Role of Nanoscale Interfacial Proximity in Contact Freezing in Water
Role of Nanoscale Interfacial Proximity in Contact Freezing in Water
复制标题
DOI：
10.1021/jacs.0c10663
复制
发表时间：
2021-01-28
影响因子：
15
通讯作者：
Haji-Akbari, Amir
中科院分区：
文献类型：
--
作者：
Hussain, Sarwar;Haji-Akbari, Amir
接触冻结是大气冰成核的一种模式，其中干冰成核颗粒（INP）与水滴之间的碰撞导致显著更快的异相成核。然而，这种增强的分子机制仍然是一个谜。虽然早期的研究将其归因于碰撞引起的瞬态扰动，但最近的实验指出了INP和自由界面的纳米级接近的关键作用。通过模拟两个模型的水状四面体液体的INP支持的纳米膜内的冰的异质成核，我们表明，这种纳米级的接近是足够的诱导速率增加与接触冷冻实验中观察到的那些相称，但只有当自由界面有一个趋势，以提高均匀成核。水被怀疑具有后一种性质，称为表面冻结倾向。因此，我们的研究结果建立在接触成核过程中的表面冻结倾向和动力学增强之间的连接。我们还观察到，更快的成核通过一种机制进行明显不同于经典的异质成核，涉及沙漏形晶核的形成，构思在任何一个接口，并具有较低的自由能的形成，由于纳米级接近的接口和调制的自由界面结构的INP。除了提供有价值的见解接触成核的物理，我们的研究结果可以帮助提高实验中的异质成核率测量的准确性，并在推进我们的理解冰成核的不均匀表面，如有机，聚合物和生物材料。
Contact freezing is a mode of atmospheric ice nucleation in which a collision between a dry ice nucleating particle (INP) and a water droplet results in considerably faster heterogeneous nucleation. The molecular mechanism of such an enhancement is, however, still a mystery. While earlier studies had attributed it to collision-induced transient perturbations, recent experiments point to the pivotal role of nanoscale proximity of the INP and the free interface. By simulating the heterogeneous nucleation of ice within INP-supported nanofilms of two model water-like tetrahedral liquids, we demonstrate that such nanoscale proximity is sufficient for inducing rate increases commensurate with those observed in contact freezing experiments, but only if the free interface has a tendency to enhance homogeneous nucleation. Water is suspected of possessing this latter property, known as surface freezing propensity. Our findings therefore establish a connection between the surface freezing propensity and kinetic enhancement during contact nucleation. We also observe that faster nucleation proceeds through a mechanism markedly distinct from classical heterogeneous nucleation, involving the formation of hourglass-shaped crystalline nuclei that conceive at either interface and that have a lower free energy of formation due to the nanoscale proximity of the interfaces and the modulation of the free interfacial structure by the INP. In addition to providing valuable insights into the physics of contact nucleation, our findings can assist in improving the accuracy of heterogeneous nucleation rate measurements in experiments and in advancing our understanding of ice nucleation on nonuniform surfaces such as organic, polymeric, and biological materials.