Fluorescence tuning of 2D montmorillonite optically active layers with beta-cyclodextrine/dye supramolecular complexes

• Dye molecules in supramolecular complexes were investigated at montmorillonite surfaces.
• Equilibrium constants for supramolecular complex formation were determined.
• Both ionic and non-ionic dyes were incorporated in 2D hybrid films.
• Orientation of dye molecules in 2D films was determined using UV-Vis spectroscopy.
• Non-ionic dye retained its fluorescence properties in 2D montmorillonite film.

Montmorillonite 2D-optically active layers were investigated using non-ionic Coumarine and cationic Pyronine dyes. The modification of thin montmorillonite films (MF) was done by single dye species and/or with β-cyclodextrine (CD) supramolecular complexes (SC). Equilibrium constants for SC formation were determined in the range 0.1·103 − 6.0·103 for temperatures 283–323 K. Thus amounts of dye incorporated in the SC with CD prepared at temperature 293 K is more than 96% for Coumarine and more than 81% for Pyronine dye. Adsorption of SC in MF was proved by detection of increased first basal reflections using X-ray diffraction. The molecular transition moments for monomeric dye species in 2D MF of SC for Pyronine absorbing at 560 nm were inclined 60° and co-adsorbed dimers or higher aggregates of molecules tilted around 33° towards montmorillonite surface. Coumarine absorption in the whole investigated spectral range indicated average molecule inclination around 28°. The angle of the Coumarine dye is favourable for the formation of J-aggregates with sufficient fluorescence intensity detected at 478 nm for solid state applications.

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