期刊
NATURE NANOTECHNOLOGY
卷 18, 期 2, 页码 177-+出版社
NATURE PORTFOLIO
DOI: 10.1038/s41565-022-01276-0
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Experimental measurements and molecular dynamics simulations show that the Nernst-Einstein relation breaks down in narrow carbon nanotube porins. K+ ion diffusion is three orders of magnitude slower in these channels due to the disintegration of water chains and the formation of K+-water clusters. This study reveals two distinct mechanisms for ion diffusion and electromigration, leading to the breakdown of the overall Nernst-Einstein relation.
For over 100 years, the Nernst-Einstein relation has linked a charged particle's electrophoretic mobility and diffusion coefficient. Here we report experimental measurements of diffusion and electromigration of K+ ions in narrow 0.8-nm-diameter single-walled carbon nanotube porins (CNTPs) and demonstrate that the Nernst-Einstein relation in these channels breaks down by more than three orders of magnitude. Molecular dynamics simulations using polarizable force fields show that K+ ion diffusion in CNTPs in the presence of a single-file water chain is three orders of magnitude slower than bulk diffusion. Intriguingly, the simulations also reveal a disintegration of the water chain upon application of electric fields, resulting in the formation of distinct K+-water clusters, which then traverse the CNTP at high velocity. Finally, we show that although individual ion-water clusters still obey the Nernst-Einstein relation, the overall relation breaks down because of two distinct mechanisms for ion diffusion and electromigration.
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