Adsorption, Mobility and Organization of Organic Molecules at Clay Surfaces Probed by Photophysics and Photochemistry.
KATHOLIEKE UNIV LEUVEN (BELGIUM)
The study of clay colloids by means of luminescent probes started a few years ago. Especially the adsorption of organic molecules on the clay surface is a point of great interest, in order to understand the catalytic properties of these surfaces on various chemical reactions. A clay surface is negatively charged. Therefore a positively charged pyrene derivative, 3-1-pyrenyl- propyltrimethylammonium bromide PN is used as fluorescent probe. This molecule is readily adsorbed at the clay surface, simply by adding the probe to a clay suspension. After adsorption the fluorescence spectra reveals a excimer fluorescence, even when the concentration of PN is very low. The excimers observed on the clay surface are however not formed by diffusion of the PN molecules to each other. Excitation spectra of the excimer emission indicate the existence of interactions between the PN molecules in the ground state.