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Brito ME, Nägele G, Denton AR. Effective interactions, structure, and pressure in charge-stabilized colloidal suspensions: Critical assessment of charge renormalization methods. J Chem Phys 2023; 159:204904. [PMID: 38014786 DOI: 10.1063/5.0180914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Accepted: 10/30/2023] [Indexed: 11/29/2023] Open
Abstract
Charge-stabilized colloidal suspensions display a rich variety of microstructural and thermodynamic properties, which are determined by electro-steric interactions between all ionic species. The large size asymmetry between molecular-scale microions and colloidal macroions allows the microion degrees of freedom to be integrated out, leading to an effective one-component model of microion-dressed colloidal quasi-particles. For highly charged colloids with strong macroion-microion correlations, nonlinear effects can be incorporated into effective interactions by means of charge renormalization methods. Here, we compare and partially extend several practical mean-field methods of calculating renormalized colloidal interaction parameters, including effective charges and screening constants, as functions of concentration and ionic strength. Within the one-component description, we compute structural and thermodynamic properties from the effective interactions and assess the accuracy of the different methods by comparing predictions with elaborate primitive-model simulations [P. Linse, J. Chem. Phys. 113, 4359 (2000)]. We also compare various prescriptions for the osmotic pressure of suspensions in Donnan equilibrium with a salt ion reservoir and analyze instances where the macroion effective charge becomes larger than the bare one. The methods assessed include single-center cell, jellium, and multi-center mean-field theories. The strengths and weaknesses of the various methods are critically assessed, with the aim of guiding optimal and accurate implementations.
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Affiliation(s)
- Mariano E Brito
- Institute of Biological Information Processing, IBI-4, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Gerhard Nägele
- Institute of Biological Information Processing, IBI-4, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Alan R Denton
- Department of Physics, North Dakota State University, Fargo, North Dakota 58108-6050, USA
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2
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Härtel A, Bültmann M, Coupette F. Anomalous Underscreening in the Restricted Primitive Model. PHYSICAL REVIEW LETTERS 2023; 130:108202. [PMID: 36962045 DOI: 10.1103/physrevlett.130.108202] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 12/19/2022] [Accepted: 02/08/2023] [Indexed: 06/18/2023]
Abstract
Underscreening is a collective term for charge correlations in electrolytes decaying slower than the Debye length. Anomalous underscreening refers to phenomenology that cannot be attributed alone to steric interactions. Experiments with concentrated electrolytes and ionic fluids report anomalous underscreening, which so far has not been observed in simulation. We present Molecular Dynamics simulation results exhibiting anomalous underscreening that can be connected to cluster formation. A theory that accounts for ion pairing confirms the trend. Our results challenge the classic understanding of dense electrolytes impacting the design of technologies for energy storage and conversion.
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Affiliation(s)
- Andreas Härtel
- Institute of Physics, University of Freiburg, Hermann-Herder-Straße 3, 79104 Freiburg, Germany
| | - Moritz Bültmann
- Institute of Physics, University of Freiburg, Hermann-Herder-Straße 3, 79104 Freiburg, Germany
| | - Fabian Coupette
- Institute of Physics, University of Freiburg, Hermann-Herder-Straße 3, 79104 Freiburg, Germany
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3
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Aguirre-Manzo LA, González-Mozuelos P. A self-consistent Ornstein-Zernike jellium for highly charged colloids (microgels) in suspensions with added salt. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:275101. [PMID: 34047280 DOI: 10.1088/1361-648x/abfe95] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 05/06/2021] [Indexed: 06/12/2023]
Abstract
This work discusses a jellium scheme, built within the framework of the multicomponent Ornstein-Zernike (OZ) equation, which is capable of describing the collective structure of suspensions of highly charged colloids with added salt, even in the presence of finite-size multivalent microions. This approach uses a suitable approximation to decouple the microion-microion correlations from the macroion-microion profiles, which in combination with the methodology from the dressed ion theory (DIT) gives a full account of the electrostatic effective potential among the colloids. The main advantages of the present contribution reside in its ability to manage the short-range potentials and non-linear correlations among the microions, as well as its realistic characterization of the ionic clouds surrounding each macroion. The structure factors predicted by this jellium scheme are contrasted with previously reported experimental results for microgel suspensions with monovalent salts (2019Phys. Rev. E100032602), thus validating its high accuracy in these situations. The present theoretical analysis is then extended to microgel suspensions with multivalent salts, which reveals the prominent influence of the counterion valence on the makeup of the effective potentials. Although the induced differences may be difficult to identify through the mesoscopic structure, our results suggest that the microgel collapsing transition may be used to enhance these distinct effects, thus giving a feasible experimental probe for these phenomena.
