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Kwan V, Consta S, Malek SMA. Variation of Surface Propensity of Halides with Droplet Size and Temperature: The Planar Interface Limit. J Phys Chem B 2024; 128:193-207. [PMID: 38127582 DOI: 10.1021/acs.jpcb.3c05701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
The radial number density profiles of halide and alkali ions in aqueous clusters with equimolar radius ≲1.4 nm, which correspond to ≲255 H2O molecules, have been extensively studied by computations. However, the surface abundance of Cl-, Br-, and I- relative to the bulk interior in these smaller clusters may not be representative of the larger systems. Indeed, here we show that the larger the cluster is, the lower the relative surface abundance of chaotropic halides is. In droplets with an equimolar radius of ≈2.45 nm, which corresponds to ≈2000 H2O molecules, the polarizable halides show a clear number density maximum in the droplet's bulk-like interior. A similar pattern is observed in simulations of the aqueous planar interface with halide salts at room temperature. At elevated temperature the surface propensity of Cl- decreases gradually, while that of I- is partially preserved. The change in the chaotropic halide location at higher temperatures than the room temperature may considerably affect photochemical reactivity in atmospheric aerosols, vapor-liquid nucleation and growth mechanisms, and salt crystallization via solvent evaporation. We argue that the commonly used approach of nullifying parameters in a force field in order to find the factors that determine the ion location does not provide transferable insight into other force fields.
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Affiliation(s)
- Victor Kwan
- Department of Chemistry, The University of Western Ontario, London, ON, Canada N6A 5B7
| | - Styliani Consta
- Department of Chemistry, The University of Western Ontario, London, ON, Canada N6A 5B7
| | - Shahrazad M A Malek
- Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John's, NL, Canada A1B 3X7
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2
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Kwan V, Maiti SR, Saika-Voivod I, Consta S. Salt Enrichment and Dynamics in the Interface of Supercooled Aqueous Droplets. J Am Chem Soc 2022; 144:11148-11158. [PMID: 35715222 DOI: 10.1021/jacs.2c01159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The interconversion reaction of NaCl between the contact-ion pair (CIP) and the solvent-separated ion pair (SSIP) as well as the free-ion state in cold droplets has not yet been investigated. We report direct computational evidence that the lower is the temperature, the closer to the surface the ion interconversion reaction takes place. In supercooled droplets the enrichment of the subsurface in salt becomes more evident. The stability of the SSIP relative to the CIP increases as the ion-pairing is transferred toward the droplet's outer layers. In the free-ion state, where the ions diffuse independently in the solution, the number density of Cl- shows a broad maximum in the interior in addition to the well-known maximum in the surface. In the study of the reaction dynamics, we find a weak coupling between the interionic NaCl distance reaction coordinate and the solvent degrees of freedom, which contrasts with the diffusive crossing of the free energy barrier found in bulk solution modeling. The H2O self-diffusion coefficient is found to be at least an order of magnitude larger than that in the bulk solution. We propose to exploit the enhanced surface ion concentration at low temperature to eliminate salts from droplets in native mass spectrometry ionization methods.
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Affiliation(s)
- Victor Kwan
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Shoubhik R Maiti
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada.,Department of Chemistry, The University of Sheffield, Sheffield S3 7HF, United Kingdom
| | - Ivan Saika-Voivod
- Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John's A1B 3X7, Canada
| | - Styliani Consta
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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3
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Rodríguez-Segundo R, Gijón A, Prosmiti R. Quantum molecular simulations of micro-hydrated halogen anions. Phys Chem Chem Phys 2022; 24:14964-14974. [PMID: 35686995 DOI: 10.1039/d2cp01396g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report the results of a detailed and accurate investigation focused on structures and energetics of poly-hydrated halides employing first-principles polarizable halide-water potentials to describe the underlying forces. Following a bottom-up data-driven potential approach, we initially looked into the classical behavior of higher-order X-(H2O)N clusters. We have located several low-lying energies, such as global and local minima, structures for each cluster, with various water molecules (up to N = 8) surrounding the halide anion (X- = F-, Cl-, Br-, I-), employing an evolutionary programming method. It is found that the F--water clusters exhibit different structural configurations than the heavier halides, however independently of the halide anion, all clusters show in general a selective growth with the anion preferring to be connected to the outer shell of the water molecule arrangements. In turn, path-integral molecular dynamics simulations are performed to incorporate explicitly nuclear quantum and thermal effects in describing the nature of halide ion microsolvation in such prototypical model systems. Our data reveal that at low finite temperatures, nuclear quantum effects affect certain structural properties, such as weakening hydrogen bonding between the halide anion and water molecules, with minor distortions in the water network beyond the first hydration shell, indicating local structure rearrangements. Such structural characteristics and the promising cluster size trends observed in the single-ion solvation energies motivated us to draw connections of small size cluster data to the limits of continuum bulk values, toward the investigation of the challenging computational modeling of bulk single ion hydration.
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Affiliation(s)
- Raúl Rodríguez-Segundo
- Institute of Fundamental Physics (IFF-CSIC), CSIC, Serrano 123, 28006 Madrid, Spain. .,Atelgraphics S.L., Mota de Cuervo 42, 28043, Madrid, Spain
| | - Alfonso Gijón
- Materials Science Institute of Madrid (ICMM-CSIC), CSIC, Sor Juana Inés de la Cruz 3, 28049 Madrid, Spain
| | - Rita Prosmiti
- Institute of Fundamental Physics (IFF-CSIC), CSIC, Serrano 123, 28006 Madrid, Spain.
