Molecular structure of ionic surfactant solution surface and effects of counter-ion therein—a joint investigation by simulation and experiment
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The main goal of the current paper is to investigate the surface structure of ionic surfactant solutions at molecular level and the influences of the counter-ion in this course. The used methods are molecular dynamics simulation and neutral impact collision ion scattering spectroscopy. The surfactants are sodium dodecyl sulfate and cesium dodecyl sulfate. With Material Studio (MS), the concentration-depth profiles of all the components in the surface layer have been simulated. With those profiles, the surface pictures of the ionic surfactant solutions are mapped out in angstrom scale and the orientation of surface active dodecyl sulfate ion at the surface dependent on its surface density is derived. Simultaneously, neutral impact collision ion scattering spectroscopy is employed to investigate the same systems experimentally. The results indicate that the surface structure is profoundly influenced by surface density of the surfactant and specificity of the counter-ion; however, the orientation of the dodecyl sulfate ion on the surface is only subjected to its surface density but hardly affected by the properties of its counter-ion. The comparison between those simulated and experimental results reveals reasonable agreements, indicating the reliability of this investigation as well as the reliability of the simulation strategy applied in these systems.
KeywordsSurface structure Surfactant solution Molecular dynamics simulation Neutral impact collision ion scattering spectroscopy
This work is supported by National Natural Science Foundation of China (Grants No. 21203251 and 21203250) and Ministry of Education of China (Ph.D. Programs Foundation Grant No. 20120133120008 and Scientific Research Foundation for Returned Scholars). The financial support from Fund for Distinguished Young Scientists of Shandong Province (Grant No. BS2013NJ008) is also gratefully thanked.
- 9.Wang C (2014) Different distributions of counterions in the surface layer of cationic surfactant solutions. J Dispers Sci Technol 35:735–738Google Scholar
- 17.Cao X, Lu K, Cui X, Shi J, Yuan S (2010) Interactions between anionic surfactants and cations. Acta Phys -Chim Sin 26:1579–1964Google Scholar
- 23.Koelsch P, Viswanath P, Motschmann H, Shapovalov V, Brezesinski G, Mohwald H, Horinek D, Netz RR, Giewekemeyer K, Salditt T, Schollmeyer H, Von Klitzing R, Daillant J, Guenoun P (2007) Specific ion effects in physicochemical and biological systems: simulations, theory and experiments. Colloids Surf A 303:110–136CrossRefGoogle Scholar
- 32.Wang C, Morgner H (2014) The dependence of surface tension on surface properties of ionic surfactant solution and the effects of counter-ion therein. Phys Chem Chem Phys 16:23338–23364Google Scholar