Intercalation Characteristics of 1,1′-Diethyl-2,2′-Cyanine and other Cationic Dyes in Synthetic Saponite: Orientation in the Interlayer

Abstract

Abstract--The basal spacings of complexes of saponite with five cationic dyes, 1,1 '-diethyl-2,2'-cyanine, crystal violet, methylene blue, l, 1 '-diethyl-2,2'-carbocyanine, and 1,1 '-diethyl-2,2'-dicarbocyanine, varied with degree of saturation of each dye. At low loading of dye to saponite, each cationic dye showed nearly the same absorption spectrum in the UV-visible region as that of its dilute aqueous solution, whereas the spectrum changed distinctly at high loading. With increasing degree of dye loading, the absorption band shifted to longer wavelength for 1,1'-diethyl-2,2'-cyanine (J band) and to shorter wavelength for the others (D, H bands). On the basis of the basal spacing of each respective dye-clay complex, the orientation of the intercalated dye molecules is proposed as follows: the major plane of the cationic dye lies horizontal to the 2:1 layer surface at low loading. With increasing loading, the dye molecules interact with adjacent dye molecules and orient vertically to the 2:1 layer at high loading near the cation-exchange capacity.

Aggregation and Decomposition of a Pseudoisocyanine Dye in Dispersions of Layered Silicates

“…The small surface area per exchangeable cation is in contrast to the large size of the PIC cations. Minimal surface area occupied by one PIC cation is about 0.9 nm 2 but in reality is probably larger due to deviation of the cation from planarity and in dependence on the cation orientation (16). An average surface area per one ion on the surface of SAz1 is 1.15 nm 2 , as calculated using CEC and surface area data.…”

“…This assumption is supported by results of further study. J-aggregation did not take place at the surface of low-charge saponite under standard conditions, occurring only at dye loadings higher than the cation exchange capacity (CEC) of the silicate (16).…”

“…PIC forms J-aggregates in aqueous solutions of higher concentrations, and at solid-liquid and gas-liquid interfaces. Aggregation increases in the solutions of inorganic salts (16). Heating a solution decreases both H-and J-aggregation in favor of monomers (17).…”

“…Enhancement of PIC aggregation was observed with the adsorption of PIC cations in various reaction systems, including solutions of polyelectrolytes (18,19) on the surface of silica (20), glass (21), and in sol-gel systems (22) as well as in various kinds of molecular films, mainly of the Langmuir-Blodgett type (23,24). Aggregation of PIC cations depends on both the composition of the PIC solution and the properties of the substrate (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26). Formation of J-aggregates occurs in anionic polyelectrolyte solutions of low PIC concentrations, whereas the presence of neutral polymers does not induce aggregation under the same conditions (18).…”

“…As mentioned above, nitrogen atoms bear the positive charge of the PIC cations and therefore interact electrostatically with negatively charged sites of the silicate. Dye cations face the silicate surface with the charged edge, keeping the longest axis parallel with the plane of the silicate (16). However, the insufficient area for the PIC cations probably causes the cations to reorient to a more perpendicular position.…”