Instituto de Química de São Carlos, Universidade de São Paulo , Caixa Postal 780,13560-970 São Carlos SP, Brasil.
Langmuir. 2017 Jan 31;33(4):891-899. doi: 10.1021/acs.langmuir.6b03898. Epub 2017 Jan 18.
In the present study, we have attempted to investigate, for the first time, the photophysical behavior of 1,1'-diethyl-2,4'-cyanine (ICY)/clay mineral hybrids in the solid state. The effects promoted by ICY loading and clay type on the spectroscopic properties were studied by UV-vis diffuse reflectance spectroscopy (DR) and different fluorescence techniques. The hybrids were characterized by X-ray diffraction (XRD) and thermogravimetric analysis (TGA). UV-vis-DR revealed the formation of ICY H-aggregates in Wyoming montmorillonite (SWy-1) and Laponite (Lap); however, J-aggregates were predominant for ICY on Arizona (SAz-1) and Barasym (SYn-1) montmorillonites. The formation of J-aggregates was favored on clays with a high layer charge density (SAz-1 and SYn-1). Increasing ICY loading leads to an increase in H-aggregates, which become predominant in all of the samples. The fluorescence spectra of ICY-Lap and ICY-SYn-1 hybrids showed two emissive bands, and they were assigned to the monomeric and J-aggregate species. The fluorescence lifetime showed consistent and distinct values for the two species. The longer fluorescence lifetime can be assigned to the ICY monomers, while the second component has a short lifetime value and may be attributed to J-aggregate emission species. Moreover, confocal fluorescence micrographs showed two different fluorescent domains; monomers (greenish domain) and J-aggregates (orange domain) can be clearly distinguished. For ICY adsorbed on SWy-1 and SAz-1, the intensities of the fluorescence spectra were very low, and it was not possible to measure the fluorescence lifetimes due to high iron content in these clays, which acts as an efficient quencher of the excited singlet state of the dye molecules. XRD and TGA curves showed that the intercalation of ICY into the interlayer regions of SWy-1, SAz-1, and SYn-1 occurred for high dye concentration only. In the case of Laponite, ICY adsorbs on the external surface of the layer. Our studies indicate that the ICY-clays, in particular, ICY-SYn-1 and ICY-Lap, are promising hybrid materials with interesting optical and photophysical properties.
在本研究中，我们首次尝试研究了 1,1'-二乙基-2,4'-氰基（ICY）/粘土矿物混合物在固态下的光物理行为。通过紫外-可见漫反射光谱（DR）和不同的荧光技术研究了 ICY 负载和粘土类型对光谱性质的影响。通过 X 射线衍射（XRD）和热重分析（TGA）对混合物进行了表征。UV-vis-DR 表明，在怀俄明蒙脱石（SWy-1）和拉蓬土（Lap）中形成了 ICY H-聚集体；然而，对于亚利桑那蒙脱土（SAz-1）和巴拉辛蒙脱土（SYn-1），ICY 主要形成 J-聚集体。具有高层电荷密度的粘土（SAz-1 和 SYn-1）有利于 J-聚集体的形成。随着 ICY 负载的增加，H-聚集体增加，在所有样品中均占主导地位。ICY-Lap 和 ICY-SYn-1 混合物的荧光光谱显示出两个发射带，它们被分配给单体和 J-聚集体物种。荧光寿命为两种物质呈现一致且明显的值。较长的荧光寿命可以分配给 ICY 单体，而第二个组成部分具有较短的寿命值，可能归因于 J-聚集体发射物种。此外，共焦荧光显微镜显示出两个不同的荧光域；单体（绿色域）和 J-聚集体（橙色域）可以清楚地区分。对于吸附在 SWy-1 和 SAz-1 上的 ICY，由于这些粘土中含有大量的铁，其作为染料分子激发单线态的有效猝灭剂，荧光光谱的强度非常低，并且无法测量荧光寿命。XRD 和 TGA 曲线表明，只有在高染料浓度下，ICY 才能插入 SWy-1、SAz-1 和 SYn-1 的层间区域。对于拉蓬土，ICY 吸附在层的外表面上。我们的研究表明，ICY-粘土，特别是 ICY-SYn-1 和 ICY-Lap，是具有有趣光学和光物理性质的有前途的混合材料。
