Infrared studies of the potential controlled adsorption of sodium dodecyl sulfate at the Au(111) electrode surface.
Quantitative subtractively normalized interfacial Fourier transform infrared reflection spectroscopy (SNIFTIRS) was used to determine the conformation and orientation of sodium dodecyl sulfate (SDS) molecules adsorbed at the single crystal Au(111) surface. The SDS molecules form a hemimicellar/hemicylindrical (phase I) structure for the range of potentials between -200 ≤ E < 450 mV and condensed (phase II) film for electrode potentials ≥500 mV vs Ag/AgCl. The SNIFTIRS measurements indicate that the alkyl chains within the two adsorbed states of SDS film are in the liquid-crystalline state rather than the gel state. However, the sulfate headgroup is in an oriented state in phase I and is disordered in phase II. The newly acquired SNIFTIR spectroscopy measurements were coupled with previous electrochemical, atomic force microscopy, and neutron reflectivity data to improve the current existing models of the SDS film adsorbed on the Au(111) surface. The IR data support the existence of a hemicylindrical film for SDS molecules adsorbed at the Au(111) surface in phase I and suggest that the structure of the condensed film in phase II can be more accurately modeled by a disordered bilayer.
Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
J Jay
JJ
Leitch
John
J
Collins
Andreas Kaspar
AK
Friedrich
Ulrich
U
Stimming
John R
JR
Dutcher
Jacek
J
Lipkowski
D000327:Adsorption; D004566:Electrodes; D006046:Gold / Q000737:chemistry*; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties
D012967:Sodium Dodecyl Sulfate; D006046:Gold