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71.
Summary The fluoroescence quenching of 1,4-dimethoxynaphthalene (1) and 1,8-dimethoxynaphthalene (2) by tetraphenylporpyrin (3), 9,10-diphenylanthracene (4), and 3-cyano-4-phenyl-6-(p-tolyl)-pyridin-2-one (5) has been studied in chloroform solution. The quenching occursvia a resonance energy transfer mechanism. The rate constant for the energy transfer (k
ET) of donor2 is slower than that of1 by the same acceptors, indicating that the steric effect dominates the ionization potential effect in all systems. The calculated critical transfer distances (R
0) are 17–72 Å. In contrast, charge transfer is the predominant pathway of electronic deexcitation in the fluorescence quenching of donors1 and2 by 7,7,8,8-tetracyanoquinone-dimethane (6) in chloroform. The roles of temperature and geometrical structure of the donors on the efficiency of fluorescence quenching of1 and2 by acceptor6 have also been studied.
Wechselwirkung des angeregten Singlett-Zustands von 1,4- und 1,8-Dimethoxynaphthalin mit einigen organischen Verbindungen: eine Untersuchung zur Fluoreszenzlöschung
Zusammenfassung Die Löschung der Fluoreszenz von 1,4-Dimethoxynaphthalin (1) und 1,8-Dimethoxynaphthalin (2) durch Tetraphenylporphyrin (3), 9,10-Diphenylanthracen (4) und 3-Cyano-4-phenyl-6-(p-tolyl)-pyridin-2-on (5) in Chloroform wurde untersucht. Die Löschung verläuft über einen Resonanzenergietransfermechanismus. Die Geschwindigkeitskonstante für den Energietransfer (k ET) ist bei gleichem Akzeptor für den Donor2 niedriger als für1. Daraus läßt sich schließen, daß in allen untersuchten Systemen der sterische Effekt über den Effekt des Ionisierungspotentials dominiert. Die berechneten kritischen Transferdistanzen betragen 17–72 Å. Im Gegensatz zu diesen Beobachtungen verläuft der vorherrschende Relaxationsmechanismus bei der Fluoreszenzlöschung von1 und2 durch 7,7,8,8-Tetracyanochinon-dimethan (6) über einencharge-transfer-Prozeß. Die Einflüsse von Temperatur und Geometrie der Verbindungen auf die Effizienz der Fluoreszenzlöschung von1 und2 durch den Akzeptor6 wurden ebenfalls untersucht.相似文献
72.
Chaikovskaya O. N. Levin P. P. Sul"timova N. B. Sokolova I. V. Kuz"min A. V. 《Russian Chemical Bulletin》2004,53(2):313-317
The spectra and kinetics of short-lived intermediates formed from aqueous (0.1 N NaOH) solutions of the natural mixture of humic and fulvic acids (HFA) were studied by laser flash photolysis using excitation wavelengths of 337, 390, 470, and 520 nm. Laser photolysis of HFA with light of 520 and 470 nm results in the formation of triplet excited states (THFA) characterized by the broad absorption spectrum with a maximum near 630 nm and lifetimes of 0.15 ms in deoxygenated solutions. The formation of two types of THFA with lifetimes of 0.1 and 2 ms and absorption spectra with maxima at 570 nm is observed under photolysis with light of 337 and 390 nm. The estimation of quantum yields of THFA gives 1 and 0.3% under photolysis with excitation wavelengths of 337 and 520 nm, respectively. The rate constants of THFA quenching by molecular oxygen are equal to (7—8)·108 L mol–1 s–1. 相似文献
73.
本文基于二氧硫对固定于增塑的聚氯乙烯膜上的芳香稠环化合物蒽的荧光熄灭,研制了二氧化硫选择性光化学敏感膜,经过组成优化 的敏感膜测定二氧化硫的浓度范围为6.59×10^-3-5.23×10^-1mol/L,校正曲线与理论推导的模拟曲线相吻合,且荧光信号具有较高的重现性,信号响应时间为5-30s. 相似文献
74.
Absolute small angle X-ray studies of concentration fluctuations were performed in order to determine thermodynamic properties of a model blend, consisting ofn-hexane and perfluoro-n-hexane. The quantities which we determined were the second derivate of the Gibbs free energy of mixing with respect to the concentration of the components, the location of the spinodal, interaction and solubility parameters, the energy gradient density coefficient as well as the correlation length of the fluctuations at various compositions and temperatures, particularly in the neighbourhood of the spinodal and the critical point. The data obtained were compared with those obtainable from the well known location of the binodal, to test the reliability of the scattering method. 相似文献
75.
The triplet nature of rare long-lived states of d0 metallocenes formed upon ligand-to-metal energy transfer was confirmed by studies of triplet-triplet charge transfer in biscyclopentadienyl
complexes Cp2MCl2 (M = Zr (1), Hf (2)). The interaction between precatalysts and substrates of catalytic polymerization systems, viz., complexes 1 and 2 and unsaturated hydrocarbons (alkenes and dienes), was studied in the region of concentrations close to catalytic values.
