期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2009
卷号：106
期号：36
页码：15176-15180
DOI：10.1073/pnas.0904800106
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Recent experimental and theoretical results have firmly established the existence of enhanced concentrations of selected ions at the air/water interface. Ion adsorption to aqueous interfaces involving complex organic molecules is relevant to biology in connection with the familiar but incompletely understood Hofmeister effects. Here, we describe resonant UV second harmonic generation (SHG) studies of the strongly chaotropic thiocyanate ion adsorbed to the interface formed by water and a monolayer of dodecanol, wherein the Gibbs free energy of adsorption was determined to be -6.7 {+/-} 1.1 and -6.3 {+/-} 1.8 kJ/mol for sodium and potassium thiocyanate, respectively, coincident with the value determined for thiocyanate at the air/water interface. Interestingly, near 4 M and higher concentrations, the resonant SHG signal increases discontinuously, indicating a structural change in the interfacial region.
