Beijing Key Laboratory of Ionic Liquids Clean Process, CAS Key Laboratory of Green Process and Engineering, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China.
Phys Chem Chem Phys. 2018 Jul 4;20(26):17773-17780. doi: 10.1039/c8cp02408a.
Ionic liquid (IL) flow in graphene oxide (GO) nanochannels plays a key role in the performance of IL- and GO-based fluidics devices and other chemical separator techniques. Here, we investigate the flow behavior of ILs in GO nanochannels via molecular dynamics simulations. The quantitative relation between slip velocity and shear stress has been identified, showing that the interfacial friction coefficient can be enhanced by almost sixty times, while the slip length is reduced by about three orders of magnitude, with the fraction of hydroxylation in graphene ranging from 0% to 15%. The great change in interfacial properties can be attributed to the structural changes of IL layers near GO, which is proved by the detailed analysis of density distribution, charge distribution and radial distribution function. Besides, the viscosity will increase as a fraction of hydroxylation because of the partial breaking of coulombic ordering of confined ILs. Meanwhile, the hydroxyls have more significant effects on IL flow than water flow in GO nanochannels due to the stronger interaction networks in IL/GO interfaces. In summary, hydroxylation can be a convincing method to regulate the IL flow in nanochannels. The quantitative properties of confined ILs in GO nanochannels and their relation to the fraction of hydroxylation could deepen the understanding of ILs and benefit the applications of ILs and GO in the fields of chemical engineering and various other nanofluidic devices.
氧化石墨烯（GO）纳米通道中的离子液体（IL）流动对于基于 IL 和 GO 的流动器件和其他化学分离技术的性能起着关键作用。在这里，我们通过分子动力学模拟研究了 IL 在 GO 纳米通道中的流动行为。确定了滑移速度与剪切应力之间的定量关系，表明界面摩擦系数可以增强近六十倍，而滑移长度减小约三个数量级，石墨烯中羟基的分数范围为 0%至 15%。界面性质的巨大变化可以归因于 GO 附近 IL 层的结构变化，这通过对密度分布、电荷分布和径向分布函数的详细分析得到了证明。此外，由于受限 IL 中库仑有序的部分破坏，羟基分数会导致粘度增加。同时，由于 IL/GO 界面上存在更强的相互作用网络，羟基对 GO 纳米通道中 IL 流动的影响比水流动的影响更为显著。综上所述，羟基化是调节纳米通道中 IL 流动的一种有效方法。GO 纳米通道中受限 IL 的定量性质及其与羟基分数的关系可以加深对 IL 的理解，并有利于 IL 和 GO 在化学工程和各种其他纳流器件领域的应用。
