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181.
A complex InAs/CdSe/ZnSe core/shell1/shell2 (CSS) structure is synthesized, where the intermediate CdSe buffer layer decreases strain between the InAs core and the ZnSe outer shell. This structure leads to significantly improved fluorescence quantum yield as compared to previously prepared core/shell structures and enables growth of much thicker shells. The shell growth is done using a layer-by-layer method in which the shell cation and anion precursors are added sequentially allowing for excellent control, and a good size distribution is maintained throughout the entire growth process. The CSS structure is characterized using transmission electron microscopy, as well as by X-ray diffraction and X-ray photoelectron spectroscopy which provide evidence for shell growth. The quantum yield for CSS with small InAs cores reaches over 70%-exceptional photoluminescence intensity for III-V semiconductor nanocrystals. In larger InAs cores there is a systematic decrease in the quantum yield, with a yield of approximately 40% for intermediate size cores down to a few percent in large cores. The CSS structures also exhibit very good photostability, vastly improved over those of organically coated cores, and transformation into water environment via ligand exchange is performed without significant decrease of the quantum yield. These new InAs/CdSe/ZnSe CSS nanocrystals are therefore promising near-IR chromophores for biological fluorescence tagging and optoelectronic devices. 相似文献
182.
Two molybdenum and three antimony corroles were isolated and characterized by NMR, EPR, and electrochemistry. The very negative reduction potentials of the (oxo)molybdenum(V) corroles are clearly related to their inactivity as oxygen transfer reagents and the unsuccessful attempts to isolate lower-valent molybdenum corroles. X-ray crystallography of the (oxo)molybdenum(V) corrole 1a and the trans-difluoroantimony(V) corrole 2c, the first of their kind, revealed that their molecular structures represent extreme cases of such complexes: a highly domed corrole with very large out-of-plane metal displacement for 1a (0.73 Angstroms) and a very flat corrole with the metal ion in its center for 2c. All three antimony corroles displayed high activity and selectivity as catalysts for the photoinduced oxidation of thioanisole by molecular oxygen, with superior results obtained in alcoholic solvents with 2c as catalyst. Allylic and tertiary benzylic CH bonds were also oxidized under those conditions, with absolute selectivity to the corresponding hydroperoxides. 相似文献
183.
In this paper, Conway's group, Co3, is characterized among simplegroups of even type with e(G) = 3, by a restriction on the p-localstructure for some odd prime p for which m2,p(G) = 3. 2000 MathematicsSubject Classification 20D05. 相似文献
184.
Shlomo Margel Eliahu Nov Inna Fisher 《Journal of polymer science. Part A, Polymer chemistry》1991,29(3):347-355
The synthesis and characterization of polychloromethylstyrene microspheres are described. The effect of various factors, e.g., monomer concentration, surfactant concentration, solvents, crosslinker, etc., on the yield, diameter, and size distribution of these microspheres was elucidated. Conditions to covalently bind various primary amino ligands to these microspheres in aqueous solution were also established. The possible routes to modify the surface of these microspheres to obtain functional groups other than chloromethyl are discussed. 相似文献
185.
Inna Elyukhina 《Journal of mathematical chemistry》2018,56(9):2617-2625
We reduce the mathematical model for a chemical reaction in a moving medium to the general nonlinear parabolic equation (GNPE) for the complex amplitude of envelope wave to analyse weakly nonlinear interactions in supercritical regions. We use the method of many scales, wave packages, modification of Mandelshtam method and take into account the group velocity of envelope wave that is typical for nonlinear dispersive medium. GNPE describes the long-term system behaviour after stability loss and its coefficients are explicitly expressed through parameters of the initial nonlinear partial differential equations. It is taking into account the location of wave packet centre out of harmonics with maximum increment. 相似文献
186.
187.
