2024-02-04
Observation of Electrostatically Driven Surface Adsorption in Mixed Surfactant Systems
Publication
Publication
J. Phys. Chem. Lett. , Volume 15 - Issue 6 p. 1596- 1602
We employed heterodyne-detected vibrational sum-frequency generation (HD-VSFG) spectroscopy to obtain a molecular-level understanding of the interaction between the anionic surfactant sodium dodecyl ammonium sulfate (SDS) and the cationic surfactant dodecyltrimethylammonium bromide (DTAB). We observed that these surfactants show a strong cooperative effect on their adsorption to the water-air interface. Even at bulk concentrations 1000 times lower than the critical micelle concentrations of SDS and DTAB, a nearly complete surface surfactant layer is observed when both surfactants are present. This strong enhancement of the surface concentrations of DS- and DTA+ can be quantitatively explained from the favorable Coulomb interaction of the oppositely charged headgroups of DS- and DTA+ and the electrostatic interactions with their counterions. The HD-VSFG results are complemented by a modified Langmuir adsorption model in which we include the free energy associated with the electrostatic interactions of the surfactant ions and their counterions.
Additional Metadata | |
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ACS | |
The Netherlands Organisation for Scientific Research (NWO) | |
doi.org/10.1021/acs.jpclett.3c03377 | |
J. Phys. Chem. Lett. | |
Organisation | Ultrafast Spectroscopy |
Vilangottunjalil, A., Versluis, J., & Bakker, H. (2024). Observation of Electrostatically Driven Surface Adsorption in Mixed Surfactant Systems. J. Phys. Chem. Lett., 15(6), 1596–1602. doi:10.1021/acs.jpclett.3c03377 |