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Persson I. Structure and size of complete hydration shells of metal ions and inorganic anions in aqueous solution. Dalton Trans 2024. [PMID: 39211949 DOI: 10.1039/d4dt01449a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/04/2024]
Abstract
The structures of nine hydrated metal ions in aqueous solution have been redetermined by large angle X-ray scattering to obtain experimental data of better quality than those reported 40-50 years ago. Accurate M-OI and M-(OI-H)⋯OII distances and M-OI(H)⋯OII bond angles are reported for the hydrated magnesium(II), aluminium(III), manganese(II), iron(II), iron(III), cobalt(II), nickel(II), copper(II) and zinc(II) ions; the subscripts I and II denote oxygen atoms in the first and second hydration sphere, respectively. Reported structures of hydrated metal ions in aqueous solution are summarized and evaluated with emphasis on a possible relationship between M-OI-OII bond angles and bonding character. Metal ions with high charge density have M-OI-OII bond angles close to 120°, indicative of a mainly electrostatic interaction with the oxygen atom in the water molecule in the first hydration shell. Metal ions forming bonds with a significant covalent contribution, as e.g. mercury(II) and tin(II), have M-OI-OII bond angles close to 109.5°. This implies that they bind to one of the free electron pairs in the water molecule. Comparison of M-O bond distances of hydrated metal ions in the solid state with one hydration shell, and in aqueous solution with in most cases at least two hydration shells, shows no significant differences. On the other hand, the X-O bond distance in hydrated oxoanions increases by ca. 0.02 Å in aqueous solution in comparison with the corresponding X-O distance in the solid state. A linear correlation is observed between volume, calculated from the van der Waals radius of the hydrated ion, and the ionic diffusion coefficient in aqueous solution. This correlation strongly indicates that monovalent metal ions, except lithium and silver(I), and singly-charged monovalent oxoanions have a single hydration shell. Divalent metal ions, bismuth(III) and the lanthanoid(III) and actinoid(III) ions have two hydration shells. Trivalent transition and tetravalent metal ions have two full hydration shells and portion of a third one. Doubly charged oxoanions have one well-defined hydration shell and an ill-defined second one.
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Affiliation(s)
- Ingmar Persson
- Department of Molecular Sciences, Swedish University of Agricultural Sciences, P.O. Box 7015, SE-750 07 Uppsala, Sweden.
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2
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Qian C, Zhou K. Ab Initio Molecular Dynamics Investigation of the Solvation States of Hydrated Ions in Confined Water. Inorg Chem 2023; 62:17756-17765. [PMID: 37855150 DOI: 10.1021/acs.inorgchem.3c02443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2023]
Abstract
Ionic transport in nanoscale channels with a critical size comparable to that of ions and solutes exhibits exceptional performance in water desalination, ion separation, electrocatalysts, and supercapacitors. However, the solvation states (SSs), i.e., the hydration structures and probability distribution, of hydrated ions in nanochannels differ from those in the bulk and the perspective of continuum theory. In this work, we conduct ab initio enhanced-sampling atomistic simulations to investigate the ion-specific SSs of monovalent ions (including Li+, Na+, K+, F-, Cl-, and I-) in the graphene channel with a width of 1 nm. Our findings highlight that the SSs of those ions are primarily determined by ion-water hydration, where ion-wall interactions play a minor role. The distribution of ions in layered confined water is a result of ion-specific hydration, which arises from the synergy of entropy and enthalpy. The free energy barriers for transitions between SSs are on the order of 1kBT, allowing for modulation through applying external fields or modifying surface properties. As the ion-wall interaction strengthens, as observed in vermiculite and carbides and nitrides of transition metal channels, the probability of near-wall SSs increases. These results help to improve the performance of nanofluidic devices and provide crucial insights for developing accurate force fields of molecular simulations or advanced theoretical approaches for ion dynamics in confined channels.