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4
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Konermann L, Kim S. Grotthuss Molecular Dynamics Simulations for Modeling Proton Hopping in Electrosprayed Water Droplets. J Chem Theory Comput 2022; 18:3781-3794. [PMID: 35544700 DOI: 10.1021/acs.jctc.2c00001] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Excess protons in water exhibit unique transport properties because they can rapidly hop along H-bonded water wires. Considerable progress has been made in unraveling this Grotthuss diffusion mechanism using quantum mechanical-based computational techniques. Unfortunately, high computational cost tends to restrict those techniques to small systems and short times. Molecular dynamics (MD) simulations can be applied to much larger systems and longer time windows. However, standard MD methods do not permit the dissociation/formation of covalent bonds, such that Grotthuss diffusion cannot be captured. Here, we bridge this gap by combining atomistic MD simulations (using Gromacs and TIP4P/2005 water) with proton hopping. Excess protons are modeled as hydronium ions that undergo H3O+ + H2O → H2O + H3O+ transitions. In accordance with ab initio MD data, these Grotthuss hopping events are executed in "bursts" with quasi-instantaneous hopping across one or more waters. The bursts are separated by regular MD periods during which H3O+ ions undergo Brownian diffusion. The resulting proton diffusion coefficient agrees with the literature value. We apply this Grotthuss MD technique to highly charged water droplets that are in a size regime encountered during electrospray ionization (5 nm radius, ∼17,000 H2O). The droplets undergo rapid solvent evaporation and occasional H3O+ ejection, keeping them at ca. 81% of the Rayleigh limit. The simulated behavior is consistent with phase Doppler anemometry data. The Grotthuss MD technique developed here should be useful for modeling the behavior of various proton-containing systems that are too large for high-level computational approaches. In particular, we envision future applications related to electrospray processes, where earlier simulations used metal cations while in reality excess protons dominate.
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Affiliation(s)
- Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Scott Kim
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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5
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Malek SMA, Kwan V, Saika-Voivod I, Consta S. Low Density Interior in Supercooled Aqueous Nanodroplets Expels Ions to the Subsurface. J Am Chem Soc 2021; 143:13113-13123. [PMID: 34375522 DOI: 10.1021/jacs.1c04142] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The interaction between water and ions within droplets plays a key role in the chemical reactivity of atmospheric and man-made aerosols. Here we report direct computational evidence that in supercooled aqueous nanodroplets a lower density core of tetrahedrally coordinated water expels the cosmotropic ions to the denser and more disordered subsurface. In contrast, at room temperature, depending on the nature of the ion, the radial distribution in the droplet core is nearly uniform or elevated toward the center. We analyze the spatial distribution of a single ion in terms of a reference electrostatic model. The energy of the system in the analytical model is expressed as the sum of the electrostatic and surface energy of a deformable droplet. The model predicts that the ion is subject to a harmonic potential centered at the droplet's center of mass. We name this effect "electrostatic confinement". The model's predictions are consistent with the simulation findings for a single ion at room temperature but not at supercooling. We anticipate this study to be the starting point for investigating the structure of supercooled (electro)sprayed droplets that are used to preserve the conformations of macromolecules originating from the bulk solution.
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Affiliation(s)
- Shahrazad M A Malek
- Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John's A1B 3X7, Canada
| | - Victor Kwan
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Ivan Saika-Voivod
- Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John's A1B 3X7, Canada.,Department of Applied Mathematics, Western University, London, Ontario N6A 3K7, Canada
| | - Styliani Consta
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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6
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Aydin F, Moradzadeh A, Bilodeau CL, Lau EY, Schwegler E, Aluru NR, Pham TA. Ion Solvation and Transport in Narrow Carbon Nanotubes: Effects of Polarizability, Cation-π Interaction, and Confinement. J Chem Theory Comput 2021; 17:1596-1605. [PMID: 33625224 DOI: 10.1021/acs.jctc.0c00827] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Understanding ion solvation and transport under confinement is critical for a wide range of emerging technologies, including water desalination and energy storage. While molecular dynamics (MD) simulations have been widely used to study the behavior of confined ions, considerable deviations between simulation results depending on the specific treatment of intermolecular interactions remain. In the following, we present a systematic investigation of the structure and dynamics of two representative solutions, that is, KCl and LiCl, confined in narrow carbon nanotubes (CNTs) with a diameter of 1.1 and 1.5 nm, using a combination of first-principles and classical MD simulations. Our simulations show that the inclusion of both polarization and cation-π interactions is essential for the description of ion solvation under confinement, particularly for large ions with weak hydration energies. Beyond the variation in ion solvation, we find that cation-π interactions can significantly influence the transport properties of ions in CNTs, particularly for KCl, where our simulations point to a strong correlation between ion dehydration and diffusion. Our study highlights the complex interplay between nanoconfinement and specific intermolecular interactions that strongly control the solvation and transport properties of ions.
