Colloidal Gold Nanostructures for Plasmonics

International audienceGold nanoparticles (Au-NPs) of high crystalline quality can now be readily synthesized in large quantities thanks to significant advances in colloidal chemistry over the past decade. Assembly of such NPs leads to the appearance of new properties, still relatively poorly explored, and is therefore particularly promising for production of cost-effective devices. Our research activities concentrate on the synthesis and assembly of gold NPs and aims at providing appropriate materials for researchers working in the various fields of plasmonics (1,2,3). Over the past years, we have been developed an expertise in the synthesis of NPs with tunable sizes and shapes, such as spheres, rods, octahedra, cubes, triangles and also micro-particles. Some of them are very promising and produced only in very few laboratories worl-wide, especially in Asia. For example, thick triangles are of particular interest for ultrasensi-tive sensing and can assemble in the edge-to-edge fashion or through face to face interactions (fig.). Microplatelets (hexagonal or triangular) are very attractive due to their large atomically flat facets and can form ordered 1D-columnar aggregates. In the literature, 3D-arrays of NPs are currently related to SERS applications. Here, we report the spontaneous self-assembly of gold NPs by simply evaporating concentrated solutions on non-patterned sub-strates. The degree of reproducibility of this method, the maximum size of the perfectly organized area and the key parameters related to a controlled-deposition are presented. We are looking for collaborations to study the properties of these unusual assemblies

Gold Nanoparticles for Plasmonics and Medicine

International audienceGold-bioconjugates are studied worldwide and promising for new technologies for health. In the long term, biodegradable gold na-noparticles (NPs) are expected to have a large impact on diagnosis through the development of new contrast agents for imaging or new ultra-sensitive sensors. Gold-NPs have a high potential as contrast agents for several bioimaging modalities such as computed tomography, pho-toacoustic imaging, dark field scattering, multi-photon luminescence, high frequency ultra-sound, quantitative phase contrast. New therapies and surgeries will develop because these gold-nano are also able to generate Reactive Oxygen Species (ROS) and heat. Our research activities concentrate on the synthesis and assembly of gold nanoparticles of high quality to provide original materials for plasmonics since 2008. The irradiation of gold NPs by short laser pulses sets off a cascade of complex transient phenomena. Following this irradiation, one observe exaltation and confinement of the incident light at the surface of the NP but also singlet oxygen generation and ROS through the injection of hot electrons (or hot holes) to a nearby molecule. In short, gold na-noparticles are nanosources of light, heat and hot carriers and the morphology of the NP is a key point for these three characteristics because competitive relaxation processes depend on the size, shape and aspect ratio of NP. We use colloidal chemistry to synthesize gold nanoparticles of controlled shape and size. The figure illustrates some of the gold NPs we propose. Contrary to spherical and rod-shaped NPs that are commercially-available, other shapes such as cubes, triangles .. and plates with tunable sizes are only produced in our lab and in few laboratories worldwide. In literature, triangular-gold nanoplates are already used for ultrasensitive sensing, and the construction of original plasmon-based optical devices. The recent discovery of a third and fourth biological transparency windows centered respectively at 1.8µm and 2.2µm and the recent commercialization of new NIR-lasers make gold-nanoplates attractive for biomedicine in this still unexplored spectral domain. The synthesis of highly uniform shapes relies on trial and error procedure because it is very hard to predict the right recipe and additional purification steps are also often required. In the future, we are eager to widen the application range of these NPs to medicine through new collaborations either with biochemists for appropriate biofunctionalization, biophysicists for imaging and physicians for therapy. As a first step towards this objective, we are developing recipes to produce Au@SiO 2 core-shell NP while waiting for precise specifications. Figure 1: illustration of some of the monodis-perse gold particles (nano-and micro-) and gold hybrids (Au@SiO2) that have been synthesized , with tunable sizes and thicknesses

Synthesis of Monodisperse Gold Nanoparticles for Plasmonics

International audienceOur research activities concentrate on the synthesis and assembly of gold nanoparticles for plasmonics that is a rapidly growing discipline at the interface of physics, chemistry and biology with promising applications. We use a seed-mediated growth method of colloidal chemistry to synthesize gold nano-and micro-particles of controlled shape and size. This morphology control provides a fine tuning of the plasmon resonance wavelength and of the local field enhancement factor. Compared to top-down materials, these gold particles of high crystalline quality offer better surface-confinement of the electromagnetic field. The figure illustrates some of the monodis-perse gold NPs and gold nanohybrids we have been synthesized. Contrary to spherical and rod-shaped NPs that are commercially-available, other shapes such as nanocubes, na-notriangles and micro-plates with tunable sizes are only produced in our lab and in few laboratories worlwide, mainly in Asia. Triangles are of particular interest for ultrasensitive sensing, and plates (hexagonal or triangular) are very attractive for the construction of original plasmon-based optical devices due to their large atomically flat facets. At the present time, the synthesis of highly uniform triangles and plates still required purification steps that render them difficult to produce. Our research is made in collaboration with various research teams expert in the different field of plasmonics and aims at providing appropriate materials to study enhanced-photochemistry, enhanced-spectroscopy and nanosources of light. In the future, we are eager to widen the application range of these NPs to sensors and metamaterials through new expected collaborations

