1
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Agles AA, Bourg IC. Structure and Dynamics of Water in Polysaccharide (Alginate) Solutions and Gels Explained by the Core-Shell Model. Biomacromolecules 2024. [PMID: 39228282 DOI: 10.1021/acs.biomac.4c00447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/05/2024]
Abstract
In both biological and engineered systems, polysaccharides offer a means of establishing structural stiffness without altering the availability of water. Notable examples include the extracellular matrix of prokaryotes and eukaryotes, artificial skin grafts, drug delivery materials, and gels for water harvesting. Proper design and modeling of these systems require detailed understanding of the behavior of water confined in pores narrower than about 1 nm. We use molecular dynamics simulations to investigate the properties of water in solutions and gels of the polysaccharide alginate as a function of the water content and polymer cross-linking. We find that a detailed understanding of the nanoscale dynamics of water in alginate solutions and gels requires consideration of the discrete nature of water. However, we also find that the trends in tortuosity, permeability, dielectric constant, and shear viscosity can be adequately represented using the "core-shell" conceptual model that considers the confined fluid as a continuum.
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Affiliation(s)
- Avery A Agles
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Ian C Bourg
- Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, United States
- High Meadows Environmental Institute, Princeton University, Princeton, New Jersey 08544, United States
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2
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Fellows AP, Duque ÁD, Balos V, Lehmann L, Netz RR, Wolf M, Thämer M. How Thick is the Air-Water Interface?─A Direct Experimental Measurement of the Decay Length of the Interfacial Structural Anisotropy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:18760-18772. [PMID: 39171356 DOI: 10.1021/acs.langmuir.4c02571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/23/2024]
Abstract
The air-water interface is a highly prevalent phase boundary impacting many natural and artificial processes. The significance of this interface arises from the unique properties of water molecules within the interfacial region, with a crucial parameter being the thickness of its structural anisotropy, or "healing depth". This quantity has been extensively assessed by various simulations which have converged to a prediction of a remarkably short length of ∼6 Å. Despite the absence of any direct experimental measurement of this quantity, this predicted value has surprisingly become widely accepted as fact. Using an advancement in nonlinear vibrational spectroscopy, we provide the first measurement of this thickness and, indeed, find it to be ∼6-8 Å, finally confirming the prior predictions. Lastly, by combining the experimental results with depth-dependent second-order spectra calculated from ab initio parametrized molecular dynamics simulations, which are also in excellent agreement with this experimental result, we shed light on this surprisingly short correlation length of molecular orientations at the interface.
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Affiliation(s)
- Alexander P Fellows
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Álvaro Díaz Duque
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Vasileios Balos
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nanociencia), 28049 Madrid, Spain
| | - Louis Lehmann
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Roland R Netz
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Martin Wolf
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Martin Thämer
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
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3
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Brookes SGH, Kapil V, Schran C, Michaelides A. The wetting of H2O by CO2. J Chem Phys 2024; 161:084711. [PMID: 39193944 DOI: 10.1063/5.0224230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2024] [Accepted: 07/24/2024] [Indexed: 08/29/2024] Open
Abstract
Biphasic interfaces are complex but fascinating regimes that display a number of properties distinct from those of the bulk. The CO2-H2O interface, in particular, has been the subject of a number of studies on account of its importance for the carbon life cycle as well as carbon capture and sequestration schemes. Despite this attention, there remain a number of open questions on the nature of the CO2-H2O interface, particularly concerning the interfacial tension and phase behavior of CO2 at the interface. In this paper, we seek to address these ambiguities using ab initio-quality simulations. Harnessing the benefits of machine-learned potentials and enhanced statistical sampling methods, we present an ab initio-level description of the CO2-H2O interface. Interfacial tensions are predicted from 1 to 500 bars and found to be in close agreement with experiment at pressures for which experimental data are available. Structural analyses indicate the buildup of an adsorbed, saturated CO2 film forming at a low pressure (20 bars) with properties similar to those of the bulk liquid, but preferential perpendicular alignment with respect to the interface. The CO2 monolayer buildup coincides with a reduced structuring of water molecules close to the interface. This study highlights the predictive nature of machine-learned potentials for complex macroscopic properties of biphasic interfaces, and the mechanistic insight obtained into carbon dioxide aggregation at the water interface is of high relevance for geoscience, climate research, and materials science.
