Counterion Effect on Interfacial Water at Charged Interfaces and Its Relevance to the Hofmeister Series
Counterion Effect on Interfacial Water at Charged Interfaces and Its Relevance to the Hofmeister Series
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DOI：
10.1021/ja412952y
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发表时间：
2014-04-30
影响因子：
15
通讯作者：
Tahara, Tahei
中科院分区：
文献类型：
--
作者：
Nihonyanagi, Satoshi;Yamaguchi, Shoichi;Tahara, Tahei
由霍夫迈斯特系列所代表的特定的反作用是非常重要的各种现象，如蛋白质沉淀，电解质溶液的表面张力，表面活性剂的相变等，我们应用外差检测振动和频产生光谱研究的反作用在带电界面上的界面水，并讨论了观察到的效果与相关的霍夫迈斯特系列。对带正电荷的十六烷基三甲基铵单分子膜/电解质溶液界面和带负电荷的十二烷基硫酸盐单分子膜/电解质界面模型体系进行了实验研究。在带正电荷的界面处，界面水的OH带的强度以Hofmeister级数的顺序降低，这表明卤素阴离子在界面上的吸附能力决定了Hofmeister级数，如Zhang和Cremer先前提出的（Curr. Opin. 2006，10，658-663）。在带负电荷的界面，另一方面，OH带强度不依赖于抗衡阳离子显着，而在界面水的氢键强度的变化是很好地与Hofmeister顺序的阳离子效应。这些结果提供了新的见解的阴离子和阳离子Hofmeister效应的分子水平的机制。
Specific counterion effects represented by Hofmeister series are important for a variety of phenomena such as protein precipitations, surface tensions of electrolytes solutions, phase transitions of surfactants, etc. We applied heterodyne-detected vibrational sum-frequency generation spectroscopy to study the counterion effect on the interfacial water at charged interfaces and discussed the observed effect with relevance to the Hofmeister series. Experiments were carried out for model systems of positively charged cetyltrimethylammonium monolayer/electrolyte solution interface and negatively charged dodecylsulfate monolayer/electrolyte interface. At the positively charged interface, the intensity of the OH band of the interfacial water decreases in the order of the Hofmeister series, suggesting that the adsorbability of halide anions onto the interface determines the Hofmeister order as previously proposed by Zhang and Cremer (Curr. Opin. Chem. Biol. 2006, 10, 658-663). At the negatively charged interfaces, on the other hand, the OH band intensity does not depend significantly on the countercation, whereas variation in the hydrogen-bond strength of the interfacial water is well correlated with the Hofmeister order of the cation effect. These results provide new insights into the molecular level mechanisms of anionic and cationic Hofmeister effects.