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Affiliation(s)
- L A Aguirre-Manzo
- Departamento de Física, Cinvestav del I. P. N., Av. Instituto Politécnico Nacional 2508, Ciudad de México, C. P. 07360, Mexico
| | - P González-Mozuelos
- Departamento de Física, Cinvestav del I. P. N., Av. Instituto Politécnico Nacional 2508, Ciudad de México, C. P. 07360, Mexico
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4
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Cats P, Evans R, Härtel A, van Roij R. Primitive model electrolytes in the near and far field: Decay lengths from DFT and simulations. J Chem Phys 2021; 154:124504. [PMID: 33810662 DOI: 10.1063/5.0039619] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Inspired by recent experimental observations of anomalously large decay lengths in concentrated electrolytes, we revisit the Restricted Primitive Model (RPM) for an aqueous electrolyte. We investigate the asymptotic decay lengths of the one-body ionic density profiles for the RPM in contact with a planar electrode using classical Density Functional Theory (DFT) and compare these with the decay lengths of the corresponding two-body correlation functions in bulk systems, obtained in previous Integral Equation Theory (IET) studies. Extensive Molecular Dynamics (MD) simulations are employed to complement the DFT and IET predictions. Our DFT calculations incorporate electrostatic interactions between the ions using three different (existing) approaches: one is based on the simplest mean-field treatment of Coulomb interactions (MFC), while the other two employ the Mean Spherical Approximation (MSA). The MSAc invokes only the MSA bulk direct correlation function, whereas the MSAu also incorporates the MSA bulk internal energy. Although MSAu yields profiles that are in excellent agreement with MD simulations in the near field, in the far field, we observe that the decay lengths are consistent between IET, MSAc, and MD simulations, whereas those from MFC and MSAu deviate significantly. Using DFT, we calculated the solvation force, which relates directly to surface force experiments. We find that its decay length is neither qualitatively nor quantitatively close to the large decay lengths measured in experiments and conclude that the latter cannot be accounted for by the primitive model. The anomalously large decay lengths found in surface force measurements require an explanation that lies beyond primitive models.
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Affiliation(s)
- P Cats
- Institute for Theoretical Physics, Center for Extreme Matter and Emergent Phenomena, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
| | - R Evans
- HH Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, United Kingdom
| | - A Härtel
- Institute of Physics, University of Freiburg, Hermann-Herder-Straße 3, Freiburg 79104, Germany
| | - R van Roij
- Institute for Theoretical Physics, Center for Extreme Matter and Emergent Phenomena, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
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5
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Dolinnyi AI. Effective Parameters of Charged Spherical Particles in 1 : 1 Electrolyte Solutions. COLLOID JOURNAL 2020. [DOI: 10.1134/s1061933x20060034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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6
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Aguirre-Manzo LA, González-Mozuelos P. Volume transition effects on the correlations and effective interactions among highly charged microgels. SOFT MATTER 2020; 16:5081-5093. [PMID: 32458939 DOI: 10.1039/d0sm00486c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Recent experimental studies have demonstrated the huge influence that the volume phase transition (VPT) has on the collective structure of highly charged thermo-responsive microgels in aqueous solution with low concentrations of added monovalent salt, thus opening a promising new route for controlling the overall properties of practical colloidal suspensions. We present here an analysis of this structure based on the effective electrostatic potential obtained with the exact methodology of the dressed ion theory (DIT). Starting with a description at the primitive model level, we determine the correlations among the components of our model system (macroions plus monovalent anions and cations) by utilizing the two-density integral equation theory, thus allowing us to consider realistic values for the microgel charges. The resulting microgel structure factors show a good agreement with the reported light scattering measurements, whereas the microscopic pair distributions reveal that in this regime the shrunken states promote an enhanced counterion absorption into the microgels. This packing of counterions inside the microgels induces strongly non-linear correlations among the microions, and in turn provokes a substantial weakening of the microgel-microgel correlations. The ensuing effective interactions are then obtained by contracting the description to the level in which only the macroions are present. We find not only that the magnitude and reach of the corresponding pair potentials are markedly inhibited in the shrunken states, but also that their general form diverges from the conventional screened Coulomb shape. This makes it necessary to rethink the concepts of effective charge and screening length.
