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1.
用电子吸收光谱法, 研究了五个电子受体系列和三个电子给体系列以及非同系列的给、受体共48个化合物间的弱电荷转移络合作用。发现所研究的同系列给体与同一受体作用; 或同系列受体与同一给体作用; 或同系列给体与同系列受体作用, 一般存在着明显的CT络合与表观不络合的现象。通常情况下, 同系序数大的化合物呈现表观不络合;有时, 同系序数大和小的化合物, 即同系物的两头均呈现表观不络合现象, 对此种现象用给、受体间前线分子轨道能级关系进行了讨论。 相似文献
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Some photosensitive molecules, such as p-N,N′-dimethylaminobenzoic acid (DMABA), Nile Red, heteropolytungstic acid (H3PW12O40, HPA) and metalloporphyrins, have been entrapped onto nano-scale pores or channels of TiO2-modified Y-Zeolite (TiO2-Y-Zeolite) and MCM41 (TiO2-MCM41) and their excited-state intermediates have been characterized in terms of the excited-state dynamics by using laser spectroscopic techniques. Through these studies, it has been found that the photo-induced electrons are generated from the intramolecular charge transfer (ICT) state of DMABA, Nile Red or metalloporphyrin (MnTPP(Cl)), followed by transferring to the TiO2-Y-Zeolite or TiO2-MCM41 more efficiently as compared to the bulk TiO2, NaY-Zeolite or MCM41. The efficient photoinduced interfacial electron transfer causes the rapid formation of radicals of those photosensitive molecules (a few tens ps). It has been also found that these photophysical properties can be applied to develop the new photocatalyst as observed by the efficient photocatalytic activities of the DMABA or Nile Red-entrapped TiO2-Y-Zeolites for the photoreduction of an azo-dye such as Methyl Orange in water. On the other hand, in case of HPA-entrapped TiO2-Y-zeolite, the electron generated from the excited-state TiO2 is transferred to HPA, followed by formation of the reduction product, heteropoly blue (HPB) which is also generated by UV irradiation of HPA. This electron transfer is analogous to the Z-scheme mechanism of plant photosynthetic systems showing two photon reactions. Because of this photoelectron transfer mechanism, the HPA-entrapped TiO2-Y-zeolite has demonstrated the synergistic enhancement of the photocatalytic decomposition of Methyl Orange and hydrogen generation from photolysis of water. 相似文献
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Pulse-radiolysis reactions were performed to study the effect of hydrogen bonding to dimethyl sulfoxide (DMSO) on the oxidation of dihydroxy benzene and biphenyl diols to phenoxyl radicals. It was observed that with DMSO as the hydrogen-bond acceptor, the oxidation process proceeds via proton-coupled electron transfer in the case of hydroquinone. For resorcinol, DMSO acts in a similar way as in the case of hydroquinone. For other biphenols, viz., 2,2′- and 4,4′-biphenyl diols, it was found that DMSO had no effect on the electron transfer. The results are explained based on the ionization potential and structure of the phenol derivatives which probably depends on the rotation of the OH bond causing different electron distribution in the transient conformation. 相似文献
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A Sarkar N Biswas S Kapoor H S Mahal C K K Nair T Mukherjee 《Research on Chemical Intermediates》2005,31(9):857-866
The oxidation of flavonoids is of great interest because of their action as antioxidants with the ability to scavenge radicals
by means of electron-transfer processes. The redox reactions of the flavonoid derivative troxerutin, (2-[3,4-bis-(2-hydroxyethoxy)
phenyl]-3[[6-deoxy-α-L-manno-pyranosyl)-β-(D-glucopyranosyl]-oxy]-5-hydroxy-7-(2-hydroxyethoxy)-4H-1-benzo-pyran-4-one), were investigated over a wide range of conditions,
using pulse radiolysis and cyclic voltammetry. The oxidation mechanism proceeds in sequential steps. One-electron redox potentials
for troxerutin were found to be +1.196, +0.846 and −0.634 V vs. NHE. 相似文献
5.
富勒烯(C60/C70)与N,N,N’,N’-四-(对甲苯基)-4,4’-二胺-1,1’-二 苯硒醚(TPDASe)间在激光光诱导条件下,发生了分子间的电子转移过程.在可见- 近红外区(600-1200nm),观测到了TPDASe阳离子自由基、富勒烯(C60/C70)激发三 线态和阴离子自由基,在苯腈溶液中,观测瞬态谱测定了电子从TPDASe转移到富勒 烯(C60/C70)激发三线态的量子转化产率(Φet^T)和电子转移常数(Ket). 相似文献
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《Composite Interfaces》2013,20(7-9):781-795
In the present study, novel biocomposites with chopped jute fibers and thermosetting polycardanol were prepared using compression molding technique for the first time. Prior to biocomposite fabrication, jute fiber bundles were surface-treated at various concentrations using 3-glycidoxypropyltrimethoxy silane (GPS) and 3-aminopropyltriethoxy silane (APS), respectively. The interfacial shear strength, flexural properties and thermal properties of jute/polycardanol biocomposites reinforced with untreated and silane-treated jute fibers were investigated by means of single fiber microbonding test, three-point flexural test, dynamic mechanical analysis, thermogravimetric analysis and thermomechanical analysis. Both GPS and APS treatments played a role in improving the interfacial adhesion, reflecting that the organofunctional groups located at the end of silane coupling agents may contribute to linking between jute fibers and a polycardanol resin. As a result, it gave rise to increased interfacial shear strength of the biocomposites. Such interfacial improvement also led to increasing the flexural strength and modulus, storage modulus, thermal stability and thermomechanical stability. 相似文献
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《Composite Interfaces》2013,20(2-3):105-129
Interfacial shear strength (IFSS) of environmentally friendly natural fiber reinforced polymer composites plays a very important role in controlling their overall mechanical performance. The IFSS of various Ramie and Kenaf fiber/epoxy composites was evaluated using the combination of micromechanical test and nondestructive acoustic emission (AE) to find the optimal conditions for desirable final performance. Dynamic contact angle was measured for Ramie and Kenaf fibers and correlated the wettability properties with interfacial adhesion. Mechanical properties of Ramie and Kenaf fibers were investigated using single-fiber tensile test and analyzed statistically by both unimodal and bimodal Weibull distributions. The effect of clamping on the real elongation for both Ramie and Kenaf fibers was evaluated as well. Two different microfailure modes, axial dedonding and fibril fracture, coming from fiber bundles and single fiber composites (SFC) were observed under tension and compression. They were evaluated optically and also determined by AE and their FFT analysis nondestructively. 相似文献