Zhang Fei, Jiang Xikai, Chen Gaofeng, He Yadong, Hu Guoqing, Qiao Rui
neoX Biotech, No. 29 Life Science Park Road, Beijing 102206, China.
State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China.
J Phys Chem Lett. 2021 Jan 14;12(1):711-716. doi: 10.1021/acs.jpclett.0c03335. Epub 2021 Jan 5.
Electric-field-driven ion emission from the free surface of a planar room-temperature ionic liquid (RTIL) film was studied by using molecular dynamics simulations. We calculated ion emission rate () as a function of the electric field normal to the RTIL/vacuum surface () and found that the logarithm of over the charge density on the surface (σ) is proportional to , in agreement with classical ion evaporation theories. The composition of emitted ions includes monomers and dimers. It was found that the monomer has to move across two barriers before emission. The fraction of dimers was found to depend on the external field and ion-ion interactions. We further performed replica exchange molecular dynamics simulations and identified different metastable states of the emitting ion near the liquid film. Our results showed that and molecular details of ion/surface determine the rate and composition of ion emission from RTIL/vacuum surfaces. Fundamental insights revealed in this study form the basis to improve ion evaporation theories and performance of electrospray applications ranging from space propulsion to nanomanufacturing.
通过分子动力学模拟研究了平面室温离子液体（RTIL）薄膜自由表面的电场驱动离子发射。我们计算了离子发射率（）作为垂直于RTIL/真空表面的电场（）的函数，发现表面电荷密度（σ）上的对数与成正比，这与经典离子蒸发理论一致。发射离子的组成包括单体和二聚体。发现单体在发射前必须跨越两个势垒。发现二聚体的比例取决于外部场和离子-离子相互作用。我们进一步进行了复制交换分子动力学模拟，并确定了液膜附近发射离子的不同亚稳态。我们的结果表明，和离子/表面的分子细节决定了RTIL/真空表面离子发射的速率和组成。本研究揭示的基本见解为改进离子蒸发理论和从空间推进到纳米制造的电喷雾应用性能奠定了基础。
