Modeling Ion Diffusion Current in Nanochannel Using Infinitesimal Distribution Resistor-Capacitor Circuits

摘要

A theoretical model that considers both the diffusion and electrical osmosis fluxes to estimate the diffusion current through a nanochannel is proposed. The equivalent impedance of a nanochannel is modeled as a series connection of finite resistor-capacitor (RC) circuits. The impedances of the electrical double layer and buffer solution in each infinitesimal RC circuit are represented using a capacitor and a resistor, respectively. The diffusion-induced current in the proposed model is position dependent due to the electrical double layer effect. Computer simulations and experiments using a nanoporous anodic aluminum oxide (AAO) thin film as the filter to separate electrolysis with an ion concentration gradient were conducted. Electrochemical impedance spectroscopy (EIS) was performed to measure the impedance of the porous AAO thin film in the frequency domain such that the capacitor and resistor can be estimated accordingly. A high degree of coincidence between the theoretical and experimental data is observed.