Ion-Current Rectification in Nanofluidic Devices - Nanofluidics: Nanoscience and Nanotechnology - page 165

The ion rectification of the nanofluidic diode is dependent on electrolyte
concentration. The experimental I-V curves under variable KCl concentrations are shown
in Figure 8.7. It is seen that current rectification is prominent at intermediate
concentrations of 1 mM and 10 mM KCl. The rectification effect is weaker at higher
concentrations, since surface charge effects become negligible. The linear I-V
characteristics were also observed at low KCl concentrations. This may be caused by
enhanced water dissociation at reverse bias or polarisation at channel entrances leading to
an increase of series resistance out of the nanochannel. 24,29

Figure 8.7 The I-V characteristics of a nanofluidic diode at different KCl concentrations (a-f). Solid circles

represent experimental data, while the dashed line has slope equal to the conductance measured
using a voltage bias range of -50 to 50 mV. Solid lines are theoretical predictions for an 120 µm
long, 40 µm wide channel with a height of 30 nm and a surface charge of 3 mC/m 2 in the avidin
half of the channel and 0 mC/m 2 in the biotin half of the channel. The biotin side is at a higher
potential under forward bias. Adapted from R. Karnik et al. , Nano Lett., 2007, 7, 547 and
reproduced with permission.