Adsorption and Aggregation of a Cationic Cyanine Dye on Smectites

The adsorption and aggregate formation of a cationic cyanine dye, 1,1‘-diethyl-2,2‘-cyanine, on montmorillonite and saponite have been investigated for aqueous suspensions and cast films. In aqueous suspensions, the cyanine dye cations formed J-aggregates on montmorillonite, while they distribute molecularly on saponite. On the other hand, the dye formed J-aggregates on both montmorillonite and saponite in the cast films. Thus, the spectroscopic features of the cyanine dye reflected the difference between montmorillonite and saponite in organizing guest species. This difference suggests that the cyanine dye can be organized in a controlled manner by the selection of host materials. The J-aggregates formed on the layered silicates may be useful for the study of optical properties of the aggregates because of their stable and confined microstructure.