Gopalakrishnan Sandhya, Jungwirth Pavel, Tobias Douglas J, Allen Heather C
Department of Chemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, Ohio 43210, USA.
J Phys Chem B. 2005 May 12;109(18):8861-72. doi: 10.1021/jp0500236.
Investigations of the air-liquid interface of aqueous salt solutions containing ammonium (NH(4)(+)) and sulfate (SO(4)(2-)) ions were carried out using molecular dynamics simulations and vibrational sum frequency generation spectroscopy. The molecular dynamics simulations show that the predominant effect of SO(4)(2-) ions, which are strongly repelled from the surface, is to increase the thickness of the interfacial region. The vibrational spectra reported are in the O-H stretching region of liquid water. Isotropic Raman and ATR-FTIR (attenuated total reflection Fourier transform infrared) spectroscopies were used to study the effect of ammonium and sulfate ions on the bulk structure of water, whereas surface sum frequency generation spectroscopy was used to study the effect of these ions on the interfacial structure of water. Analysis of the interfacial and bulk vibrational spectra reveal that aqueous solutions containing SO(4)(2-) perturb the interfacial water structure differently than the bulk and, consistent with the molecular dynamics simulations, reveal an increase in the thickness of the interfacial region.
利用分子动力学模拟和振动和频产生光谱，对含有铵离子（NH₄⁺）和硫酸根离子（SO₄²⁻）的盐水溶液的气液界面进行了研究。分子动力学模拟表明，被表面强烈排斥的SO₄²⁻离子的主要作用是增加界面区域的厚度。所报道的振动光谱位于液态水的O-H伸缩区域。采用各向同性拉曼光谱和衰减全反射傅里叶变换红外光谱（ATR-FTIR）研究铵离子和硫酸根离子对水的本体结构的影响，而表面和频产生光谱则用于研究这些离子对水的界面结构的影响。对界面和本体振动光谱的分析表明，含有SO₄²⁻的水溶液对界面水结构的扰动与本体不同，并且与分子动力学模拟一致，显示出界面区域厚度增加。
