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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 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 detailNanosphere Lithography and Hydrothermal Growth : How to Increase Surface Area and Control Reversible Wetting Properties of ZnO Nanowire Arrays ?
Colson, Pierre ULg; Schrijnemakers, Audrey ULg; Vertruyen, Bénédicte ULg et al

in Journal of Materials Chemistry (2012), 22(33), 17086-17093

Due to their large surface-area-to-volume ratio as well as their interesting intrinsic optical and electronic properties, ZnO 1D nanostructures are part of the few dominant materials for nanotechnology ... [more ▼]

Due to their large surface-area-to-volume ratio as well as their interesting intrinsic optical and electronic properties, ZnO 1D nanostructures are part of the few dominant materials for nanotechnology. In this article, we compare two different routes of using the nanosphere lithography for the manufacturing of well-aligned, density-controlled ZnO nanowires by low-temperature hydrothermal growth. The first route uses the colloidal mask as a template for the patterned growth of the nanowires, while in the second route, the nanospheres act as a mask to pattern the seed layer. SEM and XRD characterizations are performed on samples manufactured by both routes and evidence patterned well-aligned nanowires with high c-axis texturing in the first synthetic route. Oriented growth is less pronounced in the second route, as well as the ability to adsorb dye. However, for the first route the dye loading measurements reveal that the amount of N-719 adsorbed is higher than on unpatterned ZnO nanowires films, highlighting an increased interface area. Reversible hydrophobicity to superhydrophilicity transition was observed and intelligently controlled by alternation of UV illumination and dark storage. This promising synthetic route opens exciting perspectives for the production of ZnO nanowire arrays with tunable density, wetting properties and enhanced adsorption properties. [less ▲]

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See detailNanosphere Lithography: A Powerful Method for the Controlled Manufacturing of Nanomaterials
Colson, Pierre ULg; Henrist, Catherine ULg; Cloots, Rudi ULg

in Journal of Nanomaterials (2013)

The never-ending race towards miniaturization of devices induced an intense research in the manufacturing processes of the components of those devices. However, the complexity of the process combined with ... [more ▼]

The never-ending race towards miniaturization of devices induced an intense research in the manufacturing processes of the components of those devices. However, the complexity of the process combined with high equipment costs makes the conventional lithographic techniques unfavorable for many researchers. Through years, nanosphere lithography (NSL) attracted growing interest due to its compatibility with wafer-scale processes as well as its potential to manufacture a wide variety of homogeneous one-, two-, or three-dimensional nanostructures. This method combines the advantages of both top-down and bottom-up approaches and is based on a two-step process: (1) the preparation of a colloidal crystal mask (CCM) made of nanospheres and (2) the deposition of the desired material through the mask. The mask is then removed and the layer keeps the ordered patterning of the mask interstices. Many groups have been working to improve the quality of the CCMs. Throughout this review, we compare the major deposition techniques to manufacture the CCMs (focusing on 2D polystyrene nanospheres lattices), with respect to their advantages and drawbacks. In traditional NSL, the pattern is usually limited to triangular structures. However, new strategies have been developed to build up more complex architectures and will also be discussed. [less ▲]

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See detailNanostripe length dependence of plasmon-induced material deformations
Valev, V.K.; Libaers, W.; Zywietz, U. et al

in Optics Letters (2013), 38

Following the impact of a single femtosecond light pulse on nickel nanostripes, material deformations—or “nanobumps”—are created. We have studied the dependence of these nanobumps on the length of ... [more ▼]

Following the impact of a single femtosecond light pulse on nickel nanostripes, material deformations—or “nanobumps”—are created. We have studied the dependence of these nanobumps on the length of nanostripes and verified the link with plasmons. More specifically, local electric currents can melt the nanostructures in the hotspots, where hydrodynamic processes give rise to nanobumps. This process is further confirmed by independently simulating local magnetic fields, since these are produced by the same local electric currents. [less ▲]

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See detailNanostructuration induced by self-organization of polystyrene nanospheres as a template for the controlled growth of functional materials
Colson, Pierre ULg

Doctoral thesis (2011)

In the last few years, nanosphere lithography emerged as an inexpensive, material specific and high-output nanostructure fabrication process to manufacture arrays of periodic structures. The goal of this ... [more ▼]