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Affiliation(s)
- L A Aguirre-Manzo
- Departamento de Física, Cinvestav del I. P. N., Av., Instituto Politécnico Nacional 2508, Ciudad de México, C. P. 07360, Mexico.
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7
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Aguirre-Manzo LA, Ledesma-Motolinía M, Rojas-Ochoa LF, Trappe V, Callejas-Fernández J, Haro-Pérez C, González-Mozuelos P. Accounting for effective interactions among charged microgels. Phys Rev E 2019; 100:032602. [PMID: 31640009 DOI: 10.1103/physreve.100.032602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Indexed: 06/10/2023]
Abstract
We introduce a theoretical approach to describe structural correlations among charged permeable spheres at finite particle concentrations. This theory explicitly accounts for correlations among microions and between microions and macroions and allows for the proposal of an effective interaction among macroions that successfully captures structural correlations observed in poly-N-isopropyl acrylamide microgel systems. In our description the bare charge is fixed and independent of the microgel size, the microgel concentration, and the ionic strength, which contrasts with results obtained using linear response approximations, where the bare charge needs to be adapted to properly account for microgel correlations obtained at different conditions.
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Affiliation(s)
- L A Aguirre-Manzo
- Departamento de Física, Cinvestav del I. P. N., Av. Instituto Politécnico Nacional 2508, 07360 Ciudad de México, Mexico
| | - M Ledesma-Motolinía
- Departamento de Ciencias Básicas, Universidad Autónoma Metropolitana-Azcapotzalco, 02200 Ciudad de México, Mexico
| | - L F Rojas-Ochoa
- Departamento de Física, Cinvestav del I. P. N., Av. Instituto Politécnico Nacional 2508, 07360 Ciudad de México, Mexico
| | - V Trappe
- Departement de Physique, Université de Fribourg, 1700 Fribourg, Switzerland
| | | | - C Haro-Pérez
- Departamento de Ciencias Básicas, Universidad Autónoma Metropolitana-Azcapotzalco, 02200 Ciudad de México, Mexico
| | - P González-Mozuelos
- Departamento de Física, Cinvestav del I. P. N., Av. Instituto Politécnico Nacional 2508, 07360 Ciudad de México, Mexico
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8
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Quintana C, González-Mozuelos P. Nanoparticles confined to a spherical surface in the presence of an external field: Interaction forces and induced microstructure. J Chem Phys 2018; 148:234901. [PMID: 29935519 DOI: 10.1063/1.5014991] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The structural response of a set of charged nanoparticles confined to move on a spherical surface under the influence of an external field is studied by Brownian Dynamics (BD) simulations and by an integral equation approach (IEA). Considering an identical nanoparticle as the source of the external field, we analyze the force exerted by the N confined particles on the external one, as well as the corresponding potential energy, focusing on their dependence on the distance of the external particle to the center of the sphere r0. The connection of the force and potential to the equilibrium local distribution of the adsorbed particles, that is, the microstructure within the spherical monolayer induced by the external nanoparticle, which is also dependent on r0, is elucidated by this analysis. It is found that the external particle needs to surmount a considerable potential barrier when moving toward the spherical surface, although much smaller than the one generated by a uniform surface distribution with an equivalent amount of charge. This is understood in terms of the correlation hole within the confined monolayer induced by the external particle. Another interesting conclusion is that the IEA provides an accurate, almost quantitative, description of the main features observed in the BD results, yet it is much less computationally demanding. The connection of these results with the overall chemical equilibrium of charged surfactant nanoparticles in the context of Pickering emulsions is also briefly discussed.
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Affiliation(s)
- C Quintana
- Departamento de Física, Cinvestav del I. P. N., Av. Instituto Politécnico Nacional 2508, Ciudad de México, C. P. 07360, Mexico
| | - P González-Mozuelos
- Departamento de Física, Cinvestav del I. P. N., Av. Instituto Politécnico Nacional 2508, Ciudad de México, C. P. 07360, Mexico
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9
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Ojeda-Mendoza GJ, Moncho-Jordá A, González-Mozuelos P, Haro-Pérez C, Rojas-Ochoa LF. Evidence of electrostatic-enhanced depletion attraction in the structural properties and phase behavior of binary charged colloidal suspensions. SOFT MATTER 2018; 14:1355-1364. [PMID: 29379934 DOI: 10.1039/c7sm02220d] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this paper we study the structure and phase behavior of binary mixtures of charged particles at low ionic strength. Due to the large size asymmetry between both species, light scattering measurements give us access only to the partial static structure factor that corresponds to the big particles. We observe that the addition of small charged colloids produces a decrease of the main peak of the measured static structure factor and a shift to larger scattering vector values. This finding is in agreement with theory based on integral equations with the Hypernetted-Chain Closure (HNC) relation. The effective interaction between two big particles due to the presence of small particles is obtained by a HNC inversion scheme and used in numerical simulations that adequately reproduce the experiments. We find that the presence of small particles induces an electrostatic depletion screening among the big colloids, creating around them an exclusion zone for the small charged colloids greater than that caused in the case of neutral small colloids, which in turn augments the depletion effect.
