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

Impact of anatase and rutile titanium dioxide nanoparticles on uptake carriers and efflux pumps in Caco-2 gut epithelial cells

International audienceTiO2 microparticles are widely used in food products, where they are added as a white food colouring agent. This food additive contains a significant amount of nanoscale particles; still the impact of TiO2 nanoparticles (TiO2-NPs) on gut cells is poorly documented. Our study aimed at evaluating the impact of rutile and anatase TiO2-NPs on the main functions of enterocytes, i.e. nutrient absorption driven by solute-liquid carriers (SLC transporters) and protection against other xenobiotics driven by efflux pumps from the ATP-binding cassette (ABC) family. We show that acute exposure of Caco-2 cells to both anatase (12 nm) and rutile (20 nm) TiO2-NPs induce early upregulation of a battery of efflux pumps and nutrient transporters. In addition they cause overproduction of reactive oxygen species and misbalance redox repair systems, without inducing cell mortality or DNA damage. Taken together, these data suggest that TiO2-NPs may increase the functionality of gut epithelial cells, particularly their property to form a protective barrier against exogenous toxicants and to absorb nutrients

Engineered inorganic core/shell nanoparticles

International audienceIt has been for a long time recognized that nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic structures. At first, size effects occurring in single elements have been studied. More recently, progress in chemical and physical synthesis routes permitted the preparation of more complex structures. Such structures take advantages of new adjustable parameters including stoichiometry, chemical ordering, shape and segregation opening new fields with tailored materials for biology, mechanics, optics magnetism, chemistry catalysis, solar cells and microelectronics. Among them, core/shell structures are a particular class of nanoparticles made with an inorganic core and one or several inorganic shell layer(s). In earlier work, the shell was merely used as a protective coating for the core. More recently, it has been shown that it is possible to tune the physical properties in a larger range than that of each material taken separately. The goal of the present review is to discuss the basic properties of the different types of core/shell nanoparticles including a large variety of heterostructures. We restrict ourselves on all inorganic (on inorganic/inorganic) core/shell structures. In the light of recent developments, the applications of inorganic core/shell particles are found in many fields including biology, chemistry, physics and engineering. In addition to a representative overview of the properties, general concepts based on solid state physics are considered for material selection and for identifying criteria linking the core/shell structure and its resulting properties. Chemical and physical routes for the synthesis and specific methods for the study of core/shell nanoparticle are briefly discussed

Mesures in situ de temperature et concentrations sur le systeme Si-C-H dans un reacteur de depot chimique en phase vapeur

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Laser pyrolysis for the synthesis of nanoparticles of interest as active materials in Li-Ion Batteries

International audienc

Towards silicon as possible optical imaging agent?

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