4.8 Article

Contact Ion Pair Formation Is Not Necessarily Stronger than Solvent Shared Ion Pairing

Journal

JOURNAL OF PHYSICAL CHEMISTRY LETTERS
Volume 13, Issue 3, Pages 923-930

Publisher

AMER CHEMICAL SOC
DOI: 10.1021/acs.jpclett.1c03576

Keywords

-

Funding

  1. National Science Foundation [CHE2004050]

Ask authors/readers for more resources

In this study, vibrational sum frequency spectroscopy (VSFS) and pressure-area Langmuir trough measurements were used to investigate the binding of alkali metal cations to eicosyl sulfate (ESO4) surfactants at the air/water interface. The results showed that K+ had a stronger binding affinity to the fatty sulfate interface compared to Li+ and Na+, and all three cations formed ion pairs under certain conditions.
Vibrational sum frequency spectroscopy (VSFS) and pressure-area Langmuir trough measurements were used to investigate the binding of alkali metal cations to eicosyl sulfate (ESO4) surfactants in monolayers at the air/water interface. The number density of sulfate groups could be tuned by mixing the anionic surfactant with eicosanol. The equilibrium dissociation constant for K+ to the fatty sulfate interface showed 10 times greater affinity than for Li+ and approximately 3 times greater than for Na+. All three cations formed solvent shared ion pairs when the mole fraction of ESO4 was 0.33 or lower. Above this threshold charge density, Li+ formed contact ion pairs with the sulfate headgroups, presumably via bridging structures. By contrast, K+ only bound to the sulfate moieties in solvent shared ion pairing configurations. The behavior for Na+ was intermediate. These results demonstrate that there is not necessarily a correlation between contact ion pair formation and stronger binding affinity.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

4.8
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available