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See detailNanomedicine for the treatment of brain diseases
Palazzo, Claudio ULg

Scientific conference (2014, October 20)

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See detailNanometer scale organization of mixed surfactin/phosphatidylcholine monolayers
Deleu, Magali ULg; Paquot, Michel ULg; Jacques, Philippe ULg et al

in Biophysical Journal (1999), 77(4), 2304-2310

Mixed monolayers of the surface-active lipopeptide surfactin-C-15 and of dipalmitoyl phosphatidylcholine (DPPC) were deposited on mica and their nanometer scale organization was investigated using atomic ... [more ▼]

Mixed monolayers of the surface-active lipopeptide surfactin-C-15 and of dipalmitoyl phosphatidylcholine (DPPC) were deposited on mica and their nanometer scale organization was investigated using atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS). AFM topographic images revealed phase separation for mixed monolayers prepared at 0.1, 0.25, and 0.5 surfactin molar ratios. This was in agreement with the monolayer properties at the air-water interface indicating a tendency of the two compounds to form bidimensional domains in the mixed systems. The step height measured between the surfactin and the DPPC domains was 1.2 +/- 0.1 nm, pointing to a difference in molecular orientation: while DPPC had a vertical orientation, the large peptide ring of surfactin was lying on the mica surface. The N/C atom concentration ratios obtained by XPS for pure monolayers were compatible with two distinct geometric models: a random layer for surfactin and for DPPC, a layer of vertically-oriented molecules in which the polar headgroups are in contact with mica. XPS data for mixed systems were accounted for by a combination of the two pure monolayers, considering respective surface coverages that were in excellent agreement with those measured by AFM. These results illustrate the complementarity of AFM and XPS to directly probe the molecular organization of multicomponent monolayers. [less ▲]

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See detailNanometer-scale wetting transitions in mesopores: a SAXS analysis
Gommes, Cédric ULg

Conference (2015, May)

The equilibrium and metastable configurations of confined binary liquids has been a topic of research since the early work of Liu et al. in the nineties [1]. In particular, it has been proposed ... [more ▼]

The equilibrium and metastable configurations of confined binary liquids has been a topic of research since the early work of Liu et al. in the nineties [1]. In particular, it has been proposed theoretically that liquids may coexist inside nanopores in the form of layers covering uniformly the solid surface, of plugs filling locally the pore space, or of capsules floating in the middle of the pores. In the present contribution, we report in situ synchrotron small-angle scattering (SAXS) experiments on hexane/nitrobenzene solutions confined in mesoporous carbon xerogels [2]. The SAXS shows that these systems exhibit reversible temperature-induced transitions between the layer and the plug configurations. The scattering data is analyzed using a so-called plurigaussian model, which enables us to reconstruct the configurations of the confined liquids, and quantitatively analyze the wetting transitions at the nanometer-scale in terms of changing interface areas, contact angles, and triple-line lengths. [less ▲]

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See detailNanonu, maar hoe?
Van Oudheusden, Michiel ULg

Article for general public (2007)

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See detailNanoparticle Growth in Supported Nickel Catalysts during Methanation Reaction-Larger is Better
Munnik, Peter; Velthoen, Marjolein; de Jongh, Petra et al

in Angewandte Chemie International Edition (2014), 53

A major cause of supported metal catalyst deactivation is particle growth by Ostwald ripening. Nickel catalysts, used in the methanation reaction, may suffer greatly from this through the formation of [Ni ... [more ▼]

A major cause of supported metal catalyst deactivation is particle growth by Ostwald ripening. Nickel catalysts, used in the methanation reaction, may suffer greatly from this through the formation of [Ni(CO)4]. By analyzing catalysts with various particle sizes and spatial distributions, the interparticle distance was found to have little effect on the stability, because formation and decomposition of nickel carbonyl rather than diffusion was rate limiting. Small particles (3–4 nm) were found to grow very large (20–200 nm), involving local destruction of the support, which was detrimental to the catalyst stability. However, medium sized particles (8 nm) remained confined by the pores of the support displaying enhanced stability, and an activity 3 times higher than initially small particles after 150 h. Physical modeling suggests that the higher [Ni(CO)4] supersaturation in catalysts with smaller particles enabled them to overcome the mechanical resistance of the support. Understanding the interplay of particle size and support properties related to the stability of nanoparticles offers the prospect of novel strategies to develop more stable nanostructured materials, also for applications beyond catalysis. [less ▲]

