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61.
Chin-Kuen Tai Pao-Ling Yeh Chun-Chi Chang Wen-Hao Chen Rong-Hou Wu Yu-Ma Chou Bo-Cheng Wang 《Research on Chemical Intermediates》2014,40(6):2355-2362
Recently, the organic synthesis and electronic device applications of π-conjugated polymer-based materials with low energy band gap (below 2 eV) and high values of incident photon to current efficiency have been presented. In the present study, the physical properties of polythiophene (PTH) and its derivative systems (PTs) were investigated as π-conjugated low energy band gap polymers. Density functional theory with periodic boundary condition (PBC), the B3LYP functional, and the 6-31G(d) basis set was applied to determine their geometric and electronic structures and corresponding energies (E HOMO, E LUMO, and E g = E LUMO ? E HOMO) from the monomer of thiophene and its derivatives for one-dimensional (1D) extension to polymer. The effects of 3-substitution in PTs including electron-donating (CH3–, C6H13–, OH–, Cl–, OCH3–, and CHO–) and electron-withdrawing groups (Cl–, CHO–, CN–, NO2–, CF3–, and COOH–) compared with PTH were investigated. According to the calculation results, PTs with electron-donating and electron-withdrawing substituents should exhibit red- and blue-shifts, respectively, compared with PTH. These calculation results show good agreement with experimental data and provide further information for molecular design considerations. 相似文献
62.
Li-Ming Yeh 《Mathematical Methods in the Applied Sciences》1996,19(18):1489-1507
This paper concerns the well-posedness of the hydrodynamic model for semiconductor devices, a quasi-linear elliptic–parbolic–hyperbolic system. Boundary conditions for elliptic and parabolic equations are Dirichlet conditions while boundary conditions for the hyperbolic equations are assumed to be well-posed in L2 sense. Maximally strictly dissipative boundary conditions for the hyperbolic equations satisfy the assumption of well-posedness in L2 sense. The well-posedness of the model under the boundary conditions is demonstrated. 相似文献
63.
Five common food preservatives were analyzed by capillary electrochromatography, utilizing a methacrylate ester-based monolithic capillary as separation column. In order to optimize the separation of these preservatives, the effects of the pore size of the polymeric stationary phase, the pH and composition of the mobile phase on separation were examined. For all analytes, it was found that an increase in pore size caused a reduction in retention time. However, separation performances were greatly improved in monolithic columns with smaller pore sizes. The pH of the mobile phase had little influence on separation resolution, but a dramatic effect on the amount of sample that was needed to be electrokinetically injected into the monolithic column. In addition, the retention behaviors of these analytes were strongly influenced by the level of acetonitrile in the mobile phase. An optimal separation of the five preservatives was obtained within 7.0 min with a pH 3.0 mobile phase composed of phosphate buffer and acetonitrile 35:65 v/v. Finally, preservatives in real commercial products, including cold syrup, lotion, wine, and soy sauces, were successfully determined by the methacrylate ester-based polymeric monolithic column under this optimized condition. 相似文献
64.
A series of polymer-silica hybrid materials consisting of amino-terminated anionic waterborne-polyurethane (WPU) and inorganic silica particles have been prepared through a sol-gel process in the absence of an external catalyst. Typically, amino-terminated anionic WPU was first synthesized from polycaprolactone, dimethylol propionic acid, and 4,4′-methylenebis(cyclohexyl isocyanate) with specific molar ratios, followed by further reaction with triethylamine and triethylene tetramine to give as-prepared WPU. The WPU obtained was characterized by FTIR spectroscopy and gel permeation chromatography. Subsequently, a series of hybrid materials with different silica contents were prepared by performing sol-gel reactions with tetraethyl orthosilicate (TEOS) in an amino-terminated WPU matrix without the addition of an external catalyst. This was followed by examination by transmission electron microscopy and 29Si solid-state NMR. The terminated primary amine groups attached to the as-prepared WPU chains functioned as an internal base catalyst for the sol-gel process of TEOS. The effect of composition on the thermal stability, mechanical strength, surface wettability, and optical clarity of the hybrid materials was evaluated by the thermogravimetric analysis, dynamic mechanical analysis, contact angle measurement, and UV-visible transmission spectroscopy, respectively. 相似文献
65.
66.
Annealing of both cold-drawn atactic polystyrene and cold-drawn poly-methylmethacrylate at temperatures ranging from 50°C to their respective Tg's and for times ranging from 1 to 6 days gradually but completely eliminates the orientation arcing from the wide-angle X-ray diffraction pattern but induces only ~25% recovery of the cold-drawn deformation (as calculated from dimensional shrinkage). Analogous studies show that the birefringence of cold-drawn polystyrene is reduced by 57% during the annealing treatment. The results are evidence for segmental molecular motion below Tg and suggest that the molecular alignment responsible for the wide-angle X-ray diffraction arcing is not necessarily the same molecular orientation required for dimensional recovery. We have tentatively interpreted these results in terms of our recently proposed structural model consisting of both ordered domains and connecting disordered regions in the amorphous polymeric solid state. Annealing below Tg can produce chain backbone motion within the disordered regions and cause disorientation of the aligned ordered domains brought about by the initial cold-draw process. 相似文献
67.
Lin CC Yeh YC Yang CY Chen CL Chen GF Chen CC Wu YC 《Journal of the American Chemical Society》2002,124(14):3508-3509
The synthesis, characterization and biological application of mannose encapsulated gold nanoparticles (m-AuNP) are reported. m-AuNP is well dispersed and very stable without aggregation in the media of broad ion strength and pH ranges. The selective binding of m-AuNP to the mannose adhesin FimH of bacterial type 1 pili is demonstrated using transmission electron microscopy. The competition assay with free mannose suggests that m-AuNP binds FimH better than free mannose does. This work demonstrates that carbohydrate attached nanoparticles can be used as an efficient affinity label and a multi-ligand carrier in a biological system. 相似文献
68.
There is widespread interest in developing fluorescent reporters of protein kinase activity, species that can furnish a visual readout of both when and where intracellular kinases are activated in response to a stimulus. We have constructed and identified, via a combination of rational design, library synthesis, and screening, a difluorofluorescein-appended peptide-based species that responds to protein kinase C phosphorylation in a fluorescently sensitive fashion. The phosphorylation-induced divalent metal ion-mediated 265% enhancement in fluorescence proceeds with a V(max) of 8.5 micromol/min.mg and a K(m) of 20.5 microM. 相似文献
69.
The nonlinear propagation problem of optical beams in media with an intensity dependent indices of refraction is solved in the case of a fundamental gaussian beam. This solution is made possible by assuming everywhere along the propagation path a quadratic index profile. The quadratic constant is obtained self-consistently from the second term in a Taylor expansion of the local gaussian intensity. The solution constitutes an extension of the well known ABCD formalism to nonlinear propagation. 相似文献
70.