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Affiliation(s)
- Fikret Aydin
- Quantum Simulations Group, Materials Science Division, Lawrence Livermore National Laboratory, 7000 East Ave, Livermore, California 94550, United States
| | - Alireza Moradzadeh
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Camille L Bilodeau
- Department of Chemical and Biological Engineering and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Edmond Y Lau
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, 7000 East Ave, Livermore, California 94550, United States
| | - Eric Schwegler
- Quantum Simulations Group, Materials Science Division, Lawrence Livermore National Laboratory, 7000 East Ave, Livermore, California 94550, United States
| | - Narayana R Aluru
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Tuan Anh Pham
- Quantum Simulations Group, Materials Science Division, Lawrence Livermore National Laboratory, 7000 East Ave, Livermore, California 94550, United States
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7
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Kwan V, Consta S. Molecular Characterization of the Surface Excess Charge Layer in Droplets. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:33-45. [PMID: 32597645 DOI: 10.1021/jasms.0c00053] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The surface excess charge layer (SECL) in droplets has often been associated with distinct chemistry. We examine the effect of the nature of ions in the composition and structure of SECL by using molecular dynamics. We find that in the presence of simple ions the thickness of SECL is invariant not only with respect to droplet size but also with respect to the nature of the ions. In the presence of simple ions, this layer has a thickness of ∼1.5-1.7 nm but in the presence of macroions it may extend to ∼2.0 nm. The proportion of ions contained in SECL depends on the nature of the ions and the droplet size. For the same droplet size, I- and model H3O+ ions show considerably higher concentration than Na+ and Cl- ions. We identify the maximum ion concentration region, which, in nanodrops, may partially overlap with SECL. As the relative shape fluctuations decrease when microdrop size is approached, the overlap between SECL and maximum ion concentration region increases. We suggest the extension of the bilayer droplet structure assumed in the equilibrium partitioning model of Enke to include the maximum ion concentration region that may not coincide with SECL in nanodrops. We compute the ion concentrations in SECL, which are those that should enter the kinetic equation in the ion-evaporation mechanism, instead of the overall drop ion concentration that has been used.
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Affiliation(s)
- Victor Kwan
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 5B7
| | - Styliani Consta
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 5B7
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8
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Lee JK, Han HS, Chaikasetsin S, Marron DP, Waymouth RM, Prinz FB, Zare RN. Condensing water vapor to droplets generates hydrogen peroxide. Proc Natl Acad Sci U S A 2020; 117:30934-30941. [PMID: 33229543 PMCID: PMC7733789 DOI: 10.1073/pnas.2020158117] [Citation(s) in RCA: 81] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
It was previously shown [J. K. Lee et al., Proc. Natl. Acad. Sci. U.S.A, 116, 19294-19298 (2019)] that hydrogen peroxide (H2O2) is spontaneously produced in micrometer-sized water droplets (microdroplets), which are generated by atomizing bulk water using nebulization without the application of an external electric field. Here we report that H2O2 is spontaneously produced in water microdroplets formed by dropwise condensation of water vapor on low-temperature substrates. Because peroxide formation is induced by a strong electric field formed at the water-air interface of microdroplets, no catalysts or external electrical bias, as well as precursor chemicals, are necessary. Time-course observations of the H2O2 production in condensate microdroplets showed that H2O2 was generated from microdroplets with sizes typically less than ∼10 µm. The spontaneous production of H2O2 was commonly observed on various different substrates, including silicon, plastic, glass, and metal. Studies with substrates with different surface conditions showed that the nucleation and the growth processes of condensate water microdroplets govern H2O2 generation. We also found that the H2O2 production yield strongly depends on environmental conditions, including relative humidity and substrate temperature. These results show that the production of H2O2 occurs in water microdroplets formed by not only atomizing bulk water but also condensing water vapor, suggesting that spontaneous water oxidation to form H2O2 from water microdroplets is a general phenomenon. These findings provide innovative opportunities for green chemistry at heterogeneous interfaces, self-cleaning of surfaces, and safe and effective disinfection. They also may have important implications for prebiotic chemistry.
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Affiliation(s)
- Jae Kyoo Lee
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - Hyun Soo Han
- Department of Mechanical Engineering, Stanford University, Stanford, CA 94305
- Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305
| | | | - Daniel P Marron
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | | | - Fritz B Prinz
- Department of Mechanical Engineering, Stanford University, Stanford, CA 94305;
- Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305
| | - Richard N Zare
- Department of Chemistry, Stanford University, Stanford, CA 94305;
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9
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Liu YY, Hua X, Zhang Z, Zhang J, Zhang S, Hu P, Long YT. pH-Dependent Water Clusters in Photoacid Solution: Real-Time Observation by ToF-SIMS at a Submicropore Confined Liquid-Vacuum Interface. Front Chem 2020; 8:731. [PMID: 32974284 PMCID: PMC7472850 DOI: 10.3389/fchem.2020.00731] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Accepted: 07/15/2020] [Indexed: 11/13/2022] Open
Abstract
Water clusters are ubiquitously formed in aqueous solutions by hydrogen bonding, which is quite sensitive to various environment factors such as temperature, pressure, electrolytes, and pH. Investigation of how the environment has impact on water structure is important for further understanding of the nature of water and the interactions between water and solutes. In this work, pH-dependent water structure changes were studied by monitoring the changes for the size distribution of protonated water clusters by in-situ liquid ToF-SIMS. In combination with a light illumination system, in-situ liquid ToF-SIMS was used to real-time measure the changes of a light-activated organic photoacid under different light illumination conditions. Thus, the proton transfer and pH-mediated water cluster changes were analyzed in real-time. It was found that higher concentration of free protons could lead to a strengthened local hydrogen bonding network as well as relatively larger protonated water clusters in both organic acid and inorganic acid. Besides, the accumulation of protons at the liquid-vacuum interface under light illumination was observed owing to the affinity of organic molecules to the low-pressure gas phase. The application of in-situ liquid ToF-SIMS analysis in combination with in-situ light illumination system opened up an avenue to real-time investigate light-activated reactions. Besides, the results regarding water structure changes in acidic solutions showed important insights in related atmospheric and physiochemical processes.