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Affiliation(s)
- Chen Qian
- College of Energy, Soochow Institute for Energy and Materials InnovationS (SIEMIS), Jiangsu Provincial Key Laboratory for Advanced Carbon Materials and Wearable Energy Technologies, Soochow University, Suzhou 215006, China
- Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon 999077, Hong Kong, China
| | - Ke Zhou
- College of Energy, Soochow Institute for Energy and Materials InnovationS (SIEMIS), Jiangsu Provincial Key Laboratory for Advanced Carbon Materials and Wearable Energy Technologies, Soochow University, Suzhou 215006, China
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3
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Chang H, Lozier EH, Ma E, Geiger FM. Quantification of Stern Layer Water Molecules, Total Potentials, and Energy Densities at Fused Silica:Water Interfaces for Adsorbed Alkali Chlorides, CTAB, PFOA, and PFAS. J Phys Chem A 2023; 127:8404-8414. [PMID: 37775181 DOI: 10.1021/acs.jpca.3c04434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/01/2023]
Abstract
We have employed amplitude- and phase-resolved second-harmonic generation spectroscopy to investigate ion-specific effects of monovalent cations at the fused silica:water interface maintained under acidic, neutral, and alkaline conditions. We find a negligible dependence of the total potential (as negative as -400 mV at pH 14), the second-order nonlinear susceptibility (as large as 1.5 × 10-21 m2 V-1 at pH 14), the number of Stern layer water molecules (1 × 1015 cm-2 at pH 5.8), and the energy associated with water alignment upon going from neutral to high pH (ca. -24 kJ mol-1 to -48 kJ mol-1 at pH 13 and 14, close to the cohesive energy of liquid water but smaller than that of ice) on chlorides of the alkali series (M+ = Li+, Na+, K+, Rb+, and Cs+). Attempts are presented to provide estimates for the molecular hyperpolarizability of the cations and anions in the Stern layer at high pH, which arrive at ca. 20-fold larger values for αtotal ions(2) = αM+(2) + αOH-(2) + αCl-(2) when compared to water's molecular hyperpolarizability estimate from theory and point to a sizable contribution of deprotonated silanol groups at high pH. In contrast to the alkali series, a pronounced dependence of the total potential and the second-order nonlinear susceptibility on monovalent cationic (cetrimonium bromide, CTAB) and anionic (perfluorooctanoic and perfluorooctanesulfonic acid, PFOA and PFOS) surfactants was quantifiable. Our findings are consistent with a low surface coverage of the alkali cations and a high surface coverage of the surfactants. Moreover, they underscore the important contribution of Stern layer water molecules to the total potential and second-order nonlinear susceptibility. Finally, they demonstrate the applicability of heterodyne-detected second-harmonic generation spectroscopy for identifying perfluorinated acids at mineral:water interfaces.
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Affiliation(s)
- HanByul Chang
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Emilie H Lozier
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Emily Ma
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Franz M Geiger
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
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4
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Zhou K, Qian C, Liu Y. Quantifying the Structure of Water and Hydrated Monovalent Ions by Density Functional Theory-Based Molecular Dynamics. J Phys Chem B 2022; 126:10471-10480. [PMID: 36451081 DOI: 10.1021/acs.jpcb.2c05330] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
The accurate description of the structures of water and hydrated ions is important in electrochemical desalination, ion separation, and supercapacitors. In this work, we present an ab initio atomistic simulation-based study to explore the structure of water and hydrated monovalent ions (Li+, Na+, K+, Rb+, F-, and Cl-) at ambient conditions using generalized gradient approximation (GGA)-based methods with and without van der Waals correction (PBE, PBE + D3, and revPBE + D3) and recently developed strongly constrained and appropriately normed (SCAN) meta-GGA. We find that both revPBE + D3 and SCAN can well capture the structure of bulk water with +30 K artificial high temperature in contrast to overstructuring water using PBE and PBE + D3. However, being the same as PBE + D3, revPBE + D3 overestimates the structure of the hydration shell, especially for monovalent cations. Surprisingly, SCAN can well match the experimental results of hydrated monovalent ions. Detailed structure analyzes of entropy reveal that the hydration shell under the level of PBE + D3 and revPBE + D3 is more disordered and looser than SCAN. The successful prediction of the flexible SCAN functional could facilitate the exploration of complex ionic processes in the aqueous phase, the interactions of hydrated ions with surfaces, and solvation states in nanopores at an accurate, efficient, predictive, and ab initio level.
