1
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Yang P, Kumarasiri A, Hore D. Surface populations as a model for the distance-dependence of the interfacial refractive index. J Chem Phys 2024; 161:054703. [PMID: 39087546 DOI: 10.1063/5.0221234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2024] [Accepted: 07/16/2024] [Indexed: 08/02/2024] Open
Abstract
Vibrational sum frequency spectra provide information about interfaces that is sensitive to the orientation of molecules, their electronic environment, and the local electric fields. Here, we use molecular dynamics simulations in order to study a surfactant, para-cyanophenol, at the air-water interface. The volume fractions of water and the organic surfactant are considered at various points over the nanometer-scale region in a Lorentz-Lorenz model. We find that the calculated ratios of nonlinear susceptibility tensor elements are in agreement with experimental data only when this depth profile was considered. We also use these data to evaluate the ratio of the C-N hyperpolarizability tensor elements in the interfacial region.
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Affiliation(s)
- Peter Yang
- Department of Chemistry, University of Victoria, Victoria, British Columbia V8W 3V6, Canada
| | - Aruna Kumarasiri
- Department of Chemistry, University of Victoria, Victoria, British Columbia V8W 3V6, Canada
| | - Dennis Hore
- Department of Chemistry, University of Victoria, Victoria, British Columbia V8W 3V6, Canada
- Department of Computer Science, University of Victoria, Victoria, British Columbia V8W 3P6, Canada
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2
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Zhang P, Feng M, Xu X. Double-Layer Distribution of Hydronium and Hydroxide Ions in the Air-Water Interface. ACS PHYSICAL CHEMISTRY AU 2024; 4:336-346. [PMID: 39069983 PMCID: PMC11274287 DOI: 10.1021/acsphyschemau.3c00076] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Revised: 04/04/2024] [Accepted: 04/05/2024] [Indexed: 07/30/2024]
Abstract
The acid-base nature of the aqueous interface has long been controversial. Most macroscopic experiments suggest that the air-water interface is basic based on the detection of negative charges at the interface that indicates the enrichment of hydroxides (OH-), whereas microscopic studies mostly support the acidic air-water interface with the observation of hydronium (H3O+) accumulation in the top layer of the interface. It is crucial to clarify the interfacial preference of OH- and H3O+ ions for rationalizing the debate. In this work, we perform deep potential molecular dynamics simulations to investigate the preferential distribution of OH- and H3O+ ions at the aqueous interfaces. The neural network potential energy surface is trained based on density functional theory calculations with the SCAN functional, which can accurately describe the diffusion of these two ions both in the interface and in the bulk water. In contrast to the previously reported single ion enrichment, we show that both OH- and H3O+ surprisingly prefer to accumulate in interfaces but at different interfacial depths, rendering a double-layer ionic distribution within ∼1 nm near the Gibbs dividing surface. The H3O+ preferentially resides in the topmost layer of the interface, but the OH-, which is enriched in the deeper interfacial layer, has a higher equilibrium concentration due to the more negative free energy of interfacial stabilization [-0.90 (OH-) vs -0.56 (H3O+) kcal/mol]. The present finding of the ionic double-layer distribution may qualitatively offer a self-consistent explanation for the long-term controversy about the acid-base nature of the air-water interface.
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Affiliation(s)
- Pengchao Zhang
- Center
for Combustion Energy, Department of Energy and Power Engineering,
and Key Laboratory for Thermal Science and Power Engineering of Ministry
of Education, Tsinghua University, Beijing 100084, China
| | - Muye Feng
- School
of Mechanical and Power Engineering, Nanjing
Tech University, Nanjing 211816, China
| | - Xuefei Xu
- Center
for Combustion Energy, Department of Energy and Power Engineering,
and Key Laboratory for Thermal Science and Power Engineering of Ministry
of Education, Tsinghua University, Beijing 100084, China
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3
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Gaur A, Balasubramanian S. Liquid-Vapor Interface of Aqueous Ethylene Glycol Solutions: A Molecular Dynamics Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:230-240. [PMID: 38150706 DOI: 10.1021/acs.langmuir.3c02431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2023]
Abstract
While the organic constituent in an aqueous binary solution enriches its liquid-vapor (l-v) interface, the extent of enrichment can depend nonlinearly on its mole fraction. A microscopic quantification and rationalization of this behavior are crucial to understand the dependence of properties such as surface tension and evaporation rate of the solution on its composition. Extensive all-atom molecular dynamics simulations of aqueous ethylene glycol (EG) solutions show that the composition of the solution at the l-v interface deviates the most from that in the bulk solution at an EG mole fraction of 0.3. The population of EG molecules with their central C-C dihedral in the gauche conformation was found to be higher at the l-v interface than that in the bulk solution to facilitate the orientation of its hydrophobic methyl groups toward the vapor phase. Free energy calculations reveal that in dilute EG solutions, an EG molecule is most stable at the l-v interface. The behavior of vapor pressure in aqueous EG solutions is ideal and follows Raoult's law, while in contrast, the aqueous solution of dimethyl sulfoxide does not. A rationale for the same is provided through the orientational distribution of interfacial water molecules in the respective solutions.
