Bio-structuration à l'échelle micro et nanométrique

Les substrats structurés aux échelles micrométriques et nanométriques sont intéressants pour des applications biomédicales, par exemple dans des puces à ADN/protéines, pour la miniaturisation des lab-on-chip ou pour préparer des implants permettant le contrôle de l'adhésion de cellules. Dans la dernière décennie des études ont montrées, que les cellules vivantes peuvent détecter la présence de nano-structures sur les substrats sur lesquels elles adhèrent. Bien que ces mécanismes soient étudiés depuis une dizaine d'années, les mécanismes fondamentaux sont encore en cours d'études. Tant pour une étude au niveau fondamental que dans le but d'applications concrètes, il est important de développer des techniques simples pour structurer des substrats sur de grandes surfaces. Nous avons réalisé une nouvelle méthode alliant un faible coût de fabrication et la biocompatibilité pour structurer et biofonctionnaliser des substrats à l'échelle nanométrique en utilisant des membranes d'alumine poreuses comme masque. Les membranes d'alumine poreuses, préparées par électrochimie, sont naturellement organisées en un réseau hexagonal sur une surface de quelques cm . Nous les utilisons comme masque pour la structuration de surfaces. Des trous réguliers sont gravés dans le substrat à travers les membranes d'alumine poreuses. Ce substrat est ensuite utilisée lors d'une application biologique : une bicouche lipidique est déposée sur le substrat structuré pour imiter les hétérogénéités de la membrane cellulaire. La mobilité de la bicouche est étudiée par corrélation de spectroscopie de fluorescence à rayon variable. Une autre série d'expériences est faite en utilisant des membranes d'alumine poreuses comme masque d'évaporation pour créer des réseaux organisés d'îlots d'organo-silanes. Deux molécules sont utilisées elles possèdent soit une fonction amine réactive soit une longue chaîne carbonée inerte. La bio-fonctionnalisation est ensuite effectuée en utilisant la fonction amine pour accrocher un anticorps. Des études sont effectuées en parallèle, sur des substrats bio-fonctionnalisés à l'échelle micrométrique grâce au micro-contact printing. Le but de cette étude est de mettre au point une biochimie de surface permettant le contrôle de l'adhésion de cellules immunitaires, avec le but de transférer ensuite la biochimie à l'échelle nanométrique.Substrates patterned at the micro-scale and nano-scale are interesting for biomedical applications, for example, in DNA/protein nano-arrays, for miniaturized lab-on-chip applications or for making smart implants that can control adhesion of cells. In the last decade, some studies showed that living cells can detect nano-scale structures on substrates to which they adhere. Although this behaviour has been observed now for over a decade, the fundamental detection mechanism is still under investigation. Both for fundamental studies and for applications, it is important to develop facile techniques to pattern substrates on a large scale. We have realized a novel technique for patterning and bio-functionalizing substrates at the nano-scale using porous anodic alumina membranes as masks. The ordered porous anodic alumina membranes, prepared by classical electro-chemistry, are naturally organized in an hexagonal array over surface area of few square centimeters. Here we use them as mask for surface patterning. To create an array of nano holes, the substrate is dry etched through the alumina pores. In a biologically relevant application, a lipid bilayer is deposited on the patterned substrate to mimic a heterogeneous cell membrane. The mobility of the bilayer is studied by fluorescent correlation spectroscopy. In a different set of experiments, the porous alumina membranes are used as evaporation mask to create an organized array of alkyl-silane islands - either with a short carbon chain and with a reactive amine group or with a long carbon chain and non-reactive. Afterwards, biochemical functionalization is achieved by exploiting the amino-function of the amino-silane to bind an antibody. In parallel, we have started some studies of adhesion on a pattern substrate at micro-scale with immunological cells. The substrate is pattern by micro contact printing and the cell adhesion is observed by RICM. The aim of this studies is to prepare the biochemistry for the immunological cells adhesion, with the aim or transferring this to the nano-scale.AIX-MARSEILLE2-Bib.electronique (130559901) / SudocSudocFranceF

