The molecular structure of the surface of water–ethanol mixtures
- 11 May 2021
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Physical Chemistry Chemical Physics
- Vol. 23 (19), 11568-11578
- https://doi.org/10.1039/d0cp06387h
Abstract
Mixtures of water and alcohol exhibit an excess surface concentration of alcohol as a result of the amphiphilic nature of the alcohol molecule, which has important consequences for the physico-chemical properties of water–alcohol mixtures. Here we use a combination of intensity vibrational sum-frequency generation (VSFG) spectroscopy, heterodyne-detected VSFG (HD-VSFG), and core-level photoelectron spectroscopy (PES) to investigate the molecular properties of water–ethanol mixtures at the air–liquid interface. We find that increasing the ethanol concentration up to a molar fraction (MF) of 0.1 leads to a steep increase of the surface density of the ethanol molecules, and an increased ordering of the ethanol molecules at the surface. When the ethanol concentration is further increased, the surface density of ethanol remains more or less constant, while the orientation of the ethanol molecules becomes increasingly disordered. The used techniques of PES and VSFG provide complementary information on the density and orientation of ethanol molecules at the surface of water, thus providing new information on the molecular-scale properties of the surface of water–alcohol mixtures over a wide range of compositions. This information is invaluable in understanding the chemical and physical properties of water–alcohol mixtures.Funding Information
- Fundação de Amparo à Pesquisa do Estado de São Paulo (2017/11986-5)
- Agência Nacional do Petróleo, Gás Natural e Biocombustíveis (2017/11986-5)
- Conselho Nacional de Desenvolvimento Científico e Tecnológico (401581/2016-0)
- Swedish Foundation for International Cooperation in Research and Higher Education (9805/2014-01)
- Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (9805/2014-01)
- Vetenskapsrådet (2017-04162)
- Nederlandse Organisatie voor Wetenschappelijk Onderzoek
This publication has 52 references indexed in Scilit:
- Volumetric and Surface Properties of Short Chain Alcohols in Aqueous Solution–Air Systems at 293 KJournal of Solution Chemistry, 2012
- Vibrational Spectra and Molecular Orientation with Experimental Configuration Analysis in Surface Sum Frequency Generation (SFG)The Journal of Physical Chemistry C, 2007
- Competitive Molecular Adsorption at Liquid/Solid Interfaces: A Study by Sum-Frequency Vibrational SpectroscopyThe Journal of Physical Chemistry C, 2007
- Introduction: Structure and Chemistry at Aqueous InterfacesChemical Reviews, 2006
- Surfaces of Alcohol−Water Mixtures Studied by Sum-Frequency Generation Vibrational SpectroscopyThe Journal of Physical Chemistry B, 2005
- Quantitative spectral and orientational analysis in surface sum frequency generation vibrational spectroscopy (SFG-VS)International Reviews in Physical Chemistry, 2005
- Molecular Dynamics Simulations of the Liquid/Vapor Interface of Aqueous Ethanol Solutions as a Function of ConcentrationThe Journal of Physical Chemistry B, 2003
- Molecular segregation observed in a concentrated alcohol–water solutionNature, 2002
- WIDTHS OF THE ATOMIC K–N7 LEVELSAtomic Data and Nuclear Data Tables, 2001
- Molecular dynamics investigation of the surface/bulk equilibrium in an ethanol–water solutionJournal of the Chemical Society, Faraday Transactions, 1996