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排序方式: 共有175条查询结果,搜索用时 15 毫秒
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Quantum-dot quantum well CdS/HgS/CdS: Theory and experiment 总被引:1,自引:0,他引:1
Schooss D Mews A Eychmüller A Weller H 《Physical review. B, Condensed matter》1994,49(24):17072-17078
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1λ6,2,4-Thiadiazetidines and 1,2λ6,3-Oxathiazetidines From the reaction of the sulfur triimides (RN?)3S ( 2a R?(CH3)3C, 2b R?(CH3)3Si) with pentafluoroazapropene ( 11 ) the appropriate 1λ6,2,4 thiadiazetidines ( 13a, 13b ) are formed, while from ClSO2N?CCl2 ( 14 ) and 2a (CH3)3C? N?C?N? SO2Cl ( 17 ) is isolated. 2b and hexafluoroacetone ( 18 ) give the rather unstable 1,2λ6,3-oxathiazetidine ( 20 ). 相似文献
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Deacon GB Evans DJ Junk PC Lork E Mews R Zemva B 《Dalton transactions (Cambridge, England : 2003)》2005,(13):2237-2238
Addition of 15-crown-5 to [GdF(AsF6)2], both dissolved in liquid SO2, and crystallisation at -30 degrees C has led to the isolation of the tetranuclear ionic complex [Gd4F7(15-crown-5)4][AsF6]5.6 SO2 which is stable up to--10 degrees C where SO2 loss leads to loss of crystallinity. 相似文献
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Pentafluorethyl Sulfurtrifluoride: Synthesis and Reactions By oxidation of (C2F5S?)2 ( 1 ) with AgF2 at 0°C a mixture of C2F5SF3 ( 2 ) and C2F5SF5 ( 3 ) besides C2F5S(O)F ( 4 ) is formed. With elemental fluorine only 3 is isolated, an intermediate in this reaction is (C2F5SF4?)2 ( 5 ). At ?40 to ?30°C the mixture of 2, 3 and 4 was reacted with TASF and AsF5, to give TAS+ C2F5SF4? ( 6 ), TAS+ C2F5S(O)F2? ( 7 ) and C2F5SF2+AsF6? ( 8 ), respectively. While 6 and 7 decompose rapidly in solution even at low temperatures, of thermally stable 8 the solid state structure was determined by x-ray diffraction. 相似文献
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Friedrichs O Sanchez-López JC López-Cartes C Klassen T Bormann R Fernandez A 《The journal of physical chemistry. B》2006,110(15):7845-7850
In the present work we investigate the hydrogen sorption mechanism in a MgH(2)/Nb(2)O(5) composite and analyze why Nb(2)O(5) could strongly improve hydrogen sorption kinetics in magnesium. Hereby we make use of the fact that Nb(2)O(5) nanoparticles are able to reduce the milling time significantly with the achievement of excellent sorption kinetics, and can so exclude effects occurring at long-term milling that make difficult the study of the mechanism. On the basis of extensive chemical, crystalline, and microstructural characterization of the MgH(2)/Nb(2)O(5) nanopowder system, a "pathway model" is proposed, which explains the kinetic hydrogen sorption improvement by a formation of pathways of niobium oxide species with lower oxidation state that facilitate the hydrogen transport into the sample. This mechanism is shown to be supported by additional oxidation experiments, which indicate increased oxygen diffusion through these pathways. 相似文献
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Bis(dimethylamino)trifluoro sulfonium Salts: [CF3S(NMe2)2]+[Me3SiF2]‐, [CF3S(NMe2)2]+ [HF2]‐ and [CF3S(NMe2)2]+[CF3S]‐ From the reaction of CF3SF3 with an excess of Me2NSiMe3 [CF3(NMe2)2]+[Me3SiF2]‐ (CF3‐BAS‐fluoride) ( 5 ), from CF3SF3/CF3SSCF3 and Me2NSiMe3 [CF3S(NMe2)2]+‐ [CF3S]‐ ( 7 ) are isolated. Thermal decomposition of 5 gives [CF3S(NMe2)2]+ [HF2]‐ ( 6 ). Reaction pathways are discussed, the structures of 5 ‐ 7 are reported. 相似文献
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Synthesis and characterization of highly luminescent CdSe-core CdS/Zn0.5Cd0.5S/ZnS multishell nanocrystals 总被引:1,自引:0,他引:1
We report on the preparation and structural characterization of CdSe nanocrystals, which are covered by a multishell structure from CdS and ZnS. By using the newly developed successive ion layer adhesion and reaction (SILAR) technique, we could gradually change the shell composition from CdS to ZnS in the radial direction. Because of the stepwise adjustment of the lattice parameters in the radial direction, the resulting nanocrystals show a high crystallinity and are almost perfectly spherical, as was investigated by X-ray diffraction and electron microscopy. Also, due to the radial increase of the respective valence- and conduction-band offsets, the nanocrystals are well electronically passivated. This leads to a high fluorescence quantum yield of 70-85% for the amine terminated multishell particles in organic solvents and a quantum yield of up to 50% for mercapto propionic acid-covered particles in water. Finally, we present experimental results that substantiate the superior photochemical and colloidal stability of the multishell particles. 相似文献
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