In the last few years, nanosphere lithography emerged as an inexpensive, material specific and high-output nanostructure fabrication process to manufacture arrays of periodic structures. The goal of this thesis was centered on both parts of the nanosphere lithography process, namely first the optimization of monolayer colloidal masks prepared by spin coating of monodisperse polystyrene (PS) nanospheres and secondly the use of these masks to develop new attractive applications in various fields. In order to assess the quality of the manufactured colloidal crystal masks, we developed a computerized image analysis procedure (Matlab) based on SEM micrographs. We successfully performed the different stages of the image analysis in such a way to discriminate and identify each nanosphere. As a quantification of order in the self-organized nanospheres, we chose to determine the percentage of hexacoordinated nanospheres by computing the distances between each of them. We applied experimental design to spin coating to evaluate the efficiency of this method to extract and model the relationships between the experimental parameters and the degree of ordering in the particles monolayers. We identified adequate spin coating parameters to synthesize large defect-free domains, reaching up to 200 μm2, which is the highest value ever reported for samples prepared by spin coating. Statistical analysis highlighted that rapid substrate acceleration and high rotation rates are necessary to get large, well-ordered areas. We also studied the surfactant concentration usually added to the beads suspension or the use of reactive ion etching (RIE) process to modify the masks. By using PS nanosphere templates (490 nm or 250 nm diameter), we successfully manufactured large arrays of L10-Fe50Pt50 and Co nanotriangles with uniform sizes. In addition to crystallographic and microstructural characterizations, we evaluated the magnetic properties of the nanostructures both from a qualitative (MFM) and quantitative (SQUID) point of view. The magnetic stability of the single-domain FePt nanodots was evidenced by focused MOKE analysis. This is of major importance for further use in magnetic storage applications and has never been reported yet. The soft magnetic Co nanodots displayed either single domain or vortex domains states, depending on the magnetization direction. The MOKE hysteresis loops revealed an increased coercive field compared with thin films. This is probably due to a specific magnetization reversal process caused by the shape of the nanodots. Oxide nanostructures were then manufactured. The polystyrene templates (490 nm diameter) were used for the guided hydrothermal growth of well-aligned ZnO nanowires. The control of the spacing between the nanowires combined with high c-axis preferred orientation led to higher dye loading values compared with continuous unpatterned films. This was undoubtedly attributed to an increased accessible surface area due to the patterning. Moreover, the increased roughness due to the patterning induced a higher water contact angle compared with an unpatterned ZnO nanowire array. Reversible superhydrophylicity to hydrophobicity was observed and controlled by successive UV illumination and O2 annealing. The achievements attained in this work have brought a significant contribution to the field of nano- and microfabrication. New pathways were opened for interesting future work with respect to continued fundamental and applied research. [less ▲]

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See detailNanostructuration of polyamide-based polymer blends by reactive blending
Koulic, Christian; Pagnoulle, Christian; Jérôme, Robert ULg

Poster (2003, May 16)

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See detailNanostructure, Excitations, and Thermoelectric Properties of Bi2Te3-Based Nanomaterials
Aabdin, Z.; Peranio, N.; Eibl, O. et al

in Journal of Electronic Materials (2012), 41(6), 1792-1798

The effect of dimensionality and nanostructure on thermoelectric properties in Bi2Te3-based nanomaterials is summarized. Stoichiometric single-crystalline Bi2Te3 nanowires were prepared by potential ... [more ▼]

The effect of dimensionality and nanostructure on thermoelectric properties in Bi2Te3-based nanomaterials is summarized. Stoichiometric single-crystalline Bi2Te3 nanowires were prepared by potential-pulsed electrochemical deposition in a nanostructured Al2O3 matrix, yielding transport in the basal plane. Polycrystalline, textured Sb2Te3 and Bi2Te3 thin films were grown at room temperature using molecular beam epitaxy and subsequently annealed at 250A degrees C. Sb2Te3 films revealed low charge carrier density of 2.6 x 10(19) cm(-3), large thermopower of 130 V K-1, and large charge carrier mobility of 402 cm(2) V-1 s(-1). Bi-2(Te0.91Se0.09)(3) and (Bi0.26Sb0.74)(2)Te-3 nanostructured bulk samples were prepared from as-cast materials by ball milling and subsequent spark plasma sintering, yielding grain sizes of 50 nm and thermal diffusivities reduced by 60\%. Structure, chemical composition, as well as electronic and phononic excitations were investigated by x-ray and electron diffraction, nuclear resonance scattering, and analytical energy-filtered transmission electron microscopy. calculations yielded point defect energies, excitation spectra, and band structure. Mechanisms limiting the thermoelectric figure of merit for Bi2Te3 nanomaterials are discussed. [less ▲]

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See detailNanostructured carbons as catalyst supports for PEM fuel cell electrodes
Job, Nathalie ULg; Berthon-Fabry, Sandrine; Chatenet, Marian et al

in Topics in Catalysis (2009), 52

Detailed reference viewed: 19 (3 ULg)