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See detailNanoparticles in biomedical imaging
Liu, Ji ULg; Jérôme, Christine ULg; Duguet, Etienne

Scientific conference (2013, April 19)

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See detailNanoparticles in solar sail materials
Fleury-Frenette, Karl ULg

Conference (2010)

Solar sailing is a spacecraft propulsion mean exploiting the radiation pressure of sunlight. This concept is undergoing a regain of interest from the space agencies around the world partly driven by the ... [more ▼]

Solar sailing is a spacecraft propulsion mean exploiting the radiation pressure of sunlight. This concept is undergoing a regain of interest from the space agencies around the world partly driven by the development of manufacturing technologies. Typically, tens of thousands of square meters of sail materials are required to propel a spacecraft. In its most common proposed embodiment, the sail material is constituted of a thin polymer foil coated with a reflective layer on the front side and eventually an emissive layer on the back side. The photons momentum is transferred to the sail upon reflection and its thermal balance is governed by radiative processes (absorption over the solar spectrum and reemission of thermal infrared radiation). The impact of nanoparticles inclusion in the polymer foil on the sail performance will be evaluated for operation in the inner solar system. The aspects of passive thermal regulation and resistance of the polymer to UV radiation will be addressed within the framework of optical calculations based on effective media approximations. Copyright ©2010 by the International Astronautical Federation. All rights reserved. [less ▲]

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See detailNanoparticles tailored for the delivery of biopharmaceutic drugs
Grandfils, Christian ULg; Sevrin, Chantal ULg; Kuznetsova et al

Conference (2011, May 20)

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See detailNanoparticles used to darken the patina of antic black bronze: TEM observations on new experimentations
Mathis, François ULg; Tirat, Sophie; Grieten, Eva et al

Conference (2013, September)

Some studies that started in the nineties [1] proved that some antic artefacts or parts were intentionally patinated using a chemical treatment. In particular one type of patina was characterized on ... [more ▼]

Some studies that started in the nineties [1] proved that some antic artefacts or parts were intentionally patinated using a chemical treatment. In particular one type of patina was characterized on artefacts coming either from Egyptian civilization, Mycenaean period or Roman Empire. This patina has been identified as a precious material mentioned in ancient Egyptian and Roman texts. This particular material is named, depending on the artefacts’ origin, black bronze (hmty km), or corinthium aes. This patina is made on copper alloys containing gold and/or silver and is composed mainly of cuprite. It was compared with a Japanese patina which appears in medieval times but which is still in use and known under the name of shakudo. Shakudo are copper gold alloys and they are treated chemically by means of different recipes named nikomi-chakushoku which developed a black layer of cuprite on the surface. An important study of antic artefacts coming from the collections of French museums has been carried out since the beginning of the 2000’s. An experimental protocol based on non-invasive analysis was developed to analyse these very precious objects and to identify and characterize this type of patina in function of the provenance and age of the artefacts [2, 3]. However, some questions about this particular surface layers could not be resolved using this experimental protocol due to the limitation of non-invasive analytical techniques: In particular the question of the formation of the oxide layer, the colouring mechanism of this black cuprite (copper oxide which is red under natural form) and the important adherence properties. We developed a program of experimentation to make some black patina. These experimentations were based on the utilisation of the Japanese recipes, and we tried to differentiate the effect of the alloying element (Au, Ag, As) and the effects of the chemical treatment. These patinas were studied by means of various analytical methods and in particular we used TEM to characterize the fine structure of the oxide layer. The use of transmission electron microscopy (TEM) allows to evidence a hypothesis already mentioned in previous studies [4]: the presence of nanoparticles of gold in the cuprite layers and their role on the coloration of the patina making the black bronze the very first applications of nanoparticles in technical history. [less ▲]

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See detailNanopatterned monolayers of an adsorbed chromophore
Frederich, Nadia; Duwez, Anne-Sophie ULg; Nysten, Bernard et al

in Nanotechnology (2008), 19

A simple lift-off process was developed to rapidly fabricate nanopatterned photofunctional surfaces. Dye molecules of a perylene derivative (PDID) were adsorbed irreversibly on clean silicon through the ... [more ▼]