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Affiliation(s)
- Anjali Gaur
- Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560 064, India
| | - Sundaram Balasubramanian
- Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560 064, India
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4
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Tan J, Wang M, Zhang J, Ye S. Determination of the Thickness of Interfacial Water by Time-Resolved Sum-Frequency Generation Vibrational Spectroscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:18573-18580. [PMID: 38051545 DOI: 10.1021/acs.langmuir.3c02906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
The physics and chemistry of a charged interface are governed by the structure of the electrical double layer (EDL). Determination of the interfacial water thickness (diw) of the charged interface is crucial to quantitatively describe the EDL structure, but it can be utilized with very scarce experimental methods. Here, we propose and verify that the vibrational relaxation time (T1) of the OH stretching mode at 3200 cm-1, obtained by time-resolved sum frequency generation vibrational spectroscopy with ssp polarizations, provides an effective tool to determine diw. By investigating the T1 values at the SiO2/NaCl solution interface, we established a time-space (T1-diw) relationship. We find that water has a T1 lifetime of ≥0.5 ps for diw ≤ 3 Å, while it displays bulk-like dynamics with T1 ≤ 0.2 ps for diw ≥ 9 Å. T1 decreases as diw increases from ∼3 Å to 9 Å. The hydration water at the DPPG lipid bilayer and LK15β protein interfaces has a thickness of ≥9 Å and shows a bulk-like feature. The time-space relationship will provide a novel tool to pattern the interfacial topography and heterogeneity in Ångstrom-depth resolution by imaging the T1 values.
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Affiliation(s)
- Junjun Tan
- Hefei National Research Center for Physical Sciences at the Microscale, and Department of Chemical Physics, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei, Anhui 230088, China
| | - Mengmeng Wang
- Hefei National Research Center for Physical Sciences at the Microscale, and Department of Chemical Physics, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, China
| | - Jiahui Zhang
- Hefei National Research Center for Physical Sciences at the Microscale, and Department of Chemical Physics, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, China
| | - Shuji Ye
- Hefei National Research Center for Physical Sciences at the Microscale, and Department of Chemical Physics, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, China
- Hefei National Laboratory, University of Science and Technology of China, Hefei, Anhui 230088, China
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5
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Litman Y, Lan J, Nagata Y, Wilkins DM. Fully First-Principles Surface Spectroscopy with Machine Learning. J Phys Chem Lett 2023; 14:8175-8182. [PMID: 37671886 PMCID: PMC10510433 DOI: 10.1021/acs.jpclett.3c01989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Accepted: 08/29/2023] [Indexed: 09/07/2023]
Abstract
Our current understanding of the structure and dynamics of aqueous interfaces at the molecular level has grown substantially due to the continuous development of surface-specific spectroscopies, such as vibrational sum-frequency generation (VSFG). As in other vibrational spectroscopies, we must turn to atomistic simulations to extract all of the information encoded in the VSFG spectra. The high computational cost associated with existing methods means that they have limitations in representing systems with complex electronic structure or in achieving statistical convergence. In this work, we combine high-dimensional neural network interatomic potentials and symmetry-adapted Gaussian process regression to overcome these constraints. We show that it is possible to model VSFG signals with fully ab initio accuracy using machine learning and illustrate the versatility of our approach on the water/air interface. Our strategy allows us to identify the main sources of theoretical inaccuracy and establish a clear pathway toward the modeling of surface-sensitive spectroscopy of complex interfaces.
