太赫兹介电谱研究甘油-水混合物的水合动力学和协同作用
Insights into Hydration Dynamics and Cooperative Interactions in Glycerol-Water Mixtures by Terahertz Dielectric Spectroscopy
摘要：
我们报告的弛豫动力学的甘油-水混合物探测兆赫-太赫兹介电谱在50 MHz至0.5太赫兹的频率范围内，在室温下。介电弛豫谱揭示了几个极化过程在分子水平上具有不同的时间常数和介电强度，提供了一个理解的氢键网络中的甘油-水混合物。我们已经确定了甘油分子周围的水化壳层的结构和结合水的动态作为甘油浓度的函数在溶液中使用德拜弛豫模型。实验结果表明，存在一个临界甘油浓度约7.5摩尔%，这是有关的水化层中的水分子周围的甘油分子的数量。在较高的甘油浓度下，分散在甘油网络中的水分子变得丰富并最终占主导地位，并且在混合物中出现四种不同的弛豫过程。利用分子动力学模拟进一步研究了甘油-水混合物的弛豫动力学和水合结构，证实了介电谱所揭示的物理图像。
英文摘要：
We report relaxation dynamics of glycerol-water mixtures as probed by megahertz-to-terahertz dielectric spectroscopy in a frequency range from 50 MHz to 0.5 THz at room temperature. The dielectric relaxation spectra reveal several polarization processes at the molecular level with different time constants and dielectric strengths, providing an understanding of the hydrogen-bonding network in glycerol-water mixtures. We have determined the structure of hydration shells around glycerol molecules and the dynamics of bound water as a function of glycerol concentration in solutions using the Debye relaxation model. The experimental results show the existence of a critical glycerol concentration of ~7.5 mol %, which is related to the number of water molecules in the hydration layer around a glycerol molecule. At higher glycerol concentrations, water molecules dispersed in a glycerol network become abundant and eventually dominate and four distinct relaxation processes emerge in the mixtures. The relaxation dynamics and hydration structure in glycerol-water mixtures are further probed with molecular dynamics simulations, which confirm the physical picture revealed by the dielectric spectroscopy.
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