A simple lift-off process was developed to rapidly fabricate nanopatterned photofunctional surfaces. Dye molecules of a perylene derivative (PDID) were adsorbed irreversibly on clean silicon through the holes of an electron-beam lithographied polymer mask. The subsequent removal of the mask in a proper solvent results in PDID nanosized regions of width as small as 30 nm for stripes and of diameter as small as 120 nm for dots. Numerical analyses of atomic force microscopy and laser-scanning confocal microscopy images show that the dye molecules are confined to the regions defined by the lithographic process, with the integrated fluorescence intensity being essentially proportional to the size of the nanofeatures. This demonstrates that a simple organic lift-off process compatible with clean-room technology, and not involving any chemical step, is able to produce photofunctional nanopatterned surfaces, even though the dye is not chemically bonded to the silicon surface. [less ▲]

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See detailNanoporous thin films from ionically connected diblock copolymers
Yu, Haizhou; Stoffelbach, François; Detrembleur, Christophe ULg et al

in European Polymer Journal (2012), 48(5), 940-944

An ionically connected polystyrene-block-poly(ethylene oxide) diblock copolymer (PS−+PEO) has been prepared by blending a PEO block functionalized by a dimethylamino group at one extremity with a sulfonic ... [more ▼]

An ionically connected polystyrene-block-poly(ethylene oxide) diblock copolymer (PS−+PEO) has been prepared by blending a PEO block functionalized by a dimethylamino group at one extremity with a sulfonic acid terminated PS block. Proton transfer occurs from the sulfonic acid to the dimethylamino group, resulting in the formation of an ion pair acting as a junction between the two polymer blocks. This copolymer was further used to prepare thin films with a cylindrical morphology consisting of PEO cylinders embedded in a PS matrix and oriented perpendicularly to the film surface. Nanoporous thin films with sulfonate groups on the pore walls have been finally obtained after solvent extraction of the PEO microphases. The presence of those sulfonate groups was evidenced by grafting a positively charged fluorescent dye on the pore walls. [less ▲]

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See detailNanoporous Thin Films from Self-Assembled Metallo-supramolecular Block Copolymers
Fustin, Charles-André; Lohmeijer, Bas G.G.; Duwez, Anne-Sophie ULg et al

in Advanced Materials (2005), 17

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See detailNanoprecision alignment for wafer bonding
Jiang, Liudi; Pandraud, Gregory; French, Paddy James et al

in The 17th Micromechanics Europe Workshop, MME'06 (2006, September)

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See detailNanoscale membrane activity of surfactins: Influence of geometry, charge and hydrophobicity
Francius, Gregory; Dufour, Samuel; Deleu, Magali ULg et al

in Biochimica et Biophysica Acta - Biomembranes (2008), 1778

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See detailNanoscale Modification Of Supported Lipid Membranes: Synergetic Effect Of Phospholipase D And Viral Fusion Peptides
El Kirat, K.; Lins, Laurence ULg; Brasseur, Robert ULg et al

in Journal of Biomedical Nanotechnology (2005), 1(1), 1-8

Understanding the molecular bases of biomembrane fusion events is a challenging issue in current biomedical research in view of its involvement in controlling cellular functions and in mediating various ... [more ▼]

Understanding the molecular bases of biomembrane fusion events is a challenging issue in current biomedical research in view of its involvement in controlling cellular functions and in mediating various important diseases. In this study, we used atomic force microscopy (AFM) to address the crucial question as to whether negatively curved lipids influence the ability of a viral fusion peptide to perturb the organization of supported lipid bilayers. To this end, an original approach was developed that makes use of an AFM tip functionalized with phospholipase D (PLD) enzymes to generate in situ small amounts of negatively curved phosphatidic acid (PA) in mixed dioleoylphosphatidylcholine/dipalmitoylphosphatidylcholine (DOPC/DPPC) bilayers. Real-time AFM imaging revealed that this nanomodification dramatically enhanced subsequent interaction with the simian immunodeficiency virus (SIV) fusion peptide. At short incubation time, the SIV peptide induced a 1.9 nm thickness reduction of the DPPC domains, reflecting either interdigitation or fluidification of the lipids. At longer incubation time, these depressed domains transformed into elevated striated domains, protruding one to several nanometers above the bilayer surface. Two complementary experiments, i.e. addition of the peptide onto DOPC/DPPC/DOPA bilayers or onto DOPC/DPPC bilayers pretreated with a PLD solution, confirmed that both PA and SIV peptides are required to induce depressed and striated domains. Accordingly, this is the first time that a high-resolution imaging technique is used to demonstrate that negatively curved lipids affect the membrane activity of fusion peptides. We believe the nanoscale approach presented here, i.e. use of enzyme-functionalized AFM tips to modify lipid bilayers, will find exciting new applications in nanobiotechnology for the design of biomimetic surfaces. [less ▲]

