The Interaction of Alkylammonium Salts with Synthetic Clays. A Fluorescence and Laser Excitation Study

Article abstract of DOI:10.1021/j100276a032

The interaction of surfactants with synthetic clays has been studied by a steady-state and a time-resolved fluorescence quenching method.The fluorescence quenching of 4-(1-pyrenyl)butyltrimethylammonium ion (PN(1+)) adsorbed on colloidal laponite clay by coadsorbed alkylpyridinium ions showed unusual behavior.Increasing the quencher concentration at first led to an efficient quenching of PN(1+) flourescence, but on increasing the quencher concentration further a reverse effect is observed, whereby the fluorescence started to recover, only to be followed by a smaller degree of quenching.The degree of recovery was strongly dependent on the chain length of the alkylpyridinium ions, the longer the chain length the larger the degree of recovery.PN(1+) fluorescence was also quenched by laponite clay itself or cupric ion in copper-clay, where cupric ion was constructed in the clay lattice.However, coadsorbed hexadecyltrimethylammonium ions (CTAB cations) dramatically reduced the quenching.The results can be explained in terms of the change of geometrical arrengement of PN(1+) adsorbed on clay.Quenching of PN(1+) fluorescence by dimethylaniline, nitrobenzene, and nitromethane in the CTAB-laponite system obeyed Poisson type kinetics, indicating that the adsorbents exist in the form of clusters or zones on the clay surface.