Nanostructures à base de palladium : synthèse, caractérisations et étude de leurs interactions avec le dihydrogène : Applications dans la détection optique de fuite de H2

Le présent projet porte sur le développement d'une technique innovante pour la détection optique de fuites d'hydrogène. Dans ce but, les changements de propriétés plasmoniques, en présence d'hydrogène, de nanoparticules à base de Pd ont été exploités. Plus précisément, un système métal-isolant-métal précédemment développé pour la détection optique de l'hydrogène a été pris comme référence dans la conception de la structure des matériaux sélectionnés. Par conséquent, des nanoparticules avec des architectures de type coeur@coquille ont été synthétisées pour l'application ciblée. L'approche mise en œuvre dans ce projet comporte trois volets principaux. Dans un premier temps, les nanoparticules sélectionnées ont été synthétisées avec succès au moyen de voies chimiques en solution. Leurs propriétés optiques et structurelles ont également été analysées. Ensuite, pour mieux comprendre les mécanismes impliqués dans les processus de détection, une étude destinée à mieux comprendre les interactions entre les nanoparticules de palladium et l'hydrogène a été réalisée. En particulier, une étude thermodynamique du système palladium-hydrogène à l'échelle nanométrique a été réalisée. Pour y parvenir, une méthode expérimentale simple de construction de diagrammes de pression-composition-température caractérisant les interactions étudiées a été mise en œuvre. De plus, une analyse in situ de l'hydrogénation et de la déshydrogénation des nanoparticules de palladium par spectroscopie de perte d'énergie des électrons a également été réalisée. Ces expériences ont permis de mettre en évidence les étapes successives de formation et de décomposition de l'hydrure de palladium. Enfin, l'utilisation des nanoparticules synthétisées pour la détection optique de l'hydrogène a été évaluée.The present project is related to the development of an innovative optical technique for hydrogen leak detection. For this purpose, the monitoring of plasmonic properties of selected Pd-based nanoparticles in presence of hydrogen was considered. Specifically, a metal-insulator-metal system developed for optical detection of hydrogen was taken as reference in the structure design of the selected materials. Therefore, nanoparticles with core@shell architectures were synthesized for the targeted application. The approach implemented in this project consisted in three main steps. Initially, the selected nanoparticles were successfully synthesized by means of wet chemical routes. Their optical and structural properties were characterized. Then, to get more insights in the mechanisms involved in the sensing processes, a study intended to better understand the interactions between hydrogen and palladium nanoparticles was performed. Particularly, thermodynamic features of the palladium-hydrogen system at the nanoscale were probed. To achieve this, a simple experimental method for establishment of pressure-composition-temperature diagrams that characterize the studied interactions was implemented. In addition, an in-situ analysis of palladium nanoparticles hydrogenation and dehydrogenation by electron energy loss spectroscopy was also realized. These experiments allowed evidencing the successive steps in the palladium hydride formation and decomposition. Finally, the use of the synthesized nanoparticles for optical detection of hydrogen was evaluated

Recent Advances in Palladium Nanoparticles-Based Hydrogen Sensors for Leak Detection

International audienceAlong with the development of hydrogen as a sustainable energy carrier, it is imperative to develop very rapid and sensitive hydrogen leaks sensors due to the highly explosive and flammable character of this gas. For this purpose, palladium-based materials are being widely investigated by research teams because of the high affinity between this metal and hydrogen. Furthermore, nanostructured palladium may provide improved sensing performances compared to the use of bulk palladium. This arises from a higher effective surface available for interaction of palladium with the hydrogen gas molecules. Several works taking advantage of palladium nanostructures properties for hydrogen sensing applications have been published. This paper reviews the recent advances reported in the literature in this scope. The electrical and optical detection techniques, most common ones, are investigated and less common techniques such as gasochromic and surface wave acoustic sensors are also addressed. Here, the sensor performances are mostly evaluated by considering their response time and limit of detection

Au–Pd core–shell nanoparticle film for optical detection of hydrogen gas

International audienceHydrogen use, as a clean and almost infinite energy source, has an economic impact in many industries. The problem is that this gas cannot be used like any gas because of its explosiveness at 4% in the air, hence the need to know its concentration any time for security reasons. The permanent detection of hydrogen leaks is essential to monitor and to control the hydrogen concentration to prevent any possible risk. In our current research, we have developed hydrogen ultrasensitive sensors by depositing a thin film of Au-Pd core-shell nanoparticles (NPs) on a transparent glass substrate in order to detect hydrogen in its gaseous form. The colloidal Au-Pd core-shell NPs were synthesized according to a multi-reduction step method. The structural characterizations, the nature, and the density of Au-Pd core-shell NPs have been characterized by scanning electron microscopy and transmission electron microscopy. The morphology, size, and structure of Au-Pd core-shell NPs can be controlled under synthesis conditions. The size of the core-shell studied in this work is 13 nm for gold NP diameter and 0 nm-2.3 nm for palladium thicknesses. The physical properties of NPs, such as the optical absorbance response under hydrogen, strongly depend on the nature of the shell and the ratio between the core and the shell. At different hydrogen concentrations ranging from 1% to 4%, the optical response changes in the position of the surface plasmon resonance peak on the absorbance spectrum after the first loading/unloading hydrogen cycle

