INVESTIGADORES
TAGLIAZUCCHI Mario Eugenio
congresos y reuniones científicas
Título:
Ion transport in polyelectrolyte-modified nanopores
Autor/es:
MARIO TAGLIAZUCCHI; RABIN, YITZHAK; IGAL SZLEIFER
Lugar:
Ein-Gedi
Reunión:
Simposio; International Symposium on Polyelectrolytes; 2014
Institución organizadora:
Israeli Science Fundation
Resumen:
This
work introduces a molecular theory to study ion transport in nanochannels and
short nanopores modified by end-grafted polyelectrolytes. The theory explicitly
considers the coupling between the conformations of the polyelectrolyte chains,
the electrostatic and non-electrostatic interactions, the shape, charge and
volume of all molecular species in the system and the presence of ion currents.
In particular, it describes the non-equilibrium organization of the
polyelectrolyte layer and ion concentrations due to the presence of ion fluxes
in the system.
Calculation
results are presented for a short cylindrical nanopore with inner walls
modified by an end-grafted polyelectrolyte layer. Ion current flows through
this system upon applying a potential between the electrodes located in the
reservoirs. In the very low applied potential regime, where the distribution of
polyelectrolyte and ions is similar to that in equilibrium, a simple analytical
model accounts for the conductance in excellent agreement with the calculations
of the full non-equilibrium molecular theory. On the other hand, for a large
applied potential bias the theory predicts a dramatic reorganization of the
polyelectrolyte chains and the ions. This reorganization leads to non-linear
(non-ohmic) current-potential curves. Moreover, it is shown that the morphology
of the polyelectrolyte layer can be controlled by the direction and magnitude
of the ion-fluxes
The theory was
also applied to model a neutral bare pore, where the outer walls are modified
by polyelectrolyte end-grafted layers of opposite charge. This system rectifies
ionic currents: the conductivity when the positively charged polyelectrolytes
face the negatively charged electrode (on
state) is larger than when it faces the positively charged electrode (off state). Ionic rectification is a
desired property of nanopores and nanochannels as it enables applications in sensing
and energy transduction. Our work shows that current rectification can be
achieved in short neutral cylindrical nanopores by modification of the outer
walls; this strategy is appealing for experiments since the outer walls can be
chemically modified before drilling the pore. The effect of the pore dimensions and charge
density of the outer walls on current rectification were analyzed. An
analytical model was introduced that predicts the current-potential curves in
excellent agreement with the non-equilibrium molecular theory calculations.