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Affiliation(s)
- Ying-Ya Liu
- School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, China
| | - Xin Hua
- School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, China
| | - Zhiwei Zhang
- School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, China
| | - Junji Zhang
- School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, China
| | - Shaoze Zhang
- National Engineering Laboratory for Vacuum Metallurgy, Kunming University of Science and Technology, Kunming, China.,Engineering Laboratory for Advanced Battery and Materials of Yunnan Province, Kunming University of Science and Technology, Kunming, China
| | - Ping Hu
- School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, China
| | - Yi-Tao Long
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China
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10
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Xiong H, Lee JK, Zare RN, Min W. Strong Electric Field Observed at the Interface of Aqueous Microdroplets. J Phys Chem Lett 2020; 11:7423-7428. [PMID: 32804510 DOI: 10.1021/acs.jpclett.0c02061] [Citation(s) in RCA: 140] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Chemical reactions in aqueous microdroplets often exhibit unusual kinetic and thermodynamic properties not observed in bulk solution. While an electric field has been implicated at the water interface, there has been no direct measurement in aqueous microdroplets, largely due to the lack of proper measurement tools. Herein, we employ newly developed stimulated Raman excited fluorescence microscopy to measure the electric field at the water-oil interface of microdroplets. As determined by the vibrational Stark effect of a nitrile-bearing fluorescent probe, the strength of the electric field is found to be on the order of 107 V/cm. This strong electric field aligns probe dipoles with respect to the interface. The formation of the electric field likely arises from charge separation caused by the adsorption of negative ions at the water-oil interface of microdroplets. We suggest that this strong electric field might account in part for the unique properties of chemical reactions reported in microdroplets.
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Affiliation(s)
- Hanqing Xiong
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Jae Kyoo Lee
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Richard N Zare
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Wei Min
- Department of Chemistry, Columbia University, New York, New York 10027, United States
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11
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Abstract
Clusters consisting of 20 water molecules and a single cesium ion are especially stable due to their clathrate structure that is composed exclusively of three-coordinate water molecules. Clathrate stability was investigated using infrared photodissociation (IRPD) spectroscopy in the free-OH stretching region (∼3600-3800 cm-1) at ion cell temperatures between 135 and 355 K. At 275 K and colder, IRPD spectra of Cs+(H2O)20 have just one acceptor-acceptor-donor band. At higher temperatures, a higher-energy acceptor-donor band emerges and grows in intensity. Non-clathrate Na+(H2O)20 structures contain both of these bands, which do not change significantly in intensity over the temperature range. These results indicate a rapid onset in the conversion from clathrate to non-clathrate structures with temperature and suggest that some clathrate population remains even at the highest temperatures investigated. These results provide new insights into the role of entropy in clathrate stability.
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Affiliation(s)
- Christiane N Stachl
- Department of Chemistry, University of California, Berkeley, California 94720-1460, United States
| | - Evan R Williams
- Department of Chemistry, University of California, Berkeley, California 94720-1460, United States
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12
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Kwan V, Malevanets A, Consta S. Where Do the Ions Reside in a Highly Charged Droplet? J Phys Chem A 2019; 123:9298-9310. [DOI: 10.1021/acs.jpca.9b03368] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Victor Kwan
- Department of Chemistry, The University of Western Ontario, London N6A 5B7, Ontario, Canada
| | - Anatoly Malevanets
- Department of Electrical and Computer Engineering, The University of Western Ontario, London N6A 5B9, Ontario, Canada
| | - Styliani Consta
- Department of Chemistry, The University of Western Ontario, London N6A 5B7, Ontario, Canada
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13
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Egorov AV, Brodskaya EN, Laaksonen A. The Effect of Single-Atomic Ions on the Melting of Microscopic Ice Particles According to Molecular Dynamics Data. COLLOID JOURNAL 2018. [DOI: 10.1134/s1061933x1805006x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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14
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Shevkunov SV. Mechanisms for ion retention in molecular water clusters in a planar nanopore against the background of thermal fluctuations. COLLOID JOURNAL 2017. [DOI: 10.1134/s1061933x17030140] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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15
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Shevkunov SV. Structure and electric properties of sodium ion hydrate shell in nanopore with hydrophilic walls. RUSS J ELECTROCHEM+ 2016. [DOI: 10.1134/s1023193516090093] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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16
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Shevkunov SV. Effect of hydrophilic walls on the hydration of sodium cations in planar nanopores. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2016. [DOI: 10.1134/s0036024416080276] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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17
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Shevkunov SV. Structure and electric properties of the hydration shell of a singly charged chloride ion in a nanopore with hydrophilic walls. RUSS J ELECTROCHEM+ 2016. [DOI: 10.1134/s1023193516050116] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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18
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Shevkunov SV. Computer simulation of the hydration of a chloride anion in a nanopore with hydrophilic walls. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2016. [DOI: 10.1134/s0036024416050290] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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19
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Shevkunov SV. Water vapor clustering in the field of Na+ cation inside a nanopore with hydrophilic walls. 1. Spatial organization. COLLOID JOURNAL 2016. [DOI: 10.1134/s1061933x16020125] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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20
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Shevkunov SV. Hydration of Cl– ion in a planar nanopore with hydrophilic walls. 1. Molecular structure. COLLOID JOURNAL 2016. [DOI: 10.1134/s1061933x15060186] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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21
