Self-assembled monolayers of 4-mercaptopyridine on Au(111): A potential-induced phase transition in sulfuric acid solutions

Thorsten Baunach, Valentina Ivanova, Daniel Alberto Scherson, Dieter M. Kolb

Research output: Contribution to journalArticle

63 Citations (Scopus)

Abstract

In situ scanning tunneling microscopy images of self-assembled monolayers (SAMs) of 4-mercaptopyridine (4-MPy) on Au(111) recorded in neat 0.1 M H2SO4 solutions provided evidence for a potential-induced phase transition over the range 0.40-0.15 V versus saturated calomel electrode. Analysis of the data was consistent with the presence of a (5 × √3) and (10 × √3) superstructure (phase A) at the positive end, that is, 0.40 V, for which the local coverage, θloc, is about 0.2 (two 4-MPy molecules per unit cell), which compresses at the negative end, that is, 0.15 V, to yield a much denser superstructure (phase B, θloc ca. 0.5). This behavior is unlike that reported for the 4-MPy-Au(111) SAM prepared by identical means, in 0.1 M HClO4 (or in sulfate solutions of a much higher pH) for which only the (5 × √3) superstructure was observed over the same potential range. The compression associated with the phase A to phase B transition is attributed to the formation of a hydrogen-bonded network of bisulfate coordinated in turn to the 4-MPy layer via the acidic hydrogens of the pyridinium moieties. Such conditions promote better packing of adsorbed 4-MPy species, which are aided by intermolecular π-π ring interactions, resulting in higher local coverages.

Original languageEnglish
Pages (from-to)2797-2802
Number of pages6
JournalLangmuir
Volume20
Issue number7
DOIs
Publication statusPublished - 2004 Mar 30
Externally publishedYes

Fingerprint

Self assembled monolayers
sulfuric acid
Sulfuric acid
Phase transitions
Hydrogen
Scanning tunneling microscopy
hydrogen
scanning tunneling microscopy
sulfates
Electrodes
Molecules
electrodes
rings
cells
molecules
Sulfates
interactions
4-thiopyridine

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

Cite this

Self-assembled monolayers of 4-mercaptopyridine on Au(111) : A potential-induced phase transition in sulfuric acid solutions. / Baunach, Thorsten; Ivanova, Valentina; Scherson, Daniel Alberto; Kolb, Dieter M.

In: Langmuir, Vol. 20, No. 7, 30.03.2004, p. 2797-2802.

Research output: Contribution to journalArticle

Baunach, Thorsten ; Ivanova, Valentina ; Scherson, Daniel Alberto ; Kolb, Dieter M. / Self-assembled monolayers of 4-mercaptopyridine on Au(111) : A potential-induced phase transition in sulfuric acid solutions. In: Langmuir. 2004 ; Vol. 20, No. 7. pp. 2797-2802.
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