Double-layer-capacitance titration of self-assembled monolayers of ω-functionalized alkanethiols on Au(111) surface

Takashi Kakiuchi, Minehiko Iida, Shinichiro Imabayashi, Katsumi Niki

Research output: Contribution to journalArticle

118 Citations (Scopus)

Abstract

The acid-base equilibrium of ω-functionalized alkanethiol monolayers on Au(111) has been studied using the change in double-layer capacitance accompanied by the protonation-deprotonation of ω-terminals. The pK of ω-carboxyl alkanethiols on Au(111) increases by four pH units. The shift becomes greater as the alkyl chain length increases. The same magnitude of the pK shift to the acidic side occurs in the monolayers of aminoethane thiol. The surface pK varies little with the electrode potential, whereas the increase in the supporting electrolyte concentration slightly diminishes the pK shift. The drawn-out shape of the titration curves is consistent with the mean-field model taking account of the repulsive interaction between adsorbed molecules, indicating the significance of the strong electrostatic repulsion between adsorbed thiol molecules in its charged states. The magnitude of the pK shift is, more than that predicted by the mean-field model, however, and suggests the considerable contribution from other factors that stabilize the uncharged state, for example, hydrogen bonding and low dielectric constant in the vicinity of the self-assembled monolayer. The possibility of counterion binding when the degree of deprotonation is large has been suggested.

Original languageEnglish
Pages (from-to)5397-5401
Number of pages5
JournalLangmuir
Volume16
Issue number12
DOIs
Publication statusPublished - 2000 Jun 13
Externally publishedYes

Fingerprint

Deprotonation
Self assembled monolayers
Titration
Sulfhydryl Compounds
titration
Monolayers
Capacitance
capacitance
Molecules
shift
Protonation
Chain length
thiols
Electrolytes
Electrostatics
Hydrogen bonds
Permittivity
acid base equilibrium
Electrodes
molecules

ASJC Scopus subject areas

  • Colloid and Surface Chemistry
  • Physical and Theoretical Chemistry

Cite this

Double-layer-capacitance titration of self-assembled monolayers of ω-functionalized alkanethiols on Au(111) surface. / Kakiuchi, Takashi; Iida, Minehiko; Imabayashi, Shinichiro; Niki, Katsumi.

In: Langmuir, Vol. 16, No. 12, 13.06.2000, p. 5397-5401.

Research output: Contribution to journalArticle

Kakiuchi, Takashi ; Iida, Minehiko ; Imabayashi, Shinichiro ; Niki, Katsumi. / Double-layer-capacitance titration of self-assembled monolayers of ω-functionalized alkanethiols on Au(111) surface. In: Langmuir. 2000 ; Vol. 16, No. 12. pp. 5397-5401.
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