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Affiliation(s)
- G J Ojeda-Mendoza
- Departamento de Física, CINVESTAV-IPN, Av. Instituto Politécnico Nacional 2508, 07360 Ciudad de México, Mexico.
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10
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Trefalt G, Szilagyi I, Téllez G, Borkovec M. Colloidal Stability in Asymmetric Electrolytes: Modifications of the Schulze-Hardy Rule. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:1695-1704. [PMID: 28127961 DOI: 10.1021/acs.langmuir.6b04464] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The Schulze-Hardy rule suggests a strong dependence of the critical coagulation concentration (CCC) on the ionic valence. This rule is addressed theoretically and confronted with recent experimental results. The commonly presented derivation of this rule assumes symmetric electrolytes and highly charged particles. Both assumptions are incorrect. Symmetric electrolytes containing multivalent ions are hardly soluble, and experiments are normally carried out with the well-soluble salts of asymmetric electrolytes containing monovalent and multivalent ions. In this situation, however, the behavior is completely different whether the multivalent ions represent the counterions or co-ions. When these ions represent the counterions, meaning that the multivalent ions have the opposite sign than the charge of the particle, they adsorb strongly to the particles. Thereby, they progressively reduce the magnitude of the surface charge with increasing valence. In fact, this dependence of the charge density on the counterion valence is mainly responsible for the decrease of the CCC with the valence. In the co-ion case, where the multivalent ions have the same sign as the charge of the particle, the multivalent ions are repelled from the particles, and the surfaces remain highly charged. In this case, the inverse Schulze-Hardy rule normally applies, whereby the CCC varies inversely proportional to the co-ion valence.
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Affiliation(s)
- Gregor Trefalt
- Department of Inorganic and Analytical Chemistry, University of Geneva , Sciences II, 30 Quai Ernest-Ansermet, 1205 Geneva, Switzerland
| | - Istvan Szilagyi
- Department of Inorganic and Analytical Chemistry, University of Geneva , Sciences II, 30 Quai Ernest-Ansermet, 1205 Geneva, Switzerland
| | - Gabriel Téllez
- Departamento de Física, Universidad de los Andes , AA 4976, Bogotá, Colombia
| | - Michal Borkovec
- Department of Inorganic and Analytical Chemistry, University of Geneva , Sciences II, 30 Quai Ernest-Ansermet, 1205 Geneva, Switzerland
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Abstract
The accurate characterization of the electrical double layer properties of nanoparticles is of fundamental importance for optimizing their physicochemical properties for specific biotechnological and biomedical applications. In this article, we use classical solvation density functional theory and a surface complexation model to investigate the effects of the pH and the nanoparticle size on the structural and electrostatic properties of an electrolyte solution surrounding a spherical silica oxide nanoparticle. The formulation has been particularly useful for identifying dominant interactions governing the ionic driving force at a variety of pH levels and nanoparticle sizes. As a result of the energetic interplay displayed between electrostatic potential, ion-ion correlation and particle crowding effects on the nanoparticle surface titration, rich, non-trivial ion density profiles and mean electrostatic potential behavior have been found.
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Affiliation(s)
- Christian Hunley
- Department of Physics and Astronomy, The University of Texas at San Antonio, San Antonio, TX 78249-5003, USA.
| | - Marcelo Marucho
- Department of Physics and Astronomy, The University of Texas at San Antonio, San Antonio, TX 78249-5003, USA.
