été mis en place afin d’illustrer de manière concrète la convergence de la physique, de la chimie et de la biologie à l’échelle micro/nanométrique qui s’appuie sur les micro et nanotechnologies. Cet article décrit en détail ces TP et expose leur intérêt pédagogique pour la formation des étudiants ainsi que pour des enseignants-chercheurs.

10 pages; International audience; Turning off a SiC VJFET from INFINEON requires to apply a gate-to-source voltage comprised between the JFET gate threshold voltage and the punch-through voltage. Unfortunately, for applications operating over a large temperature range, these two limits vary with the temperature and reduce the useful blocking gate-to-source voltage range as the temperature rises. So, the punch-through temperature dependence is a very important feature for applications operating in a wide temperature range like aeronautic applications. This paper addresses the analysis and modeling of the punch-through phenomenon and its dependence to the temperature. The proposed model gives a good agreement with the experimental data.

International audience; SiC JFETs are experimentally tested to verify their robustness against Lightning induced strokes. The experimental set-up is fully described. A lightning surge generator is built and a SiC JFET is stressed. The full thermal response of the SiC JFET internal temperature is obtained from a specific temperature estimation technique at different time steps during the surge test. This short time thermal response is compared and validated by a conventional 1-D thermal model. This work shows that for a moderate lightning stroke, according to standards [1], the JFET temperature rise is less than 60°C, which is acceptable in most circumstances.

International audience; The aim of this paper is to investigate the ability of a vertical structure JFET to operate in an inverter leg without any internal or external diode. The JFET is characterized to show the reverse conduction capability while the gate-to-source voltage is lower than the threshold voltage. An inverter leg is tested at 540 V /5 A and 50 kHz. A specific test board is implemented to assess a safe operation over a period of time.

International audience; We present the first non-resonant and non-enhanced Raman correlation spectroscopy experiments. They are conducted on a confocal microscope combined with a Raman spectrometer. The thermal fluctuations of the Raman intensities scattered by dispersions of polystyrene particles of sub-micrometric diameters are measured and analysed by deriving the autocorrelation functions (ACFs) of the intensities. We show that for particles of diameter down to 200 nm, RCS measurements are successfully obtained in spite of the absence of any source of amplification of the Raman signal. For particles of diameter ranging from 200 to 750 nm, the ACFs present a time-decay behaviour in accordance with the model of free Brownian particles. For particles of 1000 nm in diameter, the AFCs present a different behaviour with a much smaller characteristic time. This results from the dynamics of a single-Brownian particle trapped in the confocal volume by the optical forces of the focus spot.

International audience; The sol-gel chemistry combined to a spray-drying process allowed us to control the formation of original hybrid core-shell nanoparticles constituted by molecular nanocrystals of rubrene embedded in biocompatible silicate spheres. With a good management of all the physical (gas flows, temperatures) and chemical (dye, solvent and alkoxide natures, concentrations, and hydrolysis and condensation conditions) parameters, we optimized a one-step and self-assembly process allowing to obtain nanoparticles exhibiting promising optical properties such as highly fluorescent labels (two-photon excitation) for medical imaging. Moreover, the presence of Si-OH functions on the silicate shell surface make easy to functionalize these fluorescent nanoparticles by grafting biomolecules for targeting properties. The confined nucleation and growth of rubrene nanocrystals in sol-gel silicate spheres during their drying in the air laminar flows, prevents any phase segregation or particle coalescence and stabilizes mechanically and chemically the organic cores. The first particle sizes obtained in these first experiments are ranging between 80 and 600 nm, but lower diameters will be easily prepared by increasing the solvent amount. Transmission electron microscopy was used to characterize the rubrene organic cores. The electron diffraction patterns performed at 100 K, under low-dose illumination to avoid amorphization of the samples during electron irradiation, have shown the good crystallinity of the NP rubrene cores that seem to be constituted by single rubrene nanocrystals. Finally, optical confocal microscopy, used in reflection and fluorescence modes, showed that all the core-shell particles are strongly fluorescent. This high fluorescence intensity arises from the high molecule numbers of rubrene nanocrystals, which enhance the absorption and emission cross sections.

The paper describes an integrated luminometer able to perform fluorescence (FL), room temperature phosphorescence (RTP) and chemiluminescence (CL) measurements on seawater samples. The technical details of the instrumentation are presented together with flow injection (FI) manifolds for the determination of cadmium and zinc (by FL), lead (RTP) and cobalt (CL). The analytical figures of merit are given for each manifold and results are presented for the determination of the four trace metals in seawater reference materials (NASS-5, SLEW-2) and Scheldt estuarine water samples.

This work has allowed the synthesis of hybrid nanoparticles composed by organic crystal cores embedded in organosilicate shells for the development of in vivo imaging applications(two-photon fluorescence microscopy). The synthesis of these nanoparticles has been adapted with different types of organic dyes. The composition of the silicate shell can also be modulated in order to modify the properties of dispersion in aqueous solution, the surface charge of particles or chemical functions present at the surface. Due to the dissolution of organic cores in organic solvents, different strategies of functionalization were developed in aqueous media to enhance the furtivity of these nanoparticles in vivo. These methods have led to the circulation of the nanoparticles into the bloodstream of mice. However, the circulation lifetime of these nanoparticles is short. New strategies of functionalization (click chemistry) should help in the future to extend this circulation time for the possible development of these new fluorescent tracers., Durant ce travail, la synthèse de nanoparticules hybrides composées d'un coeur organique cristallin fluorescent enrobé d'une coquille silicatée a été optimisée dans l'optique du développement d'un nouveau type de traceurs très brillants pour l'imagerie médicale (microscopie de fluorescence excitée à deux photons). La préparation des nanoparticules a pu être adaptée à différents types de fluorophores organiques. La composition de la coquille organosilicatée peut elle aussi être modulée afin de modifier les propriétés de dispersion en solution aqueuse, la charge de surface des particules ou les fonctions chimiques de surface. Le coeur organique de ces particules se dissolvant dans les solvants organiques, différentes stratégies de fonctionnalisation en milieu aqueux ont été réalisées afin d'augmenter la furtivité de ces objets in vivo. Ces différentes méthodes ont permis de faire circuler les nanoparticules dans le flux sanguins de souris. La durée de vie de circulation de ces particules restant cependant courte, de nouvelles stratégies de fonctionnalisation (chimie click) devraient permettre à l'avenir d'allonger ce temps de circulation.