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Affiliation(s)
- Yair Litman
- Yusuf
Hamied Department of Chemistry, University
of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Jinggang Lan
- Department
of Chemistry, New York University, New York, New York 10003, United States
- Simons
Center for Computational Physical Chemistry at New York University, New York, New York 10003, United States
| | - Yuki Nagata
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - David M. Wilkins
- Centre
for Quantum Materials and Technologies School of Mathematics and Physics, Queen’s University Belfast, Belfast BT7 1NN, Northern Ireland, United Kingdom
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6
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Yan Y, Li J, Huang Y, Ma L, Yang D, Wan H, Fang S, Xiao Y, Duan M, Xiong Y. Insight into surfactant adsorption performance at asphaltene surface by in-situ DPI experiment and microscopic MD simulation. Colloids Surf A Physicochem Eng Asp 2023. [DOI: 10.1016/j.colsurfa.2023.131313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
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7
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Kumarasiri A, Yang P, Hore DK. Second-Order Nonlinear Optics as an Orientation-Independent Probe of Molecular Environments at Interfaces. J Phys Chem Lett 2023; 14:4449-4453. [PMID: 37146122 DOI: 10.1021/acs.jpclett.3c00771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Measurement techniques that probe the second-order susceptibility, such as second-harmonic and sum-frequency generation, are recognized for their ability to study environments with broken centrosymmetry. As a result, they serve as reporters of molecules at surfaces because the second-order susceptibility is often zero in the adjacent bulk media. Although the signals measured in such experiments carry unique information about the interfacial environment, the challenge is to disentangle properties related to the electronic structure as they are wrapped up in the orientation distribution. Over the past 30 years, this challenge has been turned into an opportunity, as many studies have sought to learn about the arrangement of molecules at surfaces. Here we demonstrate that the flipped case is possible, where fundamental properties of the interfacial environment can be extracted in a manner that is completely independent of, and therefore oblivious to, the orientation distribution. Using p-cyanophenol adsorbed at the air-water interface as an example, we illustrate that the cyano group polarizability varies less along the direction of the C-N bond when at the surface than when the same molecules are in the bulk aqueous phase.
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Affiliation(s)
- Aruna Kumarasiri
- Department of Chemistry, University of Victoria, Victoria, British Columbia V8W 3V6, Canada
| | - Peter Yang
- Department of Chemistry, University of Victoria, Victoria, British Columbia V8W 3V6, Canada
| | - Dennis K Hore
- Department of Chemistry, University of Victoria, Victoria, British Columbia V8W 3V6, Canada
- Department of Computer Science, University of Victoria, Victoria, British Columbia V8W 3P6, Canada
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8
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Seki T, Yu CC, Chiang KY, Greco A, Yu X, Matsumura F, Bonn M, Nagata Y. Ions Speciation at the Water-Air Interface. J Am Chem Soc 2023; 145:10622-10630. [PMID: 37139910 DOI: 10.1021/jacs.3c00517] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
In typical aqueous systems, including naturally occurring sweet and salt water and tap water, multiple ion species are co-solvated. At the water-air interface, these ions are known to affect the chemical reactivity, aerosol formation, climate, and water odor. Yet, the composition of ions at the water interface has remained enigmatic. Here, using surface-specific heterodyne-detected sum-frequency generation spectroscopy, we quantify the relative surface activity of two co-solvated ions in solution. We find that more hydrophobic ions are speciated to the interface due to the hydrophilic ions. Quantitative analysis shows that the interfacial hydrophobic ion population increases with decreasing interfacial hydrophilic ion population at the interface. Simulations show that the solvation energy difference between the ions and the intrinsic surface propensity of ions determine the extent of an ion's speciation by other ions. This mechanism provides a unified view of the speciation of monatomic and polyatomic ions at electrolyte solution interfaces.
