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Long-range specific ion-ion interactions in hydrogen-bonded liquid films

Enami, Shinichi and Colussi, Agustín J. (2013) Long-range specific ion-ion interactions in hydrogen-bonded liquid films. Journal of Chemical Physics, 138 (18). Art. No. 184706. ISSN 0021-9606.

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Anions populate fluid interfaces specifically. Here, we report experiments showing that on hydrogen-bonded interfaces anions interact specifically over unexpectedly long distances. The composition of binary electrolyte (Na+, X−/Y−) films was investigated as a function of solvent, film thickness, and third ion additions in free-standing films produced by blowing up drops with a high-speed gas. These films soon fragment into charged sub-micrometer droplets carrying excess anions detectable in situ by online electrospray ionization mass spectrometry. We found that (1) the larger anions are enriched in the thinner (nanoscopic air-liquid-air) films produced at higher gas velocities in all (water, methanol, 2-propanol, and acetonitrile) tested solvents, (2) third ions (beginning at sub-μM levels) specifically perturb X−/Y− ratios in water and methanol but have no effect in acetonitrile or 2-propanol. Thus, among these polar organic liquids (of similar viscosities but much smaller surface tensions and dielectric permittivities than water) only on methanol do anions interact specifically over long, viz.: ⟨ri − rj⟩/nm = 150 (c/μM)^(−1/3), distances. Our findings point to the extended hydrogen-bond networks of water and methanol as likely conduits for such interactions.

Item Type:Article
Related URLs:
URLURL TypeDescription
Enami, Shinichi0000-0002-2790-7361
Colussi, Agustín J.0000-0002-3400-4101
Additional Information:© 2013 AIP Publishing LLC. Received 21 January 2013; accepted 18 April 2013; published online 9 May 2013. This work was financially supported by the Japan Science and Technology Agency (JST) PRESTO program, and by the U.S. National Science Foundation (NSF) Grant No. AGS-1238977. We thank H. Mishra and M. R. Hoffmann (Caltech) for helpful discussion. We are grateful to Professor Theofanous (UC Santa Barbara) for valuable advice.
Funding AgencyGrant Number
Japan Science and Technology Agency (JST) PRESTO programUNSPECIFIED
Subject Keywords:drops; electrolytes; hydrogen bonds; ionisation; liquid films; long-range order; mass spectroscopy; organic compounds; permittivity; surface tension; velocity, viscosity
Issue or Number:18
Classification Code:PACS: 68.15.+e; 77.22.Ch; 82.30.Rs; 82.45.Gj; 66.20.-d; 68.03.Cd
Record Number:CaltechAUTHORS:20130701-134821926
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Official Citation:Long-range specific ion-ion interactions in hydrogen-bonded liquid films Shinichi Enami and Agustin J. Colussi, J. Chem. Phys. 138, 184706 (2013), DOI:10.1063/1.4803652
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:39171
Deposited By: Jason Perez
Deposited On:01 Jul 2013 21:19
Last Modified:03 Oct 2019 05:04

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