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Affiliation(s)
- Ke Zhou
- College of Energy, Soochow Institute for Energy and Materials InnovationS (SIEMIS), Jiangsu Provincial Key Laboratory for Advanced Carbon Materials and Wearable Energy Technologies, Soochow University, Suzhou215006, China.,Laboratory for Multiscale Mechanics and Medical Science, SV LAB, School of Aerospace, Xi'an Jiaotong University, Xi'an710049, China
| | - Chen Qian
- Department of Mechanical Engineering, Zhejiang University, Hangzhou310058, China
| | - Yilun Liu
- Laboratory for Multiscale Mechanics and Medical Science, SV LAB, School of Aerospace, Xi'an Jiaotong University, Xi'an710049, China
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5
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Lin L, Liu Z, Premadasa UI, Li T, Ma YZ, Sacci RL, Katsaras J, Hong K, Collier CP, Carrillo JMY, Doughty B. The Unexpected Role of Cations in the Self-Assembly of Positively Charged Amphiphiles at Liquid/Liquid Interfaces. J Phys Chem Lett 2022; 13:10889-10896. [PMID: 36394318 DOI: 10.1021/acs.jpclett.2c02921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Conventional wisdom suggests that cations play a minimal role in the assembly of cationic amphiphiles. Here, we show that at liquid/liquid (L/L) interfaces, specific cation effects can modulate the assemblies of hydrophobic tails in an oil phase despite being attached to cationic headgroups in the aqueous phase. We used oligo-dimethylsiloxane (ODMS) methyl imidazolium amphiphiles to identify these specific interactions at hexadecane/aqueous interfaces. Small cations, such as Li+, bind to the O atoms in the ODMS tail and pin it to the interface, thereby imposing a kinked conformation─as evidenced by vibrational sum frequency generation spectroscopy and molecular dynamics simulations. While larger Cs+ ions more readily partition to the interface, they do not form analogous complexes. Our data not only point to ways for controlling amphiphile structure at L/L interfaces but also suggest a means for the separation of Li+, or related applications, in soft-matter electronics.
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Affiliation(s)
- Lu Lin
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Zening Liu
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Uvinduni I Premadasa
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Tianyu Li
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee37996, United States
| | - Ying-Zhong Ma
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Robert L Sacci
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - John Katsaras
- Laboratories and Soft Matter Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
- Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Kunlun Hong
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - C Patrick Collier
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Jan-Michael Y Carrillo
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
| | - Benjamin Doughty
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee37831, United States
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6
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Lunkenheimer K, Prescher D, Geggel K. Role of Counterions in the Adsorption and Micellization Behavior of 1:1 Ionic Surfactants at Fluid Interfaces─Demonstrated by the Standard Amphiphile System of Alkali Perfluoro- n-octanoates. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:891-902. [PMID: 34995078 PMCID: PMC8793141 DOI: 10.1021/acs.langmuir.1c00527] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 12/21/2021] [Indexed: 06/14/2023]
Abstract
In our latest communication, we proved experimentally that the ionic surfactant's surface excess is exclusively determined by the size of the hydrated counterion.[Lunkenheimer , Langmuir, 2017, 33, 10216-1022410.1021/acs.langmuir.7b00786]. However, at this stage of research, we were unable to decide whether this does only hold for the two or three lightest ions of lithium, sodium, and potassium, respectively. Alternatively, we could also consider the surface excess of the heavier hydrated alkali ions of potassium, rubidium, and cesium, having practically identical ion size, as being determined by the cross-sectional area of the related anionic extended chain residue. The latter assumption has represented state of art. Searching for reliable experimental results on the effect of the heavier counterions on the boundary layer, we have extended investigations to the amphiphiles' solutions of concentrations above the critical concentration of micelle formation (cmc).We provided evidence that the super-micellar solutions' equilibrium surface tension will remain constant provided the required conditions are followed. The related σcmc-value represents a parameter characteristic of the ionic surfactant's adsorption and micellization behavior. Evaluating the amphiphile's surface excess obtained from adsorption as a function of the related amphiphile's σcmc-value enables you to calculate the radius of the hydrated counterion valid in sub- and super-micellar solution likewise. The σcmc-value is directly proportional to the counterion's diameter concerned. Taking additionally into account the radii of naked ions known from crystal research, we succeeded in exactly discriminating the hydrated alkali ions' size from each other. There is a distinct sequence of hydration radii in absolute scale following the inequality, Li+ > Na+ > K+ > (NH4)+ > Rb+ > Cs+. Therefore, we have to extend our model of counterion effectiveness put forward in our previous communication. It represents a general principle of the counterion effect.
