Water molecules at interfaces of materials exhibit enigmatic properties. A variety of spectroscopic studies have observed a high-frequency motion in these water molecules, represented by a blueshift, at both hydrophobic and hydrophilic interfaces. However, the molecular mechanism behind this blueshift has remained unclear. Using Raman spectroscopy and ab initio molecular dynamics simulations, we reveal the molecular mechanism of the blueshift of water molecules around six monosaccharide isomers. In the first hydration shell, we found weak hydrogen-bonded water molecules that cannot have a stable tetrahedral water network. In the water molecules, the vibrational state of the OH bond oriented toward the bulk solvent strongly contributes to the observed blueshift. Our work suggests that the blueshift in various solutions originates from the vibrational motions of these observed water molecules.

中文翻译：

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水分子在亲水性环状化合物界面处发生蓝移的起源。

材料界面处的水分子表现出神秘的特性。各种光谱研究已经观察到这些水分子在疏水性和亲水性界面处都发生了蓝移，表现出高频运动。但是，这种蓝移背后的分子机制仍不清楚。使用拉曼光谱和从头算分子动力学模拟，我们揭示了水分子在六个单糖异构体周围发生蓝移的分子机理。在第一个水合壳中，我们发现了弱氢键结合的水分子，这些分子不能具有稳定的四面体水网络。在水分子中，朝向主体溶剂的OH键的振动状态强烈地有助于观察到的蓝移。