Solomonov I Osipova M Feldman Y Baehtz C Kjaer K Robinson IK Webster GT McNaughton D Wood BR Weissbuch I Leiserowitz L 《Journal of the American Chemical Society》2007,129(9):2615-2627
The morphology of micrometer-sized beta-hematin crystals (synthetic malaria pigment) was determined by TEM images and diffraction, and by grazing incidence synchrotron X-ray diffraction at the air-water interface. The needle-like crystals are bounded by sharp {100} and {010} side faces, and capped by {011} and, to a lesser extent, by {001} end faces, in agreement with hemozoin (malaria pigment) crystals. The beta-hematin crystals grown in the presence of 10% chloroquine or quinine took appreciably longer to precipitate and tended to be symmetrically tapered toward both ends of the needle, due to stereoselective additive binding to {001} or {011} ledges. Evidence, but marginal, is presented that additives reduce crystal mosaic domain size along the needle axis, based on X-ray powder diffraction data. Coherent grazing exit X-ray diffraction suggests that the mosaic domains are smaller and less structurally stable than in pure crystals. IR-ATR and Raman spectra indicate molecular based differences due to a modification of surface and bulk propionic acid groups, following additive binding and a molecular rearrangement in the environment of the bulk sites poisoned by occluded quinoline. These results provided incentive to examine computationally whether hemozoin may be a target of antimalarial drugs diethylamino-alkoxyxanthones and artemisinin. A variation in activity of the former as a function of the alkoxy chain length is correlated with computed binding energy to {001} and {011} faces of beta-hematin. A model is proposed for artemisinin activity involving hemozoin nucleation inhibition via artemisinin-beta-hematin adducts bound to the principal crystal faces. Regarding nucleation of hemozoin inside the digestive vacuole of the malaria parasite, nucleation via the vacuole's membranous surface is proposed, based on a reported hemozoin alignment. As a test, a dibehenoyl-phosphatidylcholine monolayer transferred onto OTS-Si wafer nucleated far more beta-hematin crystals, albeit randomly oriented, than a reference OTS-Si. 相似文献
188.
Methylation of the anionic 4-methylcarboxy 1,2,3-oxadiazolate 3-oxide occurs at either the disubstituted ring nitrogen or the oxygen of the N-oxide depending upon the conditions and reagents employed. Alkylation with methyl iodide leads to N-alkylation, while dimethyl sulfate gives O-alkylation and trifluoromethanemethylsulfonate gives a mixture of the two products. The regioselectivity of these methylations has been confirmed by X-ray diffraction of the two products, and these are in turn correlated with their theoretically predicted (B3LYP//6-311++G**) relative energies and vibrational spectra. Theoretically, N-alkylation is expected to give an isomer that is over 10 kcal mol-1 more stable than the O-alkylated product. As a neat melt the kinetic O-alkylation product cleanly isomerizes in 2 h when heated to 140 degrees C to give the thermodynamic N-methylated isomer. Taken together the results illustrate the remarkable new sydnone N-oxide derivatives which are readily accessed in this chemistry, with the N-alkylation of the sydnone N-oxide, corresponding to the first case of such an N-alkylation for a diazenium diolate. 相似文献
189.
For a system of differential equations with small parameter at a part of derivatives, a linear deviation of the argument,
and a turning point, we obtained conditions, under which its solutions are solutions of a system of differential equations
with small parameter at a part of derivatives such that its matrices possess the asymptotic expansions at |ε| ≤ ε0 with the coefficients holomorphic at |x| ≤ x
0
. The existence and the infinite differentiability of a solution of the system of differential equations with small parameter
at a part of derivatives and with a linear deviation of the argument in the presence of a turning point are proved. 相似文献
190.
Alexander S. Shaplov Elena I. Lozinskaya Ricardo Losada Christine Wandrey Alexander T. Zdvizhkov Alexander A. Korlyukov Konstantin A. Lyssenko Inna A. Malyshkina Yakov S. Vygodskii 《先进技术聚合物》2011,22(4):448-457
The achievement of high ionic conductivity in single‐ion conducting polymer electrolytes is one of the important aims for various electrochemical devices including modern lithium batteries. One way to enhance the ionic conductivity in polyelectrolyte systems is to increase the quantity of charge carriers in each monomer unit. Highly charged poly(bis‐1,3(N,N,N‐trimethylammonium)‐2‐propylmethacrylate) with one of the most conducting anions, namely dicyanamide, was prepared via free radical bulk polymerization or using ionic liquids as reaction medium. The cationic polymers of the double‐charged monomer have molar masses up to = 1,830,000 g/mol and the ionic conductivity equal to 5.51 × 10?5 S / cm at 25°C. The film forming ability, crystallinity, thermal stability, and glass transition temperatures of the new polymeric ionic liquids obtained from detailed studies are presented. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献