排序方式: 共有45条查询结果,搜索用时 15 毫秒
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Using reaction rate data collected in aprotic solvents, we have determined that the Baylis-Hillman rate-determining step is second order in aldehyde and first order in DABCO and acrylate. On the basis of these data, we have proposed a new mechanism involving a hemiacetal intermediate. The proposed mechanism was then supported using two different kinetic isotope experiments. 相似文献
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Structural control in thin layers of poly(p-phenyleneethynylene)s: photophysical studies of Langmuir and Langmuir-Blodgett films 总被引:3,自引:0,他引:3
Kim J Levitsky IA McQuade DT Swager TM 《Journal of the American Chemical Society》2002,124(26):7710-7718
We present the relationship between the spatial arrangement and the photophysical properties of fluorescent polymers in thin films with controlled structures. Eight surfactant poly(p-phenyleneethynylene)s were designed and studied. These detailed studies of the behavior of the polymers at the air-water interface, and of the photophysical properties of their transferred LB films, revealed key structure-property relationships. Some of the polymers displayed pi-aggregates that are characteristic of an edge-on structure at the air-water interface. Monolayer LB films of these polymers showed greatly reduced quantum yields relative to solution values. Other polymers exhibited a highly emissive face-on structure at the air-water interface, and did not form pi-aggregates. The combination of pressure-area isotherms and the surface pressure dependent in situ UV-vis spectra of the polymers at the air-water interface revealed different behavioral details. In addition, the UV-vis spectra, fluorescence spectra, and quantum yields of the LB films provide design principles for making highly emissive films. 相似文献
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Broadwater SJ Hickey MK McQuade DT 《Journal of the American Chemical Society》2003,125(37):11154-11155
Herein, we report a highly sensitive luminescent thin film chemosensor constructed out of a small-molecule donor/acceptor system. Two types of films were compared: one using a small-molecule crystalline donor/acceptor pair and the other using a donor-graft polymer/small-molecule acceptor pair. The acceptor selected for this proof of concept responds to acid, causing its absorption and emission bands to red-shift, which increases spectral overlap with the donor. This increase in overlap greatly enhances energy transfer from the acceptor to the donor. Signal amplification was ascertained by measuring the ratio of acceptor fluorescence when the donor was excited versus direct excitation of the acceptor. Both types of films exhibited large amplification. For the polymeric system, the mechanism of energy migration was investigated by the use of steady-state fluorescence spectroscopy. The mechanism was determined to be dominated by an exciton-hopping process. 相似文献
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Sarmiento M Mooney P Bishop JM Biswas N Cason NM Dauwe L Godfrey J Kenney VP Pemper R Rojek E Ruchti RC Shephard WD Edelstein RM Forsyth CP Gamarnik K Ginther G Kreymer AE Lipton R McQuade JM Potter DM Russ JS Spiegel L Johnson DE Buchholz D Cremaldi L Delchamps SW Mao HS Rosen JL Sakumoto W Schluter RA Sontz SB Winter C 《Physical review D: Particles and fields》1992,45(7):2244-2248
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Frontispiece: Facile Conversion of Red Phosphorus into Soluble Polyphosphide Anions by Reaction with Potassium Ethoxide 下载免费PDF全文
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Facile Conversion of Red Phosphorus into Soluble Polyphosphide Anions by Reaction with Potassium Ethoxide 下载免费PDF全文
Dr. Alina Dragulescu‐Andrasi Dr. L. Zane Miller Dr. Banghao Chen Prof. D. Tyler McQuade Prof. Michael Shatruk 《Angewandte Chemie (International ed. in English)》2016,55(12):3904-3908
Soluble polyphosphide anions were successfully generated in a number of organic solvents by the reaction between shelf‐stable red phosphorus and potassium ethoxide. The species were identified by 31P NMR spectroscopy in solution and by X‐ray crystal‐structure determination of (Bu4N)2P16 in the solid state. The reaction was scaled up to gram quantities by using a flow‐chemistry process. 相似文献
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