Search results for "sorption"
showing 10 items of 4623 documents
Bright Visible Luminescence in Silica Nanoparticles
2011
International audience; We demonstrate that a porous film of silica nanoparticles emits a bright visible luminescence associated with defects stabilized by oxygen chemisorption at oxygen deficient center sites. Time-resolved spectra excited by a tunable laser allow us to distinguish the luminescence at 1.99 eV, characteristic of the nonbridging oxygen hole center (NBOHC) (Si-O)3 Si-O*, and a fast and a slow emission: the first (lifetime τ ≈ 25 ns) is peaked at 2.27 eV with an excitation spectrum centered at 5.5 eV; the second (τ ≈ 7.5 μs) is peaked at 2.41 eV and is excited around 3.2 and 5.2 eV. Reaction in an air atmosphere leads to the disappearance of the NBOHC luminescence and of the …
Second Harmonic Emission From Dielectric Nanoresonators in the Absorption Regime
2023
We study second harmonic generation in dielectric nanocylinders as a function of the wavelength of the incident field and geometrical dimensions. Uncommonly, we consider a spectral range in which the emitted nonlinear signal is partially absorbed by the dielectric. Surprisingly, we reveal that the second harmonic efficiency does not decrease as the imaginary part of the complex dielectric refractive index increases. Indeed, the presence of higher order multipoles supported by the resonators at the fundamental wavelength can significantly boost the generated second harmonic signal even in the dielectric absorption spectral region achieving nonlinear efficiency of the same order of magnitude …
Quantum Motion of Chemisorbed Hydrogen on Ni Surfaces
1983
Quantum mechanical energy levels and wave functions have been calculated for the motion of chemisorbed hydrogen atoms on Ni surfaces. The results show considerable quantum effects for the adatom in both the ground and the excited states. The description of the adparticles as being delocalized along the surface offers a novel interpretation of several phenomena, in particular the vibrational excitations. Peer reviewed
Third order nonlinear optical properties of novel TetrathiafulvalenePhenanthroline based dyads
2011
The non-linear optical properties of π-conjugated organic molecules such as TTF and their derivatives have recently gained particular interest due to their extended π-system and the strong electron donating character. The knowledge of the nonlinear optical response, as well as the impact of the charge transfer on the nonlinearity is very important. As such systems can be used in a variety of applications. In this study we investigate the nonlinear absorption of novel tetrathiafulvalene-phenanthroline based dyads by means of the Z-scan technique.
Identification and quantification of phosphatidylcholines containing very long chain polyunsaturated fatty acid (VLC-PUFA) in bovine and human retina…
2010
The retina is one of the vertebrate tissues with the highest content in polyunsaturated fatty acids (PUFA). A large proportion of the retinal glycerophospholipids, especially those found in photoreceptor membranes, are dipolyunsaturated molecular species. Among them, dipolyunsaturated phosphatidylcholine molecular species are known to contain very long chain polyunsaturated fatty acids (VLC-PUFA) from the n-3 and n-6 series and having 24 to 36 carbon atoms (C24 to C36) and four to six double bonds. Recent interest in the role of VLC-PUFA arose from the findings that a protein named ELOngation of Very Long chain fatty acids 4 (ELOVL4) is involved in their biosynthesis and that mutations in E…
Solvatochromic behaviour of new donor–acceptor oligothiophenes
2021
Oligothiophene derivatives play a central role in the formulation of materials used in devices in the field of organic electronics. In this work, we report the results of the study of UV-vis absorption and fluorescence spectra, in several solvents, of a series of oligothiophenes recently synthesized in our laboratory. The studied oligothiophenes present different structures due to several factors: the donor– acceptor (D–A) or acceptor–donor–acceptor (A–D–A) architecture, the number of thiophene rings in the backbone (ranging from three to eight), the number and position of solubilizing octyl chains in the backbone, and the type of acceptor moieties (from Knoevenagel condensation either with…
Predicting tire/pavement noise impact reduction using numerical simulation and experimental data for open graded asphalt mixture
2013
The environmental impact of noise from roads and highways traffic is relevant in urban and rural areas. The use of open-graded asphalt pavements reduces significantly the noise, entrapping the acoustic waves inside the porous structure of the material. In this paper we propose a simulation approach in order to predict the acoustic properties of the asphalt mixture from geometrical and topological indicators. In detail we have generated, using a Random Sequential Adsorption model, synthetic samples starting from the same grading and bitumen contents of real samples manufactured in laboratory. We have measured the acoustic adsorption coefficient of the real samples and we have investigated th…
Recent progress in metal-organic frameworks (MOFs) for CO2 capture at different pressures
2022
Global climate change ensued by the rise in atmospheric CO2 levels is one of the greatest challenges our planet is facing today. This worldwide distress demands technologies that can contribute to our society toward “negative carbon emissions”. Carbon capture and storage (CCS) technologies are in in important role for capturing CO2 from existing emission sources, such as industrial and energy production point sources, before new more prominent modifications to the energy infrastructure can be implemented. Recently, alongside point source capture, direct air capture (DAC) processes have emerged as highly sought-after technologies that are able to capture CO2 from the ambient air. Alongside t…
Copper Induces a Core Plasmon in Intermetallic Au(144,145)–xCux(SR)60 Nanoclusters
2015
The electronic structure and optical absorption spectra of intermetallic thiol-stabilized gold-copper clusters, having 144-145 metal atoms and 60 thiols, were studied by ab initio computations. The widely known icosahedral-based cluster model from the work of Lopez-Acevedo et al. (2009) was used, and clusters doped with one to 30 copper atoms were considered. When doped inside the metal core, copper induces dramatic changes in the optical spectrum as compared to the previously studied all-gold Au144(SR)60. An intense broad absorption peak develops in the range 535-587 nm depending on the amount of doping and doping sites. This result agrees very well with recent experiments by the Dass grou…
Single Crystal Sub‐Nanometer Sized Cu6(SR)6 Clusters: Structure, Photophysical Properties, and Electrochemical Sensing
2016
Organic ligand-protected metal nanoclusters have attracted extensively attention owing to their atomically precise composition, determined atom-packing structure and the fascinating properties and promising applications. To date, most research has been focused on thiol-stabilized gold and silver nanoclusters and their single crystal structures. Here the single crystal copper nanocluster species (Cu6(SC7H4NO)6) determined by X-ray crystallography and mass spectrometry is presented. The hexanuclear copper core is a distorted octahedron surrounded by six mercaptobenzoxazole ligands as protecting units through a simple bridging bonding motif. Density functional theory (DFT) calculations provide…