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Affiliation(s)
- Samuel G H Brookes
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom
- Lennard-Jones Centre, University of Cambridge, Trinity Ln, Cambridge CB2 1TN, United Kingdom
| | - Venkat Kapil
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
- Lennard-Jones Centre, University of Cambridge, Trinity Ln, Cambridge CB2 1TN, United Kingdom
- Department of Physics and Astronomy, University College London, 17-19 Gordon Street, London WC1H 0AH, United Kingdom
- Thomas Young Centre and London Centre for Nanotechnology, 19 Gordon Street, London WC1H 0AH, United Kingdom
| | - Christoph Schran
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom
- Lennard-Jones Centre, University of Cambridge, Trinity Ln, Cambridge CB2 1TN, United Kingdom
| | - Angelos Michaelides
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
- Lennard-Jones Centre, University of Cambridge, Trinity Ln, Cambridge CB2 1TN, United Kingdom
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4
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Smirnov KS. Effects of Surface Charge Distribution and Electrolyte Ions on the Nonlinear Spectra of Model Solid-Water Interfaces. Molecules 2024; 29:3758. [PMID: 39202839 PMCID: PMC11356812 DOI: 10.3390/molecules29163758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2024] [Revised: 07/31/2024] [Accepted: 08/01/2024] [Indexed: 09/03/2024] Open
Abstract
Molecular dynamics simulations of model charged solid/water interfaces were carried out to provide insight about the relationship between the second-order nonlinear susceptibility χ(2) and the structure of the interfacial water layer. The results of the calculations reveal that the density fluctuations of water extend to about 12 Å from the surface regardless of the system, while the orientational ordering of molecules is long-ranged and is sensitive to the presence of electrolytes. The charge localization on the surface was found to affect only the high-frequency part of the Im[χ(2)] spectrum, and the addition of salt has very little effect on the spectrum of the first water layer. For solid/neat water interfaces, the spectroscopically active part of the liquid phase has a thickness largely exceeding the region of density fluctuations, and this long-ranged nonlinear activity is mediated by the electric field of the molecules. The electrolyte ions and their hydration shells act in a destructive way on the molecular field. This effect, combined with the screening of the surface charge by ions, drastically reduces the thickness of the spectroscopic diffuse layer. There is an electrolyte concentration at which the nonlinear response of the diffuse layer is suppressed and the χ(2) spectrum of the interface essentially coincides with that of the first water layer.
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Affiliation(s)
- Konstantin S Smirnov
- Univ. Lille, CNRS, UMR 8516 - LASIRe - Laboratoire Avancé de Spectroscopie pour les Interactions la Réactivité et l'Environnement, F-59000 Lille, France
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5
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Creazzo F, Luber S. Water-air interface revisited by means of path-integral ab initio molecular dynamics. Phys Chem Chem Phys 2024; 26:21290-21302. [PMID: 39078670 PMCID: PMC11305098 DOI: 10.1039/d4cp02500h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2024] [Accepted: 07/21/2024] [Indexed: 07/31/2024]
Abstract
Although nuclear quantum effects (NQEs) have been considered on bulk liquid water, the impact of these latter on the air-water interface has not yet been reported. Herein, by performing and comparing ab initio molecular dynamics (AIMD) and path integral AIMD (PI-AIMD) simulations, we reveal the impact of NQEs on structural, dynamical and electronic properties as well as IR spectra of the air-water interface at room temperature. NQEs, being able to describe a more accurate proton delocalization in H-bonded system than AIMD, reveal a different structural arrangement and dynamical behaviour of both bulk and interfacial water molecules in comparison to AIMD results. A more de-structured and de-bound water arrangement and coordination are identified when the quantum nature of nuclei are considered for both bulk and interfacial water molecules. Structural properties, such as inter-/intra-molecular bond lengths, coordination numbers and H-bonding angles of bulk and interfacial water molecules here calculated, are affected by NQEs mitigating the overstructured description given by AIMD. Further evidences of an AIMD overstructured description of bulk water are in the computed IR spectra, where an increased absorption peak intensity and an increased strength of the hydrogen-bond network are alleviated by NQEs. In addition, NQEs show a valuable impact on the electronic structure of the air-water interface, reducing the total valence bandwidth and the electronic energy band-gap when passing from bulk to interfacial water. This work proves how NQEs significantly affect properties and features of the air-water interface, that are essential to accurately describe H-bonded interfacial systems.
