Surface Charge Density Determination of Single Conical Nanopores Based on Normalized Ion Current Rectification

Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, USA.
Langmuir (Impact Factor: 4.38). 12/2011; 28(2):1588-95. DOI: 10.1021/la203106w
Source: PubMed

ABSTRACT Current rectification is well known in ion transport through nanoscale pores and channel devices. The measured current is affected by both the geometry and fixed interfacial charges of the nanodevices. In this article, an interesting trend is observed in steady-state current-potential measurements using single conical nanopores. A threshold low-conductivity state is observed upon the dilution of electrolyte concentration. Correspondingly, the normalized current at positive bias potentials drastically increases and contributes to different degrees of rectification. This novel trend at opposite bias polarities is employed to differentiate the ion flux affected by the fixed charges at the substrate-solution interface (surface effect), with respect to the constant asymmetric geometry (volume effect). The surface charge density (SCD) of individual nanopores, an important physical parameter that is challenging to measure experimentally and is known to vary from one nanopore to another, is directly quantified by solving Poisson and Nernst-Planck equations in the simulation of the experimental results. The flux distribution inside the nanopore and the SCD of individual nanopores are reported. The respective diffusion and migration translocations are found to vary at different positions inside the nanopore. This knowledge is believed to be important for resistive pulse sensing applications because the detection signal is determined by the perturbation of the ion current by the analytes.


Available from: Jingyu Feng, Apr 22, 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To improve the development of gated nanofluidic devices for emerging applications, analytical expressions are derived to investigate the gate manipulation of surface charge property and ionic conductance in a pH-regulated nanochannel with overlapped electric double layers (EDLs). Results show that the EDL overlap effect is relatively significant at low pH and salt concentration when a negative gate potential is applied. If pH is low, the EDL overlap effect on the field control of zeta potential of the nanochannel is remarkable at large positive gate voltage, while that effect on ionic conductance is significant at large negative gate voltage.
    Sensors and Actuators B Chemical 08/2015; 215. DOI:10.1016/j.snb.2015.03.053 · 3.84 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Fast and reversible modulation of ion flow through nanosized apertures is important for many nanofluidic applications, including sensing and separation systems. Here, we present the first demonstration of a reversible plasmon-controlled nanofluidic valve. We show that plasmonic nanopores (solid-state nanopores integrated with metal nanocavities) can be used as a fluidic switch upon optical excitation. We systematically investigate the effects of laser illumination of single plasmonic nanopores and experimentally demonstrate photoresistance switching where fluidic transport and ion flow are switched on or off. This is manifested as a large (∼1-2 orders of magnitude) increase in the ionic nanopore resistance and an accompanying current rectification upon illumination at high laser powers (tens of milliwatts). At lower laser powers, the resistance decreases monotonically with increasing power, followed by an abrupt transition to high resistances at a certain threshold power. A similar rapid transition, although at a lower threshold power, is observed when the power is instead swept from high to low power. This hysteretic behavior is found to be dependent on the rate of the power sweep. The photoresistance switching effect is attributed to plasmon-induced formation and growth of nanobubbles that reversibly block the ionic current through the nanopore from one side of the membrane. This explanation is corroborated by finite-element simulations of a nanobubble in the nanopore that show the switching and the rectification.
    Nano Letters 12/2014; 15(1). DOI:10.1021/nl504516d · 12.94 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Through the molecular dynamics simulations, the ionic currents in physically realistic nanochannels with consideration of the thermal motion of channel walls are observed. It is found that the ionic current changes a little as the surface charge density increases from 0 to -0.3C/m2 with a huge decrease at -0.3C/m2 when the electric filed strength is 0.25V/nm. The Cl-ion current shows a decrease-increase profile as the surface charge density increases, while there is an increase-decrease trend in the Na+ ion current with the turning point at -0.075C/m2. By the statistic of the concentration and velocity distributions, the location of Na+ ions which provide main contribution to the current moves from the center of the channel to the charged surface as surface charge density increases from 0 to -0.225C/m2. The two parts included in current carriers have different concentrations and mobility. So the different contributions of the two parts Na+ ions and Cl-ions cause the feature of ionic current.
    2013 International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO); 08/2013