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Affiliation(s)
- Klaus Lunkenheimer
- Max-Planck-Institut
für Kolloid- und Grenzflächenforschung, Am Mühlenberg 1, Potsdam D-14476, Germany
| | - Dietrich Prescher
- Max-Planck-Institut
für Kolloid- und Grenzflächenforschung, Am Mühlenberg 1, Potsdam D-14476, Germany
| | - Katrina Geggel
- Max-Planck-Institut
für Kolloid- und Grenzflächenforschung, Am Mühlenberg 1, Potsdam D-14476, Germany
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7
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Kameda Y, Tsutsui K, Amo Y, Usuki T, Ikeda K, Otomo T. Direct Observation of Scattering Angle Dependence of the Inelasticity Effect on the Interference Term Obtained from Time-of-Flight Neutron Diffraction Experiments. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2021. [DOI: 10.1246/bcsj.20210315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Yasuo Kameda
- Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-machi, Yamagata 990-8560, Japan
| | - Kana Tsutsui
- Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-machi, Yamagata 990-8560, Japan
| | - Yuko Amo
- Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-machi, Yamagata 990-8560, Japan
| | - Takeshi Usuki
- Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-machi, Yamagata 990-8560, Japan
| | - Kazutaka Ikeda
- Institute of Material Structure Science, KEK, 1-1 Oho, Ibaraki 305-080, Japan
| | - Toshiya Otomo
- Institute of Material Structure Science, KEK, 1-1 Oho, Ibaraki 305-080, Japan
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8
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Kameda Y, Kowaguchi M, Tsutsui K, Amo Y, Usuki T, Ikeda K, Otomo T. Experimental Determination of Relationship between Intramolecular O-D Bond Length and Its Stretching Vibrational Frequency of D 2O Molecule in the Liquid State. J Phys Chem B 2021; 125:11285-11291. [PMID: 34605237 DOI: 10.1021/acs.jpcb.1c07527] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Experimental evidence has been obtained for the structure-spectra relationship of hydrogen bonds in aqueous solutions. Intramolecular O-D distance, rOD, has been determined by the least-squares fitting analysis of the neutron interference term in the high-Q region observed for pure D2O and concentrated aqueous solutions. The average O-D stretching frequency, νOD, has been obtained from the position of the center of gravity of the observed ATR-IR O-D stretching band. The linear relationship between rOD and νOD has been confirmed in the liquid state. The slope of dνOD/drOD is evaluated to be -21 000 ± 1000 cm-1 Å-1.
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Affiliation(s)
- Yasuo Kameda
- Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, 1-4-12, Kojirakawa-machi, Yamagata City, Yamagata 990-8560, Japan
| | - Misaki Kowaguchi
- Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, 1-4-12, Kojirakawa-machi, Yamagata City, Yamagata 990-8560, Japan
| | - Kana Tsutsui
- Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, 1-4-12, Kojirakawa-machi, Yamagata City, Yamagata 990-8560, Japan
| | - Yuko Amo
- Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, 1-4-12, Kojirakawa-machi, Yamagata City, Yamagata 990-8560, Japan
| | - Takeshi Usuki
- Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, 1-4-12, Kojirakawa-machi, Yamagata City, Yamagata 990-8560, Japan
| | - Kazutaka Ikeda
- Institute of Material Structure Science, KEK, Tsukuba, Ibaraki 305-080, Japan
| | - Toshiya Otomo
- Institute of Material Structure Science, KEK, Tsukuba, Ibaraki 305-080, Japan
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9
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Watanabe H, Arai N, Nozaki E, Han J, Fujii K, Ikeda K, Otomo T, Ueno K, Dokko K, Watanabe M, Kameda Y, Umebayashi Y. Local Structure of Li + in Superconcentrated Aqueous LiTFSA Solutions. J Phys Chem B 2021; 125:7477-7484. [PMID: 34196549 DOI: 10.1021/acs.jpcb.1c04693] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
It has been reported that aqueous lithium ion batteries (ALIBs) can operate beyond the electrochemical window of water by using a superconcentrated electrolyte aqueous solution. The liquid structure, particularly the local structure of the Li+, which is rather different from conventional dilute solution, plays a crucial role in realizing the ALIB. To reveal the local structure around Li+, the superconcentrated LiTFSA (TFSA: bis(trifluoromethylsulfonil)amide) aqueous solutions were investigated by means of Raman spectroscopic experiments, high-energy X-ray total scattering measurements, and the neutron diffraction technique with different isotopic composition ratios of 6Li/7Li and H/D. The Li+ local structure changes with the increase of the LiTFSA concentration; the oligomer ([Lip(TFSA)q](p-q)+ (q > 2) forms at the molar fraction of LiTFSA (xLiTFSA) > 0.25. The average structure can be determined in which two water molecules and two oxygen atoms of TFSA anion(s) coordinate to the Li+ in the superconcentrated LiTFSA aqueous solution (LiTFSA)0.25(H2O)0.75. In addition, the intermolecular interaction between the neighboring water molecules was not found, and the hydrogen-bonded interaction in the solution should be significantly weak. According to the coordination number of the oxygen atom (TFSA or H2O), a variety of TFSA- and H2O coordination manners would exist in this solution; in particular, the oligomer is formed in which the monodentate TFSA cross-links Li+.
