The fluorescence properties of coumarine dye intercalated in a swelling clay

The fluorescence properties of coumarine dye incorporated into swelling clays were studied. Preparation of the clay-coumarine composite was carried out as follows: a swelling clay was added and mixed intimately into the water solution containing the corresponding quantity of coumarine. Next, the resulting suspension was dried for 12 h at room temperature for making a filmy clay-coumarine composite. The TG-DTA and the X-ray diffraction data showed that the coumarine molecules could be immobilized and thermally stabilized at the melting temperature of ca 75°C in the interlayers of the swelling clay. In addition, as the quantity of intercalated coumarine increased, a pronounced stepwise change was observed in the basal spacings from 13.0 to 18.5 A. Such a geometric change of the flat-shaped coumarine chromophore significantly influenced the fluorescence properties. The quantum efficiency of fluorescence near 480 nm is discussed in connection with concentration quenching. Also, the red shift of the emission maximum was elucidated by the charge stability of N atoms in the coumarine chromophore.