Specific ion effects on interfacial water structure near macromolecules

被引：296

作者：

Chen, Xin ^{[1
]}

Yang, Tinglu ^{[1
]}

Kataoka, Sho ^{[1
]}

Cremer, Paul S. ^{[1
]}

机构：

[1] Texas A&M Univ, Dept Chem, College Stn, TX 77843 USA

来源：

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY | 2007年 / 129卷 / 40期

关键词：

D O I：

10.1021/ja073869r

中图分类号：

O6 [化学];

学科分类号：

0703 ;

摘要：

We investigated specific ion effects on interfacial water structure next to macromolecules with vibrational sum frequency spectroscopy (VSFS). Poly-(N-isopropylacrylamide) was adsorbed at the air/ water interface for this purpose. It was found that the presence of salt in the subphase could induce the reorganization of water adjacent to the macromolecule and that the changes depended greatly on the specific identity and concentration of the salt employed. Ranked by their propensity to orient interfacial water molecules, sodium salts could be placed in the following order: NaSCN > NaClO4 > Nal > NaNO3 approximate to NaBr > NaCl > pure water approximate to NaF approximate to Na2SO4. This ordering is a Hofmeister series. On the other hand, varying the identity of the cation exhibited virtually no effect. We also showed that the oscillator strength in the OH stretch region was linearly related to changes in the surface potential caused by anion adsorption. This fact allowed binding isotherms to be abstracted from the VSFS data. Such results offer direct evidence that interfacial water structure can be predominantly the consequence of macromolecule-ion interactions.

引用

页码：12272 / 12279

页数：8

共 56 条

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