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91.
92.
A possibility of obtaining local, effective, energy-dependent polarization and absorption potentials from experimental cross-sections for electron scattering is investigated. Potentials have been fitted with the help of the genetic algorithm on large sets of experimental data for e-He, e-Ne and e-Ar elastic scattering at impact energies 20-3000 eV. The obtained potentials reproduce the cross-sections within experimental errors. 相似文献
93.
Ab initio complete optimizations at MP2/6-31++G** level have been performed in the T-shaped geometry of the benzene-benzene and benzene-naphthalene complexes. To check the effect of the basis set superposition error (BSSE), optimizations have been done in the BSSE corrected and BSSE uncorrected potential energy surfaces. The BSSE effect in the calculation of the Hessian has also been evaluated to check its influence in the frequency values. Quantum theory atoms in molecules (QTAIM) calculations have also been performed on both dimers. Intermolecular energies differ around a 25% when the optimization is performed with or without counterpoise corrected gradients. The influence of BSSE is also noticeable in the distances. Frequency shifts show big changes because of the BSSE. Thus, uncorrected values are up 350% larger than corrected ones. The hypotheses given in the literature to explain the origin of the blue-shifting hydrogen bond do not seem to give a suitable explanation for all characteristics of the behavior found in the studied systems. 相似文献
94.
Ramos CI Santana Marques MG Correia AJ Serra VV Tomé JP Tomé AC Neves MG Cavaleiro JA 《Journal of the American Society for Mass Spectrometry》2007,18(4):762-768
Reductions involving more than one electron with formation of the M+ and [M+2H]+ ions were observed for electrosprayed meso-tris(N-methylpyridinium-4-yl)porphyrin iodides, MI3. These reductions were studied by using different solvents and flow rates. Formation of the [M+2H]+ ions occurred only for protic solvents and to a larger extent at lower flow rates. The type of the fourth substituent does
not seem to affect the reduction processes. Formation of the two reduced species, M+ and [M+2H]+ ions, may occur through the participation of counter ion/solvent clusters. Reduction of multiply charged, non-metallated
species with formation of [M+nH]+ ions (n>1) was not observed before in positive mode electrospray mass spectrometry. 相似文献
95.
Wojciech Macyk Konrad Szaciłowski Grażyna Stochel Marta Buchalska Joanna Kuncewicz Przemysław Łabuz 《Coordination chemistry reviews》2010,254(21-22):2687-2701
Titanium dioxide photosensitization may be achieved in various ways, involving surface modification with appropriate species. The photosensitization process requires a visible light-induced electron or hole injection into conduction or valence band, respectively. Efficiency of this process depends on electronic interaction between the photosensitizer moiety (surface complex) and TiO2 particle. At least two types of the charge injection mechanisms may be distinguished—in the first, charge is transferred from the excited state of the sensitizer molecule to the conduction or valence band while the second mechanism involves a direct molecule-to-band charge transfer (MBCT). The MBCT process can be realized by surface titanium(IV) complexes with various organic and sometimes inorganic ligands. Catechol, phthalic acid or salicylic acid derivatives, as well as cyanometallate anions, upon chemisorption at TiO2 surface constitute an especially interesting group of ligands to yield various titanium(IV) surface complexes. Geometry of these complexes, electronic structures and possibility of their use as photosensitizers of TiO2 are discussed on the basis of experimental data and quantum-chemical modeling. Also prospective applications of photoinduced electron transfer and photocatalytic activity of such systems are presented. 相似文献
96.
This work examines the influence of the amount of silver nanoparticles added to polyacrylonitrile spinning solutions on their rheological properties as well as the structure and properties of the fibers produced. The influence of the amount of silver nanoparticles on the supramolecular structure of nanocomposite polyacrylonitrile precursor fibers, their porosity, as well as thermal and tensile strength properties was determined. The distribution of the nano‐ additive in fiber cross‐sections and on the surface was estimated. It was found that the addition of silver nanoparticles to polyacrylonitrile precursor fibers in an amount of up to 1.5% does not cause a decrease in the susceptibility of the fiber matter to deformation at the drawing stage. The produced fibers were characterized by an increased total volume of pores of 0.35 cm3/g and tenacity of more than 34 cN/tex. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
97.
Andrzej Swinarew Beata Piekarnik Zbigniew Grobelny Andrzej Stolarzewicz Jurate Simokaitienė Egle Andrikaityte Juozas V. Gražulevičius 《Macromolecular Symposia》2011,308(1):8-11
Summary: The polymerization of (9-carbazolyl)methylthiirane in the presence of cyclic oligo(potassium glycidoxide) as the macroinitiator activated 18-crown-6 leads to polythioether with the molecular masses relatively near to the calculated ones. This polythioether dispersed in a commercially available transparent polymer gives a new blue photoluminescent material. 相似文献
98.
Korn Md Andrade JB Jesus DS Lemos VA Bandeira ML Santos WN Bezerra MA Amorim FA Souza AS Ferreira SL 《Talanta》2006,69(1):16-24
Lead is recognized worldwide as a poisonous metal. Thus, the determination of this element is often required in environmental, biological, food and geological samples. However, these analyses are difficult because such samples contain relatively low concentrations of lead, which fall below the detection limit of conventional analytical techniques such as flame atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry. Several preconcentration procedures to determine lead have therefore been devised, involving separation techniques such as liquid-liquid extraction, solid phase extraction, coprecipitation and cloud point extraction. Citing 160 references, this paper offers a critical review of preconcentration procedures for determining lead using spectroanalytical techniques. 相似文献
99.
Jiao L Hao E Fronczek FR Vicente MG Smith KM 《Chemical communications (Cambridge, England)》2006,(37):3900-3902
A new route to benzoporphyrins is reported in which readily available vicinal dibromoporphyrins are bis-allylated using the Suzuki reaction, cyclized by way of olefin metathesis and finally oxidized to give mono-, di-, or tri-benzoporphyrins. 相似文献
100.
Ongayi O Vicente MG Ou Z Kadish KM Kumar MR Fronczek FR Smith KM 《Inorganic chemistry》2006,45(4):1463-1470
The high-yield preparation of metallo-benzoylbiliverdins 9, 10, and 11 from either oxidation of dodeca-substituted porphyrin 6 in the presence of NaNO2/TFA and air followed by metalation or by reaction of the Ni(II) or Cu(II) complexes of 6 with m-chloroperoxybenzoic acid in pyridine under air is reported. The X-ray structures of complexes 9 and 10 and the electrochemistry and spectroelectrochemistry of metallo-benzoylbiliverdins 9-11 are presented and discussed. 相似文献