Adsorption, Mobility and Organization of Organic Molecules at Clay Surfaces Probed by Photophysics and Photochemistry.
KATHOLIEKE UNIV LEUVEN (BELGIUM)
1. Non-homogenous distribution of adsorbed molecules- Catonic detergent molecules form clusters upon adsorption on a clay surface. The same behaviour has been observed for detergentlike molecules such as the pyrene derivatives, used in our study as molecular probe. For the latter, this non-homogenous distribution results in ground state complexes and a very efficient excimer formation. The photophysical properties of these detergentlike molecules are now used to gain more information about this cluster formation. 2. Influence of the chain length of coadsorbed detergent molecules- In non-aqueous media, adsorbed molecules on a clay surface are more or less homogenous distributed and are lying flat on the clay surface. In aqueous, hydrophobic interactions results in the formation of clusters on the clay surface. The chain length of the detergent molecules plays an important role in influencing for example the intermolecular excimer formation of the adsorbed pyrene probes and the quenching of a pyrene derivative by pyridinium ions with various chain lengths. 3. Influence of the preparation method on the final distribution of the adsorbed molecules- Clay samples have been made by adding a concentrated solution of probe to the clay suspensions. When the probe is added in a more diluted way, differences are observed in the fluorescence spectra. 4. Influence of the structure of the detergent molecules- Analogeous experiments as with those one tailed detergents has now been performed with a two tailed detergent, namely didodecyldimethylammonium chloride DDAC.