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Affiliation(s)
- Hikari Watanabe
- Graduate School of Science and Technology, Niigata University, 8050 Ikarashi, 2-no-cho, Nishi-ku, Niigata City 950-2181, Japan
| | - Nana Arai
- Graduate School of Science and Technology, Niigata University, 8050 Ikarashi, 2-no-cho, Nishi-ku, Niigata City 950-2181, Japan
| | - Erika Nozaki
- Graduate School of Science and Technology, Niigata University, 8050 Ikarashi, 2-no-cho, Nishi-ku, Niigata City 950-2181, Japan
| | - Jihae Han
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan
| | - Kenta Fujii
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan
| | - Kazutaka Ikeda
- Institute of Materials Structure Science, KEK, Tsukuba 305-0801, Japan
| | - Toshiya Otomo
- Institute of Materials Structure Science, KEK, Tsukuba 305-0801, Japan
| | | | | | | | - Yasuo Kameda
- Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, 1-4-12, Kojirakawa-machi, Yamagata City, Yamagata 990-8560, Japan
| | - Yasuhiro Umebayashi
- Graduate School of Science and Technology, Niigata University, 8050 Ikarashi, 2-no-cho, Nishi-ku, Niigata City 950-2181, Japan
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Alizadeh S, Abdollahy M, Darban AK, Mohseni M. Nitrate ions effects on solvent extraction of rare earth elements from aqueous solutions by D2EHPA: Experimental studies and molecular simulations. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.116015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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11
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Nguyen MTH, Tichacek O, Martinez-Seara H, Mason PE, Jungwirth P. Resolving the Equal Number Density Puzzle: Molecular Picture from Simulations of LiCl(aq) and NaCl(aq). J Phys Chem B 2021; 125:3153-3162. [PMID: 33534574 DOI: 10.1021/acs.jpcb.0c10599] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The change in number densities of aqueous solutions of alkali chlorides should be qualitatively predictable. Typically, as cations get larger, the number density of the solution decreases. However, aqueous solutions of lithium and sodium chloride exhibit at ambient conditions practically identical number densities at equal molalities despite different ionic sizes. Here, we provide an atomistic interpretation of this experimentally observed anomalous behavior using molecular dynamics simulations. The obtained results show that the rigidity of the Li+ first and second solvation shells and the associated compromised hydrogen bonding result in practically equal average water densities in the local hydration regions for Li+ and Na+ despite different sizes of the cations. In addition, in more distant regions from the cations, the water densities of these two solutions also coincide. These findings thus provide an atomistic interpretation for matching number densities of LiCl and NaCl solutions. In contrast, the number density differences between NaCl and KCl solutions as well as between LiCl and KCl solutions behave in a regular fashion with lower number densities of solutions observed for larger cations.
