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Wu H, Li H, Solis FJ, Olvera de la Cruz M, Luijten E. Asymmetric electrolytes near structured dielectric interfaces. J Chem Phys 2018; 149:164701. [PMID: 30384706 DOI: 10.1063/1.5047550] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The ion distribution of electrolytes near interfaces with dielectric contrast has important consequences for electrochemical processes and many other applications. To date, most studies of such systems have focused on geometrically simple interfaces, for which dielectric effects are analytically solvable or computationally tractable. However, all real surfaces display nontrivial structure at the nanoscale and have, in particular, a nonuniform local curvature. Using a recently developed, highly efficient computational method, we investigate the effect of surface geometry on ion distribution and interface polarization. We consider an asymmetric 2:1 electrolyte bounded by a sinusoidally deformed solid surface. We demonstrate that even when the surface is neutral, the electrolyte acquires a nonuniform ion density profile near the surface. This profile is asymmetric and leads to an effective charging of the surface. We furthermore show that the induced charge is modulated by the local curvature. The effective charge is opposite in sign to the multivalent ions and is larger in concave regions of the surface.
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Affiliation(s)
- Huanxin Wu
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
| | - Honghao Li
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | - Francisco J Solis
- School of Mathematical and Natural Sciences, Arizona State University, Glendale, Arizona 85069, USA
| | | | - Erik Luijten
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
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2
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Wu H, Luijten E. Accurate and efficient numerical simulation of dielectrically anisotropic particles. J Chem Phys 2018; 149:134105. [DOI: 10.1063/1.5048203] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Huanxin Wu
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
| | - Erik Luijten
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
- Department of Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, Illinois 60208, USA
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Wu H, Han M, Luijten E. Dielectric effects on the ion distribution near a Janus colloid. SOFT MATTER 2016; 12:9575-9584. [PMID: 27847942 DOI: 10.1039/c6sm01675h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Spherical Janus colloids, particles with different surface properties on their two hemispheres, are generally heterogeneous in permittivity. This dielectric heterogeneity may affect their behavior in electrolytes and external electric fields, but is typically not taken into account in computational studies. We apply the iterative dielectric solver developed by Barros and Luijten [Phys. Rev. Lett., 2014, 113, 017801] in combination with preconditioning techniques that can accurately and efficiently compute the polarization of dielectrically anisotropic particles. Employing this approach, we systematically study the ion distribution around neutral and charged Janus particles with various permittivities, immersed in symmetric and asymmetric electrolytes. We demonstrate that neutral Janus colloids may carry a nonzero dipole moment in asymmetric salts. For charged Janus colloids, dielectric effects can substantially influence the electric double layer. These findings also have implications for other dielectrically anisotropic entities, such as proteins.
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Affiliation(s)
- Huanxin Wu
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
| | - Ming Han
- Graduate Program in Applied Physics, Northwestern University, Evanston, Illinois 60208, USA
| | - Erik Luijten
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA and Department of Materials Science and Engineering Northwestern University, Evanston, Illinois 60208, USA. and Department of Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, Illinois 60208, USA
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dos Santos AP, Girotto M, Levin Y. Simulations of Polyelectrolyte Adsorption to a Dielectric Like-Charged Surface. J Phys Chem B 2016; 120:10387-10393. [DOI: 10.1021/acs.jpcb.6b06002] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Alexandre P. dos Santos
- Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970 Porto Alegre, RS, Brazil
| | - Matheus Girotto
- Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970 Porto Alegre, RS, Brazil
| | - Yan Levin
- Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970 Porto Alegre, RS, Brazil
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Wang ZY, Ma Z. Examining the Contributions of Image-Charge Forces to Charge Reversal: Discrete Versus Continuum Modeling of Surface Charges. J Chem Theory Comput 2016; 12:2880-8. [DOI: 10.1021/acs.jctc.6b00057] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Zhi-Yong Wang
- School
of Optoelectronic Information, Chongqing University of Technology, Chongqing 400054, China
| | - Zengwei Ma
- School
of Optoelectronic Information, Chongqing University of Technology, Chongqing 400054, China
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Linse P, Lue L. Green's function for a spherical dielectric discontinuity and its application to simulation. J Chem Phys 2015; 140:044903. [PMID: 25669579 DOI: 10.1063/1.4862148] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present rapidly convergent expressions for the Green's function of the Poisson equation for spherically symmetric systems where the dielectric constant varies discontinuously in the radial direction. These expressions are used in Monte Carlo simulations of various electrolyte systems, and their efficiency is assessed. With only the leading term of the expansion included, a precision of the polarization energy of 0.01 kJ mol(-1) or better was achieved, which is smaller than the statistical uncertainty of a typical simulation. The inclusion of the dielectric inhomogeneity leads to a 2.5-fold increase of the computational effort, which is modest for this type of model. The simulations are performed on six types of systems having either (i) a uniform surface charge distribution, (ii) a uniform volume charge distribution, or (iii) mobile ions, which were neutralized by mobile counterions. The ion density distributions are investigated for different dielectric conditions. These spatial distributions are discussed in terms of the importance of (i) the direct mean-field Coulomb interaction, (ii) the surface charge polarization at the dielectric discontinuity, and/or (iii) the change in the attractive Coulomb correlations.