For organometallic π-complexes, it has been shown for the first time that, in the case of the unsaturated hydrocarbons, the
efficiency of energy transfer obeys the Perrin equation. The process occurs at distances R
0 close to the diameter of the interacting molecules and is well described by the exchange-resonant mechanism of interaction.
In the case of the cyclopentadiene-Cp2MCl2 (M = Zr, Hf) systems, R
0 = 14.6 Å. A linear relationship between the critical radius of the quenching sphere R
0 and the number of carbon atoms in a linear α-olefin has been revealed for the first time and evidences the formation of a
π-complex between the precatalyst and substrate molecules.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 35–39, January, 2007. 相似文献
76.
Ferreira H Lúcio M Lima JL Matos C Reis S 《Analytical and bioanalytical chemistry》2005,382(5):1256-1264
In this work the interaction of a non-steroidal anti-inflammatory drug (NSAID), diclofenac, with egg yolk phosphatidylcoline (EPC) liposomes, used as cell-membrane models, was quantified by determination of the partition coefficient. The liposome/aqueous phase partition coefficient was determined by derivative spectrophotometry, fluorescence quenching, and measurement of zeta-potential. Theoretical models based on simple partition of the diclofenac between two different media, were used to fit the experimental data, enabling the determination of Kp. The three techniques used yielded similar results. The effects of the interaction on the membranes characteristics were further evaluated, either by studying membrane potential changes or by effects on membrane fluidity. The liposome membrane potential and the size and size-homogeneity of liposomes were measured by light scattering. The effects of diclofenac on the internal viscosity or fluidity of the membrane were determined by use of spectroscopic probes—a series of n-(9-anthroyloxy) fatty acids in which the carboxyl terminal group is located at the interfacial region of the membrane and the fluorescent anthracene group is attached at different positions along the fatty acid chain. The location of the diclofenac on the membrane was also evaluated, by fluorescence quenching using the same series of fluorescent probes. Because the fluorescent anthracene group is attached at different positions along the fatty acid chain, it is possible to label at a graded series of depths in the bilayer. The interactions between the drug and the probe are a means of predicting the location of the drug on the membrane. 相似文献
77.
采用不同材料作为有机电致发光器件(OELDs)的电极, 制备了基本结构为[阳极/NPB(40 nm)]/Alq3(50 nm)/阴极]的异质结双层器件, 并通过改变OELDs器件的阴极或阳极来研究电极材料对器件光电性能的影响. 研究结果表明, 各器件电流-电压(I-V)关系的基本特征与陷阱电荷限制电流(TCLC)机制的拟合情况相符. 由于有机材料本身能级的无序性以及载流子迁移率对温度和电场的依赖性, 不同电极的载流子注入能力与其功函数并无直接关系. 双层器件中由于空穴传输层的引入, 使得载流子复合区域位于有机层异质结界面处, 降低了金属阴极对激子的猝灭作用, 从而大大提高了器件性能. 此外, 金属电极OLEDs器件结构具有的微腔效应会导致发射光谱的位移和谱峰宽度变窄, 这表明通过对金属电极的表面改性和优化可使器件性能超过常规结构的器件. 相似文献
78.
WU Ren-Ping YU Yan GU Ying Yun GUO Jin-Yu 《结构化学》2007,26(5):562-566
Deep color glass-ceramics is prepared by using gold tailings as the main raw material, and Cr2O3 is added as nucleation agent. Influence of different Cr2O3 additions on crystallization structure and properties of CaO-MgO-Al2O3-SiO2 glass-ceramics has been discussed so as to select optimum additions. DTA is employed to determine optimum crystallization and nucleation temperatures; XRD and SEM are used to characterize microstructure of each sample; and performance indexes, such as water absorption, bulk density, flexural strength and so on, are also determined. Experimental results show that when 3wt% Cr2O3 is introduced, fine glass-ceramics with diopside as the main crystal and Ca-Fe diopside as the second-crystal is obtained, and its corresponding performance indexes are as follows: water absorption 0.12%, bulk density 2.56 g/cm3, and flexural strength 70.01 Mpa. 相似文献
79.
二溴羟基苯基荧光酮—乳化剂OP荧光熄灭法测定微量铬(Ⅵ) 总被引:11,自引:3,他引:11
本文基于Cr(Ⅵ)-二溴羟基苯基荧光酮(DBH-PF)-OP体系的荧光熄灭效应,提出一种测定痕量铬(Ⅵ)的新荧光方法。在pH2.4-4.1的HCl-NaAc缓冲介质和OP存在下,Cr(Ⅵ)与DBH-PF形成1:2的橙红色络合物,络合物的最大激发发工和发射波长分别是365mm和528nm。铬(Ⅵ)量在0.05-1.5μg/25ml范围内与△F呈线性关系,检测限是2.0ng/ml。方法用于电镀废液,废 相似文献
80.