Eduardo R. Cruz-Chu, Aleksei Aksimentiev, and Klaus Schulten.
Ionic current rectification through silica nanopores.
Journal of Physical Chemistry C, 113:1850-1862, 2009.
(PMC: 2658614)
CRUZ2009
Ions confined in nanopores can produce ionic current rectification, i.e., where ionic current measurements are higher for one voltage polarity than for the same voltage with opposite polarity, producing an asymmetric current-voltage (I-V) curve. This behavior has been observed in polymer and silicon-based nanopores; however the cause of the asymmetry was not clear. By means of molecular dynamics MD simulations, we have performed a systematic study of the KCl conductance in silica nanopores. Six silica nanopores with different surface topographies were simulated. Ten voltage biases were tested using 1M KCl. We found that ion-binding spots at the silica surfaces, such as dangling atoms, have effects on the ionic concentration and electrostatic potential inside the nanopore. These effects produce the asymmetry in the I-V curve. Conversely, silica surfaces without ion-binding spots show a symmetric I-V curve. An atomic-level description of the current rectification phenomena is presented.
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