J-aggregation and its characterization in Langmuir-Blodgett films of merocyanine dyes.
J-aggregation and its characterization in Langmuir-Blodgett films of merocyanine dyes.
复制标题
部花青染料 Langmuir-Blodgett 薄膜中的 J 聚集及其表征。
DOI：
10.1016/j.cis.2004.09.003
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发表时间：
2004
影响因子：
15.6
通讯作者：
S. Kuroda
中科院分区：
文献类型：
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作者：
S. Kuroda
LB膜是通过将空气-水界面处形成的单分子层连续转移到固体基底上来构建的。LB技术在制备分子聚集体中的优点之一在于它可以通过在空气-水界面处混合来使用各种分子。混合系统可能表现出单个组分所没有观察到的新特性。这种方法将是有用的，例如，在功能染料的J-聚集体的形成和控制的研究，吸引了科学和技术的关注。在本文中，我主要是根据我们最近的结果，部花菁这一主题进行综述。LB膜的mercury染料，与花生酸（C20）混合，表现出J-聚集体的形成，并已作为典型的系统，揭示了作为单分子层构建的纳米级分子聚集体的物理和结构方面。在具有苯并噻唑作为供体核（缩写为DS）的mercury染料的LB膜的情况下，电子自旋共振（ESR）光谱已经成功地确定了染料分子相对于浸渍方向的特征面内取向，这导致发现了LB膜的浸渍过程中的流动取向效应，作为LB膜中经常观察到的光学二向色性的起源。本文在介绍了ESR谱的基础上，讨论了混合膜中汞的J聚集及其表征的三个主要问题。第一个主题是观察和控制J-聚集体的大小在花生酸基质中的染料的稀释极限的甲基取代的DS（6-Me-DS）。原子力显微镜（AFM）图案的摩尔比的依赖性允许识别染料域。J-波段光学峰分析的基础上库恩的扩展偶极模型，辅以飞秒泵浦探测光谱的新应用，产生的J-聚集体的大小为103。第二个主题是通过混合两种不同的染料分子来控制J带的峰值波长。第一种情况是形成J的6-Me-DS和非形成J的Mercury类似物DO与苯并恶唑而不是DS的苯并噻唑的混合物。第二种情况是两种J-形成染料的混合物，但具有不同的J-带峰位置，6-Me-DS和5-Cl-DS的另一种类似物。将呈现取决于摩尔混合比的光学峰位移。最后一个主题是关于染料分子在J-聚集体中的电子态的阐明。光诱导ESR（LESR）的DS膜与稳定的同位素（15 N或13 C）取代的染料提供了明确的证据，光诱导电荷转移的超精细结构的检测。此外，13 C-富集染料的红外（IR）光谱鉴定发色团中相关碳的IR吸收峰。结果表明，与由供体和受体部分组成的孤立的mercury相比，J-聚集体中染料的分子内电荷转移增强。最后，5-Cl-DS中的Cl连接导致LESR光谱中的氮超精细耦合的显著增强。这些例子和其他人证明了LB膜的部花青在研究的纳米级分子聚集体在单层组装的潜力。
Langmuir–Blodgett (LB) films are constructed by successively transferring monomolecular layers formed at the air–water interface onto solid substrates. One of the advantages of the LB technique in fabricating molecular aggregates lies in the fact that it can employ various kinds of molecules by mixing them at the air–water interface. The mixed system may exhibit new properties that are not observed for individual components. This method would be useful, for example, in the studies of the formation and control of the J-aggregates of functional dyes that attract attention both in science and technology. In this paper, I review this subject mainly based on our recent results in merocyanines. LB films of merocyanine dyes, mixed with arachidic acid (C20), exhibit J-aggregate formation and have been serving as typical systems in revealing the physical and structural aspects of nanosized molecular aggregates constructed as monolayers. In the case of LB films of a merocyanine dye having benzothiazole as donor nucleus (abbreviated as DS), electron spin resonance (ESR) spectroscopy has been successful in determining the characteristic in-plane orientation of dye molecules with respect to the dipping direction, which led to the discovery of the flow orientation effect during the dipping process of LB films as the origin of optical dichroism often observed in LB films. In this article, after an introduction of ESR spectroscopy, three major topics on the merocyanine J-aggregation and its characterization in mixed films are discussed. The first topic is the observation and control of the size of J-aggregates in the dilution limit of dyes in arachidic acid matrix for a methyl-substituted DS (6-Me-DS). Dependence of atomic force microscopy (AFM) patterns on the molar ratio allows the identification of dye domains. J-band optical peak analysis based on the Kuhn's extended dipole model, supplemented by a novel application of femtosecond pump-probe optical spectroscopy, yields the size of the J-aggregates of 103. The second topic is the control of the J-band peak wavelengths by mixing two different kinds of dye molecules. The first case is the mixture of a J-forming 6-Me-DS and non-J-forming merocyanine analog, DO with benzo-oxazole instead of benzothiazole of DS. The second case is the mixture of both J-forming dyes but with different J-band peak positions, 6-Me-DS and another analog of 5-Cl-DS. The optical peak shifts depending on the molar mixing ratio will be presented. The last topic is related to the elucidation of electronic states of dye molecules in the J-aggregates. Light-induced ESR (LESR) of DS films with stable isotope (15N or13C)-substituted dyes provide clear evidence for the photoinduced charge transfer by the detection of hyperfine structures. Moreover, infrared (IR) spectroscopy of13C-enriched dye identifies the IR absorption peak of the relevant carbon in the chromophore. The results give evidence for the enhanced intramolecular charge transfer of dyes in the J-aggregates compared with an isolated merocyanine composed of donor and acceptor moiety. Lastly, the Cl attachment in 5-Cl-DS leads to a significant enhancement of the nitrogen hyperfine coupling in the LESR spectra. These examples and others demonstrate the potential of LB films of merocyanines in the studies of the nanosized molecular aggregates in monolayer assemblies.
DOI：
--
发表时间：
--
期刊：
Ferroelectrics (in press)
影响因子：
--
作者：
Noritaka Kato;Takeshi Araki;Yoshiaki Uesu
通讯作者：
Yoshiaki Uesu