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121.
Sylwia Kondej 《Annales Henri Poincare》2012,13(6):1451-1467
We study a three-dimensional nonrelativistic quantum system with a delta-type potential. The support of this potential is determined by a circle and straight line in ${\mathbb{R}^3}$ . We show that a special symmetry of our system induces embedded eigenvalues, and breaking this symmetry leads to resonances. 相似文献
122.
Krzysztof Strzelec Natalia Bączek Sylwia Ostrowska Karolina Wąsikowska Małgorzata Iwona Szynkowska Jacek Grams 《Comptes Rendus Chimie》2012,15(11-12):1065-1071
A novel thiol-terminated polythiourethanes were synthesized from low-molecular-weight di- and multifunctional mercaptans and diisocyanates and employed as curing agent of epoxy resin. The curing reaction of epoxy resin and thermal properties of cured products were investigated with differential scanning calorimetry. Evaluation of climatic ageing resistance was made by the change in mechanical properties. Mechanical studies indicated that the application of polythiourethane has toughening effect and significantly increases ageing resistance of the cured resins. The results of this study indicate that molecular structure and functionality of polythiourethane oligomers are of critical importance in governing the curing mechanism, structure of the network and final properties of epoxy compositions. 相似文献
123.
The possible existence of the CF(5)(-), CCl(5)(-), SiF(5)(-), SiCl(5)(-), GeF(5)(-), and GeCl(5)(-) anions has been investigated using ab initio methods. The species containing Si and Ge as central atoms were found to adopt the D(3h)-symmetry trigonal bipyramidal equilibrium structures whose thermodynamic stabilities were confirmed by examining the most probable fragmentation channels. The ab initio re-examination of the electronic stabilities of the SiF(5)(-), SiCl(5)(-), GeF(5)(-), and GeCl(5)(-) anions [using the OVGF(full) method with the 6-311+G(3df) basis set] led to the very large vertical electron detachment (VDE) energies of 9.316 eV (SiF(5)(-)) and 9.742 eV (GeF(5)(-)), whereas smaller VDEs of 6.196 and 6.452 eV were predicted for the SiCl(5)(-) and GeCl(5)(-) species, respectively. By contrast, the high-symmetry and structurally compact anionic CF(5)(-) and CCl(5)(-) systems cannot exist due to the strongly repulsive potential predicted for the X(-) (F(-) or Cl(-)) approaching the CX(4) (CF(4) or CCl(4)). The formation of weakly bound CX(4)···X(-) (CF(4)···F(-) and CCl(4)···Cl(-)) anionic complexes (consisting of pseudotetrahedral neutral CX(4) with the weakly tethered X(-)) might be expected at low temperatures (approaching 0 K), whereas neither CX(5)(-) (CF(5)(-), CCl(5)(-)) systems nor CX(4)···X(-) (CF(4)···F(-) and CCl(4)···Cl(-)) complexes can exist in the elevated temperatures (above 0K) due to their susceptibility to the fragmentation (leading to the X(-) loss). 相似文献
124.
Chromatographic analysis of ionic liquids on different types of packings offers interesting possibility to determine their retention mechanism. As a consequence, the major interactions between stationary phase ligands and analyzed chemical entities can be defined. The main aim of this work was to analyze cations of ionic liquids on chemically bonded stationary phases with specific structural properties. The attempt to predict the main interactions between positive ions of ionic liquids and stationary phase ligands was undertaken. For that purpose, butyl, octyl, octadecyl, phenyl, aryl, mixed, alkylamide, and cholesterolic packings were chosen and applied to the analysis of six most commonly used ionic liquids' cations. Obtained results indicate mainly dispersive and pi-pi type of interaction part in the retention mechanism of analyzed compounds. 相似文献
125.
Different types of columns with specific structural properties were used for the separation of mixtures of ionic liquid cations. Two of them were home-made packings and the other two were commercial stationary phases. One of the home-made packings contained cholesterol ligands bonded chemically to silica (SG-CHOL) whereas the other one was a mixed stationary phase (SG-MIX) with cyanopropyl, aminopropyl, phenyl, octyl, and octadecyl ligands. RP-18e Innovation ChromolithTM Performance and Macrosphere 300 C4 packings were also used. A comparison of the separation possibilities offered by these columns for the substances in question revealed significant differences in performance. Packings containing surface-bonded functional groups that are able to undergo protonation are not suitable for separation of such compounds under the given analysis conditions (pH = 4). The best results were obtained for two alkyl stationary phases: butyl and octadecyl. Cluster analysis has also been performed for comparison of the ionic liquid cation properties. 相似文献
126.
Ptasińska S Echt O Denifl S Stano M Sulzer P Zappa F Stamatovic A Scheier P Märk TD 《The journal of physical chemistry. A》2006,110(27):8451-8456
We report on attachment of free electrons to fullerenes C(n) (n = 60, 70, 76, 78, 80, 82, 84, 86) and to Sc(3)N@C(80). The attachment cross sections exhibit a strong resonance at 0 eV for all species. The overall shape of the anion yield versus electron energy is quite similar for the higher fullerenes, with a minimum around 1 eV and a maximum which gradually shifts from 6 eV for C(60) to approximately 4 eV for large n. The endohedral Sc(3)N@C(80) exhibits a particularly shallow minimum and a maximum below 4 eV. We model autoionization of the anions with due consideration of the internal energy distributions. The relatively low electron affinity of Sc(3)N@C(80) is reflected in its reduced ion yield at higher attachment energies. 相似文献
127.
