Optimal Voltage for Nanoparticle Detection with Thin Nanopores

The resistive-pulse technique provides a fast and label-free method for nanoparticle detection. In order to achieve a higher sensitivity, thin nanopores, such as silicon nitride pores, are usually considered. In this paper, nanoparticle detection has been mimicked by simulations. We found the surface charges of the particle can affect the current blockade obviously in short pores, especially under high electric fields. For particles with a surface charge density higher than -0.02 C/m2, its current blockade ratio depends on the applied voltage closely. From our simulation results, an optimal voltage can be found for the particle detection, under which the current blockade ratio does not depend on the surface charge density of the particle. This optimal voltage was obtained by the balance of current increase and decrease caused by cations and anions, respectively, due to the negative surface charges of particles. From the systematical study, the optimal voltage was found to work like a property of the system which only depends on the electrolyte type. We think our finding can provide some help to the accurate particle detection in experiments.