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See detailNanoscale Properties Of Mixed Fengycin/Ceramide Monolayers Explored Using Atomic Force Microscopy
Eeman, M.; Deleu, Magali ULg; Paquot, Michel ULg et al

in Langmuir (2005), 21(6),

To gain insight into the interactions between fengycin and skin membrane lipids, mixed fengycin/ceramide monolayers were investigated using atomic force microscopy (AFM) (monolayers supported on mica) and ... [more ▼]

To gain insight into the interactions between fengycin and skin membrane lipids, mixed fengycin/ceramide monolayers were investigated using atomic force microscopy (AFM) (monolayers supported on mica) and surface pressure-area isotherms (monolayers at the air-water interface). AFM topographic images revealed phase separation in mixed monolayers prepared at 20 °C/pH 2 and composed of 0.25 and 0.5 fengycin molar ratios, in the form of two-dimensional (2-D) hexagonal crystalline domains of ceramide surrounded by a fengycin-enriched fluid phase. Surface pressure-area isotherms as well as friction and adhesionAFMimages confirmed that the two phases had different molecular orientations: while ceramide formed a highly ordered phase with crystalline chain packing, fengycin exhibited a disordered fluid phase with the peptide ring lying horizontally on the substrate. Increasing the temperature and pH to values corresponding to the skin parameters, i.e., 37 °C/pH 5, was found to dramatically affect the film organization. At low fengycin molar ratio (0.25), the hexagonal ceramide domains transformed into round domains, while at higher ratio (0.5) these were shown to melt into a continuous fengycin/ceramide fluid phase. These observations were directly supported by the thermodynamic analysis (deviation from the additivity rule, excess of free energy) of the monolayer properties at the air-water interface. Accordingly, this study demonstrates that both the environmental conditions (temperature,pH)andfengycin concentration influence the molecular organization of mixed fengycin/ceramide monolayers.Webelieve that the ability to modulate the formation of 2-D domains in the skin membrane may be an important biological function of fengycin, which should be increasingly investigated in future pharmacological research. [less ▲]

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See detailNanoscaleorganization of mixed fengycin/lipid monolayers
Eeman, Marc; Deleu, Magali ULg; Paquot, Michel ULg et al

Poster (2004)

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See detailNanosession: Multiferroic Thin Films and Heterostructures
Burton, J. D.; Yin, J; Li, X. G. et al

in Heber, J; Schlom, D; Tokura, Y (Eds.) et al Frontiers in Electronic Materials (2012)

This chapter presents the theoretical and experimental evidence of a novel magnetoelectric mechanism producing a giant resistive switching effect at the interface between a ferroelectric perovskite oxide ... [more ▼]

This chapter presents the theoretical and experimental evidence of a novel magnetoelectric mechanism producing a giant resistive switching effect at the interface between a ferroelectric perovskite oxide, BaTiO3 (BTO), and a complex oxide manganite electrode, La1-xSrxMnO3. It presents a detailed study of the magnetic properties of multiferroic hybrid systems consisting of BTO as the ferroelectric and Ni or Fe3O4 as the ferromagnetic layers. The chapter discusses the possibility of achieving electric control of the magnetization, possibly at room temperature, through a specific (trilinear) coupling of the polarization with two other non-polar lattice instabilities which occurs in the so-called hybrid improper ferroelectrics. First-principles modelling techniques are used to investigate a promising system: BiFeO3/LaFeO3 superlattice. It presents the investigation of the multiferroic properties in TbMnO3 thin films with soft X-ray resonant magnetic scattering (XRMS) performed at the UE46-PGM1 beamline of BESSY II. [less ▲]

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