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Affiliation(s)
- Fabrizio Creazzo
- Department of Chemistry, University of Zurich, Zurich, Switzerland.
| | - Sandra Luber
- Department of Chemistry, University of Zurich, Zurich, Switzerland.
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Liu Z. How Molecular Orientation Affects the Static Permittivity Profile of the Polar and Nonpolar Liquid-Liquid Interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:15092-15098. [PMID: 39001873 DOI: 10.1021/acs.langmuir.4c01424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/15/2024]
Abstract
The dielectric permittivity across the liquid-liquid interface presents an intrinsic response, with respect to the instantaneous interface reference. We hypothesize that dielectric responses across the nonpolar and polar liquid-liquid interfaces have different behaviors and underlying mechanisms. Molecular dynamics simulations were used to compare and contrast the dielectric response of a nonpolar (1,2-dichloroethane/water) and a polar (1-octanol/water) liquid-liquid interface system. We found that the enhanced dielectric permittivity at the nonpolar interface is attributed to the increased water dipole orientation and polarization density. In the case of the polar interface, strong association of the immiscible solvents inhibits the molecular dipole orientation, counteracting the effect from the enhanced surface water polarization density and resulting in a standard dielectric response. Detailed knowledge of the hydrogen bond networks and molecular dipole orientation with respect to the specific instantaneous interfacial and bulk regions reveals the effect of molecular proximity and the interaction with the opposing interfacial molecules on the mechanism of the dielectric permittivity response across the liquid-liquid interface phase boundary.
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Affiliation(s)
- Zhu Liu
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou 311215, China
- College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310012, China
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory, Shenzhen 518107, China
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7
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Shikata K, Kasahara K, Watanabe NM, Umakoshi H, Kim K, Matubayasi N. Influence of cholesterol on hydrogen-bond dynamics of water molecules in lipid-bilayer systems at varying temperatures. J Chem Phys 2024; 161:015102. [PMID: 38958163 DOI: 10.1063/5.0208008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2024] [Accepted: 06/17/2024] [Indexed: 07/04/2024] Open
Abstract
Cholesterol (Chol) plays a crucial role in shaping the intricate physicochemical attributes of biomembranes, exerting a considerable influence on water molecules proximal to the membrane interface. In this study, we conducted molecular dynamics simulations on the bilayers of two lipid species, dipalmitoylphosphatidylcholine (DPPC) and palmitoyl sphingomyelin; they are distinct with respect to the structures of the hydrogen-bond (H-bond) acceptors. Our investigation focuses on the dynamic properties and H-bonds of water molecules in the lipid-membrane systems, with a particular emphasis on the influence of Chol at varying temperatures. Notably, in the gel phase at 303 K, the presence of Chol extends the lifetimes of H-bonds of the oxygen atoms acting as H-bond acceptors within DPPC with water molecules by a factor of 1.5-2.5. In the liquid-crystalline phase at 323 K, on the other hand, H-bonding dynamics with lipid membranes remain largely unaffected by Chol. This observed shift in H-bonding states serves as a crucial key to unraveling the subtle control mechanisms governing water dynamics in lipid-membrane systems.
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Affiliation(s)
- Kokoro Shikata
- Division of Chemical Engineering, Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Kento Kasahara
- Division of Chemical Engineering, Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Nozomi Morishita Watanabe
- Division of Chemical Engineering, Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Hiroshi Umakoshi
- Division of Chemical Engineering, Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Kang Kim
- Division of Chemical Engineering, Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Nobuyuki Matubayasi
- Division of Chemical Engineering, Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
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8
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Tóth Ugyonka H, Hantal G, Szilágyi I, Idrissi A, Jorge M, Jedlovszky P. Spatial organization of the ions at the free surface of imidazolium-based ionic liquids. J Colloid Interface Sci 2024; 676:989-1000. [PMID: 39068842 DOI: 10.1016/j.jcis.2024.07.041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2024] [Revised: 07/02/2024] [Accepted: 07/05/2024] [Indexed: 07/30/2024]
Abstract
HYPOTHESIS Experimental information on the molecular scale structure of ionic liquid interfaces is controversial, giving rise to two competing scenarios, namely the double layer-like and "chessboard"-like structures. This issue can be resolved by computer simulation methods, at least for the underlying molecular model. Systematically changing the anion type can elucidate the relative roles of electrostatic interactions, hydrophobic (or, strictly speaking, apolar) effects and steric restrictions on the interfacial properties. SIMULATIONS Molecular dynamics simulation is combined with intrinsic analysis methods both at the molecular and atomic levels, supplemented by Voronoi analysis of self-association. FINDINGS We see no evidence for the existence of a double-layer-type arrangement of the ions, or for their self-association at the surface of the liquid. Instead, our results show that cation chains associate into apolar domains that protrude into the vapour phase, while charged groups form domains that are embedded in this apolar environment at the surface. However, the apolar chains largely obscure the cation groups, to which they are bound, while the smaller and more mobile anions can more easily access the free surface, leading to a somewhat counterintuitive net excess of negative charge at the interface. Importantly, this excess charge could only be identified by applying intrinsic analysis.
