Forcing Aggregation of Cyanine Dyes with Salts: A Fine Line between Dimers and Higher Ordered Aggregates
Forcing Aggregation of Cyanine Dyes with Salts: A Fine Line between Dimers and Higher Ordered Aggregates
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DOI：
10.1021/la502124b
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发表时间：
2014-08-19
期刊：
影响因子：
3.9
通讯作者：
Heyne, Belinda
中科院分区：
文献类型：
--
作者：
Mooi, Sara M.;Keller, Samantha N.;Heyne, Belinda
这是罕见的读到关于花青素染料的文献，而没有他们的聚集讨论。考虑到它们在水溶液中自组织的倾向，它们引起了人们的高度兴趣，这导致了它们的二聚体和高有序聚集体形成的有趣的光物理性质。由于其广泛的应用范围，包括染料敏化太阳能电池，目前对其聚集体的研究需求很大。然而，它们在高盐溶液中的聚集研究尚不充分，而高离子强度对其聚集的影响往往被忽视。在之前的一项研究中，我们的团队确定了特定离子效应的作用，特别是匹配水亲和性的必要性，以诱导阳离子菁染料噻唑橙的聚集。为了促进对这一主题的理解，我们在这篇文章中介绍了花青素染料的不同聚集反应，因为一个单一的单价盐可以在不同的这些染料中引起不同的聚集反应。通过吸收光谱结合化学计量学分析，我们确定了染料固有的单体-二聚体平衡取决于其几何形状。更有趣的是，结合DFT计算的实验数据表明，不仅染料的几何形状，而且其电荷位置在阳离子菁染料和阴离子相互作用形成的聚集体形态中起作用。人们认为，接触离子对的形成和离子对内产生的有效电荷筛选是高阶聚集的原因。
It is uncommon to read about cyanine dyes in the literature and not have their aggregation discussed. They are of high interest considering their propensity to undergo self-organization in aqueous solution, leading to interesting photophysical properties resulting from the formation of their dimers and higher ordered aggregates. Currently, the study of their aggregation is in high demand due to their diverse application range including dye-sensitized solar cells. However, their aggregation in high salt solutions is under studied, and the effect on aggregation in congruence with high ionic strength is often overlooked. In a previous study, our group established the role of specific ion effects and in particular the necessity of matching water affinity to induce aggregation of a cationic cyanine dye, thiazole orange. In order to advance the understanding of this topic, we present in this article the diverse aggregation of cyanine dyes, as a single monovalent salt can cause different aggregation responses in a variety of these dyes. We established via absorption spectroscopy combined with chemometric analyses that the inherent monomer-dimer equilibrium of a dye depends on its geometry. More interestingly, experimental data coupled with DFT calculations reveal that not only the geometry of a dye but also its charge location plays a role in the aggregate morphology formed by the interaction of a cationic cyanine dye and an anion. It is thought that contact ion pair formation and effective charge screening generated within that ion pair are responsible for aggregates with a greater order.