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101.
van Vugt LK Veen SJ Bakkers EP Roest AL Vanmaekelbergh D 《Journal of the American Chemical Society》2005,127(35):12357-12362
As-grown single-crystal InP nanowires, covered with a surface oxide, show a photoluminescence efficiency that strongly varies from wire to wire. We show that the luminescence efficiency of single-crystal InP nanowires can be improved by photoassisted wet chemical etching in a butanol solution containing HF and the indium-coordinating ligand trioctylphosphine oxide. Electron-hole photogeneration, electron scavenging, and oxidative dissolution combined with surface passivation by the indium-coordinating ligand are essential elements to improve the luminescence efficiency. Time traces of the luminescence of surface-passivated wires show strong oscillations resembling the on-off blinking observed with single quantum dots. These results reflect the strong influence of a single or a few nonradiative recombination center(s) on the luminescence properties of an entire wire. 相似文献
102.
It is shown that for a large class of Lie groups (called weakly algebraic groups) including all connected semisimple Lie groups the following holds: for any probability measure on the Lie group the set of all two-sided convolution factors is compact if and only if the centralizer of the support of inG is compact. This is applied to prove that for any connected Lie groupG, any homomorphism of any real directed (submonogeneous) semigroup into the topological semigroup of all probability measures onG is locally tight. 相似文献
103.
104.
Let M be an array (), where each of its cells is colored in one of two colors. We give a necessary and sufficient condition for the existence of a partition of M into n diagonals, each containing at least one cell of each color. As a consequence, it follows that if each color appears in at least cells, then such a partition exists. The proof uses results on completion of partial Latin squares. 相似文献
105.
Vuluga D Legros J Crousse B Bonnet-Delpon D 《Chemical communications (Cambridge, England)》2008,(40):4954-4955
Gold nanoparticles (AuNPs) coated with hexafluoroisopropanol moieties were prepared, and their surface was changed through simple hydrogen bond association with various amines, which allow orientation of the solubility of these AuNPs in determined organic solvents. 相似文献
106.
Errikos Kounalis Dr. Martin Lutz Dr. Ing. Daniël L. J. Broere 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(58):13280-13284
A naphthyridine-derived expanded pincer ligand is described that can host two copper(I) centers. The proton-responsive ligand can undergo reversible partial and full dearomatization of the naphthyridine core, which enables cooperative activation of H2 giving an unusual butterfly-shaped Cu4H2 complex. 相似文献
107.
Thierry M. Faure Luc Pastur François Lusseyran Yann Fraigneau Danièle Bisch 《Experiments in fluids》2009,47(3):395-410
This experimental study reports flow developments inside a parallelepipedic cavity of variable shape and dimensions. That
flow is generated by the interaction between a laminar boundary layer and the cavity, which creates shear-layer oscillations.
The aim is to understand the three-dimensional flow morphology varying the Reynolds number and the cavity shape. Flow visualizations
are obtained in a plane situated inside the cavity in order to get the dynamical structures. Dimensional analysis of the cavity
flow teaches that three dimensionless numbers are necessary for the flow reduction. This is confirmed by experimental results
pointing thresholds of appearance of instabilities identified for some combinations of Reynolds number and geometric parameters.
The key mechanisms for their existence are centrifugal effects induced by a vortex of spanwise axis with sufficient intensity,
and viscous effects due to the wall confinement of the cavity. Their destruction is linked to flow transition to turbulence
above a limiting convective velocity generated by the vortex of spanwise axis. These instabilities are generally present in
a spanwise row of counter-rotating pairs of vortices, but for some cases, isolated pairs are also identified. Secondary modulations
of primary instabilities are also present for particular parameters. Results permit to discriminate the relevant scales associated
with the shear layer and the inner cavity flow. 相似文献
108.
We have prepared high-quality assemblies of monodisperse CdSe quantum dots and employed a combination of electrochemical gating and electrical and optical techniques to study orbital occupation in these quantum-dot solids. Electron occupation in localized states is important in some cases and can be unambiguously distinguished from occupation of the nanocrystal eigenstates. In addition, all excitonic transitions show a red-shift in the transition energy, due to the presence of electron charge. We infer that the energy of the S electrons is determined by the quantum-confinement energy and by Coulomb repulsions of the S electron with all other electrons in the assembly. By using a simple electron-repulsion model, we explain observed differences in the electron-addition energy for different samples, the broadening of the electron occupation as a function of electrochemical potential, and the strong dependence of the electron-addition energy on nanocrystal diameter. 相似文献
109.
Liljeroth P Zeijlmans van Emmichoven PA Hickey SG Weller H Grandidier B Allan G Vanmaekelbergh D 《Physical review letters》2005,95(8):086801
The density-of-states function of individual colloidal PbSe nanocrystals varying in diameter between 3 and 7 nm is measured by resonant tunneling spectroscopy. It is in semiquantitative agreement with tight-binding calculations, but the energy separation between electron (hole) levels of S and P symmetry is systematically smaller than predicted by the theory. These results provide an explanation for the second and third excitonic optical transitions, which have been debated for a long time. 相似文献
110.
Paul H.J.Kouwer Paula de Almeida Onno ven den Boomen Zaskia H.Eksteen-Akeroyd Roel Hammink Maarten Jaspers Stijn Kragt Mathijs F.J.Mabesoone Roeland J.M.Nolte Alan E.Rowan Martin G.T.A.Rutten Vincent A.A.Le Sage Daniёl C.Schoenmakers Chengfen Xing Jialiang Xu 《中国化学快报》2018,29(2):281-284
The gelation temperature and mechanical properties of aqueous ethylene glycol-decorated polyisocyanide solutions strongly depends on the length of the glycol tail. Copolymerisation of monomers with different tail lengths allows for precise engineering of the gel properties. 相似文献