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71.
The process of electron transport plays an essential role in the fundamental phenomena of life like photosynthesis, respiration and vision as well as in photoelectronic devices. However, the molecular mechanisms of the electron way and factors governing the transport rate in such systems are still unclear. Several groups have reported theoretical approaches for searching the mechanisms by using statistical mechanics, coherent dynamics and quantum mechanics. The current density vector inside the semiconducting layer is determined. In this paper we consider the problem of transport of electron promoted in the electrochemical cell constructed of two electrodes with the dye molecules immersed in. We describe the process of electron promotion by refractive light wave on the vacuum–semiconductor boundary as well as on the semiconducting electrode and the dye molecule layer in terms of extended phenomenological electrodynamics formalism. The results of our theoretical model show that such a theoretical approach will give more information on the mechanism of electron transport and will give insight in the determination of some electric features of materials. 相似文献
72.
A polyacrylate/polyurethane (P(A) / P(U)) composite coating has been prepared bycrosslinking an acetoacetylated polyacrylate with a vinylic group terminated polyurethaneat room temperature. A model Michael reaction between ethyl acetoacetate (EAA) andmethyl acrylate (MA) was designed to study the crosslinking mechanism. It was foundthat the two active hydrogen atoms in acetoacetyl group can both add to vinylic groupsand the yield of mono- and bis-adducts are much affected by the molar ratio of acetoacetylto vinylic groups. Higher crosslinking degree and better properties could be obtained withdecreasing the molar ratio of the two active groups from 1/1 to 0.6/1 in the compositecoatings. 相似文献
73.
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75.
Martín-Matute B Bogár K Edin M Kaynak FB Bäckvall JE 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(20):5832-5842
A range of ruthenium cyclopentadienyl (Cp) complexes have been prepared and used for isomerization of allylic alcohols to the corresponding saturated carbonyl compounds. Complexes bearing CO ligands show higher activity than those with PPh3 ligands. The isomerization rate is highly affected by the substituents on the Cp ring. Tetra(phenyl)methyl-substituted catalysts rapidly isomerize allylic alcohols under very mild reaction conditions (ambient temperature) with short reaction times. Substituted allylic alcohols have been isomerized by employing Ru-Cp complexes. A study of the isomerization catalyzed by [Ru(Ph5Cp)(CO)2H] (14) indicates that the isomerization catalyzed by ruthenium hydrides partly follows a different mechanism than that of ruthenium halides activated by KOtBu. Furthermore, the lack of ketone exchange when the isomerization was performed in the presence of an unsaturated ketone (1 equiv), different from that obtained by dehydrogenation of the starting allylic alcohol, supports a mechanism in which the isomerization takes place within the coordination sphere of the ruthenium catalyst. 相似文献
76.
Radiation-chemical transformations of chloride solutions in the presence of iodide additives were studied by pulse radiolysis.
Radical anion Cl2
⋅− oxidize I− ion, while in the secondary reactions Cl2 reacts with I− to form a mixed trihalide ion ICl2
−. A reaction model that satisfactorily describes the experimental data was proposed.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1336–1340, June, 2005. 相似文献
77.
78.
H2CCF自由基与HNCO反应机理的理论研究 总被引:4,自引:0,他引:4
采用密度泛函理论的B3LYP方法, 在6-311++G(d,p)基组水平上研究了H2CCF自由基与HNCO的微观反应机理, 优化了反应过程中的反应物、中间体、过渡态和产物, 为了获得更精确的能量信息, 还在QCISD(T)/6-311++G(d,p)基组水平上计算了各物质的能量.振动分析结果和IRC分析结果证实了中间体和过渡态的真实性, 计算所得的成键临界点电荷密度的变化也确认了反应过程.对于H2CCF自由基与HNCO反应, 我们找到了六条可行的反应通道, 结果分析表明通道H2CCF+HNCO→IM3→TS5→H2CCFH+NCO控制步骤活化能最低, 是该反应的主要通道, 在此反应过程中有稳定的氢键复合物IM3生成, 还表现出氢原子迁移的反应特征. 相似文献
79.
C. Joly S. Goizet J. C. Schrotter J. Sanchez M. Escoubes 《Journal of membrane science》1997,130(1-2):63-74
The effect of introduction of silica particles prepared by the sol-gel technique on the gas transport properties of a polyimide film was studied. The sorption and permeation of N2, O2, CO2, H2 and CH4 were studied and correlated with morphological changes in the polymer structure. From sorption isotherms, we observed that the composite membrane presents higher solubility coefficients than the polyimide one. The solubility coefficient ratio between the composite and the polyimide is about 1.5–2.0. The isotherms were analyzed in terms of the dual mode sorption. The Henry's coefficient and the Langmuir's affinity and saturation constants were obtained allowing to calculate the Langmuir to Henry concentration ratios as function of the gas pressure. These ratios decrease until zero within a certain pressure range as long as the Langmuir's mode is acting and they are higher for the polyimide membrane when compared with the composite one. This study was completed with calorimetric measurements during the sorption. The gas interaction energy in kJ/mol decreases within the same pressure range as previously described. The measured energies are higher for the polyimide film when compared with the composite one because the polyimide membrane presents a stronger energetic effect caused by a higher Langmuir's contribution. From permeation studies at 3.155 Pa, the composite membrane showed higher permeability coefficients and permselectivities than the polyimide one. All these results were explained, taking into account the difference on the imidization degree of both membranes and the morphological changes which may be induced by the silica nodules in the organic/inorganic interphases. 相似文献
80.
Tian S.-J. Xi G.-X. Cheng Q.-T. Lou X.-D. Li J.-H. 《Journal of Thermal Analysis and Calorimetry》1998,53(3):825-833
The inclusion complex of benzaldehyde (BA) with β-cyclodextrin (β-CD) was prepared and was studied by thermal analysis and
X-ray diffractometry. The composition of the complex was identified by TG and elemental analysis as β-CD·BA·9H2O. TG and DSC studies showed that the thermal dissociation of β-CD·BA·9H2O took place in three stages: dehydration in the range 70-120°C; dissociation of β-CD·BA in the range 235-270°C; and decomposition
of β-CD above 280°C. The kinetics of dissociation of β-CD·BA in flowing dry nitrogen was studied by means of TG both at constant
temperature and at linearly increasing temperature. The results showed that the dissociation of β-CD·BA was dominated by a
one-dimensional random nucleation and subsequent growth process (A2). The activation energy E was 124. 8 kJ mol-1, and the pre-exponential factor A 5.04·1011 min-1.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献