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Visualization of potential induced formation of water-insoluble surfactant aggregates by epi-fluorescence microscopy

TitleVisualization of potential induced formation of water-insoluble surfactant aggregates by epi-fluorescence microscopy
Publication TypeJournal Article
Year of Publication2002
AuthorsShepherd, J, Yang, Y, Bizzotto, D
JournalJournal of Electroanalytical Chemistry
Volume524
Pagination54-61
Date PublishedMay
Type of ArticleProceedings Paper
ISBN Number0022-0728
Keywordsac voltammetry, ADSORPTION, aggregates, Au(111), chronocoulometry, electrode, FLUORESCENCE, GOLD, INTERFACES, MERCURY-ELECTRODES, microscopy, MONOLAYERS, PHOSPHATIDYLCHOLINE, PHOSPHOLIPID, SCANNING-TUNNELING-MICROSCOPY, SELF-ASSEMBLED MONOLAYERS, spectroelectrochemistry, SPECTROSCOPIC CHARACTERIZATION, SURFACES
Abstract

Epi-fluorescence imaging of the adsorption and desorption of a 3 mol% 1,1’-dioctadecyl-3,3,3’,3’-tetramethylindodicarbocyanine perchlorate/octadecanol layer from/to a Au(111) electrode \ electrolyte interface is demonstrated. Since fluorescence near a metal surface is quenched, only molecules away from the metal surface could be observed. At adsorption potentials, no fluorescence was observed. An increase in the fluorescence and the number of desorbed particles was observed when scanning the potential to the negative desorption values. Scanning the potential back to the adsorption value resulted in a decrease in the fluorescence and the number of desorbed particles. A significant hysteresis in the adsorption/desorption processes was observed and the existence of an intermediate pre-adsorbed form of the surfactant was demonstrated and characterized. The morphology of the desorbed layer was strongly influenced by the potential program used to effect desorption. Desorption by potential step created aggregates that were larger than those created by potential sweep. For this system, the potential controls the separation or distance between the aggregates or desorbed species and the metal surface in a repeatable way. (C) 2002 Published by Elsevier Science B.V.

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