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Affiliation(s)
- Takakazu Seki
- Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
- Graduate School of Science and Technology, Hirosaki University, Hirosaki 036-8561, Aomori, Japan
| | - Chun-Chieh Yu
- Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Kuo-Yang Chiang
- Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Alessandro Greco
- Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Xiaoqing Yu
- Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Fumiki Matsumura
- Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Mischa Bonn
- Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Yuki Nagata
- Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
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9
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Degoulange D, Pandya R, Deschamps M, Skiba D, Gallant B, Gigan S, de Aguiar H, Grimaud A. Direct imaging of micrometer-thick interfaces in salt-salt aqueous biphasic systems. Proc Natl Acad Sci U S A 2023; 120:e2220662120. [PMID: 37068232 PMCID: PMC10151592 DOI: 10.1073/pnas.2220662120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 03/26/2023] [Indexed: 04/19/2023] Open
Abstract
Unlike the interface between two immiscible electrolyte solutions (ITIES) formed between water and polar solvents, molecular understanding of the liquid-liquid interface formed for aqueous biphasic systems (ABSs) is relatively limited and mostly relies on surface tension measurements and thermodynamic models. Here, high-resolution Raman imaging is used to provide spatial and chemical resolution of the interface of lithium chloride - lithium bis(trifluoromethanesulfonyl)imide - water (LiCl-LiTFSI-water) and HCl-LiTFSI-water, prototypical salt-salt ABSs found in a range of electrochemical applications. The concentration profiles of both TFSI anions and water are found to be sigmoidal thus not showing any signs of a positive adsorption for both salts and solvent. More striking, however, is the length at which the concentration profiles extend, ranging from 11 to 2 µm with increasing concentrations, compared to a few nanometers for ITIES. We thus reveal that unlike ITIES, salt-salt ABSs do not have a molecularly sharp interface but rather form an interphase with a gradual change of environment from one phase to the other. This knowledge represents a major stepping-stone in the understanding of aqueous interfaces, key for mastering ion or electron transfer dynamics in a wide range of biological and technological settings including novel battery technologies such as membraneless redox flow and dual-ion batteries.
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Affiliation(s)
- Damien Degoulange
- Chimie du Solide et de l’Energie, UMR 8260, Collège de France,75231 Cedex 05Paris, France
- Sorbonne Université,75006Paris, France
- Réseau sur le Stockage Electrochimique de l’Energie, CNRS FR3459,80039Amiens Cedex, France
| | - Raj Pandya
- Laboratoire Kastler Brossel, Ecole Normale Supérieure, Université PSL, CNRS, Sorbonne Université, Collège de France,75005Paris, France
- Department of Physics, Cavendish Laboratory, University of Cambridge, CambridgeCB3 0HE, United Kingdom
| | - Michael Deschamps
- Réseau sur le Stockage Electrochimique de l’Energie, CNRS FR3459,80039Amiens Cedex, France
- CNRS, Conditions Extrêmes et Matériaux : Haute Température et Irradiation, UPR3079, Université d'Orléans,45071Orléans, France
| | - Dhyllan A. Skiba
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Betar M. Gallant
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Sylvain Gigan
- Laboratoire Kastler Brossel, Ecole Normale Supérieure, Université PSL, CNRS, Sorbonne Université, Collège de France,75005Paris, France
| | - Hilton B. de Aguiar
- Laboratoire Kastler Brossel, Ecole Normale Supérieure, Université PSL, CNRS, Sorbonne Université, Collège de France,75005Paris, France
| | - Alexis Grimaud
- Chimie du Solide et de l’Energie, UMR 8260, Collège de France,75231 Cedex 05Paris, France
- Sorbonne Université,75006Paris, France
- Réseau sur le Stockage Electrochimique de l’Energie, CNRS FR3459,80039Amiens Cedex, France
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, MA02467
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10
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Yu CC, Seki T, Chiang KY, Tang F, Sun S, Bonn M, Nagata Y. Polarization-Dependent Heterodyne-Detected Sum-Frequency Generation Spectroscopy as a Tool to Explore Surface Molecular Orientation and Ångström-Scale Depth Profiling. J Phys Chem B 2022; 126:6113-6124. [PMID: 35849538 PMCID: PMC9421650 DOI: 10.1021/acs.jpcb.2c02178] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 07/01/2022] [Indexed: 11/28/2022]
Abstract
Sum-frequency generation (SFG) spectroscopy provides a unique optical probe for interfacial molecules with interface-specificity and molecular specificity. SFG measurements can be further carried out at different polarization combinations, but the target of the polarization-dependent SFG is conventionally limited to investigating the molecular orientation. Here, we explore the possibility of polarization-dependent SFG (PD-SFG) measurements with heterodyne detection (HD-PD-SFG). We stress that HD-PD-SFG enables accurate determination of the peak amplitude, a key factor of the PD-SFG data. Subsequently, we outline that HD-PD-SFG can be used not only for estimating the molecular orientation but also for investigating the interfacial dielectric profile and studying the depth profile of molecules. We further illustrate the variety of combined simulation and PD-SFG studies.
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Affiliation(s)
- Chun-Chieh Yu
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Takakazu Seki
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Kuo-Yang Chiang
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Fujie Tang
- Department
of Physics, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Shumei Sun
- Department
of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Mischa Bonn
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Yuki Nagata
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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