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Aggregation-induced emission (AIE) in THF–water mixtures To understand whether a water-nonsoluble conjugated organic molecule is AIE active, a simple and practical method is usually to add a large amount of water into the organic solution of the compound and record the changes of fluorescence intensity.14,15 FLA-Cn are highly soluble in common organic solvents, such as THF, dichloromethane, chloroform and toluene. Since water is the non-solvent for FLA-Cn, the molecules of FLA-Cn must have aggregated in THF–water mixtures with high water content like other 9,10-diarylvinylanthracene derivatives.10,13,15 The absorption and emission spectra of FLA-Cn in THF–water mixtures are shown in Fig. 1. FLA-Cn are AIE-active with weak fluorescence in molecularly dissolved solution with fluorescence quantum yields (F) of 3.8–4.9% but increased fluorescence intensities in aqueous suspensions with F of 21–29% at high water content (THF/water ¼ 1/9) (Fig. 1a–c). Because of the large internal steric hindrance between the 1,8-positions of the anthracene ring and the b-positions of the vinylene moieties, the conjugated backbone of 9,10-diaryl-vinylanthracene has been forced to twist strongly.10i,15a,b In molecularly dissolved solution, the intramolecular torsion motion is relatively free, which facilitates nonradiative relaxation pathways and affords weak fluorescence emission. However, in aqueous media, the intramolecular vibration and rotation are seriously restricted by molecular selfaggregation, causing the aqueous suspensions to exhibit strongly aggregation-induced emission. On the other hand, there are no significant differences for the absorption spectra of FLA-Cn in solution and aqueous suspension (Fig. 1d). This implies that the molecular stacking in aqueous media is probably loose. |
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yhc0316: 金币+50, 翻译EPI+1 2014-10-20 13:53:48
yhc0316: 金币+50, 翻译EPI+1 2014-10-20 13:53:48
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在THF-水混合物中的聚合诱导发光（AIE） 了解一种非水溶性共轭有机分子是否具有AIE活跃，一个简单实用的方法通常是添加大量的水进入该化合物的有机溶液，并记录荧光强度的变化【14,15】。 FLA-Cn在THF，二氯甲烷，氯仿和甲苯等在普通有机溶剂中具有高度可溶性。因为对FLA-Cn而言，水是在非溶剂，因此在THF-水混合物中FLA-Cn的分子必定发生高含水量聚合，就像其他9,10 - 二芳基乙烯基蒽衍生物一样【10,13,15】。FLA-Cn在THF - 水混合物中的吸收和发光光谱见图 1。FLA-Cn具有AIE活性，在分子溶解的溶液中有弱荧光，荧光量子产率（F）为3.8-4.9％，但在高水含量（THF：水 = 1：9）的水悬浮液中荧光强度增加，荧光量子产率（F）为21-29％（图1a-c）。因为1,8位上的蒽环和β位置上的亚乙烯基团的之间的大的内部空间位阻，9,10 - 二芳基 - 乙烯基蒽的共轭主链已被迫强烈扭曲【10i，15a，b】。在分子溶于溶液时，分子内的扭转运动是相对自由的，这促进了无发光弛豫途径，并使其具有弱荧光发光。然而，在含水介质中，分子内的振动和转动都严重受分子自聚集的限制，使水性悬浮液表现出强烈的聚合诱导发光。另一方面，FLA-Cn的吸收光谱在溶液和水悬浮液中没有明显差异（图1d）。这意味着，在含水介质中分子的堆叠可能是松散的。 |
2楼2014-10-20 11:56:55