Aggregation and decomposition of a pseudoisocyanine dye in dispersions of layered silicates
Aggregation and decomposition of a pseudoisocyanine dye in dispersions of layered silicates
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DOI：
10.1006/jcis.2001.8140
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发表时间：
2002-03-15
影响因子：
9.9
通讯作者：
Fujita, T
中科院分区：
文献类型：
--
作者：
Bujdák, J;Iyi, N;Fujita, T
使用可见光谱研究了由假异花青（PIC）溶液和分散的层状硅酸盐组成的反应体系的光学性质。使用两个系列的减电荷蒙脱石作为硅酸盐材料。每个系列由八个具有不同层电荷的样品组成，这些样品是由一种母材制备的。观察到的趋势用不同层电荷、结构和来源的另一系列二八面体和三八面体蒙脱石进行了验证。硅酸盐的层电荷密度显着影响PIC阳离子的聚集。除了 J-聚集体的形成之外，还观察到染料光谱漂白。电荷密度非常低的硅酸盐既不会引起染料的显着聚集，也不会引起光谱漂白。在具有中等表面电荷的层状硅酸盐分散体中发现了最高水平的 PIC J 聚集体形成。然而，在某些情况下也观察到可逆的光谱漂白。由于阳离子尺寸较大和硅酸盐表面相对较高的电荷密度所产生的张力，PIC 染料阳离子在吸附过程中可能会改变其构象。随着时间的推移，随着染料阳离子的重新排列和重新分布，漂白的染料至少部分地恢复。相比之下，电荷密度非常高的硅酸盐（合成带云石和氟锂蒙脱石）的存在导致 PIC 快速且不可逆地分解。也许，由硅酸盐表面的高电荷密度引起的吸附染料阳离子的张力，导致发色团的显着不稳定和分解反应。 (C) 2002 年爱思唯尔科学（美国）。
The optical properties of reaction systems composed from a pseudoisocyanine (PIC) solution and dispersed layered silicates were studied using visible spectroscopy. Two series of reduced-charge montmorillonites were used as the silicate materials. Each series consisted of eight samples with different layer charges, which were prepared from one parent material. Observed trends were verified with another series of dioctahedral and trioctahedral smectites of different layer charges, structure, and origin. The layer charge density of the silicates significantly affected the aggregation of PIC cations. In addition to the formation of J-aggregates, dye spectral bleaching was also observed. Silicates with very low charge densities induced neither significant aggregation nor spectral bleaching of the dye. The highest levels of PIC J-aggregate formation were found in dispersions of the layered silicates with a medium surface charge. However, reversible spectral bleaching was also observed in some cases. PIC dye cations probably change their conformations during the adsorption process, due to the tension resulting from the large size of the cations and the relatively high charge density at the silicate surface. The bleached dye recovers, at least partially, with the rearrangement and redistribution of the dye cations over the time. In contrast, the presence of silicates with very high charge densities (synthetic taeniolite and fluorohectorite) led to the very fast and irreversible decomposition of the PIC. Perhaps, the tension in adsorbed dye cations, induced by the high charge density at the silicate surface, resulted in significant destabilization and a decomposition reaction of the chromophore. (C) 2002 Elsevier Science (USA).