Photoprocesses on Colloidal Clay Systems. 2. Quenching Studies and the Effect of Surfactants on the Luminescent Properties of Pyrene and Pyrene Derivatives Adsorbed on Clay Colloids

Article abstract of DOI:10.1021/j100241a037

The cationic fluorescent probe <4-(1-pyrenyl)butyl>trimethylammonium bromide (PN⁺) is adsorbed by the colloidal particles of the clay minerals montmorillonite and kaolin.The emission spectrum, polarization of fluorescence measurements, and transient fluorescence decay characteristics of PN⁺ are used to study the nature of its adsorbed state.Quaternary ammonium surfactants of varying hydrocarbon chain length cause a rearrangement of the PN⁺ molecules on the surface and decrease its interaction with the mineral surface.Quenching studies with nonionic andcationic molecules indicate that diffusion on the surface of montmorillonite is reduced below that observed in aqueous solution while the apparent rates obtained with kaolin particles are increased.Montmorillonite particles with a surfactant bilayer surrounding their surfaces are formed by the addition of an excess amount of surfactant to the colloid.The emission spectrum and the steady-state quenching studies yield information on the location of pyrene on these particles, as well as on the nature of the colloidal particles.