Comparison of Photophysical Properties of the Hemicyanine Dyes in Ionic and Nonionic Solvents
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- 作者：Taekyu Shim ; Myoung Hee Lee ; Doseok Kim ; Yukio Ouchi
- 刊名：Journal of Physical Chemistry B
- 出版年：2008
- 出版时间：February 21, 2008
- 年：2008
- 卷：112
- 期：7
- 页码：1906 - 1912
- 全文大小：170K
- 年卷期：v.112,no.7(February 21, 2008)
- ISSN：1520-5207
文摘
The fluorescence properties of 4-[4-(dimethylamino)styryl]-1-n-alkylpyridinium bromide (hemicyanine)dissolved in solvents of different polarities and viscosities (methanol, ethylene glycol, tetra-ethylene glycol,glycerol, benzyl alcohol, pyridine, and two ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate,[BMIM]BF4, and 1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM]PF6) were investigated. Significant increase in the fluorescence quantum yield and the fluorescence decay lifetime was observed withthe increase in the viscosity of the solvent medium. It is because the intramolecular rotational motion of themolecule becomes more difficult in viscous liquid, which leads to a decrease in the nonradiative decay processes.The fluorescence quantum yields for all of the solutions followed a semiempirical law that depends only onthe solvent viscosity. The correlation function C(t) was obtained for each solution by joining fluorescencedecay curves measured at different wavelengths. From the fitted results of C(t), we observed the distinctivefeature unique to the ionic liquids, in which the correlation functions for ionic liquid solutions are fitted tobe biphasic, while they are monophasic for other solvents. The fluorescence maximum of hemicyanine dissolvedin these ionic liquids red-shifted following the increase in the excitation wavelength.