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Affiliation(s)
- Man Thi Hong Nguyen
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 542/2, 160 00 Prague 6, Czech Republic
| | - Ondrej Tichacek
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 542/2, 160 00 Prague 6, Czech Republic
| | - Hector Martinez-Seara
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 542/2, 160 00 Prague 6, Czech Republic
| | - Philip E Mason
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 542/2, 160 00 Prague 6, Czech Republic
| | - Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 542/2, 160 00 Prague 6, Czech Republic
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12
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Ohkubo K, Yanagisawa K, Kamimura A, Fujii K. Physicochemical and Structural Properties of a Hydrophobicity/Hydrophilicity Switchable Ionic Liquid. J Phys Chem B 2020; 124:3784-3790. [PMID: 32293893 DOI: 10.1021/acs.jpcb.0c02067] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Herein, we report the physicochemical and structural properties of a new solubility-switchable ionic liquid (IL) comprising the glycerammonium (GA) cation with a hydrophilic group, the GA cation attached to an acetal-based protective group [protected GA (PGA)], and bis(trifluoromethanesulfonyl)amide (TFSA). The interionic volumes (Vinter) of the hydrophobic [PGA][TFSA] and hydrophilic [GA][TFSA] ILs were evaluated based on solution density, revealing weaker ion-ion interactions in these relative to conventional ILs. The [PGA][TFSA] and [GA][TFSA] also exhibit poor ion-conducting properties, with up to an order of magnitude lower ionic conductivity (σ) and self-diffusion coefficient (D), as compared with conventional ILs. Radial distribution functions derived from high-energy X-ray total scattering experiments [Gexp(r)] and molecular dynamics (MD) simulations [GMD(r)] indicate that nearest-neighbor ion-ion interactions in the [PGA][TFSA] and [GA][TFSA] are comparable to those in imidazolium-based IL. Conversely, these are appreciably weakened at the second- and third-neighbors and thus less structured in the long range (r > 12 Å) and very different from the highly ordered imidazolium IL. The atom-atom pair correlation function derived from the MD simulations disclose that at a local scale, specific interactions are absent, with only an electrostatic interaction in the [PGA][TFSA], whereas the GA cations interact with TFSA anions via hydrogen bonding of diol groups in the GA and O atoms in the TFSA. No hydrogen bonding group within the PGA cation leads to weak ion-hydration resulting in a phase separation of [PGA][TFSA] and water; in contrast, the GA cations are easily hydrogen-bonded with water molecules to be miscible in aqueous solutions.
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Affiliation(s)
- Kota Ohkubo
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan
| | - Keiya Yanagisawa
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan
| | - Akio Kamimura
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan
| | - Kenta Fujii
- Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan
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13
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Roy S, Wu L, Goverapet Srinivasan S, Stack AG, Navrotsky A, Bryantsev VS. Hydration structure and water exchange kinetics at xenotime-water interfaces: implications for rare earth minerals separation. Phys Chem Chem Phys 2020; 22:7719-7727. [PMID: 32215419 DOI: 10.1039/d0cp00087f] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Hydration of surface ions gives rise to structural heterogeneity and variable exchange kinetics of water at complex mineral-water interfaces. Here, we employ ab initio molecular dynamics (AIMD) simulations and water adsorption calorimetry to examine the aqueous interfaces of xenotime, a phosphate mineral that contains predominantly Y3+ and heavy rare earth elements. Consistent with natural crystal morphology, xenotime is predicted to have a tetragonal prismatic shape, dominated by the {100} surface. Hydration of this surface induces multilayer interfacial water structures with distinct OH orientations, which agrees with recent crystal truncation rod measurements. The exchange kinetics between two adjacent water layers exhibits a wide range of underlying timescales (5-180 picoseconds), dictated by ion-water electrostatics. Adsorption of a bidentate hydroxamate ligand reveals that {100} xenotime surface can only accommodate monodentate coordination with water exchange kinetics strongly depending on specific ligand orientation, prompting us to reconsider traditional strategies for selective separation of rare-earth minerals.
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Affiliation(s)
- Santanu Roy
- Chemical Sciences Division, Oak Ridge National Laboratory, 1 Bethel Valley Rd., Oak Ridge, TN 37830, USA.
| | - Lili Wu
- Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California Davis, 1 Shields Avenue, Davis, CA 95616, USA
| | | | - Andrew G Stack
- Chemical Sciences Division, Oak Ridge National Laboratory, 1 Bethel Valley Rd., Oak Ridge, TN 37830, USA.
| | - Alexandra Navrotsky
- Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California Davis, 1 Shields Avenue, Davis, CA 95616, USA
| | - Vyacheslav S Bryantsev
- Chemical Sciences Division, Oak Ridge National Laboratory, 1 Bethel Valley Rd., Oak Ridge, TN 37830, USA.
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15
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Kiyohara K, Kawai Y. Hydration of monovalent and divalent cations near a cathode surface. J Chem Phys 2019; 151:104704. [PMID: 31521095 DOI: 10.1063/1.5113738] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Hydration of monovalent (Li+, Na+, K+, and Cs+) and divalent (Mg2+, Ca2+, Sr2+, and Ba2+) cations on a cathode surface was studied by a classical molecular dynamics simulation. The potential of mean force (PMF) for each cation species was calculated as a function of the distance from the cathode surface, and the potential barriers for dehydrating the first and second hydration shells near the cathode surface were estimated. The positions of the minimum of the PMF closest to the cathode surface were found to be in the order Li+ < Na+ < Mg2+ < Ca2+ < Sr2+ < Ba2+ < K+ < Cs+. It was found that Li+, Mg2+, Ca2+, Sr2+, and Ba2+ ions are most likely doubly hydrated when they are adsorbed on the cathode surface without an applied voltage, whereas Na+, K+, and Cs+ ions are most likely singly hydrated at room temperature. On the other hand, when a voltage of 1 V was applied to the electrodes, all the cation species that we studied appeared most likely to be singly hydrated on the cathode surface. The depths of the potential well closest to the cathode surface under an applied voltage of 1 V were found to be in the order Ba2+ < Sr2+ < Ca2+ < Mg2+ for the divalent cations and Li+ < Na+ < K+ < Cs+ for the monovalent cations in the set of models that we used. These orders coincide with the Hofmeister series from the kosmotropic to the chaotropic.
