# Controlling ionic current through a nanopore by tuning pH: a Local Equilibrium Monte Carlo study

## TL;DR

This study models a nanofluidic transistor that uses pH to control ionic current through nanopores, employing Local Equilibrium Monte Carlo simulations to understand charge effects and ion selectivity.

## Contribution

It introduces a simulation framework combining Monte Carlo and Nernst-Planck equations to analyze pH-dependent ionic conductance in nanopores with different geometries.

## Key findings

- pH influences nanopore surface charge and ion selectivity
- Depletion zones form under certain pH conditions affecting conductance
- Simulation results match experimental trends in nanopore behavior

## Abstract

The purpose of this work is to create a model of a nanofluidic transistor which is able to mimic the effects of pH on nanopore conductance. The pH of the electrolyte is an experimentally controllable parameter through which the charge pattern can be tuned: pH affects the ratio of the protonated/deprotonated forms of the functional groups anchored to the surface of the nanopore (for example, amino and carboxyl groups). Thus, the behavior of the bipolar transistor changes as it becomes ion selective in acidic/basic environments. We relate the surface charge to pH and perform particle simulations (Local Equilibrium Monte Carlo) with different nanopore geometries (cylindrical and double conical). The simulations form a self consistent system with the Nernst-Planck equation with which we compute ionic flux. We discuss the mechanism behind pH-control of ionic current: formation of depletion zones.