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12
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Kjellander R. Nonlocal electrostatics in ionic liquids: The key to an understanding of the screening decay length and screened interactions. J Chem Phys 2016; 145:124503. [DOI: 10.1063/1.4962756] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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13
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Finlayson SD, Bartlett P. Non-additivity of pair interactions in charged colloids. J Chem Phys 2016; 145:034905. [DOI: 10.1063/1.4959122] [Citation(s) in RCA: 16] [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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14
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González-Mozuelos P. Effective electrostatic interactions among charged thermo-responsive microgels immersed in a simple electrolyte. J Chem Phys 2016; 144:054902. [DOI: 10.1063/1.4941324] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- P. González-Mozuelos
- Departamento de Física, Cinvestav del I. P. N., Av. Instituto Politécnico Nacional 2508, Mexico, Distrito Federal, C. P. 07360, Mexico
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15
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Huang N, Tao J, Wei S, Chen M, Wei C, Li L. Counter-ion specificity explored in abnormal expansion of supra-molecular aggregates in aqueous solution of alkaline metal salts. J Chem Phys 2015; 143:114901. [DOI: 10.1063/1.4930854] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Ningdong Huang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, China
| | - Jiaojiao Tao
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, China
| | - Shenghui Wei
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, China
| | - Mingming Chen
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, China
| | - Chengsha Wei
- CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, China
| | - Liangbin Li
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, China
- CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, China
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16
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Abstract
The stability of colloidal suspensions is crucial in a wide variety of processes, including the fabrication of photonic materials and scaffolds for biological assemblies. The ionic strength of the electrolyte that suspends charged colloids is widely used to control the physical properties of colloidal suspensions. The extensively used two-body Derjaguin-Landau-Verwey-Overbeek (DLVO) approach allows for a quantitative analysis of the effective electrostatic forces between colloidal particles. DLVO relates the ionic double layers, which enclose the particles, to their effective electrostatic repulsion. Nevertheless, the double layer is distorted at high macroion volume fractions. Therefore, DLVO cannot describe the many-body effects that arise in concentrated suspensions. We show that this problem can be largely resolved by identifying effective point charges for the macroions using cell theory. This extrapolated point charge (EPC) method assigns effective point charges in a consistent way, taking into account the excluded volume of highly charged macroions at any concentration, and thereby naturally accounting for high volume fractions in both salt-free and added-salt conditions. We provide an analytical expression for the effective pair potential and validate the EPC method by comparing molecular dynamics simulations of macroions and monovalent microions that interact via Coulombic potentials to simulations of macroions interacting via the derived EPC effective potential. The simulations reproduce the macroion-macroion spatial correlation and the virial pressure obtained with the EPC model. Our findings provide a route to relate the physical properties such as pressure in systems of screened Coulomb particles to experimental measurements.
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17
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Barrios-Contreras EA, González-Tovar E, Guerrero-García GI. The dominance of small ions in the electric double layer of size- and charge-asymmetric electrolytes: a mean-field study on the charge reversal and surface charge amplification. Mol Phys 2015. [DOI: 10.1080/00268976.2015.1018853] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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18
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Ovanesyan Z, Medasani B, Fenley MO, Guerrero-García GI, de la Cruz MO, Marucho M. Excluded volume and ion-ion correlation effects on the ionic atmosphere around B-DNA: theory, simulations, and experiments. J Chem Phys 2014; 141:225103. [PMID: 25494770 PMCID: PMC4265039 DOI: 10.1063/1.4902407] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 11/12/2014] [Indexed: 12/19/2022] Open
Abstract
The ionic atmosphere around a nucleic acid regulates its stability in aqueous salt solutions. One major source of complexity in biological activities involving nucleic acids arises from the strong influence of the surrounding ions and water molecules on their structural and thermodynamic properties. Here, we implement a classical density functional theory for cylindrical polyelectrolytes embedded in aqueous electrolytes containing explicit (neutral hard sphere) water molecules at experimental solvent concentrations. Our approach allows us to include ion correlations as well as solvent and ion excluded volume effects for studying the structural and thermodynamic properties of highly charged cylindrical polyelectrolytes. Several models of size and charge asymmetric mixtures of aqueous electrolytes at physiological concentrations are studied. Our results are in good agreement with Monte Carlo simulations. Our numerical calculations display significant differences in the ion density profiles for the different aqueous electrolyte models studied. However, similar results regarding the excess number of ions adsorbed to the B-DNA molecule are predicted by our theoretical approach for different aqueous electrolyte models. These findings suggest that ion counting experimental data should not be used alone to validate the performance of aqueous DNA-electrolyte models.
