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

Direct link
Alcohols at the Aqueous Surface: Chain Length and Isomer Effects
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics. Swedish University for Agricultural Sciences, Department of Chemistry and Biotechnology.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
Helsinki University, Department of Physics.
Show others and affiliations
2016 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 9, 6648-6656 p.Article in journal (Refereed) Published
Abstract [en]

Surface-active organic molecules at the liquid-vapor interface are of great importance in atmospheric science. Therefore, we studied the surface behavior of alcohol isomers with different chain lengths (C4-C6) in aqueous solution with surface- and chemically sensitive X-ray photoelectron spectroscopy (XPS), which reveals information about the surface structure on a molecular level. Gibbs free energies of adsorption and surface concentrations are determined from the XPS results using a standard Langmuir adsorption isotherm model. The free energies of adsorption, ranging from around -15 to -19 kJ/mol (C4-C6), scale linearly with the number of carbon atoms within the alcohols with ΔGAds/CH2 ≈ -2 kJ/mol. While for the linear alcohols, surface concentrations lie around 2.4 x 1014 molecules/cm2 at the bulk concentrations where monolayers are formed, the studied branched alcohols show lower surface concentrations of around 1.6 x 1014 molecules/cm2, both of which are in line with the molecular structure and their orientation at the interface. Interestingly, we find that there is a maximum in the surface enrichment factor for linear alcohols at low concentrations, which is not observed for the shorter branched alcohols. This is interpreted in terms of a cooperative effect, which we suggest to be the result of more effective van der Waals interactions between the linear alcohol alkyl chains at the aqueous surface, making it energetically even more favorable to reside at the liquid-vapor interface. 

Place, publisher, year, edition, pages
2016. Vol. 18, no 9, 6648-6656 p.
National Category
Physical Chemistry Condensed Matter Physics
URN: urn:nbn:se:uu:diva-265221DOI: 10.1039/c5cp06463eISI: 000371139400030PubMedID: 26868637OAI: oai:DiVA.org:uu-265221DiVA: diva2:865089
Swedish Research CouncilSwedish Foundation for Strategic Research Carl Tryggers foundation
Available from: 2015-10-26 Created: 2015-10-26 Last updated: 2016-04-05Bibliographically approved
In thesis
1. Exploring the Surface of Aqueous Solutions: X-ray photoelectron spectroscopy studies using a liquid micro-jet
Open this publication in new window or tab >>Exploring the Surface of Aqueous Solutions: X-ray photoelectron spectroscopy studies using a liquid micro-jet
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The surface behavior of biologically or atmospherically relevant chemical compounds in aqueous solution has been studied using surface-sensitive X-ray photoelectron spectroscopy (XPS). The aim is to provide information on the molecular-scale composition and distribution of solutes in the surface region of aqueous solutions. In the first part, the distribution of solutes in the surface region is discussed, where in particular single molecular species are studied. Concentration-dependent studies on succinic acid and various alkyl-alcohols, where also parameters such as pH and branching are varied, are analyzed using different approaches that allow the quantification of surface concentrations. Furthermore, due to the sensitivity of XPS to the chemical state, reorientation of linear and branched alkyl-alcohols at the aqueous surface as a function of concentration is observed. The results are further discussed in terms of hydrophilic and hydrophobic interactions in the interfacial region, where the three-dimensional hydrogen bonded water structure terminates. In the second part, mixed solutions of compounds, both ionic and molecular, are inspected. Again concentration, but also co-dissolution of other chemical compounds, are varied and differences in the spatial distribution and composition of the surface region are discussed. It is found that the guanidinium ion has an increased propensity to reside at the surface, which is explained by strong hydration in only two dimensions and only weak interactions between the aromatic π-system and water. Ammonium ions, on the other hand, which require hydration in three dimensions, are depleted from the surface region. The presence of strongly hydrated electrolytes out-competes neutral molecules for hydrating water molecules leading to an enhanced abundance of molecules, such as succinic acid, in the interfacial region. The partitioning is quantified and discussed in the context of atmospheric science, where the impact of the presented results on organic loading of aerosol particles is emphasized.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 88 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1313
X-ray Photoelectron spectroscopy, liquid micro-jet, air-water interface, inorganic salt, carboxylic acid, alcohol, isomers, hydration.
National Category
Atom and Molecular Physics and Optics Condensed Matter Physics Chemical Sciences
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
urn:nbn:se:uu:diva-265210 (URN)978-91-554-9399-8 (ISBN)
Public defence
2015-12-18, Häggsalen, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Available from: 2015-11-27 Created: 2015-10-25 Last updated: 2016-01-13

Open Access in DiVA

The full text will be freely available from 2017-02-12 01:00
Available from 2017-02-12 01:00

Other links

Publisher's full textPubMed

Search in DiVA

By author/editor
Walz, Marie-MadeleineWerner, JosephinaEkholm, Victor
By organisation
Molecular and condensed matter physics
In the same journal
Physical Chemistry, Chemical Physics - PCCP
Physical ChemistryCondensed Matter Physics

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 573 hits
ReferencesLink to record
Permanent link

Direct link