Oligomeric and polymeric surfactants for the transfer of luminescent ZnO nanocrystals to water

International audienceThe water dispersion of luminescent nanocrystals (NCs) synthesized in organic solvent by encapsulation in a surfactant bilayer is a promising strategy for preserving the optical properties of NCs. The phase transfer of highly monodispersed ZnO NCs using the monomer, dimer, trimer and polymer of a series of alkyl ammonium surfactants is compared. Transfer yields over 60% could be obtained with the oligomers and the polymer. In contrast, we observed no measurable transfer using the single chain surfactant. NMR spectroscopy, including DOSY and NOESY, demonstrated that increasing the oligomerization number ameliorates the stability within the coating bilayer. The NCs exhibit a strong luminescence in water and show long term chemical and photo-chemical stability

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

Sample preparation for an optimized extraction of localized metabolites in lichens: Application to Pseudevernia furfuracea

International audienceLichens are symbiotic organisms known for producing unique secondary metabolites with attractive cosmetic and pharmacological properties. In this paper, we investigated three standard methods of preparation of Pseudevernia furfuracea (blender grinding, ball milling, pestle and mortar). The materials obtained were characterized by electronic microscopy, nitrogen adsorption and compared from the point of view of extraction. Their microscopic structure is related to extraction efficiency. In addition, it is shown using thalline reactions and mass spectrometry mapping (TOF-SIMS) that these metabolites are not evenly distributed throughout the organism. Particularly, atranorin (a secondary metabolite of interest) is mainly present in the cortex of Pseudevernia furfuracea. Finally, using microwave assisted extraction (MAE) we obtained evidence that an appropriate preparation can increase the extraction efficiency of atranorin by a factor of fiv

Simultaneous Quantification and Visualization of Titanium Dioxide Nanomaterial Uptake at the Single Cell Level in an In Vitro Model of the Human Small Intestine

International audienceUseful properties render titanium dioxide nanomaterials (NMs) to be one of the most commonly used NMs worldwide. TiO2 powder is used as food additives (E171), which may contain up to 36% nanoparticles. Consequently, humans could be exposed to comparatively high amounts of NMs that may induce adverse effects of chronic exposure conditions. Visualization and quantification of cellular NM uptake as well as their interactions with biomolecules within cells are key issues regarding risk assessment. Advanced quantitative imaging tools for NM detection within biological environments are therefore required. A combination of the label-free spatially resolved dosimetric tools, microresolved particle induced X-ray emission and Rutherford backscattering, together with high resolution imaging techniques, such as time-of-flight secondary ion mass spectrometry and transmission electron microscopy, are applied to visualize the cellular translocation pattern of TiO2 NMs and to quantify the NM-load, cellular major, and trace elements in differentiated Caco-2 cells as a function of their surface properties at the single cell level. Internalized NMs are not only able to impair the cellular homeostasis by themselves, but also to induce an intracellular redistribution of metabolically relevant elements such as phosphorus, sulfur, iron, and copper

Consecuencias económicas de la prohibición del Plástico en Colombia

Trabajo de InvestigaciónEl plástico es un material orgánico y que durante su fabricación son muchos los usos para obtener diferentes formas, además de su utilización económica para la industria y su bajo costo de fabricación, es inevitable no estar rodeados de artículos hechos a base de este componente. Sin embargo, el plástico se ha convertido en un problema que con el pasar de los días se va creciendo, dado que se encuentra en casi todos los productos que utilizamos a diario, ya sea en consumo personal o en las actividades y hasta en los alimentos. La producción y consumo de plásticos en el mundo durante los últimos años ha aumentado de forma acelerada, alcanzando cifras alarmantes y cuya consecuencia principal es la contaminación del entorno y el medio ambiente, poniendo en peligro las especies que habitan los ecosistemas del planeta, principalmente los océanos, mares y ríos; razón por la cual se es necesario empezar a revisar este tema y así tomar las diferentes decisiones que permitan dar una solución de fondo y así reducir el consumo, apoyándose en programas para la reutilización y el reciclaje de desechos impulsados por el Estado y la población en general.1. Capítulo 1: Introducción 2. Capítulo 2: Marco de Referencia 3. Resultados y Discusión de resultados 4. Conclusiones 5. ReferenciasPregradoEconomist

Copolymères à base d'ADN (synthèse, auto-assemblage, applications)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Structures chimio-mécaniques entretenues (couplage entre une réaction à autocatalyse acide et un gel de polyélectrolyte)

Lorsque des réactions chimiques non-linéaires évoluent loin de leur état d'équilibre thermodynamique et sont couplées au processus de transport par diffusion moléculaire, des instabilités spatiales et spatio-temporelles peuvent apparaître. Dans un réacteur chimique entretenu par des flux de réactifs, nous étudions de tels systèmes de réaction-diffusion mis en oeuvre dans des gels de polyélectrolytes. Les variations volumiques du gel induites par les changements d'état chimique de la réaction génèrent une grande variété de structures morphologiques stationnaires ou dynamiques. Les changements de tailles du gel support contribuent à faire naître de nouvelles instabilités. Nous tentons de comprendre la contribution apportée par les différents processus (réaction-diffusion, changement de taille) sur la dynamique résultante du système. Ces études participent à la conception de nouveaux systèmes "intelligents" autonomes.BORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

Synthesis of ultrasmall metal nanoparticles and continuous shells at the liquid/liquid interface in Ouzo emulsions

International audienceHerein, we report a novel method to synthesize metal nanoparticle-shells (NP-shells) and continuous shells at the liquid/liquid interface, via an interfacial reaction in an Ouzo emulsion. Ouzo emulsions spontaneously form submicronic droplets with a narrow size distribution, without any energy-intensive process. The Ouzo system in this work comprises water, tetrahydrofuran (THF) and butylated hydroxytoluene (BHT), and forms BHT-rich droplets (similar to 100 nm). The addition of a reducing agent (NaBH4) in the aqueous phase, and of a metal precursor (AuPPh3Cl and/or Pd(PPh3)(2)Cl-2) in the BHT-rich droplets, results in the formation of Au nanoparticles (AuNPs), continuous Pd shells, or bimetallic shells, at the interface of the droplets. Control over the NP-shell size was achieved by the addition of a water-soluble polymer during the synthesis, which in turn leads to smaller NP-shells

The Ouzo effect: A tool to elaborate high-payload nanocapsules

International audienc