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Tse YLS, Chen C, Lindberg GE, Kumar R, Voth GA. Propensity of Hydrated Excess Protons and Hydroxide Anions for the Air-Water Interface. J Am Chem Soc 2015; 137:12610-6. [PMID: 26366480 DOI: 10.1021/jacs.5b07232] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Significant effort has been undertaken to better understand the molecular details governing the propensity of ions for the air-water interface. Facilitated by computationally efficient reactive molecular dynamics simulations, new and statistically conclusive molecular-scale results on the affinity of the hydrated excess proton and hydroxide anion for the air-water interface are presented. These simulations capture the dynamic bond breaking and formation processes (charge defect delocalization) that are important for correctly describing the solvation and transport of these complex species. The excess proton is found to be attracted to the interface, which is correlated with a favorable enthalpic contribution and consistent with reducing the disruption in the hydrogen bond network caused by the ion complex. However, a recent refinement of the underlying reactive potential energy function for the hydrated excess proton shows the interfacial attraction to be weaker, albeit nonzero, a result that is consistent with the experimental surface tension measurements. The influence of a weak hydrogen bond donated from water to the protonated oxygen, recently found to play an important role in excess hydrated proton transport in bulk water, is seen to also be important for this study. In contrast, the hydroxide ion is found to be repelled from the air-water interface. This repulsion is characterized by a reduction of the energetically favorable ion-water interactions, which creates an enthalpic penalty as the ion approaches the interface. Finally, we find that the fluctuation in the coordination number around water sheds new light on the observed entropic trends for both ions.
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Affiliation(s)
- Ying-Lung Steve Tse
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, and Computation Institute, The University of Chicago , Chicago, Illinois 60637, United States
| | - Chen Chen
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, and Computation Institute, The University of Chicago , Chicago, Illinois 60637, United States.,College of Chemistry and Molecular Sciences, Hubei Key Lab of Electrochemical Power Sources, Wuhan University , Wuhan 430072, China
| | - Gerrick E Lindberg
- Department of Chemistry and Biochemistry, Northern Arizona University , Flagstaff, Arizona 86011, United States
| | - Revati Kumar
- Department of Chemistry, Louisiana State University , Baton Rouge, Louisiana 70803, United States
| | - Gregory A Voth
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, and Computation Institute, The University of Chicago , Chicago, Illinois 60637, United States
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Liu F, Wang F, Jia G, Huang K. Molecular dynamics simulation of the cooperative effect by different force fields in monosodium glutamate aqueous solution. RSC Adv 2015. [DOI: 10.1039/c4ra11328d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Different force fields (GROMOS and OPLS) in conjunction with different water (SPC, SPCE, TIP3P, TIP4P and TIP5P) were assessed using molecular dynamics simulations of monosodium glutamate (MSG) aqueous solution.
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Affiliation(s)
- Fenghai Liu
- Sichuan University
- College of Electronic and Information Engineering
- Cheng Du
- China
| | - Feng Wang
- Sichuan Normal University
- College of Physics and Electronic Engineering
- Cheng Du
- China
| | - Guozhu Jia
- Sichuan Normal University
- College of Physics and Electronic Engineering
- Cheng Du
- China
| | - Kama Huang
- Sichuan University
- College of Electronic and Information Engineering
- Cheng Du
- China
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24
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Shevkunov SV. The hydrate shell of a Cl− ion in a planar nanopore. Thermodynamic stability. RUSS J ELECTROCHEM+ 2014. [DOI: 10.1134/s102319351412009x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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25
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Shevkunov SV. Thermodynamic characteristics of the hydrate shell of a Na+ ion in a plane nanopore with hydrophobic walls. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2014. [DOI: 10.1134/s0036024414120309] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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26
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Shevkunov SV. Water vapor clustering in the field of a chlorine anion occurring in a planar nanopore with structureless walls. COLLOID JOURNAL 2014. [DOI: 10.1134/s1061933x14040139] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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27
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Boda A, Ali SM. From microhydration to bulk hydration of Rb+ metal ion: DFT, MP2 and AIMD simulation study. J Mol Liq 2013. [DOI: 10.1016/j.molliq.2012.12.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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28
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Semino R, Martí J, Guàrdia E, Laria D. Excess protons in mesoscopic water-acetone nanoclusters. J Chem Phys 2012. [DOI: 10.1063/1.4766201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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29
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Daub CD, Cann NM. Molecular Dynamics Simulations to Examine Structure, Energetics, and Evaporation/Condensation Dynamics in Small Charged Clusters of Water or Methanol Containing a Single Monatomic Ion. J Phys Chem A 2012; 116:10488-95. [DOI: 10.1021/jp308217q] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Christopher D. Daub
- Department of Chemistry, Queen’s University, 90 Bader
Lane, Kingston,
Ontario, Canada K7L3N6
| | - Natalie M. Cann
- Department of Chemistry, Queen’s University, 90 Bader
Lane, Kingston,
Ontario, Canada K7L3N6
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30
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Boda A, De S, Ali SM, Tulishetti S, Khan S, Singh JK. From microhydration to bulk hydration of Sr2+ metal ion: DFT, MP2 and molecular dynamics study. J Mol Liq 2012. [DOI: 10.1016/j.molliq.2012.05.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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31
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First principles study and database analyses of structural preferences for sodium ion (Na+) solvation and coordination. Struct Chem 2012. [DOI: 10.1007/s11224-012-0032-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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32
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Ahadi E, Konermann L. Ejection of Solvated Ions from Electrosprayed Methanol/Water Nanodroplets Studied by Molecular Dynamics Simulations. J Am Chem Soc 2011; 133:9354-63. [DOI: 10.1021/ja111492s] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Elias Ahadi
