Search results for "layer"
showing 10 items of 2667 documents
Ultra-thin film sensors based on porphyrin-5-ylphosphonate diesters for selective and sensitive dual-channel optical detection of mercury(II) ions
2020
International audience; Reusable dual-channel optical sensors for Hg2+ ions were prepared by Langmuir-Schaefer (LS) method from amphiphilic (trans-A2)BC-type porphyrins functionalized at meso-positions of the tetrapyrrolic macrocycle by sterically demanding diethoxyphosphoryl and mesityl groups as well as electron donating RO, RS or RNH substituents (R = n-C8H17). These three novel amphiphilic porphyrin derivatives were synthesized in good yields and their floating films at the air⎯water interface were investigated. In these monolayers, porphyrin molecules display a slipped stack-of-card orientation, but their strong π stacking is prohibited by bulky diethoxyphosphoryl and mesityl groups. T…
Insertion of Magnetic Bimetallic Oxalate Complexes into Layered Double Hydroxides
2006
Bimetallic oxalate complexes have been successfully inserted into layered double hydroxides as ferromagnetic oxalate-bridged oligomers. Different preparation methods afford different sizes and compositions for the oligomers. In all cases, no magnetic ordering has been observed above 2 K.
Synthesis of a New Copper-Azobenzene Dicarboxylate Framework in the Form of Hierarchical Bulk Solids and Thin Films without and with Patterning
2011
Reaction of copper(II) acetate with azobenzene-4,4′-dicarboxylic acid results in the formation of a metal–organic framework with the unexpected stoichiometry of Cu(II):ligand of 2:1. The bulk synthesis results in microspheres assembled from either nanobricks or nanoflakes, depending on the ratio of the reactants in solution. While the former behaves like a bulk solid with clear reflections in the X-ray and electron diffraction experiments, the latter obviously is dominated by surface effects, with a significant fraction of slightly expanded elemental cells and a significantly increased outer surface area. The material could also be deposited on a variety of surfaces using a stepwise layer-b…
Influence of the Interlayer Space on the Water Oxidation Performance in a Family of Surfactant-Intercalated NiFe-Layered Double Hydroxides
2019
Layered double hydroxides (LDHs) are low dimensional materials that act as benchmark catalysts for the oxygen evolution reaction (OER). Many LDH properties affecting the OER have been studied to reach the optimal efficiency but no systematic studies concerning the influence of the interlayer space have been developed. In this context, these materials allow a large tunability in their chemical composition enabling the substitution of the interlayer anion and therefore modifying exclusively the basal space. Here, we synthesize by anion exchange reactions a surfactantintercalated family of NiFe-LDHs with increasing basal spacing ranging from 8.0 to 31.6 Å (one of the largest reported so far fo…
Polystyrene as Graphene Film and 3D Graphene Sponge Precursor
2019
[EN] Polystyrene as a thin film on arbitrary substrates or pellets form defective graphene/graphitic films or powders that can be dispersed in water and organic solvents. The materials were characterized by visible absorption, Raman and X-ray photoelectron spectroscopy, electron and atomic force microscopy, and electrochemistry. Raman spectra of these materials showed the presence of the expected 2D, G, and D peaks at 2750, 1590, and 1350 cm(-1), respectively. The relative intensity of the G versus the D peak was taken as a quantitative indicator of the density of defects in the G layer.
From dewetting to wetting molecular layers: C60 on CaCO3(10 ̅14) as a case study.
2012
We report the formation of extended molecular layers of C-60 molecules on a dielectric surface at room temperature. In sharp contrast to previous C-60 adsorption studies on prototypical ionic crystal surfaces, a wetting layer is obtained when choosing the calcite (CaCO3)(10 (1) over bar4) surface as a substrate. Non-contact atomic force microscopy data reveal an excellent match of the hexagonal lattice of the molecular layer with the unit cell dimension of CaCO3(10 (1) over bar4) in the [01 (1) over bar0] direction, while a lattice mismatch along the [(4) over bar(2) over bar 61] direction results in a large-scale moire modulation. Overall, a (2 x 15) wetting layer is obtained. The distinct…
Metallization of the Na 14 Cl 13 Cluster
1994
The structure and energetics of multiple-excess-electron alkali halide clusters Na14Cl14-n, (1 ≤ n ≤ 6) is studied by ab initio calculations using norm-conserving pseudopotentials and local-spin-density-functional theory. Analysis of various electronic properties (Kohn-Sham one-electron eigenvalue spectra, ionization potentials, participation ratios of Kohn-Sham orbitals), as well as multiple F-center formation energies, suggests that these clusters can be characterized as Nan(NaCl)14-n having a "phase-separated" metallic part NaI. The Na14Cl9 (or Na14Cl9+) cluster exhibits a face (surface) segregated metallic Na5 (Na5+) overlayer, the stability of which is demonstrated by a molecular-dynam…
Faceting and structural anisotropy of nanopatterned CdO(110) layers
2005
CdO(110) layers with a self-organized surface structure have been grown on (10math0) sapphire (m plane) substrates by metal-organic vapor phase epitaxy. The epitaxial relationships between layer and substrate have been determined and a crystallographic model that accounts for the CdO in-plane orientation, which results in a reduced lattice mismatch when the CdO[001] direction is perpendicular to the sapphire c axis, has been proposed. Although the measured lattice parameters indicate that the layers are almost fully relaxed, an anisotropic mosaicity is detected with symmetrical rocking curves attaining minimum values when measured along the CdO[math10] direction. The layer morphology consis…
Geometric Analysis of Type B Aortic Dissections Shows Aortic Remodeling After Intervention Using Multilayer Stents
2020
Recently, multilayer stents for type B aortic dissections (TBAD) have been proposed to decrease false lumen flow, increase and streamline true lumen flow, and retain branch vessel patency. We aimed to provide a protocol with standardized techniques to investigate aortic remodeling of TBAD by multilayer flow modulators (MFM) in static geometric and hemodynamic analyses. Combining existing literature and new insights, a standardized protocol was designed. Using pre- and postoperative CT scans, geometric models were constructed, lumen dimensions were calculated, computational fluid dynamics (CFD) models were composed, and velocity and pressures were calculated. Sixteen TBAD cases treated with …
X-ray fluorescence investigation of gilded and enamelled silver: The case study of four medieval processional crosses from central Italy
2013
Abstract The presence of multilayered structures is common in such cultural artefacts as paintings, corroded metals, objects that underwent a whatever form of surface qualification. One of the most usual and complete ways to investigate such structures is observing a cross section, which requires sampling. There are however situations where at least part of the stratigraphic information can be derived non-destructively: the literature shows that X-ray fluorescence (XRF) has frequently been used, in recent years, for this purpose, with special regard to paintings and gilded metals. Aim of this paper is to further explore the suitability of XRF-based techniques to characterise multilayered st…