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Affiliation(s)
- Zaven Ovanesyan
- Department of Physics and Astronomy, The University of Texas at San Antonio, San Antonio, Texas 78249-5003, USA
| | - Bharat Medasani
- Department of Physics and Astronomy, The University of Texas at San Antonio, San Antonio, Texas 78249-5003, USA
| | - Marcia O Fenley
- Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306, USA
| | - Guillermo Iván Guerrero-García
- Instituto de Física, Universidad Autónoma de San Luis Potosí, Álvaro Obregón 64, 78000 San Luis Potosí, San Luis Potosí, Mexico
| | - Mónica Olvera de la Cruz
- Department of Chemistry and Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | - Marcelo Marucho
- Department of Physics and Astronomy, The University of Texas at San Antonio, San Antonio, Texas 78249-5003, USA
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19
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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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20
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Huang N, Tao J, Liu J, Wei S, Li L, Wu Z. Specific ion effects induced by mono-valent salts in like charged aggregates in water. SOFT MATTER 2014; 10:4236-4240. [PMID: 24828119 DOI: 10.1039/c3sm52925h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
While salt mediated association between similarly charged poly-electrolytes occurs in a broad range of biological and colloidal systems, the effects of mono-valent salts remains little known experimentally. In this communication we systematically study influences of assorted mono-valent salts on structures of and interactions in two dimensional ordered bundles of charged fibrils assembled in water using Small Angle X-ray Scattering (SAXS). By quantitatively analyzing the scattering peak features, we discern two competing effects with opposite influences due to partitioning of salts in the aqueous complex. While electrostatic effects from salts residing between the fibrils suppress attraction between fibrils and expand the bundles, it is compensated by external osmotic pressure from peripheral salts in the aqueous media. The balance between the two effects varies for different salts and gives rise to ion-specific equilibrium behavior as well as structure of ordered bundles in salty water. The specific ions effects in like charged aggregates can be attributed to preferential distribution of ions inside or outside the bundles, correlated to the ranking of ions in Hofmeister series for macromolecules. Unlike conventional studies on Hofmeister effects by thermodynamic measurements relying on modeling for data interpretation, our study is based directly on structural analysis and is model-insensitive.
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Affiliation(s)
- Ningdong Huang
- National Synchrotron Radiation Lab, College of Nuclear Science and Technology, University of Science and Technology of China, Hefei, China.
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Kuzovkov VN, Kotomin EA. Static and dynamic screening effects in the electrostatic self-assembly of nano-particles. Phys Chem Chem Phys 2014; 16:25449-60. [DOI: 10.1039/c4cp02448f] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
3D structure of self-assembled and oppositely charged nanoparticles.
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Affiliation(s)
- V. N. Kuzovkov
- Institute for Solid State Physics
- University of Latvia
- Riga, Latvia
| | - E. A. Kotomin
- Max-Planck Institute for Solid State Research
- Stuttgart, Germany
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Guerrero-García GI, González-Mozuelos P, Olvera de la Cruz M. Large counterions boost the solubility and renormalized charge of suspended nanoparticles. ACS NANO 2013; 7:9714-9723. [PMID: 24180597 DOI: 10.1021/nn404477b] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Colloidal particles are ubiquitous in biology and in everyday products such as milk, cosmetics, lubricants, paints, or drugs. The stability and aggregation of colloidal suspensions are of paramount importance in nature and in diverse nanotechnological applications, including the fabrication of photonic materials and scaffolds for biological assemblies, gene therapy, diagnostics, targeted drug delivery, and molecular labeling. Electrolyte solutions have been extensively used to stabilize and direct the assembly of colloidal particles. In electrolytes, the effective electrostatic interactions among the suspended colloids can be changed over various length scales by tuning the ionic concentration. However, a major limitation is gelation or flocculation at high salt concentrations. This is explained by classical theories, which show that the electrostatic repulsion among charged colloids is significantly reduced at high electrolyte concentrations. As a result, these screened colloidal particles are expected to aggregate due to short-range attractive interactions or dispersion forces as the salt concentration increases. We discuss here a robust, tunable mechanism for colloidal stability by which large counterions prevent highly charged nanoparticles from aggregating in salt solutions with concentrations up to 1 M. Large counterions are shown to generate a thicker ionic cloud in the proximity of each charged colloid, which strengthens short-range repulsions among colloidal particles and also increases the corresponding renormalized colloidal charge perceived at larger separation distances. These effects thus provide a reliable stabilization mechanism in a broad range of biological and synthetic colloidal suspensions.
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