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Affiliation(s)
- Kenji Kiyohara
- Inorganic Functional Materials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Ikeda, Osaka 563-8577, Japan
| | - Yusuke Kawai
- Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan
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16
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Liu C, Min F, Liu L, Chen J. Hydration properties of alkali and alkaline earth metal ions in aqueous solution: A molecular dynamics study. Chem Phys Lett 2019. [DOI: 10.1016/j.cplett.2019.04.045] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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17
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Kameda Y, Sato K, Hasebe R, Amo Y, Usuki T, Umebayashi Y, Ikeda K, Otomo T. Solvation Structure of Li + in Methanol and 2-Propanol Solutions Studied by ATR-IR and Neutron Diffraction with 6Li/ 7Li Isotopic Substitution Methods. J Phys Chem B 2019; 123:4967-4975. [PMID: 31094512 DOI: 10.1021/acs.jpcb.9b03477] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Neutron diffraction measurements have been carried out on 10 mol % LiTFSA (TFSA: bis(trifluoromethylsulfonil)amide) solutions in methanol- d4 and 2-propanol- d8 to obtain information on the solvation structure of Li+. The detailed coordination structure of solvent molecules within the first solvation shell of Li+ was determined through the least-squares fitting analysis of the difference function between normalized scattering cross sections observed for 6Li/7Li isotopically substituted sample solutions. The nearest-neighbor Li+···O distance and coordination number determined for the 10 mol % LiTFSA-methanol- d4 solution are rLiO = 1.98 ± 0.02 Å and nLiO = 3.8 ± 0.6, respectively. In the 2-propanol- d8 solution, it has been revealed that 2-propanol- d8 molecules within the first solvation shell of Li+ take at least two different coordination geometries with the intermolecular nearest-neighbor Li+···O distance of rLiO = 1.93 ± 0.04 Å. The Li+···O coordination number, nLiO = 3.3 ± 0.3, is determined. Ion-pair formation in the LiTFSA-methanol and LiTFSA-2-propanol solutions has been investigated by the attenuated total reflection infrared spectroscopic method. Mole fractions of free, Li+-bound, and aggregated TFSA- are derived from the peak deconvolution analysis of vibrational bands observed for TFSA-.
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Affiliation(s)
- Yasuo Kameda
- Department of Material and Biological Chemistry, Faculty of Science , Yamagata University , Yamagata , Yamagata 990-8560 , Japan
| | - Koichi Sato
- Department of Material and Biological Chemistry, Faculty of Science , Yamagata University , Yamagata , Yamagata 990-8560 , Japan
| | - Ryo Hasebe
- Department of Material and Biological Chemistry, Faculty of Science , Yamagata University , Yamagata , Yamagata 990-8560 , Japan
| | - Yuko Amo
- Department of Material and Biological Chemistry, Faculty of Science , Yamagata University , Yamagata , Yamagata 990-8560 , Japan
| | - Takeshi Usuki
- Department of Material and Biological Chemistry, Faculty of Science , Yamagata University , Yamagata , Yamagata 990-8560 , Japan
| | - Yasuhiro Umebayashi
- Graduate School of Science and Technology , Niigata University , 8050 Ikarashi, 2-no-cho , Nishi-ku, Niigata City 950-2181 , Japan
| | - Kazutaka Ikeda
- Institute of Material Structure Science , KEK , Tsukuba , Ibaraki 305-080 , Japan
| | - Toshiya Otomo
- Institute of Material Structure Science , KEK , Tsukuba , Ibaraki 305-080 , Japan
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Kameda Y, Amo Y, Usuki T, Umebayashi Y, Ikeda K, Otomo T. Origin of the Difference in Ion-Water Distances Determined by X-ray and Neutron Diffraction Measurements for Aqueous NaCl and KCl Solutions. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2019. [DOI: 10.1246/bcsj.20180283] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Yasuo Kameda
- Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
| | - Yuko Amo
- Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
| | - Takeshi Usuki
- Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
| | - Yasuhiro Umebayashi
- Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan
| | - Kazutaka Ikeda
- Institute of Material Structure Science, KEK, Tsukuba, Ibaraki 305-080, Japan
| | - Toshiya Otomo
- Institute of Material Structure Science, KEK, Tsukuba, Ibaraki 305-080, Japan
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Daub CD, Hänninen V, Halonen L. Ab Initio Molecular Dynamics Simulations of the Influence of Lithium Bromide on the Structure of the Aqueous Solution-Air Interface. J Phys Chem B 2019; 123:729-737. [PMID: 30605330 PMCID: PMC6727360 DOI: 10.1021/acs.jpcb.8b10552] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
We
present the results of ab initio molecular dynamics simulations
of the solution–air interface of aqueous lithium bromide (LiBr).
