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We developed a new method to measure the average aggregation number of large rod-like micelles using static fluorescence self-quenching of a solubilized fluorophore. The method is based on the increase of self-quenching of micelle-solubilized pyrene through excimer formation. We consider the effect of random distribution of pyrene in micelles and the micellar size distribution. The measured average aggregation < n> M is based on a new M-weighted averaging similar to our exponential-weighted averaging in the transient decay method. We apply this method to study the effect of a large concentration of salt on the average aggregation behavior of sodium dodecyl sulfate (SDS) and cetyle tetraammonium bromide (crAB). The sizes increase with increasing ionic concentrations. For 80S, we used the thermodynamic model developed by Missel et at. to calculate < n > M which we compare with experimental results.

The influence of solution pH and electrode potential on the structure, composition, thermal stability and electrochemical reactivity of chemisorbed bromine on well-defined Pd(100) electrode surfaces was investigated by a combination of electrochemistry and ultrahigh vacuum surface spectroscopy. Br- ions chemisorbed oxidatively to form zerovalent Pd(100)- (2x2)-Br and Pd(100)-c(2x2)-Br adlattices. In acidic and neutral solutions, the surface coverages increased as the electrode potential was made more positive. The presence of Br- in solution induced anodic dissolution of Pd at pH < 7; however, at high overpotentials, the formation of a passivating film of PdBr2 precluded further surface dissolution. The surface coordination chemistry of Pd(100) exposed to Br- solutions at pH 10 resembled that of homogeneous halo-Pd complexes in which the only stable species at very alkaline solutions were metal hydroxides and/or metal-hydroxo complexes; that is, no Br chemisorption transpired on Pd(100) at pH 10.