Computer simulation study on the structural-optical related properties of a pyrene-functionalized fluorescent film.
Computer simulation study on the structural-optical related properties of a pyrene-functionalized fluorescent film.
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DOI：
10.1021/la701801a
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发表时间：
2008-01
期刊：
影响因子：
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通讯作者：
Jing Liu;Yuqian Fang;Chenggang Chen
中科院分区：
文献类型：
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作者：
Jing Liu;Yuqian Fang;Chenggang Chen
通过分子动力学模拟研究了芘功能化膜的结构性质和与结构相关的光学性质，以及硝基苯存在下的薄膜。结果表明，在平衡状态下(1)薄膜的芘分子采用准共面结构，其中荧光团分子通过较长的柔性间隔片附着在玻璃板表面；(2)一对芘环之间的距离从4 a到10 a以上，但相当多的芘分子分布在4 - 5 a的距离内，表明薄膜的荧光应具有单体发射和准分子发射的双重特征；(3)硝基苯的引入导致在适合形成准分子的距离内芘分子的居群减少，表明膜的准分子发射会降低；(4)进入的硝基苯分子插入先前形成的芘环共面结构之间，并与其中一个形成配合物。考虑到硝基苯是贫电子的非荧光化合物，而芘是富电子的化合物，可以预期，在芘与硝基苯之间的距离和取向合理的情况下，配合物的形成必然导致芘向硝基苯的激发转移。这表明硝基苯的引入不仅减少了芘的准分子数量，而且抑制了荧光团的单体发射。模拟研究的所有期望与实验观察基本一致。
Molecular dynamics simulations were carried out to investigate the structural properties and the structure related optical properties of a pyrene-functionalized film and also the film in the presence of nitrobenzene. It has been shown that at equilibrium (1) the pyrene molecules of the film, of which the fluorophore molecules have been attached to a glass plate surface via relatively long flexible spacers, adopt quasi-coplanar structures; (2) the distance between a pair of pyrene rings populates from 4 A to longer than 10 A, but quite a large number of pyrene molecules populate within distances between 4 and 5 A, indicating that the fluorescence of the film should be characterized by both monomer emission and excimer emission; (3) introduction of nitrobenzene into the system results in a decrease of the population of pyrene molecules within the distances suitable for the formation of excimers, suggesting that excimer emission of the film would be decreased; and (4) the incoming nitrobenzene molecules insert themselves in between the previously formed coplanar structures of pyrene rings and form a complex with one of them. Considering that nitrobenzene is an electron-poor compound and nonfluorescent and that pyrene is an electron-rich one, it is expected that the formation of the complex must result in an excitation transfer from pyrene to nitrobenzene, provided that the distance between them and the orientations of them are reasonable. This indicates that the introduction of nitrobenzene not only decreases the number of excimers of pyrene but also quenches the monomer emission of the fluorophore. All the expectations from the simulation studies are basically consistent with the experimental observations.