External reflection fourier transform infrared spectroscopy of surfactants at the air-water interface: Separation of bulk and adsorbed surfactant signals

Richard A. Campbell, James P R Day, Colin D. Bain

Research output: Contribution to journalArticlepeer-review

Abstract

External reflection Fourier transform infrared spectroscopy (ERFTIRS) has been used to obtain spectra of monolayers of the hydrocarbon surfactant octaethylene glycol monodecyl ether (C10E8) and the fluorocarbon surfactant ammonium perfluorononanoate (APFN) at the expanding liquid surface of an overflowing cylinder. The use of target factor analysis (TFA) to separate out the contributions of water, adsorbed surfactant, and dissolved surfactant is demonstrated. For both surfactants, there is a linear relationship between the component weight of the adsorbed surfactant, obtained by TFA, and the surface excess determined independently by ellipsometry or neutron reflection. This linear relationship suggests that the monolayers behave like isotropic films with a constant density. A sensitivity of less than 10% of a monolayer is demonstrated. The benefits of using a multivariate curve fitting procedure to analyze sets of ER-FTIR spectra are discussed and some potential pitfalls are identified. This technique is also applicable to static interfaces.

Original languageEnglish
Pages (from-to)993-1001
Number of pages9
JournalApplied Spectroscopy
Volume59
Issue number8
DOIs
Publication statusPublished - 1 Aug 2005

Keywords

  • Air-water interface
  • APFN
  • ATR
  • Attenuated total reflection
  • Dynamic surface excess
  • External reflection FT-IR spectroscopy
  • Overflowing cylinder
  • Surfactant adsorption
  • Target factor analysis
  • TFA

Fingerprint

Dive into the research topics of 'External reflection fourier transform infrared spectroscopy of surfactants at the air-water interface: Separation of bulk and adsorbed surfactant signals'. Together they form a unique fingerprint.

Cite this