uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Molecular Sinkers: X-ray Photoemission and Atomistic Simulations of Benzoic Acid and Benzoate at the Aqueous Solution/Vapor Interface
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
Show others and affiliations
2012 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 116, no 43, 13017-13023 p.Article in journal (Refereed) Published
Abstract [en]

In this work we, for the first time, provide a detailed microscopic picture of the behavior of benzoic acid at the aqueous solution/vapor interface in its neutral as well as in its dissociated form (benzoate). This is achieved through a combination of highly surface-sensitive X-ray photoelectron spectroscopy experiments and fully atomistic molecular simulations. We show that drastic changes occur in the interface behavior of the neutral acid upon release of the proton. The benzoic acid molecules are found to be strongly adsorbed in the interface layer with the planes of the aromatic rings oriented almost parallel to the water surface. In contrast, in the benzoate form the carboxylate group shows a sinker-like behavior while the aromatic ring acts as a buoy, oriented nearly perpendicular to the surface. Furthermore, a significant fraction of the molecular ions move from the interface layer into the bulk of the solution. We rationalize these findings in terms of the very different hydration properties of benzoic acid's carboxylic group in the two charge states. The molecule has an amphiphilic nature and the deprotonation thus changes the hydrophobic/hydrophilic balance between the nonpolar aromatic and the polar carboxylic parts of the molecule. That, consequently, leads to a pronounced reorientation of the molecule at the interface.

Place, publisher, year, edition, pages
2012. Vol. 116, no 43, 13017-13023 p.
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
URN: urn:nbn:se:uu:diva-151434DOI: 10.1021/jp300956jISI: 000310482800014OAI: oai:DiVA.org:uu-151434DiVA: diva2:409927
Available from: 2011-04-11 Created: 2011-04-11 Last updated: 2013-01-09Bibliographically approved
In thesis
1. Aqueous Solutions as seen through an Electron Spectrometer: Surface Structure, Hydration Motifs and Ultrafast Charge Delocalization Dynamics
Open this publication in new window or tab >>Aqueous Solutions as seen through an Electron Spectrometer: Surface Structure, Hydration Motifs and Ultrafast Charge Delocalization Dynamics
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In spite of their high abundance and importance, aqueous systems are enigmatic on the microscopic scale. In order to obtain information about their geometrical and electronic structure, simple aqueous solutions have been studied experimentally by photo- and Auger electron spectroscopy using the novel liquid micro-jet technique in conjunction with synchrotron radiation. The thesis is thematically divided into three parts.

In the first part we utilize the surface sensitivity of photoelectron spectroscopy to probe the distributions of solutes near the water surface. In agreement with recent theoretical predictions we find that large polarizable anions, such as I- and ClO4-, display enhanced surface propensities compared to smaller rigid ions. Surface effects arising from ion-ion interactions at higher electrolyte concentrations and as function of pH are investigated. Studies of linear mono-carboxylic acids and benzoic acid show that the neutral molecular forms of such weak acids are better stabilized at the water surface than their respective conjugate base forms.

The second part examines what type of information core-electron spectra can yield about the chemical state and hydration structure of small organic molecules in water. We demonstrate that the method is sensitive to the protonation state of titratable functional groups and that core-level lineshapes are dependent on local water hydration configurations. Using a combination of photoelectron and X-ray absorption spectroscopy we also show that the electronic re-arrangement upon hydrolysis of aldehydes yields characteristic fingerprints in core-level spectra.

In the last part of this thesis we study ultrafast charge delocalization dynamics in aqueous solutions using resonant and off-resonant Auger spectroscopy. Intermolecular Coulombic decay (ICD) is found to occur in a number of core-excited solutions where excess energy is transferred between the solvent and the solute. The rate of ultrafast electron delocalization between hydrogen bonded water molecules upon oxygen 1s resonant core-excitation is found to decrease upon solvation of inorganic ions.

The presented work is illustrative of how core-level photoelectron spectroscopy can be valuable in the study of fundamental phenomena in aqueous solutions.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 118 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 828
Keyword
Water, Aqueous solutions, Ions, Molecular Hydration, Electron dynamics, Atmospheric Chemistry, Hydrolysis, Acid-Base Chemistry, Interatomic Coulombic Decay, ICD, Liquid Micro-Jet, X-ray Photoelectron Spectroscopy, XPS, Auger Electron Spectroscopy, AES, MAX-lab, BESSY
National Category
Physical Sciences
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-151435 (URN)978-91-554-8083-7 (ISBN)
Public defence
2011-06-01, Polhemssalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2011-05-11 Created: 2011-04-11 Last updated: 2011-07-01Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Authority records BETA

Söderström, JohanBjörneholm, Olle

Search in DiVA

By author/editor
Söderström, JohanBjörneholm, Olle
By organisation
Surface and Interface Science
In the same journal
Journal of Physical Chemistry B
Condensed Matter Physics

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 585 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf