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Publication Type
Journal Article
UWI Author(s)
Author, Analytic
Calvente, J.; Luque, A.; Andreu, R.; Mulder, Willem H..; Olloqui-Sariego, J.
Author Affiliation, Ana.
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Article Title
Analytical Expressions for Proton Transfer Voltammetry: Analogy to Surface Redox Voltammetry with Frumkin Interactions
Medium Designator
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Connective Phrase
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Journal Title
Analytical Chemistry
Translated Title
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Reprint Status
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Date of Publication
2013
Volume ID
85
Issue ID
9
Page(s)
4475-4482
Language
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Connective Phrase
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Location/URL
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ISSN
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Notes
http:; pubs.acs.org/doi/pdf/10.1021/ac303661g
Abstract
Theory for interfacial proton transfer voltammetry of a molecular film containing any acid/base loading has been developed under equilibrium conditions. Diagnostic criteria to disentangle the interplay between diffuse layer and ionization effects are outlined. Easy-to-use analytical expressions for the voltammetric features are derived for the particular case of an invariant diffuse layer effect, which turn out to be entirely analogous to those for a surface redox conversion with Frumkin interactions. It is demonstrated that, regardless of the electrolyte concentration, significant ionization of the external acid groups located nearby the diffuse layer is sufficient for the fulfillment of this relevant particular case. A strategy is outlined to determine the amount, the intrinsic pKa, and the burial depth of the voltammetrically active groups from the surface concentration dependence of the main voltammetric features. Self-assembled monolayers of 11-mercaptoundecanoic acid deposited on Au(111), containing higher amounts of buried carboxylic groups than previously reported, have been studied to assess more critically the influence of electrostatic effects on the ionization process. Preliminary evidence suggests that the protonation/deprotonation voltammetric wave involves physisorbed rather than chemisorbed thiol molecules. Application of the present theoretical approach to this system reveals that the voltammetrically active carboxylic groups are located close to the electrode surface and become more acidic upon increasing their surface concentration.....
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