FLUORESCENCE PROBE SPECTROELECTROCHEMISTRY AT SILVER ELECTRODES IN DIMETHYLFORMAMIDE AND AQUEOUS HEXADECYLTRIMETHYLAMMONIUM CHLORIDE

Fluorescence spectra of pyrene measured by directing incident light at rough Ag electrodes in thin-layer electrochemical cells and collecting emitted light at a 22.5-degrees angle of detector to incident beam were studied as a function of applied potential. In homogeneous dimethylformide (DMF), maximum fluorescence occurred close to the potential of zero charge (PZC) of polycrystalline Ag. The potential dependence of fluorescence in DMF is attributed to weak adsorption of pyrene on Ag. In aqueous micellar solutions of CTAC, pyrene is strongly associated with surfactant. The maximum fluorescence of pyrene in 0.1 M CTAC/0.05 M NaOH in two types of thin-layer cells was found at potentials just before those causing electrolytic evolution of hydrogen gas. Potential dependence of pyrene fluorescence is interpreted in terms of the potential dependence of the amount of adsorbed surfactant on the electrode and/or to structural reorganization of surfactant aggregates on the surface. A rough Ag-foil electrode was more robust than vapor-deposited Ag films in aqueous micellar media at potentials where hydrogen was evolved.