Shanghai Institute of Applied Physics, Chinese Academy of Sciences, P.O. Box 800-, 204, Shanghai 201800, China.
Phys Chem Chem Phys. 2009 Nov 14;11(42):9898-902. doi: 10.1039/b907926m. Epub 2009 Aug 26.
The dynamics of water inside nanochannels is of great importance for biological activities as well as for the design of molecular sensors, devices, and machines, particularly for sea water desalination. When confined in specially sized nanochannels, water molecules form a single-file structure with concerted dipole orientations, which collectively flip between the directions along and against the nanotube axis. In this paper, by using molecular dynamics simulations, we observed a net flux along the dipole-orientation without any application of an external electric field or external pressure difference during the time period of the particular concerted dipole orientations of the molecules along or against the nanotube axis. We found that this unique special-directional water transportation resulted from the asymmetric potential of water-water interaction along the nanochannel, which originated from the concerted dipole orientation of the water molecules that breaks the symmetry of water orientation distribution along the channel within a finite time period. This finding suggests a new mechanism for achieving high-flux water transportation, which may be useful for nanotechnology and biological applications.
纳米通道内水的动力学对于生物活性以及分子传感器、设备和机器的设计都非常重要，特别是对于海水淡化。当水分子被限制在特定尺寸的纳米通道内时，它们会形成具有协同偶极取向的单列结构，这些偶极子会沿着和逆着纳米管轴的方向集体翻转。在本文中，通过使用分子动力学模拟，我们观察到在没有施加外部电场或外部压力差的情况下，在分子沿着或逆着纳米管轴的特定协同偶极取向的时间段内，存在沿着偶极取向的净通量。我们发现，这种独特的特殊方向的水输运是由于纳米通道内沿水-水相互作用的不对称势引起的，这种不对称势源于水分子的协同偶极取向，它在有限的时间内打破了沿通道内的水分子取向分布的对称性。这一发现为实现高通量水输运提供了一种新的机制，可能对纳米技术和生物应用有用。