Improving/Boosting perovskite solar cells performance by using high quality TiO2/graphene-based nanocomposites as electron transport layer

International audienceIn the context of energy transition, development of efficient and cost-effective solar cells is a major objective to establish an optimal energy mix. The 3 rd generation of photovoltaic cells emerged to develop high efficient and low-cost cells combining the use of abundant materials and easy processes. Among them, photovoltaic cells based on perovskite materials demonstrated several significant advances with power conversion efficiencies up to 22% [1][2]. Nevertheless, efforts remain to be performed to improve the charge generation and collection of this kind of cell. Titanium dioxide mesoporous layer, while remaining an important component for perovskite structuration and electron transport in high efficiency devices, can indeed still promote charge trapping and recombination. As carbon nanostructures are good electron transporters, the use of TiO2/graphene nanocomposites seems to be a relevant strategy to reduce recombination phenomena and thus improve electron collection [3]. To achieve high quality of nanocomposites presenting well-controlled physical properties suitable for efficient and stable solar cells, we use the singular technique of laser pyrolysis, which enables to synthetize nanoparticles in a single step with a continuous flow. Attention is payed to the materials properties and their role and effect within solar cells. Tests were conducted with a MAPI-Cl perovskite deposited in a single-step following a reported procedure [4]. Our first results show a better electron injection efficiency from the perovskite to the mesoporous TiO2 layer with graphene, observed through steady-state photoluminescence spectroscopy. This tendency has been reinforced by devices performance that show larger photocurrents and smaller series resistance under standard illumination. More generally an increase in power conversion efficiency from 14.1 % to 15.1 % for these devices is reached for perovskite solar cells containing graphene in the mesoporous layer, demonstrating the benefit of the laser pyrolysis process for the production of high quality electron transport layer

Analysis of cellular responses of macrophages to zinc ions and zinc oxide nanoparticles: a combined targeted and proteomic approach

Two different zinc oxide nanoparticles, as well as zinc ions, are used to study the cellular responses of the RAW 264 macrophage cell line. A proteomic screen is used to provide a wide view of the molecular effects of zinc, and the most prominent results are cross-validated by targeted studies. Furthermore, the alteration of important macrophage functions (e.g. phagocytosis) by zinc is also investigated. The intracellular dissolution/uptake of zinc is also studied to further characterize zinc toxicity. Zinc oxide nanoparticles dissolve readily in the cells, leading to high intracellular zinc concentrations, mostly as protein-bound zinc. The proteomic screen reveals a rather weak response in the oxidative stress response pathway, but a strong response both in the central metabolism and in the proteasomal protein degradation pathway. Targeted experiments confirm that carbohydrate catabolism and proteasome are critical determinants of sensitivity to zinc, which also induces DNA damage. Conversely, glutathione levels and phagocytosis appear unaffected at moderately toxic zinc concentrations

Molecular responses of mouse macrophages to copper and copper oxide nanoparticles inferred from proteomic analyses

The molecular responses of macrophages to copper-based nanoparticles have been investigated via a combination of proteomic and biochemical approaches, using the RAW264.7 cell line as a model. Both metallic copper and copper oxide nanoparticles have been tested, with copper ion and zirconium oxide nanoparticles used as controls. Proteomic analysis highlighted changes in proteins implicated in oxidative stress responses (superoxide dismutases and peroxiredoxins), glutathione biosynthesis, the actomyosin cytoskeleton, and mitochondrial proteins (especially oxidative phosphorylation complex subunits). Validation studies employing functional analyses showed that the increases in glutathione biosynthesis and in mitochondrial complexes observed in the proteomic screen were critical to cell survival upon stress with copper-based nanoparticles; pharmacological inhibition of these two pathways enhanced cell vulnerability to copper-based nanoparticles, but not to copper ions. Furthermore, functional analyses using primary macrophages derived from bone marrow showed a decrease in reduced glutathione levels, a decrease in the mitochondrial transmembrane potential, and inhibition of phagocytosis and of lipopolysaccharide-induced nitric oxide production. However, only a fraction of these effects could be obtained with copper ions. In conclusion, this study showed that macrophage functions are significantly altered by copper-based nanoparticles. Also highlighted are the cellular pathways modulated by cells for survival and the exemplified cross-toxicities that can occur between copper-based nanoparticles and pharmacological agents

Usefulness of Tc-99m Sestamibi studies for monitoring response to therapy in patients with high grade gliomas: a preliminary study

Congrès sous l’égide de la Société Française de Génie Biologique et Médical (SFGBM).National audienceEarly and late Sestamibi studies were acquired in addition to conventional MRI protocol in 14 patients with high-grade gliomas to monitor an antiangiogenic treatment. Global and local indices were deduced from these SPECT studies and were compared with progression free survival (PFS) and overall survival (OS). Variations of intensity in late studies were not correlated with PFS, but were related to OS. This suggests the possible role of Sestamibi for monitoring response to treatment

