Institut Charles Gerhardt Montpellier, UMR-CNRS 5253, Université Montpellier 2 and ENSCM, Montpellier, France.
Phys Rev Lett. 2012 Jul 20;109(3):035701. doi: 10.1103/PhysRevLett.109.035701. Epub 2012 Jul 18.
Freezing of water in hydrophilic nanopores (D=1.2 nm) is probed at the microscopic scale using x-ray diffraction, Raman spectroscopy, and molecular simulation. A freezing scenario, which has not been observed previously, is reported; while the pore surface induces orientational order of water in contact with it, water does not crystallize at temperatures as low as 173 K. Crystallization at the surface is suppressed as the number of hydrogen bonds formed is insufficient (even when including hydrogen bonds with the surface), while crystallization in the pore center is hindered as the curvature prevents the formation of a network of tetrahedrally coordinated molecules. This sheds light on the concept of an ubiquitous unfreezable water layer by showing that the latter has a rigid (i.e., glassy) liquidlike structure, but can exhibit orientational order.
利用 X 射线衍射、拉曼光谱和分子模拟，在微观尺度上研究了亲水性纳米孔（D=1.2nm）中水分的冻结过程。报告了一种以前未观察到的冻结情况；尽管孔表面诱导与之接触的水的取向有序，但在低至 173 K 的温度下，水不会结晶。由于形成的氢键数量不足（即使包括与表面的氢键），表面处的结晶受到抑制，而曲率阻止四面体配位分子网络的形成，从而阻碍了孔中心处的结晶。这表明无处不在的不可冻结水层的概念，因为后者具有刚性（即玻璃态）液态结构，但可以表现出取向有序。