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Affiliation(s)
- Per Linse
- Physical Chemistry, Department of Chemistry, Lund University, P.O. Box 124, S-221 00 Lund, Sweden
| | - Leo Lue
- Department of Chemical and Process Engineering, University of Strathclyde, James Weir Building, 75 Montrose Street, Glasgow G1 1XJ, United Kingdom
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dos Santos AP, Levin Y. Electrolytes between dielectric charged surfaces: Simulations and theory. J Chem Phys 2015; 142:194104. [PMID: 26001444 DOI: 10.1063/1.4921221] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
We present a simulation method to study electrolyte solutions in a dielectric slab geometry using a modified 3D Ewald summation. The method is fast and easy to implement, allowing us to rapidly resum an infinite series of image charges. In the weak coupling limit, we also develop a mean-field theory which allows us to predict the ionic distribution between the dielectric charged plates. The agreement between both approaches, theoretical and simulational, is very good, validating both methods. Examples of ionic density profiles in the strong electrostatic coupling limit are also presented. Finally, we explore the confinement of charge asymmetric electrolytes between neutral surfaces.
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Affiliation(s)
- Alexandre P dos Santos
- Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS, Brazil
| | - Yan Levin
- Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS, Brazil
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Jurij R, Per L. MOLSIM: A modular molecular simulation software. J Comput Chem 2015; 36:1259-74. [PMID: 25994597 PMCID: PMC5033024 DOI: 10.1002/jcc.23919] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Revised: 03/23/2015] [Accepted: 03/26/2015] [Indexed: 11/06/2022]
Abstract
The modular software MOLSIM for all-atom molecular and coarse-grained simulations is presented with focus on the underlying concepts used. The software possesses four unique features: (1) it is an integrated software for molecular dynamic, Monte Carlo, and Brownian dynamics simulations; (2) simulated objects are constructed in a hierarchical fashion representing atoms, rigid molecules and colloids, flexible chains, hierarchical polymers, and cross-linked networks; (3) long-range interactions involving charges, dipoles and/or anisotropic dipole polarizabilities are handled either with the standard Ewald sum, the smooth particle mesh Ewald sum, or the reaction-field technique; (4) statistical uncertainties are provided for all calculated observables. In addition, MOLSIM supports various statistical ensembles, and several types of simulation cells and boundary conditions are available. Intermolecular interactions comprise tabulated pairwise potentials for speed and uniformity and many-body interactions involve anisotropic polarizabilities. Intramolecular interactions include bond, angle, and crosslink potentials. A very large set of analyses of static and dynamic properties is provided. The capability of MOLSIM can be extended by user-providing routines controlling, for example, start conditions, intermolecular potentials, and analyses. An extensive set of case studies in the field of soft matter is presented covering colloids, polymers, and crosslinked networks.
