美国南加州大学Alexander V. Benderskii小组的最新研究提出了界面水对外加电场的不对称响应。 2021年6月2日，国际知名学术期刊《自然》发表了这一成果。

该课题组人员提出了一项针对这个问题的实验研究。研究人员在单层石墨烯电极附近测量了重水（D₂O）的振动和频生成光谱，以研究其对受控电化学条件下的外部电场的响应。OD拉伸的光谱显示出对于正性对比负极电荷的明显不对称性。当负电荷低于5 × 10¹²电子每平方厘米时，观察到非氢键OD基团指向石墨烯表面的峰值频率为每厘米2700次。

在中性或正极电位下，这种“自由OD”峰突然消失，而光谱显示氢键OD物种的宽峰(在2,300-2,650波数)。米勒定律将振动和频率产生响应与介电常数联系起来。观察到的与每米±3 × 10⁸伏特电场线性响应的偏差对人们对将界面水作为简单介质处理的有效性提出了质疑。

研究人员表示，他们对界面水的介电响应的理解，它在水溶液界面处掩盖了溶剂化性能和反应速率，依赖于线性响应近似：外部电场引发线性比例偏振。这意味着对场的符号具有反对称性。然而，原子模拟已经提出，界面水的极化可能与显著偏离线性响应。

附：英文原文

Title: Asymmetric response of interfacial water to applied electric fields

Author: Angelo Montenegro, Chayan Dutta, Muhammet Mammetkuliev, Haotian Shi, Bingya Hou, Dhritiman Bhattacharyya, Bofan Zhao, Stephen B. Cronin, Alexander V. Benderskii

Issue&Volume: 2021-06-02

Abstract: Our understanding of the dielectric response of interfacial water, which underlies the solvation properties and reaction rates at aqueous interfaces, relies on the linear response approximation: an external electric field induces a linearly proportional polarization. This implies antisymmetry with respect to the sign of the field. Atomistic simulations have suggested, however, that the polarization of interfacial water may deviate considerably from the linear response. Here we present an experimental study addressing this issue. We measured vibrational sum-frequency generation spectra of heavy water (D2O) near a monolayer graphene electrode, to study its response to an external electric field under controlled electrochemical conditions. The spectra of the OD stretch show a pronounced asymmetry for positive versus negative electrode charge. At negative charge below 5 × 1012 electrons per square centimetre, a peak of the non-hydrogen-bonded OD groups pointing towards the graphene surface is observed at a frequency of 2,700 per centimetre. At neutral or positive electrode potentials, this ‘free-OD’ peak disappears abruptly, and the spectra display broad peaks of hydrogen-bonded OD species (at 2,300–2,650 per centimetre). Miller’s rule1 connects the vibrational sum-frequency generation response to the dielectric constant. The observed deviation from the linear response for electric fields of about ±3 × 108 volts per metre calls into question the validity of treating interfacial water as a simple dielectric medium.

DOI: 10.1038/s41586-021-03504-4

Source: https://www.nature.com/articles/s41586-021-03504-4