Biphasic Resistive Pulses and Ion Concentration Modulation during Particle Translocation through Cylindrical Nanopores

Abstract

We investigated the biphasic resistive pulses during particle translocation through cylindrical nanopores at low salt concentration by simulation, and the effects of electrolyte concentration, surface charge, electric potential, and pore geometry were systematically discussed. The formation of positive peaks in the pulses is ascribed to the surface charge on the particle and the pore. The peak current enhancement/decline ratio increases linearly with the particle surface charge density but decreases with the salt concentration increase. We find that there is an optimum electric potential for the peak current enhancement ratio to reach the maximum value. When a negatively charged particle is at the orifice of the pore on the low/high potential side, the ion concentration inside and around the pore is significantly depleted/enriched, while inverse electric potential or inverse surface charge has an opposite effect. The extent of such ion modulation is larger with a longer pore. The peak current enhancement/decline ratio is quantitatively linked to the percent of ion concentration enrichment/depletion inside and around the pore, by considering particle occupied volume and concentration change.