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Title: Observation of Ordered Structures in Counterion Layers near Wet Charged Surfaces: A Potential Mechanism for Charge Inversion

Abstract

Charged (e.g., colloidal) particles in aqueous solutions will sometimes behave as though their effective charge has reversed, rather than reduced, by the attracted counterions. This is counterintuitive because it increases the electrostatic energy, but it has been proposed that lateral ordering of the ions could lower the free energy and favor overcharging (charge inversion). Using X-ray diffraction, we have observed sharp diffraction peaks from incommensurate Er3+ counterion monolayers near charged surfaces formed by floating molecular monolayers. When the counterion lattice does not match the molecular surface lattice, this means that there is no specific attachment of ions, and thus the ionic lattice is formed due to interactions between charges in the counterlayer. Therefore, the existence of incommensurate ion lattices indicates that counterion ordering is a realistic mechanism. However, in this system our data rule out a well-known proposed “physical” mechanism—the Wigner liquid phase driven by Coulomb interactions.

Authors:
 [1];  [1];  [2];  [2];  [1]
  1. Northwestern Univ., Evanston, IL (United States)
  2. Univ. of Chicago, IL (United States)
Publication Date:
Research Org.:
Northwestern Univ., Evanston, IL (United States)
Sponsoring Org.:
National Science Foundation (NSF); USDOE
OSTI Identifier:
1418555
Grant/Contract Number:  
AC02-06CH11357; NSF/CHE-1346572
Resource Type:
Accepted Manuscript
Journal Name:
Langmuir
Additional Journal Information:
Journal Volume: 32; Journal Issue: 1; Journal ID: ISSN 0743-7463
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Counterions; Lattices; Ions; Monolayers; Molecular structure

Citation Formats

Miller, Mitchell, Chu, Miaoqi, Lin, Binhua, Meron, Mati, and Dutta, Pulak. Observation of Ordered Structures in Counterion Layers near Wet Charged Surfaces: A Potential Mechanism for Charge Inversion. United States: N. p., 2015. Web. doi:10.1021/acs.langmuir.5b04058.
Miller, Mitchell, Chu, Miaoqi, Lin, Binhua, Meron, Mati, & Dutta, Pulak. Observation of Ordered Structures in Counterion Layers near Wet Charged Surfaces: A Potential Mechanism for Charge Inversion. United States. doi:10.1021/acs.langmuir.5b04058.
Miller, Mitchell, Chu, Miaoqi, Lin, Binhua, Meron, Mati, and Dutta, Pulak. Tue . "Observation of Ordered Structures in Counterion Layers near Wet Charged Surfaces: A Potential Mechanism for Charge Inversion". United States. doi:10.1021/acs.langmuir.5b04058. https://www.osti.gov/servlets/purl/1418555.
@article{osti_1418555,
title = {Observation of Ordered Structures in Counterion Layers near Wet Charged Surfaces: A Potential Mechanism for Charge Inversion},
author = {Miller, Mitchell and Chu, Miaoqi and Lin, Binhua and Meron, Mati and Dutta, Pulak},
abstractNote = {Charged (e.g., colloidal) particles in aqueous solutions will sometimes behave as though their effective charge has reversed, rather than reduced, by the attracted counterions. This is counterintuitive because it increases the electrostatic energy, but it has been proposed that lateral ordering of the ions could lower the free energy and favor overcharging (charge inversion). Using X-ray diffraction, we have observed sharp diffraction peaks from incommensurate Er3+ counterion monolayers near charged surfaces formed by floating molecular monolayers. When the counterion lattice does not match the molecular surface lattice, this means that there is no specific attachment of ions, and thus the ionic lattice is formed due to interactions between charges in the counterlayer. Therefore, the existence of incommensurate ion lattices indicates that counterion ordering is a realistic mechanism. However, in this system our data rule out a well-known proposed “physical” mechanism—the Wigner liquid phase driven by Coulomb interactions.},
doi = {10.1021/acs.langmuir.5b04058},
journal = {Langmuir},
number = 1,
volume = 32,
place = {United States},
year = {2015},
month = {12}
}

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