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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33
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Shevkunov SV. Crisis of stability of hydration shell of Na+ ion in condensing water vapor. COLLOID JOURNAL 2011. [DOI: 10.1134/s1061933x11020128] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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34
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Shevkunov SV. Nucleation of water vapor on Na+Cl− ion pairs: Computer simulation. COLLOID JOURNAL 2011. [DOI: 10.1134/s1061933x11010170] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Saeki M, Ishiuchi SI, Sakai M, Hashimoto K, Fujii M. Structural Evolution of (1-NpOH)n Clusters Studied by R2PI and IR Dip Spectroscopies. J Phys Chem A 2010; 114:11210-5. [DOI: 10.1021/jp102849q] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Morihisa Saeki
- Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan, Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan, and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 minami-Osawa, Hachioji, 192-0397, Japan
| | - Shun-ichi Ishiuchi
- Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan, Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan, and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 minami-Osawa, Hachioji, 192-0397, Japan
| | - Makoto Sakai
- Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan, Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan, and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 minami-Osawa, Hachioji, 192-0397, Japan
| | - Kenro Hashimoto
- Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan, Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan, and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 minami-Osawa, Hachioji, 192-0397, Japan
| | - Masaaki Fujii
- Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan, Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan, and Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 minami-Osawa, Hachioji, 192-0397, Japan
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37
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Arillo Flores OI, Bernal-Uruchurtu MI. Charge Separation Process in Water Clusters Containing HCl. Molecular Dynamics Study Using Semiempirical Hamiltonians. J Phys Chem A 2010; 114:8975-83. [DOI: 10.1021/jp101803r] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Oscar Ivan Arillo Flores
- Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos 62209, Mexico
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38
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Ahadi E, Konermann L. Surface Charge of Electrosprayed Water Nanodroplets: A Molecular Dynamics Study. J Am Chem Soc 2010; 132:11270-7. [DOI: 10.1021/ja1041989] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Elias Ahadi
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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39
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Xu J, Izvekov S, Voth GA. Structure and Dynamics of Concentrated Hydrochloric Acid Solutions. J Phys Chem B 2010; 114:9555-62. [DOI: 10.1021/jp102516h] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Jianqing Xu
- Department of Chemistry, James Franck Institute, and Computation Institute, University of Chicago, 5735 S. Ellis Ave, Chicago, Illinois 60637; and Center for Biophysical Modeling and Simulation and Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850
| | - Sergei Izvekov
- Department of Chemistry, James Franck Institute, and Computation Institute, University of Chicago, 5735 S. Ellis Ave, Chicago, Illinois 60637; and Center for Biophysical Modeling and Simulation and Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850
| | - Gregory A. Voth
- Department of Chemistry, James Franck Institute, and Computation Institute, University of Chicago, 5735 S. Ellis Ave, Chicago, Illinois 60637; and Center for Biophysical Modeling and Simulation and Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850
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40
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Yan T, Wang Y, Knox C. On the Structure of Ionic Liquids: Comparisons between Electronically Polarizable and Nonpolarizable Models I. J Phys Chem B 2010; 114:6905-21. [DOI: 10.1021/jp9089112] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Tianying Yan
- Institute of New Energy Material Chemistry and Department of Material Chemistry, Nankai University, Tianjin 300071, China, Key Laboratory of Frontiers in Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, 55 East Zhongguancun Road, Beijing, 100190, China, and Center for Biophysical Modeling and Simulation and Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850
| | - Yanting Wang
- Institute of New Energy Material Chemistry and Department of Material Chemistry, Nankai University, Tianjin 300071, China, Key Laboratory of Frontiers in Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, 55 East Zhongguancun Road, Beijing, 100190, China, and Center for Biophysical Modeling and Simulation and Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850
| | - Craig Knox
- Institute of New Energy Material Chemistry and Department of Material Chemistry, Nankai University, Tianjin 300071, China, Key Laboratory of Frontiers in Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, 55 East Zhongguancun Road, Beijing, 100190, China, and Center for Biophysical Modeling and Simulation and Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850
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41
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Yamashita T, Voth GA. Properties of hydrated excess protons near phospholipid bilayers. J Phys Chem B 2010; 114:592-603. [PMID: 19924872 DOI: 10.1021/jp908768c] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The behavior of the hydrated excess proton near different lipid membranes is studied with the third generation of the multistate empirical valence bond (MS-EVB3) model [Wu, Y. J.; Chen, H. N.; Wang, F.; Paesani, F.; Voth, G. A. J. Phys. Chem. B 2008, 112, 467]. Dioleoylphosphatidylcholine (DOPC), dioleoylphosphatidylethanolamine (DOPE), and dioleoylphosphatidylglycerol (DOPG) are selected as example lipids. In spite of the differences of the head groups, the molecular dynamics simulations show that all the lipid membranes have a proton-collecting antenna effect with no free energy barrier between the bulk water and interface regions. By comparison with classical hydronium model simulations, it is found that an appropriate description of proton Grotthuss shuttling and associated charge defect delocalization are necessary to obtain the correct free energy profile for the hydrated excess proton. In addition, nanosecond time scale sampling is essential to evaluate the free energy profiles, because certain slow motions are needed to stabilize the excess proton in the deep membrane interface region. It is also found that the lateral diffusion coefficients are 1 order of magnitude smaller in the interface region than in bulk water for all the lipids. These coefficients are almost the same as those of the lipid head groups. Finally, since the lipid phosphates may possibly be protonated due to the proton antenna effect of the membrane, phosphate group protonation is investigated and discussed within the MS-EVB framework.
