Departamento de Química Física, Universidad del País Vasco UPV/EHU, Apartado 644, 48080-Bilbao, Spain.
Langmuir. 2010 Jan 19;26(2):930-7. doi: 10.1021/la902414n.
Absorption and fluorescence spectroscopies with linearly polarized light are applied to characterize the adsorbed species of rhodamine 6G (R6G) laser dye in ordered organophilic laponite (Lap) clay films for low dye loadings. The organophilic character of the clay was controlled by the number of organic surfactant dodecyl-trimethylammonium (C12TMA) cations intercalated into the interlayer space of the clay. Experimental results suggest that for moderate to high surfactant contents (>70% of the total cation exchange capacity, CEC, of the clay) the accessibility of the interlayer space for R6G molecules is reduced. In these cases, the first stage in the adsorption of R6G molecules is at the external surface, where dye molecules can self-associate even for very low dye loading (around 0.1%CEC), probably for the limitation of the external surface area. The presence of a nonfluorescent H-type aggregate with a short-displaced coplanar structure and a fluorescent oblique head-to-tail J aggregate is reported. The inclined structure of this J aggregate is stabilized by the surfactant molecules at the external surface.
采用线偏振光的吸收和荧光光谱法来表征低染料负载下罗丹明 6G（R6G）激光染料在有序亲油性皂石（Lap）粘土膜中的吸附物种。粘土的亲油性由插入粘土层间空间的有机表面活性剂十二烷基三甲基铵（C12TMA）阳离子的数量控制。实验结果表明，对于中等至高表面活性剂含量（>粘土总阳离子交换容量（CEC）的 70%），R6G 分子进入层间空间的可及性降低。在这些情况下，R6G 分子的吸附的第一阶段是在外部表面，在那里即使染料负载非常低（约 0.1%CEC），染料分子也可以自组装，可能是由于外部表面积的限制。报道了具有短位移共面结构的非荧光 H 型聚集体和荧光斜交头对头 J 聚集体的存在。这种 J 聚集体的倾斜结构由外部表面的表面活性剂分子稳定。
