Changing Hydrogen-Bond Structure during an Aqueous Liquid–Liquid Transition Investigated with Time-Resolved and Two-Dimensional Vibrational Spectroscopy

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• 作者：Jeroen R. Bruijn ; Tibert H. van der Loop ; Sander Woutersen
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2016
• 出版时间：March 3, 2016
• 年：2016
• 卷：7
• 期：5
• 页码：795-799
• 全文大小：377K
• ISSN：1948-7185

文摘

We investigate the putative liquid–liquid phase transition in aqueous glycerol solution, using the OD-stretch mode in dilute OD/OH isotopic mixtures to probe the hydrogen-bond structure. The conversion exhibits Avrami kinetics with an exponent of n = 2.9 ± 0.1 (as opposed to n = 1.7 observed upon inducing ice nucleation and growth in the same sample), which indicates a transition from one liquid phase to another. Two-dimensional infrared (2D-IR) spectroscopy shows that the initial and final phases have different hydrogen-bond structures: the former has a single Gaussian distribution of hydrogen-bond lengths, whereas the latter has a bimodal distribution consisting of a broad distribution and a narrower, ice-like distribution. The 2D-IR spectrum of the final phase is identical to that of ice/glycerol at the same temperature. Combined with the kinetic data this suggests that the liquid–liquid transformation is immediately followed by a rapid formation of small (probably nanometer-sized) ice crystals.