128.
Prof. René T. Boeré Janis Derendorf Prof. Carsten Jenne Dr. Sylwia Kacprzak Dr. Mathias Keßler Rainer Riebau Prof. Sebastian Riedel Dr. Tracey L. Roemmele Monika Rühle Dr. Harald Scherer Thomas Vent‐Schmidt Jonas Warneke Prof. Stefan Weber 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(15):4447-4459
The perhalogenated closo‐dodecaborate dianions [B12X12]2? (X=H, F, Cl, Br, I) are three‐dimensional counterparts to the two‐dimensional aromatics C6X6 (X=H, F, Cl, Br, I). Whereas oxidation of the parent compounds [B12H12]2? and benzene does not lead to isolable radicals, the perhalogenated analogues can be oxidized by chemical or electrochemical methods to give stable radicals. The chemical oxidation of the closo‐dodecaborate dianions [B12X12]2? with the strong oxidizer AsF5 in liquid sulfur dioxide (lSO2) yielded the corresponding radical anions [B12X12] ? ? (X=F, Cl, Br). The presence of radical ions was proven by EPR and UV/Vis spectroscopy and supported by quantum chemical calculations. Use of an excess amount of the oxidizing agent allowed the synthesis of the neutral perhalogenated hypercloso‐boranes B12X12 (X=Cl, Br). These compounds were characterized by single‐crystal X‐ray diffraction of dark blue B12Cl12 and [Na(SO2)6][B12Br12] ? B12Br12. Sublimation of the crude reaction products that contained B12X12 (X=Cl, Br) resulted in pure dark blue B12Cl12 or decomposition to red B9Br9, respectively. The energetics of the oxidation processes in the gas phase were calculated by DFT methods at the PBE0/def2‐TZVPP level of theory. They revealed the trend of increasing ionization potentials of the [B12X12]2? dianions by going from fluorine to bromine as halogen substituent. The oxidation of all [B12X12]2? dianions was also studied in the gas phase by mass spectrometry in an ion trap. The electrochemical oxidation of the closo‐dodecaborate dianions [B12X12]2? (X=F, Cl, Br, I) by cyclic and Osteryoung square‐wave voltammetry in liquid sulfur dioxide or acetonitrile showed very good agreement with quantum chemical calculations in the gas phase. For [B12X12]2? (X=F, Cl, Br) the first and second oxidation processes are detected. Whereas the first process is quasi‐reversible (with oxidation potentials in the range between +1.68 and +2.29 V (lSO2, versus ferrocene/ferrocenium (Fc0/+))), the second process is irreversible (with oxidation potentials ranging from +2.63 to +2.71 V (lSO2, versus Fc0/+)). [B12I12]2? showed a complex oxidation behavior in cyclic voltammetry experiments, presumably owing to decomposition of the cluster anion under release of iodide, which also explains the failure to isolate the respective radical by chemical oxidation. 相似文献
129.
Enhanced Water Splitting at Thin Film Tungsten Trioxide Photoanodes Bearing Plasmonic Gold–Polyoxometalate Particles
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Dr. Renata Solarska Krzysztof Bienkowski Dr. Sylwia Zoladek Aldona Majcher Dr. Tomasz Stefaniuk Prof. Pawel J. Kulesza Prof. Jan Augustynski 《Angewandte Chemie (International ed. in English)》2014,53(51):14196-14200
Tungsten trioxide (WO3) is one of a few stable semiconductor materials liable to produce solar fuel by photoelectrochemical water splitting. To enhance its visible light conversion efficiency, we incorporated plasmonic gold nanoparticles (Au NPs) derivatized with polyoxometalate (H3PMo12O40) species into WO3. The combined plasmonic and catalytic effect of Au NPs anchored to the WO3 surface resulted in a large increase of water photooxidation currents. Shielding the Au NPs with polyoxometalates appears to be an effective means to avoid formation of recombination centers at the photoanode surface. 相似文献
130.
A novel analytical approach has been developed for the determination of selected drugs (milrinone, enalapril, carvedilol, spironolactone, acenocumarol, ticlopidine, cilazapril) and their metabolites (2‐oxoticlopidine, cilazaprilat, canrenone, 5′‐hydroxycarvedilol, O‐desmethyl‐carvedilol, enalaprilat) in human urine, based on a miniaturized extraction technique; semiautomatic microextraction by packed sorbent, using a new digitally controlled syringe, followed by ultra high pressure liquid chromatography separation combined with UV detection. During method optimization, the extraction parameters as the type of sorbent material, type and volume of elution solution, number of extraction cycles, volume and pH of sample, type and volume of washing solution were studied. The chromatographic separation of the target analytes was performed with a core–shell analytical column using 0.05% trifluoroacetic acid in water and acetonitrile in gradient elution mode. The limits of quantification ranged from 0.016 to 0.045 μg/mL. Under the optimized conditions, extraction efficiency was higher than 70.1% for drugs and their metabolites. Due to its simplicity and speed, this method was successfully applied to the quantitation of selected compounds in urine samples. 相似文献