KCl ultra-thin films with polar and non-polar surfaces grown on Si(111)7x7

International audienceThe growth of ultra-thin KCl films on the Si(111)7 3 7 reconstructed surface has been investigated as a function of KCl coverage and substrate temperature. The structure and morphology of the films were characterized by means of scanning tunneling microscopy (STM) under ultra-high vacuum (UHV) conditions. Detailed analysis of the atomically resolved STM images of islands grown at room and high temperatures (400 K–430 K) revealed the presence of KCl(001) and KCl(111) islands with the ratio between both structures depending on the growth temperature. At room temperature, the growth of the first layer, which covers the initial Si(111)7 3 7 surface, contains double/triple atomic layers of KCl(001) with a small fraction of KCl(111) islands. The high temperature growth promotes the appearance of large KCl(111) areas, which are built up by three atomic layers. At room and high temperatures, flat and atomically well-defined ultra-thin KCl films can be grown on the Si(111)7 3 7 substrate. The formation of the above mentioned (111) polar films is interpreted as a result of the thermally activated dissociative adsorption of KCl molecules on Si(111)7 3 7, which produces an excess of potassium on the Si surface

Magnetic properties of self-organized Co dimer nanolines on Si/Ag(110)

International audienceWe demonstrate the kinetically controlled growth of one-dimensional Co nanomagnets with a high lateral order on a nanopatterned Ag(110) surface. First, self-organized Si nanoribbons are formed upon submonolayer condensation of Si on the anisotropic Ag(110) surface. Depending on the growth temperature, individual or regular arrays (with a pitch of 2 nm) of Si nanoribbons can be grown. Next, the Si/Ag(110) system is used as a novel one-dimensional Si template to guide the growth of Co dimer nanolines on top of the Si nanoribbons, taking advantage of the fact that the thermally activated process of Co diffusion into the Si layer is efficiently hindered at 220 K. Magnetic characterization of the Co nanolines using X-ray magnetic circular dichroism reveals that the first atomic Co layer directly adsorbed onto the Si nanoribbons presents a weak magnetic response. However, the second Co layer exhibits an enhanced magnetization, strongly suggesting a ferromagnetic ordering with an in-plane easy axis of magnetization, which is perpendicular to the Co nanolines

Membranes d'alumine nano-poreuses pour l'élaboration de nanostructures

Les membranes d'alumine nano-poreuses suscitent depuis quelques années un grand intérêt dans la synthèse de nano-objets. Ces membranes présentent des pores très verticaux naturellement organisés en un réseau hexagonal (structure en nid d'abeilles). Le diamètre des pores peut varier entre 20 et 200nm espacés de 60 à 540nm et l'épaisseur de la membrane peut varier de 100nm à plusieurs centaines de m. Durant ces travaux de thèse, deux approches ont été envisagées pour synthétiser des nano-structures. La première consiste à utiliser ces membranes comme nano-réservoirs. La couche barrière formée au fond de la membrane dont l'épaisseur est environ égale au diamètre des pores est diminuée à 10nm par voie chimique. Puis des dépôts de divers matériaux (Au, Co, Si) ont été réalisés dans des membranes avec des pores de 180nm et 40nm préalablement dégazées. Ces objets 3D ont été fabriqués sous ultra-vide (10-10 mbar), concfinés à l'intérieur des nano-réservoirs, transparents aux électrons. Les études en TEM permettent d'avoir accès à la morphologie des nanoparticules, qui se révèlent être cristallines, selon plusieurs directions cristallographiques. En vue plane, perpendiculairement à l'interface, pour ceux déposés au fond du nano-réservoir et en vue transverse pour ceux déposés sur les parois. Il a par ailleurs été possible de réaliser des études de recuits in-situ en température (RT à 1000 C) dansle TEM pour des particules d'or. La seconde approche repose sur l'utilisation des membranes ouvertes comme masque pour l'évaporation. Cette technique permet de dupliquer le motif de la membrane sur le substrat préalablement nettoyé pour former un réseau de nanoparticules correspondant au matériau déposé. Nous avons réalisé de manière reproductible, sous ultravide,des réseaux de plots d'or à l'aide de membranes dont le diamètre des pores est de 180 nmThe nanoporous alumina membrane rise in recent years a great interest in the synthesis of nanoobjects. These membranes have pores naturally very vertical organized in a hexagonal lattice(honeycomb structure). The pore diameter may vary between 20 and 200nm spaced 60 to 540nmand the thickness of the membrane can vary from 100nm several hundred microns. During this thesis work, two approaches have been explored to synthesize nano-structures. The first is touse these membranes as nano-tanks. The barrier layer formed at the bottom of the membrane whose thickness is about equal to the diameter of pores is reduced to 10nm by chemical etching. Then deposits from materials (Au, Co, Si) were performed in membranes with pores of 180nmand 40nm previously degassed. These 3D objects have been produced under ultra-high vacuum(10-10 mbar), confined within nano-tanks, transparent to electrons. TEM studies allow accessto the morphology of nanoparticles, which are proving to be crystallin, according to several crystallographic directions. In plane view perpendicular to the interface for those deposited atthe bottom of the nano-tank and cross-sectional view for those deposited on the walls. It has also been possible to perform studies of in-situ annealing (RT to 1000 C) in TEM of Au particles. The second approach relies on the use of membranes opened as an evaporation mask. This technique allows to duplicate the pattern of the membrane to the substrate previously cleaned, to form a network of nanoparticles corresponding to the material deposited. We have achieved reproducible, gold dot arrays, under UHV conditions using membranes with a pore size of 180 nm.AIX-MARSEILLE2-Bib.electronique (130559901) / SudocSudocFranceF

