X-ray photoelectron spectroscopy and differential capacitance study of thiol-functional polysiloxane films on gold supports

Patrick A. Johnson, Rastislav Levicky

Research output: Contribution to journalArticle

Abstract

Polymeric molecules containing multiple thiol groups (polythiols) provide tenacious attachment to metal surfaces such as gold. Polythiol films are also well suited for subsequent derivatization with biomacromolecules through remnant free thiol groups of the film. In this study, 1-3 nm thick layers of a commercial polythiol, poly((mercaptopropyl)methylsiloxane) (PMPMS), are investigated with X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy. XPS is used to reveal the surface coverage of thiolate-Au bonds between the polythiol and the metal support, which is found to be approximately 30% lower than that in alkanethiol self-assembled monolayers. The surface density of thiolate-Au bonds did not depend on film thickness provided sufficient PMPMS material was present. Differential capacitance measurements show that the effective dielectric barrier presented by PMPMS films under aqueous environments corresponds closely to their physical thickness, with even ∼1 nm films remaining impermeable to electrolyte species. Modification of the films with an oligoethylene glycol compound was also examined, in anticipation of future applications in label-free, impedance-based biomolecular diagnostics.

Original languageEnglish (US)
Pages (from-to)9621-9627
Number of pages7
JournalLangmuir
Volume20
Issue number22
DOIs
StatePublished - Oct 26 2004

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Siloxanes
polysiloxanes
Sulfhydryl Compounds
thiols
Gold
Silicones
Capacitance
X ray photoelectron spectroscopy
capacitance
photoelectron spectroscopy
gold
x rays
Metals
impedance
Glycols
Capacitance measurement
Self assembled monolayers
Electrochemical impedance spectroscopy
Electrolytes
metal surfaces

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Colloid and Surface Chemistry

Cite this

X-ray photoelectron spectroscopy and differential capacitance study of thiol-functional polysiloxane films on gold supports. / Johnson, Patrick A.; Levicky, Rastislav.

In: Langmuir, Vol. 20, No. 22, 26.10.2004, p. 9621-9627.

Research output: Contribution to journalArticle

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