Drastically Reduced Ion Mobility in a Nanopore Due to Enhanced Pairing and Collisions between Dehydrated Ions

Abstract

Ion transport through nanopores is a process of fundamental significance in nature and in engineering practice. Over the past decade, it has been found that the ion conductivity in nanopores could be drastically enhanced and different mechanisms have been proposed to explain this observation. To date, most reported studies have been carried out with relatively dilute electrolytes while ion transport in nanopores under high electrolyte concentrations (>1 M) has been rarely explored. Through systematic experimental and atomistic simulation studies with NaCl solutions, here we show that at high electrolyte concentrations, ion mobility in small nanopores could be significantly reduced from the corresponding bulk value. Subsequent molecular dynamics studies indicate that in addition to the low mobility of surface-bound ions in the Stern layer, enhanced pairing and collisions between partially dehydrated ions of opposite charges also make important contributions to the reduced ion mobility. Furthermore, we show that the extent of mobility reduction depends on the association constant between cations and anions in different electrolytes with a more drastic reduction for a larger association constant.

Low-Noise Nanopore Enables In-Situ and Label-Free Tracking of a Trigger-Induced DNA Molecular Machine at the Single-Molecular Level

“…Accordingly, with increasing μ B *, the variations in the radial distribution functions (RDF) of anions [g ca (r) in Figure S14d], solvent molecules [g cd (r) in Figure S14e], and cations [g cc (r) in Figure S14f] around each cation demonstrate the weakened ionic correlations and enhanced ion hydration, which corresponds well with the previous atomistic simulation. 55 Further, we calculate the ratio of the standard deviation of density s(ρ c *) to density ρ c * and the ratio of the standard deviation of mobility s(M c *) to mobility M c * for the cations in Figure 3f. The simulation result illustrates that the addition of a higher dielectric solvent reduces the fluctuations in both the number and mobility of the ions.…”

Influence of charge carrier density, mobility and diffusivity on conductivity–temperature dependence in polyethylene oxide–based gel polymer electrolytes

“…The collision of surface-bound ions in the Stern-layer also induces the ion mobility to be lower. 31 The increase in the electrolyte Stokes drag coefficient shown in Figure 12 proves the momentum of transport ions decreased with increasing temperature. Based on Figure 7, it can be concluded that the increase in electrolyte conductivity with temperature is attributed to the increase in charge carrier concentration, not the mobility and diffusivity of carrier ions.…”

Solid-State Nanopore for Molecular Detection

“…FIB tools are used with various charged ions such as Ga + [116,117] and He + [115,118] and allowing to crate pore Fig. 2 Fabrication methods of SSNP: a 3D schematic diagram of nanopore (top-left), which is fabricated with the combination of FIB milling and TEM based drilling on SiN membrane (2D schematics, right) and a TEM image of fabricated nanopore (bottom-left) [61]. b Mechanism of controlled dielectric breakdown (CDB) to form pore on SiN membrane (top) [49] and a sequence of TEM images of nanopore formation dependence of ionic current level in CDB (bottom) [62].…”