Bhattacharjee Sanchari, Khan Sandip
Department of Chemical & Biochemical Engineering, Indian Institute of Technology Patna, Patna, 801103, India.
Phys Chem Chem Phys. 2022 Jan 19;24(3):1803-1813. doi: 10.1039/d1cp01821c.
Molecular dynamics (MD) simulations were applied to investigate the wettability of aqueous hydrophilic and hydrophobic imidazolium-based ionic liquid (IL) nano-droplets on a graphite surface under a perpendicular electric field. Imminent transformation in the droplet configuration was observed at = 0.08 V Å both for hydrophobic ILs 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][NTF] and SPC/E water droplets. However, for the hydrophilic IL, 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM][BF], the droplet was entirely elongated to column-shaped at = 0.09 V Å for lower weight percentages of ILs and at = 0.15 V Å for a higher weight percentage of ILs (, 50 wt%). We explored the impact of the electric field through various parameters such as mass and charge density distribution across the droplet, contact angle of the droplet, orientation of water dipoles, and hydrogen bond analysis. The external electric field was found to influence the orientation of water dipoles and the accumulation of charge at various interfaces was observed with an increase in an electric field, which finally leads to shape deformation and depletion of ions from the liquid-vapor interface of the droplet. However, this behavior strongly depends on the hydrophilicity or hydrophobicity of the ILs and thus, is critically examined for both the ILs.
应用分子动力学（MD）模拟研究了在垂直电场作用下，亲水性和疏水性咪唑基离子液体（IL）水纳米液滴在石墨表面的润湿性。对于疏水性离子液体1-乙基-3-甲基咪唑双（三氟甲基磺酰）亚胺[EMIM][NTF]和SPC/E水滴，在 = 0.08 V Å时均观察到液滴构型的明显转变。然而，对于亲水性离子液体1-乙基-3-甲基咪唑四氟硼酸盐[EMIM][BF]，当离子液体重量百分比较低时，在 = 0.09 V Å时液滴完全拉长为柱状；当离子液体重量百分比较高（，50 wt%）时，在 = 0.15 V Å时液滴完全拉长为柱状。我们通过各种参数探索了电场的影响，如液滴上的质量和电荷密度分布、液滴的接触角、水偶极子的取向以及氢键分析。发现外部电场会影响水偶极子的取向，并且随着电场增加，在各种界面处观察到电荷积累，这最终导致液滴形状变形以及离子从液滴的液-气界面耗尽。然而，这种行为强烈依赖于离子液体的亲水性或疏水性，因此，对这两种离子液体都进行了严格研究。
