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    Adsorption of N-Decyl-N,N,N-trimethylammonium Triflate (DeTATf), a Cationic Surfactant, on the Au(111) Electrode Surface

    Year: 2007

    Journal: Langmuir, 2007, 23 (4), pp 1784–1791, 20111221

    Authors: Christa L. Brosseau, Erin Sheepwash, Ian J. Burgess, Ewa Cholewa, Sharon G. Roscoe, and Jacek Lipkowski

    Organizations: Department of Chemistry and Biochemistry, University of Guelph, Ontario, Canada N1G 2W1, Department of Chemistry, University of Saskatchewan, Saskatoon, Canada S79 5C9, and Department of Chemistry, Acadia University, Nova Scotia, Canada B4P 2R6

    The adsorption behavior of the cationic surfactant N-decyl-N,N,N-trimethylammonium triflate (DeTATf) on the Au(111) electrode surface was characterized using cyclic voltammetry, differential capacity, and chronocoulometry. The thermodynamics of the ideally polarized electrode have been employed to determine the Gibbs excess and the Gibbs energy of adsorption. The results show that the adsorption of DeTATf has a multistate character. At low bulk DeTATf concentrations, the adsorption state is consistent with the formation of an adsorbed film of nearly flat molecules. At higher concentrations this film may represent a three-dimensional aggregated state. At negative potentials and charge densities close to 0 μC cm-2, the data suggest the formation of a film of tilted molecules oriented with the hydrocarbon tail toward the metal surface and the polar head toward the solution. A surprising result of this study is that DeTATf displays adsorption characteristics of a zwitterionic rather than a cationic surfactant. This behavior indicates that the adsorbed species is an ion pair.