轴向电场对纳米管道中溶液离子径向分布的影响

Influence of axial applied potential gradient on ion radial distribution in liquid confined in cylindrical nanotubes

用分子动力学模拟的方法,研究了轴向外加电场强度对圆柱形纳米管道中NaCl溶液离子径向密度分布的影响.仿真结果表明,纳米管道两端的外加电场强度增大时,系统的瞬时动能增加.离子获得较大的径向动能就可以克服所在位置势能束缚,运动到使原来浓度峰值减小的径向位置,以保证系统的自由能减小,从而导致离子径向浓度峰值变小.壁面电荷密度越小,离子受到壁面电荷的束缚就越小,这一现象越明显.由于离子的径向分布对电渗流有直接影响,因此这一仿真对电渗流的理论研究和利用外电场实现离子分离的纳流体器件的设计具有重要的参考价值.

The effect of an axial applied potential gradient on the ion distribution of sodium chlorine solution confined in cylindrical nanotubes is investigated with a molecular dynamics simulation model. The simulation results indicate that with the axial applied potential gradient increasing the instantaneous kinetic energy of the system enhances. Obtaining higher radial instantaneous energy, the ions escape from their position and move to other place to reduce the free energy of the system. Thus the peak value of the ion radial density is decreased. With lower surface charge density this phenomenon is more evident. Since the ion radial distributions in liquid directly affect the electroosmotic flow, this study is useful for electroosmotic flow research and the design of nanofluidic devices for species separation by applied potential gradient.