Enhancement of Pd Catalytic Activity toward Ethanol Electrooxidation by Atomic Layer Deposition of SnO 2 onto TiO 2 Nanotubes

International audiencePalladium nanoparticles and SnO2 layers have been grown by two successive steps of atomic layer deposition onto TiO2 nanotubes (TNTs). The three-dimensional nanostructured catalytic systems have been studied for ethanol electrooxidation in alkaline media. Characterization by scanning and transmission electron microscopies, X-ray photoelectron spectroscopy, and X-ray diffraction indicates the high conformity, the high purity, and the perfect stoichiometry of Pd and SnO2 deposits onto the TNTs. The electrochemical investigations performed by cyclic voltammetry and chronoamperometry have revealed the beneficial effect of the annealing of the support toward ethanol electrooxidation reaction. The comparison of the catalytic activity with literature shows that such SnO2-based substrates exhibits highly promising performances

Atomic layer deposition of HfO2 for integration into three-dimensional metal–insulator–metal devices

International audienceHfO2 nanotubes have been fabricated via a template-assisted deposition process for further use in three-dimensional metal–insulator–metal (MIM) devices. HfO2 thin layers were grown by Atomic Layer Deposition (ALD) in anodic alumina membranes (AAM). The ALD was carried out using tetrakis(ethylmethylamino)hafnium and water as Hf and O sources, respectively. Long exposure durations to the precursors have been used to maximize the penetration depth of the HfO2 layer within the AAM and the effect of the process temperature was investigated. The morphology, the chemical composition, and the crystal structure were studied as a function of the deposition parameters using transmission and scanning electron microscopies, X-ray photoelectron spectroscopy, and X-ray diffraction, respectively. As expected, the HfO2 layers grown at low-temperature (T=150∘C) were amorphous, while for a higher temperature (T=250∘C), polycrystalline films were observed. The electrical characterizations have shown better insulating properties for the layers grown at low temperature. Finally, TiN/HfO2/TiN multilayers were grown in an AAM as proof-of-concept for three-dimensional MIM nanostructures

3D-nanoarchitectured Pd/Ni catalysts prepared by atomic layer deposition for the electrooxidation of formic acid

Three-dimensionally (3D) nanoarchitectured palladium/nickel (Pd/Ni) catalysts, which were prepared by atomic layer deposition (ALD) on high-aspect-ratio nanoporous alumina templates are investigated with regard to the electrooxidation of formic acid in an acidic medium (0.5 M H2SO4). Both deposition processes, Ni and Pd, with various mass content ratios have been continuously monitored by using a quartz crystal microbalance. The morphology of the Pd/Ni systems has been studied by electron microscopy and shows a homogeneous deposition of granularly structured Pd onto the Ni substrate. X-ray diffraction analysis performed on Ni and NiO substrates revealed an amorphous structure, while the Pd coating crystallized into a fcc lattice with a preferential orientation along the [220]-direction. Surface chemistry analysis by X-ray photoelectron spectroscopy showed both metallic and oxide contributions for the Ni and Pd deposits. Cyclic voltammetry of the Pd/Ni nanocatalysts revealed that the electrooxidation of HCOOH proceeds through the direct dehydrogenation mechanism with the formation of active intermediates. High catalytic activities are measured for low masses of Pd coatings that were generated by a low number of ALD cycles, probably because of the cluster size effect, electronic interactions between Pd and Ni, or diffusion effects

Electrochemistry and Nanotechnologies: The New Challenges

Digital simulation tools are jointly employed for the design of an existing aircraft engine components manufacturing cell to be enhanced through automated robotic deburring. The application of 3D Motion Simulation is illustrated for layout and material handling system design. Discrete Event Simulation is applied to analyze different scenarios and improve the cell performance with regards to two key objectives: (a) optimization of the batch throughput time for the part number fabricated in the manufacturing cell; (b) utilization increase of the automated deburring station by processing additional part numbers coming from other manufacturing cells in the same production department