Electrolytic transport through a synthetic nanometer-diameter pore
Electrolytic transport through a synthetic nanometer-diameter pore
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DOI：
10.1073/pnas.0500796102
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发表时间：
2005-07-26
影响因子：
11.1
通讯作者：
Timp, G
中科院分区：
文献类型：
--
作者：
Ho, C;Qiao, R;Timp, G
我们使用聚焦紧密的高能电子束在10纳米厚的氮化硅薄膜中溅射原子，从而产生了单一的、合成的纳米直径的孔。随后，我们测量了离子电导随时间、溶液浓度和孔径的变化，以推断电导率和离子在孔中的迁移率。在稀溶液浓度下，孔道电导率远大于体相电导率，在稀溶液浓度下，德拜长度大于孔半径，而在高浓度时，孔道电导率与体相相当或小于体相电导率。我们用多尺度模拟离子通过气孔的传输来解释这些观测结果。离子在孔道中的输运用Poisson-Nernst-Planck耦合方程和Stokes方程来描述，离子浓度、速度和电势是自洽求解的。我们发现，测量结果与孔壁中固定负电荷的存在以及由于固定电荷和离子靠近孔壁而导致的离子迁移率降低是一致的。
We have produced single, synthetic nanometer-diameter pores by using a tightly focused, high-energy electron beam to sputter atoms in 10-nm-thick silicon nitride membranes. Subsequently, we measured the ionic conductance as a function of time, bath concentration, and pore diameter to infer the conductivity and ionic mobility through the pores. The pore conductivity is found to be much larger than the bulk conductivity for dilute bath concentrations, where the Debye length is larger than the pore radius, whereas it is comparable with or less than the bulk for high bath concentrations. We interpret these observations by using multiscale simulations of the ion transport through the pores. Molecular dynamics is used to estimate the ion mobility, and ion transport in the pore is described by the coupled Poisson-Nernst-Planck and the Stokes equations that are solved self-consistently for the ion concentration and velocity and electrical potential. We find that the measurements are consistent with the presence of fixed negative charge in the pore wall and a reduction of the ion mobility because of the fixed charge and the ion proximity to the pore wall.