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Affiliation(s)
- Takefumi Yamashita
- Center of Biophysical Modeling and Simulation and Department of Chemistry, University of Utah, 315 South 1400 East, Room 2020, Salt Lake City, Utah 84112-0850, USA
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42
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Shevkunov SV. Charge separation in Na+Cl-(H2O) n clusters in water vapors. 2. Free energy. COLLOID JOURNAL 2010. [DOI: 10.1134/s1061933x10010126] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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43
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De S, Ali SM, Ali A, Gaikar VG. Micro-solvation of the Zn2+ ion-a case study. Phys Chem Chem Phys 2009; 11:8285-94. [PMID: 19756285 DOI: 10.1039/b902422k] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The structures and thermodynamic parameters of hydrated zinc ion clusters incorporating a single zinc ion and up to eighteen water molecules have been determined with a quantum mechanical hybrid density functional, namely B3LYP using cc-PVDZ basis functions for H and O and a split valence 6-31G (d, p) basis function for Zn. The geometries for all the zinc ion water clusters are optimized with several initial guess structures and without imposing any initial symmetry restriction. Zinc metal ion is found to be preferably four coordinated for smaller sizes of hydrated cluster but attains an octahedral coordination for larger sizes (n >or= 11) of hydrated cluster. Structures with seven or more than seven water molecules attached directly to the central zinc ion are not found. The calculated gas phase coordination number in the first solvation sphere of a large hydrated zinc metal ion is found to be six and the same is also confirmed in the force field based classical molecular dynamics simulation study for an aqueous zinc ion and thus confirms the experimental findings. The equilibrium zinc-oxygen distance of 2.09328 A at the present B3LYP level of study is in excellent agreement with the X-ray diffraction result of 2.093 +/- 0.002 A for a hexahydrated zinc cluster.
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Affiliation(s)
- Sulagna De
- Chemical Engineering Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
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44
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Hock C, Schmidt M, Kuhnen R, Bartels C, Ma L, Haberland H, van Issendorff B. Calorimetric observation of the melting of free water nanoparticles at cryogenic temperatures. PHYSICAL REVIEW LETTERS 2009; 103:073401. [PMID: 19792643 DOI: 10.1103/physrevlett.103.073401] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2009] [Indexed: 05/28/2023]
Abstract
We present an experimental study of the thermodynamics of free, size-selected water cluster anions consisting of 48 and 118 molecules. The measured caloric curves of the clusters are bulklike at low temperatures but show a well-defined, particle-size specific transition at 93+/-3 K for (H2O)48- and 118+/-3 K for (H2O)118-. At the transition temperature the heat capacity strongly increases, which marks the onset of melting.
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Affiliation(s)
- C Hock
- Universität Freiburg, Hermann-Herder-Strasse 3, Freiburg 79104, Germany
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45
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Shevkunov SV. Polarization effects in Cl−(H2O) n clusters. Computer simulation. COLLOID JOURNAL 2009. [DOI: 10.1134/s1061933x0903017x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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46
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Jungwirth P. Spiers Memorial Lecture. Ions at aqueous interfaces. Faraday Discuss 2009; 141:9-30; discussion 81-98. [PMID: 19227348 DOI: 10.1039/b816684f] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Studies of aqueous interfaces and of the behavior of ions therein have been profiting from a recent remarkable progress in surface selective spectroscopies, as well as from developments in molecular simulations. Here, we summarize and place in context our investigations of ions at aqueous interfaces employing molecular dynamics simulations and electronic structure methods, performed in close contact with experiment. For the simplest of these interfaces, i.e. the open water surface, we demonstrate that the traditional picture of an ion-free surface is not valid for large, soft (polarizable) ions such as the heavier halides. Both simulations and spectroscopic measurements indicate that these ions can be present and even enhanced at surface of water. In addition we show that the ionic product of water exhibits a peculiar surface behavior with hydronium but not hydroxide accumulating at the air/water and alkane/water interfaces. This result is supported by surface-selective spectroscopic experiments and surface tension measurements. However, it contradicts the interpretation of electrophoretic and titration experiments in terms of strong surface adsorption of hydroxide; an issue which is further discussed here. The applicability of the observed behavior of ions at the water surface to investigations of their affinity for the interface between proteins and aqueous solutions is explored. Simulations show that for alkali cations the dominant mechanism of specific interactions with the surface of hydrated proteins is via ion pairing with negatively charged amino acid residues and with the backbone amide groups. As far as halide anions are concerned, the lighter ones tend to pair with positively charged amino acid residues, while heavier halides exhibit affinity to the amide group and to non-polar protein patches, the latter resembling their behavior at the air/water interface. These findings, together with results for more complex molecular ions, allow us to formulate a local model of interactions of ions with proteins with the aim to rationalize at the molecular level ion-specific Hofmeister effects, e.g. the salting out of proteins.
