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Surface Behavior of Hydrated Guanidinium and Ammonium Ions: A Comparative Study by Photoelectron Spectroscopy and Molecular Dynamics
- Source :
- The Journal of Physical Chemistry B. 118:7119-7127
- Publication Year :
- 2014
- Publisher :
- American Chemical Society (ACS), 2014.
-
Abstract
- Through the combination of surface sensitive photoelectron spectroscopy and molecular dynamics simulation, the relative surface propensities of guanidinium and ammonium ions in aqueous solution are characterized. The fact that the N 1s binding energies differ between these two species was exploited to monitor their relative surface concentration through their respective photoemission intensities. Aqueous solutions of ammonium and guanidinium chloride, and mixtures of these salts, have been studied in a wide concentration range, and it is found that the guanidinium ion has a greater propensity to reside at the aqueous surface than the ammonium ion. A large portion of the relative excess of guanidinium ions in the surface region of the mixed solutions can be explained by replacement of ammonium ions by guanidinium ions in the surface region in combination with a strong salting-out effect of guanidinium by ammonium ions at increased concentrations. This interpretation is supported by molecular dynamics simulations, which reproduce the experimental trends very well. The simulations suggest that the relatively higher surface propensity of guanidinium compared with ammonium ions is due to the ease of dehydration of the faces of the almost planar guanidinium ion, which allows it to approach the water-vapor interface oriented parallel to it.
- Subjects :
- inorganic chemicals
Guanidinium chloride
Surface Properties
Inorganic chemistry
Binding energy
Molecular Dynamics Simulation
Physical Chemistry
complex mixtures
Ion
chemistry.chemical_compound
Molecular dynamics
X-ray photoelectron spectroscopy
Ammonium Compounds
Materials Chemistry
Fysik
Ammonium
Physical and Theoretical Chemistry
Guanidine
Ions
Fysikalisk kemi
Range (particle radiation)
Aqueous solution
Photoelectron Spectroscopy
organic chemicals
Water
Surfaces, Coatings and Films
chemistry
Physical Sciences
biological sciences
Salts
Gases
Subjects
Details
- ISSN :
- 15205207 and 15206106
- Volume :
- 118
- Database :
- OpenAIRE
- Journal :
- The Journal of Physical Chemistry B
- Accession number :
- edsair.doi.dedup.....e8ab846d455fe7abc9424015d371c8ea