Light-emitting properties of donor-acceptor and donor-acceptor-donor dyes in solution, solid, and aggregated states: structure-property relationship of emission behavior
Light-emitting properties of donor-acceptor and donor-acceptor-donor dyes in solution, solid, and aggregated states: structure-property relationship of emission behavior
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DOI：
10.1039/c5ra18231j
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发表时间：
2015-01-01
期刊：
影响因子：
3.9
通讯作者：
Kusakaki, Yutarou
中科院分区：
文献类型：
--
作者：
Ishi-i, Tsutomu;Ikeda, Kei;Kusakaki, Yutarou
在本文中，我们报告了一系列基于三苯胺的供体-受体型染料在溶液、固态以及极性水介质中聚集态的发光行为的系统研究。随着溶剂极性从非极性环己烷增加到极性 DMF，发射带发生红移，荧光量子产率降低。在THF/水介质中，在低水体积中发射被淬灭，而在高水体积中发射被恢复并增加。 In a low water volume, the dye molecules exist in a monomeric form, and the fluorescence quenching increases with increasing water fraction, similar to that observed in the solvent-polarity-dependence study.相反，染料分子在高体积的水中聚集。 This is probably because the inside of aggregates is less polar than the outside, thus preventing nonradiative deactivation and recovering the emission. This unusual emission was achieved by triphenylamine-based dyes containing a relatively strong acceptor moiety such as quinoxaline, benzothiadiazole, and thiadiazolopyridine, providing longer-wavelength red and near-IR emission. In the benzothiadiazole-based dyes, when the phenyl groups in the donor moieties were replaced with methyl groups, the fluorescence quantum yield decreased, indicating that the triphenylamine donor moiety is suitable for emission in the aggregated state.三苯胺的非平面结构破坏了有序堆积并产生有序度较低的球形聚集体，即使在极性水介质中也能实现有效的光发射。
In this paper, we report a systematic study on the light-emitting behavior of a series of triphenylamine-based donor-acceptor-type dyes in the solution and solid states as well as in the aggregated state in polar aqueous media. The emission band shifted bathochromically along with the decrease in the fluorescence quantum yield as the solvent polarity was increased from nonpolar cyclohexane to polar DMF. In a THF/water medium, the emission was quenched in a low water volume, whereas the emission was recovered and increased in a high water volume. In a low water volume, the dye molecules exist in a monomeric form, and the fluorescence quenching increases with increasing water fraction, similar to that observed in the solvent-polarity-dependence study. In contrast, the dye molecules aggregated in a high water volume. This is probably because the inside of aggregates is less polar than the outside, thus preventing nonradiative deactivation and recovering the emission. This unusual emission was achieved by triphenylamine-based dyes containing a relatively strong acceptor moiety such as quinoxaline, benzothiadiazole, and thiadiazolopyridine, providing longer-wavelength red and near-IR emission. In the benzothiadiazole-based dyes, when the phenyl groups in the donor moieties were replaced with methyl groups, the fluorescence quantum yield decreased, indicating that the triphenylamine donor moiety is suitable for emission in the aggregated state. The nonplanar structure of triphenylamine disrupts an ordered packing and produces a less-ordered spherical aggregate, leading to an efficient light emission even in polar aqueous media.