Au@Pd core-shell nanostructures: synthesis and related optical properties

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Post-synthetic functionalization and ligand exchange reactions in gold(i) phenylthiolate-based coordination polymers

SSCI-VIDE+CDFA+ADMInternational audienceGold thiolate coordination polymers (CPs) are anisotropic materials with 1D or 2D networks exhibiting a large palette of photoluminescence properties. In this paper, we show that, from both lamellar acid and ester, [Au(p-SPhCO2X)]n CPs (X = H, Me), it is possible to perform post-synthesis esterification or saponification reactions. Three new 2D phases with X = Na, K and Cs were isolated. In addition, ligand exchange reactions were carried out from 1D [Au(p-SPh)]n CP and 2D [Au(p-SPhCO2X)]n CPs (X = H, Me) and the transformations from 1D to 2D structures and vice versa point out a mechanism of dissolution and recrystallization that is governed by the nature of the ligands and the presence of weak interactions. The obtained compounds exhibit solid state and RT photoemission characteristic of their structure

Imaging Radial Distribution Functions of Complex Particles by Relayed Dynamic Nuclear Polarization

The physical properties of many modern multi-component materials are determined by their internal microstructure. Tools capable of characterizing complex nanoscale architectures in composite materials are, therefore, essential to design materials with targeted properties. Depending on the morphology and the composition, structures may be measured by laser diffraction, scattering methods, or by electron microscopy. However, it can be difficult to obtain contrast in materials where all the components are organic, which is typically the case for formulated pharmaceuticals, or multi-domain polymers. In nuclear magnetic resonance (NMR) spectroscopy, chemical shifts allow a clear distinction between organic components and can in principle provide the required chemical contrast. Here, we introduce a method to obtain radial images of the internal structure of multi-component particles from NMR measurements of the relay of nuclear hyperpolarization obtained from dynamic nuclear polarization. The method is demonstrated on two samples of hybrid core–shell particles composed of a core of polystyrene with a shell of mesostructured silica filled with the templating agent CTAB and is shown to yield accurate images of the core–shell structures with a nanometer resolution.LR

Imaging radial distribution functions of complex particles by relayed dynamic nuclear polarization

The physical properties of many modern multi-component materials are determined by their internal microstructure. Tools capable of characterizing complex nanoscale architectures in composite materials are, therefore, essential to design materials with targeted properties. Depending on the morphology and the composition, structures may be measured by laser diffraction, scattering methods, or by electron microscopy. However, it can be difficult to obtain contrast in materials where all the components are organic, which is typically the case for formulated pharmaceuticals, or multi-domain polymers. In nuclear magnetic resonance (NMR) spectroscopy, chemical shifts allow a clear distinction between organic components and can in principle provide the required chemical contrast. Here, we introduce a method to obtain radial images of the internal structure of multi-component particles from NMR measurements of the relay of nuclear hyperpolarization obtained from dynamic nuclear polarization. The method is demonstrated on two samples of hybrid core–shell particles composed of a core of polystyrene with a shell of mesostructured silica filled with the templating agent CTAB and is shown to yield accurate images of the core–shell structures with a nanometer resolution.Investments for the Future Programme IdEx Bordeaux-LAPHIABottom-up fabrication of nanostructured silicon-based materials with unprecedented optical propertie

Imaging Radial Distribution Functions of Complex Particles by Relayed Dynamic Nuclear Polarization

The physical properties of many modern multi-component materials are determined by their internal microstructure. Tools capable of characterizing complex nanoscale architectures in composite materials are, therefore, essential to design materials with targeted properties. Depending on the morphology and the composition, structures may be measured by laser diffraction, scattering methods, or by electron microscopy. However, it can be difficult to obtain contrast in materials where all the components are organic, which is typically the case for formulated pharmaceuticals, or multi-domain polymers. In nuclear magnetic resonance (NMR) spectroscopy, chemical shifts allow a clear distinction between organic components and can in principle provide the required chemical contrast. Here, we introduce a method to obtain radial images of the internal structure of multi-component particles from NMR measurements of the relay of nuclear hyperpolarization obtained from dynamic nuclear polarization. The method is demonstrated on two samples of hybrid core–shell particles composed of a core of polystyrene with a shell of mesostructured silica filled with the templating agent CTAB and is shown to yield accurate images of the core–shell structures with a nanometer resolution