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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

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See detailNanostructured carbons as supports for catalysts and electrocatalysts
Job, Nathalie ULg

Conference (2009, January 20)

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See detailNanostructured catalysts by sol-gel process
Lambert, Stéphanie ULg; Heinrichs, Benoît ULg

Conference (2014, April 25)

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See detailNanostructured mesoporous TiO2, ZrO2 and SiO2 synthesis by using the non-ionic Cm(EO)n - inorganic alkoxyde system : toward a better understanding on the formation mechanism
Blin, Jean-Luc; Léonard, Alexandre ULg; Gigot, Laurent et al

in Studies in Surface Science and Catalysis (2003), 146

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See detailNanostructured PMMA: from lamellar sheets to double-layered vesicles
Koulic, Christian; Jérôme, Robert ULg

in Macromolecules (2004), 37(3), 888-893

PMMA was nanostructured by similar to100 nm liposome-like vesicular objects by melt blending with 20 wt % of a symmetric poly(styrene)-b-poly(isoprene)-b-poly(methyl methacrylate) (PS-b-PIP-b-PMMA ... [more ▼]

PMMA was nanostructured by similar to100 nm liposome-like vesicular objects by melt blending with 20 wt % of a symmetric poly(styrene)-b-poly(isoprene)-b-poly(methyl methacrylate) (PS-b-PIP-b-PMMA) triblock copolymer in the dry-brush regime. Whenever the blend was prepared by casting toluene solution, thus under zero-shear conditions, a continuous network of lamellar copolymer sheets was formed in PMMA, which however underwent a transition to the aforementioned vesicles upon application of large amplitude oscillatory shear. [less ▲]

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See detailNanostructured polyamide by reactive blending. 1. Effect of the reactive diblock composition
Koulic, Christian; Jérôme, Robert ULg

in Macromolecules (2004), 37(9), 3459-3469

Reactive blending of phthalic anhydride end-capped polystyrene-b-polyisoprene diblock (PS-b-PIP-anh) with 80 wt % of polyamide 12 (PA12) results in the very rapid formation of a PS-b-PIP-b-PA triblock ... [more ▼]

Reactive blending of phthalic anhydride end-capped polystyrene-b-polyisoprene diblock (PS-b-PIP-anh) with 80 wt % of polyamide 12 (PA12) results in the very rapid formation of a PS-b-PIP-b-PA triblock copolymer, which self-assembles with formation of characteristic nanoobjects, within the polyamide matrix. For instance, a vesicular nanostructure is formed in the particular case of a symmetric, lamellar-forming diblock copolymer. This morphology actually complies with the lower curvature possible for ABC lamellae diluted in a continuous C phase under shear. In contrast, when the diblock composition is typically asymmetric (at constant molecular weight), vesicles disappear in favor of a core-shell morphology with a cucumber-like suborganization. This spontaneous nanostructuration of the PA12 matrix is quite general. Indeed substitution of an amorphous primary amine end-capped styrene/acrylonitrile random copolymer (SAN-NH2) for PA12 results in exactly the same phase morphology upon reactive blending with PS-b-PIP-anh. [less ▲]

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See detailNanostructured polyamide by reactive blending. 2. Transition from nanovesicles to cucumber-like core-shell nanoobjects
Koulic, Christian; Jérôme, Robert ULg

in Progress in Colloid and Polymer Science (2004), 129

Polyamide 12 (PA 12) has been nanostructured by reactive blending with 20 wt% of a symmetric anhydride end-capped polystyrene-b-polyisoprene (PS-b-PIP-anh) The liposome-like nanovesicles which are ... [more ▼]

Polyamide 12 (PA 12) has been nanostructured by reactive blending with 20 wt% of a symmetric anhydride end-capped polystyrene-b-polyisoprene (PS-b-PIP-anh) The liposome-like nanovesicles which are originally formed in the polyamide matrix (PA 12) are converted into cucumber-like core-shell nanoobjects upon increasing the volume fraction of PS by addi-j tion of homo PS of a molecular weight lower than the PS block. The key effect of the molecular weight of homoPS with respect to the PS bloc,k has been emphasized. The same nanoobjects can be prepared by direct blending of PA12 with 20 wt% of an asymmetric reactive PS-b-PIP-anh diblock with the same molecular weight and a higher PS content compared to the symmetric diblock. The interesting point is that the thickness of the rubbery envelope of the core-shell nanoobjects changes with the method used for their preparation at constant PA12/ PS/PIP composition, as result of a change in the molecular weight of the shell forming block. [less ▲]

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See detailNanostructured polymer blends: from core/shell nanoobjects to continuous three-phase morphologies
Lei, Liangcai; Detrembleur, Christophe ULg; Jeusette, Mélanie et al

in Macromolecular Materials and Engineering (2011), 296(2), 122-130

A PS-b-PIP-b-PMMA copolymer has been melt-blended with homo-PMMA with a similar molecular weight as the PMMA block. For a 50:50 wt.-% mixture, the components form 3D bicontinuous lamellae. Upon annealing ... [more ▼]

A PS-b-PIP-b-PMMA copolymer has been melt-blended with homo-PMMA with a similar molecular weight as the PMMA block. For a 50:50 wt.-% mixture, the components form 3D bicontinuous lamellae. Upon annealing at 190 °C, a more regular network is observed, which consists of PMMA and 55 nm-thick bilayered lamellae of triblock copolymer, both being continuous. This co-continuity persists even when of the homo-PMMA is twice that of the PMMA block in the copolymer. For 30:70 and 20:80 wt.-% copolymer/homopolymer pair, the copolymer forms cylindrical and spherical phases, respectively. Blends have also been prepared by solvent casting. Large domains of copolymer interconnected by few lamellae are observed in the 50:50 blend that reorganize into a bicontinuous network upon annealing. [less ▲]

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