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Affiliation(s)
- Reščič Jurij
- Department of Physical Chemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, PO Box 537, SI-1001, Ljubljana, Slovenia
| | - Linse Per
- Department of Chemistry, Physical Chemistry, Lund University, PO Box 124, SE-221 00, Lund, Sweden
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Lue L, Linse P. Ions confined in spherical dielectric cavities modeled by a splitting field-theory. J Chem Phys 2015; 142:144902. [DOI: 10.1063/1.4917256] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Curtis RA, Lue L. Depletion forces due to image charges near dielectric discontinuities. Curr Opin Colloid Interface Sci 2015. [DOI: 10.1016/j.cocis.2014.12.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Guerrero García GI, Olvera de la Cruz M. Polarization Effects of Dielectric Nanoparticles in Aqueous Charge-Asymmetric Electrolytes. J Phys Chem B 2014; 118:8854-62. [DOI: 10.1021/jp5045173] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Guillermo Iván Guerrero García
- Department of Materials Science and Engineering, and ‡Department of
Chemical and Biological
Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Monica Olvera de la Cruz
- Department of Materials Science and Engineering, and ‡Department of
Chemical and Biological
Engineering, Northwestern University, Evanston, Illinois 60208, United States
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12
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Levin Y, dos Santos AP. Ions at hydrophobic interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:203101. [PMID: 24769502 DOI: 10.1088/0953-8984/26/20/203101] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We review the present understanding of the behavior of ions at the air-water and oil-water interfaces. We argue that while the alkali metal cations remain strongly hydrated and are repelled from the hydrophobic surfaces, the anions must be classified into kosmotropes and chaotropes. The kosmotropes remain strongly hydrated in the vicinity of a hydrophobic surface, while the chaotropes lose their hydration shell and can become adsorbed to the interface. The mechanism of adsorption is still a subject of debate. Here, we argue that there are two driving forces for anionic adsorption: the hydrophobic cavitational energy and the interfacial electrostatic surface potential of water. While the cavitational contribution to ionic adsorption is now well accepted, the role of the electrostatic surface potential is much less clear. The difficulty is that even the sign of this potential is a subject of debate, with the ab initio and the classical force field simulations predicting electrostatic surface potentials of opposite sign. In this paper, we will argue that the strong anionic adsorption found in the polarizable force field simulations is the result of the artificial electrostatic surface potential present in the classical water models. We will show that if the adsorption of anions were as large as predicted by the polarizable force field simulations, the excess surface tension of the NaI solution would be strongly negative, contrary to the experimental measurements. While the large polarizability of heavy halides is a fundamental property and must be included in realistic modeling of the electrolyte solutions, we argue that the point charge water models, studied so far, are incompatible with the polarizable ionic force fields when the translational symmetry is broken. The goal for the future should be the development of water models with very low electrostatic surface potential. We believe that such water models will be compatible with the polarizable force fields, which can then be used to study the interaction of ions with hydrophobic surfaces and proteins.
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Affiliation(s)
- Yan Levin
- Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS, Brazil
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Takae K, Onuki A. Applying electric field to charged and polar particles between metallic plates: Extension of the Ewald method. J Chem Phys 2013; 139:124108. [DOI: 10.1063/1.4821085] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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González-Mozuelos P, Guerrero-García GI, Olvera de la Cruz M. An exact method to obtain effective electrostatic interactions from computer simulations: The case of effective charge amplification. J Chem Phys 2013; 139:064709. [DOI: 10.1063/1.4817776] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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15
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Guerrero-García GI, Olvera de la Cruz M. Inversion of the Electric Field at the Electrified Liquid–Liquid Interface. J Chem Theory Comput 2012; 9:1-7. [DOI: 10.1021/ct300673m] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
| | - Mónica Olvera de la Cruz
- Department of Materials
Science,
Northwestern University, Evanston, Illinois 60208, United States
- Department of Chemical Engineering,
Northwestern University, Evanston, Illinois 60208, United States
- Department of Chemistry, Northwestern
University, Evanston, Illinois 60208, United States
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Cherstvy AG, Winkler RG. Polyelectrolyte adsorption onto oppositely charged interfaces: image-charge repulsion and surface curvature. J Phys Chem B 2012; 116:9838-45. [PMID: 22794191 DOI: 10.1021/jp304980e] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
We analyze theoretically the influence of low-dielectric boundaries on the adsorption of flexible polyelectrolytes onto planar and spherical oppositely charged surfaces in electrolyte solutions. We rationalize to what extent polymer chains are depleted from adsorbing interfaces by repulsive image forces. We employ the WKB (Wentzel-Kramers-Brillouin) quantum mechanical method for the Green function of the Edwards equation to determine the adsorption equilibrium. Scaling relations are determined for the critical adsorption strength required to initiate polymer adsorption onto these low-dielectric supports. Image-force repulsion shifts the equilibrium toward the desorbed state, demanding larger surface charge densities and polyelectrolyte linear charge densities for the adsorption to take place. The effect is particularly pronounced for a planar interface in a low-salt regime, where a dramatic change in the scaling behavior for the adsorption-desorption transition is predicted. For the adsorbed state, polymers with higher charge densities are displaced further from the interface by image-charge repulsions. We discuss relevant experimental evidence and argue about possible biological applications of the results.
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Affiliation(s)
- A G Cherstvy
- Institute for Physics and Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany.
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Wang ZY, Ma YQ. A molecular simulation study on the role of ion sizes and dielectric images in near-surface ion distribution far from the strong coupling limit. J Chem Phys 2012; 136:234701. [DOI: 10.1063/1.4729311] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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Colla TE, dos Santos AP, Levin Y. Equation of state of charged colloidal suspensions and its dependence on the thermodynamic route. J Chem Phys 2012; 136:194103. [DOI: 10.1063/1.4718367] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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