Direct and co-catalytic oxidative aromatization of 1,4-dihydropyridines and related substrates using gold nanoparticles supported on carbon nanotubes

International audienceA heterogeneous catalyst was assembled by stabilization of gold nanoparticles on carbon nanotubes. The resulting nanohybrid was used in the catalytic aerobic oxidation of 1,4-dihydropyridines. The system proved very efficient on the investigated substrates either directly or in the presence of a quinone co-catalyst. Pyridines have found applications in various domains such as in the synthesis of drugs, 1 herbicides, 2 or insecticides. 3 In addition, the pyridine scaffold plays a central role in living systems since nicotinamide adenine dinucleotide (NAD + / NADH) and nicotinamide adenine dinucleotide phosphate (NADP + /NADPH) are key pyridine-incorporating co-factors involved in oxido-reduction processes. 4 Among the various methods developed for the synthesis of pyridine derivatives, 5 the oxidation of Hantzsch 1,4-dihydropyridines is likely one of the most straightforward approaches. The Hantzsch pyridine synthesis is a multi-component process which involves an aldehyde, two equivalents of a β-keto ester, and a nitrogen atom source. The initial condensation affords a dihydro-pyridine intermediate which can be oxidized, in a second step, into the corresponding pyridine. This reaction was reported for the first time in 1881 by Arthur Hantzsch. 6 Numerous reagents have been reported to promote the second step-oxidative aromatization reaction and include, for example , copper bromide, 7 ferric chloride, 8 palladium on carbon, 9 manganese dioxide, 10 and tert-butylhydroperoxide. 11 However, the oxidation of dihydropyridines is not always easy when substrates bear sensitive functional groups and there is still the quest for mild and general protocols. Also, some of the reported procedures lead to the formation of by-products which can be difficult to remove from the reaction mixture. Therefore, the development of milder, sustainable, and more effective methods for the oxidative aromatization of 1,4-dihydropyridines is sound. In the present article, we report the assembly and use of a recyclable CNT-supported gold catalyst for the selective and mild aerobic oxidation of 1,4-dihydropyridines (DHPs) and related substrates (Fig. 1). The CNT-gold catalyst was assembled using a layer-by-layer approach according to a previously reported procedure Fig. 1 Overview of the catalytic assembly and catalyzed oxidation process studied in the present work

Decarbonizing the cement and concrete sector: Integration of the full value chain to reach net zero emissions in Europe

ISSN:1755-1315ISSN:1755-130

Gold Nanoparticles for Plasmonics and Medicine

International audienceGold-bioconjugates are studied worldwide and promising for new technologies for health. In the long term, biodegradable gold na-noparticles (NPs) are expected to have a large impact on diagnosis through the development of new contrast agents for imaging or new ultra-sensitive sensors. Gold-NPs have a high potential as contrast agents for several bioimaging modalities such as computed tomography, pho-toacoustic imaging, dark field scattering, multi-photon luminescence, high frequency ultra-sound, quantitative phase contrast. New therapies and surgeries will develop because these gold-nano are also able to generate Reactive Oxygen Species (ROS) and heat. Our research activities concentrate on the synthesis and assembly of gold nanoparticles of high quality to provide original materials for plasmonics since 2008. The irradiation of gold NPs by short laser pulses sets off a cascade of complex transient phenomena. Following this irradiation, one observe exaltation and confinement of the incident light at the surface of the NP but also singlet oxygen generation and ROS through the injection of hot electrons (or hot holes) to a nearby molecule. In short, gold na-noparticles are nanosources of light, heat and hot carriers and the morphology of the NP is a key point for these three characteristics because competitive relaxation processes depend on the size, shape and aspect ratio of NP. We use colloidal chemistry to synthesize gold nanoparticles of controlled shape and size. The figure illustrates some of the gold NPs we propose. Contrary to spherical and rod-shaped NPs that are commercially-available, other shapes such as cubes, triangles .. and plates with tunable sizes are only produced in our lab and in few laboratories worldwide. In literature, triangular-gold nanoplates are already used for ultrasensitive sensing, and the construction of original plasmon-based optical devices. The recent discovery of a third and fourth biological transparency windows centered respectively at 1.8µm and 2.2µm and the recent commercialization of new NIR-lasers make gold-nanoplates attractive for biomedicine in this still unexplored spectral domain. The synthesis of highly uniform shapes relies on trial and error procedure because it is very hard to predict the right recipe and additional purification steps are also often required. In the future, we are eager to widen the application range of these NPs to medicine through new collaborations either with biochemists for appropriate biofunctionalization, biophysicists for imaging and physicians for therapy. As a first step towards this objective, we are developing recipes to produce Au@SiO 2 core-shell NP while waiting for precise specifications. Figure 1: illustration of some of the monodis-perse gold particles (nano-and micro-) and gold hybrids (Au@SiO2) that have been synthesized , with tunable sizes and thicknesses