posted on 2023-11-29, 18:36authored byMahdi Khatibi, Seyed Nezameddin Ashrafizadeh
This research delves into investigating
ion transport behavior
within nanochannels, enhanced through modification with a negatively
charged polyelectrolyte layer (PEL), aimed at achieving superior control.
The study examines two types of electric fieldsdirect current
and alternating current with square, sinusoidal, triangular, and sawtooth
waveformsto understand their impact on ion transport. Furthermore,
the study compares symmetric (cylindrical) and asymmetric (conical)
nanochannel geometries to assess the influence of overlapping electrical
double layers (EDLs) in generating specific electrokinetic behaviors
such as ionic current rectification (ICR) and ion selectivity. The
research employs the finite element method to solve the coupled Poisson–Nernst–Planck
and Navier–Stokes equations under unsteady-state conditions.
By considering factors such as electrolyte concentration, soft layer
charge density, and electric field type, the study evaluates ion transport
performance in charged nanochannels, investigating effects on concentration
polarization, electroosmotic flow (EOF), ion current, rectification,
and ion selectivity. Notably, the study accounts for ion partitioning
between the PEL and electrolyte to simulate real conditions. Findings
reveal that conical nanochannels, due to improved EDL overlap, significantly
enhance ion transport and related characteristics compared to cylindrical
ones. For instance, under ηε = ηD = 0.8, ημ = 2, C0 = 20 mM, and NPEL/NA = 80 mol m–3 conditions, the average
EOF for conical and cylindrical geometries is 0.1 and 0.008 m/s, respectively.
Additionally, the study explores ion selectivity and rectification
based on the electric field type, unveiling the potential of nanochannels
as ion gates or diodes. In cylindrical nanochannels, the ICR remains
at unity, with lower ion selectivity across waveforms compared to
conical channels. Furthermore, rectification and ion selectivity trends
are identified as Rf,square > Rf,DC > Rf,triangular > Rf,sinusoidal > Rf,sawtooth and Ssawtooth > Ssinusoidal > Striangular > SDC > Ssquare for conical nanochannels. Our study of ion transport
control in
nanochannels, guided by tailored electric fields and unique geometries,
offers versatile applications in the field of Analytical Chemistry.
This includes enhanced sample separation, controlled drug delivery,
optimized pharmaceutical analysis, and the development of advanced
biosensing technologies for precise chemical analysis and detection.
These applications highlight the diverse analytical contributions
of our methodology, providing innovative solutions to challenges in
chemical analysis and biosensing.