We find that, in agreement with the experimental data and previous
simulation results with empirical polarizable force field models,
Br– anions prefer to accumulate just below the first
molecular water layer near the interface, whereas Li+ cations
remain deeply buried several molecular layers from the interface,
even at very high concentration. The separation of ions has a profound
effect on the average orientation of water molecules in the vicinity
of the interface. We also find that the hydration number of Li+ cations in the center of the slab Nc,Li+–H2O ≈ 4.7 ±
0.3, regardless of the salt concentration. This estimate is consistent
with the recent experimental neutron scattering data, confirming that
results from nonpolarizable empirical models, which consistently predict
tetrahedral coordination of Li+ to four solvent molecules,
are incorrect. Consequently, disruption of the hydrogen bond network
caused by Li+ may be overestimated in nonpolarizable empirical
models. Overall, our results suggest that empirical models, in particular
nonpolarizable models, may not capture all of the properties of the
solution–air interface necessary to fully understand the interfacial
chemistry.
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Affiliation(s)
- Christopher D Daub
- Department of Chemistry , University of Helsinki , P.O. Box 55, Helsinki 00014 , Finland
| | - Vesa Hänninen
- Department of Chemistry , University of Helsinki , P.O. Box 55, Helsinki 00014 , Finland
| | - Lauri Halonen
- Department of Chemistry , University of Helsinki , P.O. Box 55, Helsinki 00014 , Finland
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Kameda Y, Amo Y, Usuki T, Umebayashi Y, Ikeda K, Otomo T. Neutron Diffraction Study on Partial Pair Correlation Functions of Water at Ambient Temperature. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2018. [DOI: 10.1246/bcsj.20180205] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Yasuo Kameda
- Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
| | - Yuko Amo
- Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
| | - Takeshi Usuki
- Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
| | - Yasuhiro Umebayashi
- Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan
| | - Kazutaka Ikeda
- Institute of Material Structure Science, KEK, Tsukuba, Ibaraki 305-080, Japan
| | - Toshiya Otomo
- Institute of Material Structure Science, KEK, Tsukuba, Ibaraki 305-080, Japan
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21
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Wang HW, Vlcek L, Neuefeind JC, Page K, Irle S, Simonson JM, Stack AG. Decoding Oxyanion Aqueous Solvation Structure: A Potassium Nitrate Example at Saturation. J Phys Chem B 2018; 122:7584-7589. [PMID: 29991255 DOI: 10.1021/acs.jpcb.8b05895] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The ability to probe the structure of a salt solution at the atomic scale is fundamentally important for our understanding of many chemical reactions and their mechanisms. The capability of neutron diffraction to "see" hydrogen (or deuterium) and other light isotopes is exceptional for resolving the structural complexity around the dissolved solutes in aqueous electrolytes. We have made measurements using oxygen isotopes on aqueous nitrate to reveal a small hydrogen-bonded water coordination number (3.9 ± 1.2) around a nitrate oxyanion. This is compared to estimates made using the existing method of nitrogen isotope substitution and those of computational simulations (>5-6 water molecules). The low water coordination number, combined with a comparison to classical molecular dynamics simulations, suggests that ion-pair formation is significant. This insight demonstrates the utility of experimental diffraction data for benchmarking atomistic computer simulations, enabling the development of more accurate intermolecular potentials.
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22
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Pethes I. The structure of aqueous lithium chloride solutions at high concentrations as revealed by a comparison of classical interatomic potential models. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2018.05.044] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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