Search results for "Chalcogenide"
showing 10 items of 141 documents
Synthesis and functionalization of chalcogenide nanotubes
2010
New synthetic approaches to MS 2 (M = Sn, Nb, Mo, W) chalcogenide nanostructures are highlighted. Most chalcogenide particles can be functionalized directly with inorganic nanoparticles such as Au, ZnO or MnO. Depending on the Pearson hardness of the metal involved, the functionalization may be reversible or irreversible. A covalent functionalization strategy is based on a steric shielding of the coordination sphere of transition metal atoms in such a way that only coordination sites are available for bonding to the chalcogenide surface. This allows the immobilization of fluorophors, redox active groups or proteins onto chalcogenide nanoparticle.
Chalcogenide-capped triiron clusters [Fe3(CO)9(μ3-E)2], [Fe3(CO)7(μ3-CO)(μ3-E)(μ-dppm)] and [Fe3(CO)7(μ3-E)2(μ-dppm)] (E = S, Se) as proton-reduction…
2019
Chalcogenide-capped triiron clusters [Fe3(CO)7(μ3-CO)(μ3-E)(μ-dppm)] and [Fe3(CO)7(μ3-E)2(μ-dppm)] (E = S, Se) have been examined as proton-reduction catalysts. Protonation studies show that [Fe3(CO)9(μ3-E)2] are unaffected by strong acids. Mono-capped [Fe3(CO)7(μ3-CO)(μ3-E)(μ-dppm)] react with HBF4.Et2O but changes in IR spectra are attributed to BF3 binding to the face-capping carbonyl, while bicapped [Fe3(CO)7(μ3-E)2(μ-dppm)] are protonated but in a process that is not catalytically important. DFT calculations are presented to support these protonation studies. Cyclic voltammetry shows that [Fe3(CO)9(μ3-Se)2] exhibits two reduction waves, and upon addition of strong acids, proton-reducti…
Proximity Effects on the Charge Density Wave Order and Superconductivity in Single-Layer NbSe2
2021
Collective electronic states such as the charge density wave (CDW) order and superconductivity (SC) respond sensitively to external perturbations. Such sensitivity is dramatically enhanced in two dimensions (2D), where 2D materials hosting such electronic states are largely exposed to the environment. In this regard, the ineludible presence of supporting substrates triggers various proximity effects on 2D materials that may ultimately compromise the stability and properties of the electronic ground state. In this work, we investigate the impact of proximity effects on the CDW and superconducting states in single-layer (SL) NbSe2 on four substrates of diverse nature, namely, bilayer graphene…
Supercontinuum generation in chalcogenides : application to gas spectroscopy in atmospheric band III
2023
This thesis work aims to contribute to the development of new fiber sources emitting over a wide range of wavelengths in the IR, in particular to detect greenhouse gases in the mid-infrared range. Our spectroscopy results with nitrous oxide N2O and methane CH4 are obtained in band III. To achieve this, the generation of supercontinuum (SC) covering band III was made possible by using chalcogenide optical fibers, purified and free of highly toxic elements according to REACH regulations, in particular arsenic and antimony. The fibrable vitreous composition belonging to the Ge-Se-Te ternary system fits perfectly into the context of sustainable development, it is the one that has been identifie…
Hybrid chalcogenide nanoparticles: 2D-WS2 nanocrystals inside nested WS2 fullerenes.
2013
The MOCVD assisted formation of nested WS2 inorganic fullerenes (IF-WS2) was performed by enhancing surface diffusion with iodine, and fullerene growth was monitored by taking TEM snapshots of intermediate products. The internal structure of the core–shell nanoparticles was studied using scanning electron microscopy (SEM) after cross-cutting with a focused ion beam (FIB). Lamellar reaction intermediates were found occluded in the fullerene particles. In contrast to carbon fullerenes, layered metal chalcogenides prefer the formation of planar, plate-like structures where the dangling bonds at the edges are stabilized by excess S atoms. The effects of the reaction and annealing temperatures o…
ChemInform Abstract: The Valence States of Nickel, Tin, and Sulfur in the Ternary Chalcogenide Ni3Sn2S2 - XPS, 61Ni and 119Sn Moessbauer Investigatio…
2010
Photoluminescence Enhancement by Band Alignment Engineering in MoS 2 /FePS 3 van der Waals Heterostructures
2022
Single-layer semiconducting transition metal dichalcogenides (2H-TMDs) display robust excitonic photoluminescence emission, which can be improved by controlled changes to the environment and the chemical potential of the material. However, a drastic emission quench has been generally observed when TMDs are stacked in van der Waals heterostructures, which often favor the nonradiative recombination of photocarriers. Herein, we achieve an enhancement of the photoluminescence of single-layer MoS2 on top of van der Waals FePS3. The optimal energy band alignment of this heterostructure preserves light emission of MoS2 against nonradiative interlayer recombination processes and favors the charge t…
Structural-relaxation phenomena in As–S glasses as probed by combined PAL/DBAR technique
2015
Abstract Experimental techniques exploring phenomena of positron–electron interaction, namely the positron annihilation lifetime spectroscopy and Doppler broadening of annihilation radiation, are shown to be very informative tools to study radiation- and thermally-induced phenomena in chalcogenide glasses of binary As–S system. Time-dependent processes of free-volume voids agglomeration (expansion), fragmentation (refining) and disappearing (contraction) are identified as main stages of physical aging in S-rich glasses, while a competitive channel of coordination topological defects formation associated with void charging becomes significant in a vicinity of near-stoichiometric glass compos…
<title>Photoinduced AsSeS thin film phase plates as adaptive optics mirrors for eye aberration correction</title>
2008
Amorphous chalcogenide thin films are excellent materials for holographic recordings. AsSeS thin film coating is a useful optical material for it's thickness to be easily corrected with the use of exposure to light and consecutive chemical etching. Following properties allow to treat the surface of AsSeS chalcogenide films and to use them in adaptive optics systems for correction of the optical wavefront. Hereby, we characterize AsSeS film properties to be used for correction of optical aberrations of the human eye. The thickness of the film is characterized with the method of spectrodensitometry and the surface profile depth with a Hartman- Shack waveform analyzator.
Mid-infrared strong spectral broadening in microstructured tapered chalcogenide AsSe fiber
2012
We report on the generation of a supercontinuum in a chalcogenide microstructured tapered fiber. The suspended core diameter of the fiber is reduced from 5.5 μm to 0.8 μm in the waist of the tapered region. The zero dispersion wavelength is below 2 μm in the tapered region. To pump the fiber, we use a modelocked laser of 4 ps, with a central wavelength of 1960 nm. With only 150 W peak power in the fiber a supercontinuum is generated from 1300 to 2600 nm taking the supercontinuum wavelength edge at -30 dB from the continuum.