Influence of the Dielectric Constant on the Ionic Current Rectification of Bipolar Nanopores

Journal Article · Thu May 02 00:00:00 EDT 2024 · ACS Nano

DOI:https://doi.org/10.1021/acsnano.4c03546· OSTI ID:2478068

Córdoba, Andrés ^[1]; Montes de Oca, Joan Manuel ^[1]; Darling, Seth B. ^[1]; de Pablo, Juan J. ^[2]

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1. Univ. of Chicago, IL (United States); Energy Frontier Research Centers (EFRC) (United States). Advanced Materials for Energy-Water Systems (AMEWS); Argonne National Laboratory (ANL), Argonne, IL (United States)
2. Univ. of Chicago, IL (United States); Argonne National Laboratory (ANL), Argonne, IL (United States)

In this paper, we investigate how the dielectric constant, ϵ, of an electrolyte solvent influences the current rectification characteristics of bipolar nanopores. It is well recognized that bipolar nanopores with two oppositely charged regions rectify current when exposed to an alternating electric potential difference. Here, we consider dilute electrolytes with NaCl only and with a mixture of NaCl and charged nanoparticles. These systems are studied using two levels of description, all-atom explicit water molecular dynamics (MD) simulations and coarse-grained implicit solvent MD simulations. The charge density and electric potential profiles and current-voltage relationship predicted by the implicit solvent simulations with ϵ = 11.3 show good agreement with the predictions from the explicit water simulations. Under nonequilibrium conditions, the predictions of the implicit solvent simulations with a dielectric constant closer to the one of bulk water are significantly different from the predictions obtained with the explicit water model. Further, these findings are closely aligned with experimental data on the dielectric constant of water when confined to nanometric spaces, which suggests that ϵ decreases significantly compared to its value in the bulk. Moreover, the largest electric current rectification is observed in systems containing nanoparticles when ϵ = 78.8. Using enhanced sampling, we have shown that this larger rectification arises from the presence of a significantly deeper minimum in the free energy of the system with a larger ϵ, and when a negative voltage bias is applied. Since implicit solvent models and mean-field continuum theories are often used to design Janus membranes based on bipolar nanopores, this work highlights the importance of properly accounting for the effects of confinement on the dielectric constant of the electrolyte solvent. The results presented here indicate that the dielectric constant in implicit solvent simulations may be used as an adjustable parameter to approximately account for the effects of nanometric confinement on aqueous electrolyte solvents.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 2478068
• Journal Information: ACS Nano, Journal Name: ACS Nano Journal Issue: 19 Vol. 18; ISSN 1936-0851
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
bipolar nanopores
dielectric constant
electric current rectification
molecular dynamics
nanoparticles
power generation
water