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J Am Chem Soc. 2019 Mar 13;141(10):4264-4272. doi: 10.1021/jacs.8b08488. Epub 2019 Feb 26.

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

Author information

1
Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering , Southeast University , Nanjing 211189 , China.
2
China Education Council Key Laboratory of MEMS , Southeast University , Nanjing 210096 , China.
3
Department of Mechanical Engineering , Vanderbilt University , Nashville , Tennessee 37235-1592 , United States.

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.

PMID:
30773010
DOI:
10.1021/jacs.8b08488

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