期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 109, 期 50, 页码 20326-20331出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1214204109
关键词
liquid surface scattering; ion density profile; surface excess charge; Poisson-Boltzmann; Debye-Huckel hole
资金
- University of Illinois at Chicago Graduate Fellowship
- Graduate Assistance in Areas of National Need program
- National Science Foundation [CHE-0910825, CHE-0809164, CHE-0822838]
- Department of Energy Office of Basic Energy Sciences [DE-AC02-06CH11357]
- Direct For Mathematical & Physical Scien [0809164] Funding Source: National Science Foundation
- Division Of Chemistry [0809164] Funding Source: National Science Foundation
- Division Of Chemistry
- Direct For Mathematical & Physical Scien [0822838] Funding Source: National Science Foundation
Ion distributions play a central role in various settings-from biology, where they mediate the electrostatic interactions between charged biomolecules in solution, to energy storage devices, where they influence the charging properties of supercapacitors. These distributions are determined by interactions dictated by the chemical properties of the ions and their environment as well as the long-range nature of the electrostatic force. Recent theoretical and computational studies have explored the role of correlations between ions, which have been suggested to underlie a number of counterintuitive results, such as like-charge attraction. However, the interdependency between ion correlations and other interactions that ions experience in solution complicates the connection between physical models of ion correlations and the experimental investigation of ion distributions. We exploit the properties of the liquid/liquid interface to vary the coupling strength Gamma of ion-ion correlations from weak to strong while monitoring their influence on ion distributions at the nanometer scale with X-ray reflectivity and the macroscopic scale with interfacial tension measurements. These data are in agreement with the predictions of a parameter-free density functional theory that includes ion-ion correlations and ion-solvent interactions over the entire range of experimentally tunable correlation coupling strengths (from 0.8 to 3.7). This study provides evidence for a sharply defined electrical double layer for large coupling strengths in contrast to the diffuse distributions predicted by mean field theory, thereby confirming a common prediction of many ion correlation models. The reported findings represent a significant advance in elucidating the nature and role of ion correlations in charged soft matter.
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