Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31 Leninsky Prospect, 119071 Moscow, Russia.
Phys Chem Chem Phys. 2019 Oct 24;21(41):23036-23043. doi: 10.1039/c9cp04259h.
Hydrophobic surfaces with large slip lengths have the potential to enhance electro-osmotic flows. Existing theories of electroosmosis in hydrophobic channels postulate immobile surface charges and/or make a number of simplifying assumptions by considering mostly weakly charged surfaces and thin diffuse layers compared to channel dimension. In this paper, we extend prior models by focusing on planar and cylindrical nanochannels. Our theory accounts for a hydrodynamic slip and a mobility of surface charges, and is valid not only on the scale of the nanochannel with thin diffuse layers, but also on the scale of the overlapping diffuse layer. The model is simple enough to allow us to derive analytical approximations for the electro-osmotic velocities even when the surface potential and charge density are quite large. We also present numerical solutions to validate the analysis and illustrate the variation of electro-osmotic velocities in response to changes in the channel size, potential, surface charge and its mobility, hydrodynamic slip length, and salt concentration. Our results are directly relevant for carbon nanotubes, graphene nanochannels, and conventional nanoporous membranes.
具有较大滑移长度的疏水表面具有增强电动渗透流的潜力。现有的疏水通道电动渗透理论假设固定的表面电荷，或者通过考虑与通道尺寸相比主要是弱电荷表面和薄的扩散层来做出许多简化假设。在本文中，我们通过关注平面和圆柱形纳米通道来扩展先前的模型。我们的理论考虑了流体动力滑移和表面电荷的迁移率，不仅在具有薄扩散层的纳米通道尺度上有效，而且在重叠扩散层的尺度上也有效。该模型足够简单，即使表面电势和电荷密度非常大，我们也可以推导出电动渗透速度的解析近似值。我们还提出了数值解来验证分析并说明电动渗透速度响应通道尺寸、电势、表面电荷及其迁移率、流体动力滑移长度和盐浓度变化的变化。我们的结果与碳纳米管、石墨烯纳米通道和传统的纳米多孔膜直接相关。
