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Long-Range Hofmeister Effects of Anionic and Cationic Amphiphiles

Enami, Shinichi and Colussi, Agustín J. (2013) Long-Range Hofmeister Effects of Anionic and Cationic Amphiphiles. Journal of Physical Chemistry B, 117 (20). pp. 6276-6281. ISSN 1520-6106.

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Specific ion effects at aqueous interfaces play key roles in many important phenomena. We recently reported that ions interact specifically over unexpectedly long distances on the surface of sub-micromolar electrolyte solutions (Enami et al. J. Chem. Phys. 2012, 136, 154707). Whether the anionic and cationic headgroups of the organic amphiphiles present at most water/hydrophobe interfaces act similarly or display new behaviors, however, is not known. Here we report the results of experiments in which we apply online electrospray ionization mass spectrometry (ESI-MS) to investigate how carboxylate, RCOO– (R = CH3, C5H11, C7H15), and alkylammonium, R′(CH_3)_(3)N+ (R′ = CH_3, C_(14)H_29), ions affect the ratio χ = I–/Br– at the aerial interface of 1 μM (NaI + NaBr) aqueous solutions. We found that χ is systematically but selectively depressed by these ionic amphiphiles and minimally affected by the neutral surfactant 1-octanol. The depressing effects induced by cationic headgroups are stronger than those caused by anionic surfactants and always increase with the length of the alkyl chains.

Item Type:Article
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URLURL TypeDescription
Enami, Shinichi0000-0002-2790-7361
Colussi, Agustín J.0000-0002-3400-4101
Additional Information:© 2013 American Chemical Society. Received: February 4, 2013; Revised: April 22, 2013; Published: April 26, 2013. This work was financially supported by the Japan Science and Technology Agency (JST) PRESTO program. We are grateful to Michael Hoffmann and Himanshu Mishra of Caltech for helpful discussion.
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Japan Science and Technology Agency (JST) PRESTO programUNSPECIFIED
Issue or Number:20
Record Number:CaltechAUTHORS:20130709-110548577
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Official Citation:Long-Range Hofmeister Effects of Anionic and Cationic Amphiphiles Shinichi Enami and Agustín J. Colussi The Journal of Physical Chemistry B 2013 117 (20), 6276-6281
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:39272
Deposited By: Jason Perez
Deposited On:10 Jul 2013 14:34
Last Modified:03 Oct 2019 05:05

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