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          Institute: MPI für Polymerforschung     Collection: MPI Polymerforschung     Display Documents



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ID: 28406.0, MPI für Polymerforschung / MPI Polymerforschung
Impedance spectroscopy studies of interfacial acid-base reactions of self-assembled monolayers
Authors:Schweiss, R.; Werner, C.; Knoll, Wolfgang
Language:English
Date of Publication (YYYY-MM-DD):2003-01-02
Title of Journal:Journal of Electroanalytical Chemistry
Journal Abbrev.:J. Electroanal. Chem.
Volume:540
Start Page:145
End Page:151
Review Status:not specified
Audience:Not Specified
Abstract / Description:Electrochemical impedance spectroscopy (EIS) at fixed potential was performed with gold electrodes covered with self-assembled monolayers (SAMs) of derivatized thiols on gold including mercaptopropionic acid (MPAc), mercaptododecylamine (MDAm), mercaptohexadecanoic acid (MHAc) and hexadecanethiol (HDT) using electrochemically inactive electrolytes. A simple equivalent circuit of the total interfacial capacitance in series with the solution resistance was found to fit the impedance spectra. Dissociation of acidic groups and protonation of basic groups on the surface give rise to an increase of the total interfacial capacitance which can be monitored by means of ac impedance. The interfacial capacitance changes with pH reflect a titration curve and this allows for an estimation of surface pK-values. The magnitude of the changes of the capacitances due to ionization were dependent on the hydrocarbon chain length of the monolayer and on the ionic strength. In agreement with other techniques, surface pK values were found to be significantly different as compared with the corresponding molecular moities dissolved in aqueous solution. © 2002 Elsevier Science B.V. All rights reserved.
Free Keywords:impedance spectroscopy; self-assembled monolayers; interfacial charge; double layer capacitance; surface pK
Comment of the Author/Creator:Date: 2003, JAN 2
External Publication Status:published
Document Type:Article
Affiliations:MPI für Polymerforschung
External Affiliations:Polymer Res Inst, Dept Biocompatible Mat, Hohe Str 6, D-01069 Dresden, Germany; Univ Toronto, Dept Mech & Ind Engn, Toronto, ON M5S 3G8, Canada
Identifiers:ISI:000180836800018 [ID No:1]
ISSN:0022-0728 [ID No:2]
LOCALID:P-03-4
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