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Affiliation(s)
- Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic and Center for Complex Molecular Systems and Biomolecules, Prague, Czech Republic.
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47
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Iuchi S, Chen H, Paesani F, Voth GA. Hydrated Excess Proton at Water−Hydrophobic Interfaces. J Phys Chem B 2008; 113:4017-30. [DOI: 10.1021/jp805304j] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Satoru Iuchi
- Department of Chemistry and Center for Biophysical Modeling and Simulation, University of Utah, 315 South 1400 East, Room 2020, Salt Lake City, Utah 84112-0850
| | - Hanning Chen
- Department of Chemistry and Center for Biophysical Modeling and Simulation, University of Utah, 315 South 1400 East, Room 2020, Salt Lake City, Utah 84112-0850
| | - Francesco Paesani
- Department of Chemistry and Center for Biophysical Modeling and Simulation, University of Utah, 315 South 1400 East, Room 2020, Salt Lake City, Utah 84112-0850
| | - Gregory A. Voth
- Department of Chemistry and Center for Biophysical Modeling and Simulation, University of Utah, 315 South 1400 East, Room 2020, Salt Lake City, Utah 84112-0850
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48
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Kurtz I, Kraut J, Ornekian V, Nguyen MK. Acid-base analysis: a critique of the Stewart and bicarbonate-centered approaches. Am J Physiol Renal Physiol 2008; 294:F1009-31. [PMID: 18184741 DOI: 10.1152/ajprenal.00475.2007] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
When approaching the analysis of disorders of acid-base balance, physical chemists, physiologists, and clinicians, tend to focus on different aspects of the relevant phenomenology. The physical chemist focuses on a quantitative understanding of proton hydration and aqueous proton transfer reactions that alter the acidity of a given solution. The physiologist focuses on molecular, cellular, and whole organ transport processes that modulate the acidity of a given body fluid compartment. The clinician emphasizes the diagnosis, clinical causes, and most appropriate treatment of acid-base disturbances. Historically, two different conceptual frameworks have evolved among clinicians and physiologists for interpreting acid-base phenomena. The traditional or bicarbonate-centered framework relies quantitatively on the Henderson-Hasselbalch equation, whereas the Stewart or strong ion approach utilizes either the original Stewart equation or its simplified version derived by Constable. In this review, the concepts underlying the bicarbonate-centered and Stewart formulations are analyzed in detail, emphasizing the differences in how each approach characterizes acid-base phenomenology at the molecular level, tissue level, and in the clinical realm. A quantitative comparison of the equations that are currently used in the literature to calculate H+concentration ([H+]) is included to clear up some of the misconceptions that currently exist in this area. Our analysis demonstrates that while the principle of electroneutrality plays a central role in the strong ion formulation, electroneutrality mechanistically does not dictate a specific [H+], and the strong ion and bicarbonate-centered approaches are quantitatively identical even in the presence of nonbicarbonate buffers. Finally, our analysis indicates that the bicarbonate-centered approach utilizing the Henderson-Hasselbalch equation is a mechanistic formulation that reflects the underlying acid-base phenomenology.
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Affiliation(s)
- Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic and Center for Complex Molecular Systems and Biomolecules, 16610 Prague 6, Czech Republic;
| | - Bernd Winter
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, D-12489 Berlin, Germany;
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50
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Li S, Cao Z, Peng Y, Liu L, Wang Y, Wang S, Wang JQ, Yan T, Gao XP, Song DY, Shen PW. Molecular dynamics simulation of LiTFSI-acetamide electrolytes: structural properties. J Phys Chem B 2008; 112:6398-410. [PMID: 18444674 DOI: 10.1021/jp710898h] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The liquid structures of nonaqueous electrolytes composed of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and acetamide, with LiTFSI/acetamide molar ratios of 1:2, 1:4, and 1:6, were studied by molecular dynamics simulations. The simulations indicate that the Li+ cations prefer to be six-coordinate by the sulfonyl oxygen atoms of the TFSI- anions and the carbonyl oxygen atoms of the acetamide molecules, rather than by the most electronegative nitrogen atom of the TFSI- anion. Therefore, close Li+-TFSI- contact pairs exist in the system. The TFSI- anion prefers to provide only one of four possible oxygen atoms to coordinate to the same Li+ cation. Three conformations (cis, trans, and gauche) of the TFSI- anions were found to coexist in the liquid electrolyte. At high salt concentrations, the TFSI- anions mainly adopt the gauche conformation in order to provide more oxygen atoms to coordinate to different Li+ cations, while simultaneously reducing the repulsion among the Li+ cations. On the other hand, the fraction of TFSI- anions adopting the cis conformation is largest for the system with the molar ratio of 1:6, in which many clusters, mainly composed of the Li+ cations and the TFSI- anions, are immersed in the acetamide molecules. The size and charge distribution of clusters were also investigated. In the system with the molar ratio of 1:2, nearly all of the ions in the PBC (periodic boundary conditions) box aggregate into a bulky cluster that gradually disassembles into small clusters with decreasing salt concentration. The addition of acetamide molecules was found to effectively relax the liquid electrolyte structure, and the system with the molar ratio of 1:4 was found to exhibit a more homogeneous liquid structure than the other two electrolyte systems with molar ratios of 1:2 and 1:6.
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Affiliation(s)
- Shu Li
- Institute of New Energy Material Chemistry, Department of Material Chemistry, Nankai University, Tianjin 300071, China
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