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Affiliation(s)
- Helga Tóth Ugyonka
- Department of Chemistry, Eszterházy Károly Catholic University, Leányka utca 12, H-3300 Eger, Hungary
| | - György Hantal
- PULS Group, Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 3, D-91058 Erlangen, Germany
| | - István Szilágyi
- MTA-SZTE Lendület Biocolloids Research Group, Department of Physical Chemistry and Materials Science, Interdisciplinary Excellence Center, University of Szeged, H-6720 Szeged, Hungary
| | - Abdenacer Idrissi
- University of Lille, CNRS UMR 8516 -LASIRe - Laboratoire Avancé de Spectroscopie pour les Interactions la Réactivité et l'environnement, 59000 Lille, France
| | - Miguel Jorge
- Department of Chemical and Process Engineering, University of Strathclyde, 75 Montrose Street, Glasgow G1 1XJ, United Kingdom
| | - Pál Jedlovszky
- Department of Chemistry, Eszterházy Károly Catholic University, Leányka utca 12, H-3300 Eger, Hungary.
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9
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Gale CD, Derakhshani-Molayousefi M, Levinger NE. Shape of AOT Reverse Micelles: The Mesoscopic Assembly Is More Than the Sum of the Parts. J Phys Chem B 2024; 128:6410-6421. [PMID: 38900154 DOI: 10.1021/acs.jpcb.4c02569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
AOT reverse micelles are a common and convenient model system for studying the effects of nanoconfinement on aqueous solutions. The reverse micelle shape is important to understanding how the constituent components come together to form the coherent whole and the unique properties observed there. The shape of reverse micelles impacts the amount of interface present and the distance of the solute from the interface and is therefore vital to understanding interfacial properties and the behavior of solutes in the polar core. In this work, we use previously introduced measures of shape, the coordinate-pair eccentricity (CPE) and convexity, and apply them to a series of simulations of AOT reverse micelles. We simulate the most commonly used force field for AOT reverse micelles, the CHARMM force field, but we also adapt the OPLS force field for use with AOT, the first work to do so, in addition to using both 3- and 4-site water models. Altogether, these simulations are designed to examine the impact of the force field on the shape of the reverse micelles in detail. We also study the time autocorrelation of shape, the water rotational anisotropy decay, and how the CPE changes between the water pool and AOT tail groups. We find that although the force field changes the shape noticeably, AOT reverse micelles are always amorphous particles. The shape of the micelles changes on the order of 10 ns. The water rotational dynamics observed match the experiment and demonstrate slower dynamics relative to bulk water, suggesting a two-population model that fits a core/shell hypothesis. Taken together, our results indicate that it is likely not possible to create a perfect force field that can reproduce every aspect of the AOT reverse micelle accurately. However, the magnitude of the differences between simulations appears relatively small, suggesting that any reasonably derived force field should provide an acceptable model for most work on AOT reverse micelles.
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Affiliation(s)
- Christopher D Gale
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | | | - Nancy E Levinger
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
- Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado 80523, United States
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10
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de la Puente M, Laage D. Impact of interfacial curvature on molecular properties of aqueous interfaces. J Chem Phys 2024; 160:234504. [PMID: 38888129 DOI: 10.1063/5.0210884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Accepted: 05/28/2024] [Indexed: 06/20/2024] Open
Abstract
The curvature of soft interfaces plays a crucial role in determining their mechanical and thermodynamic properties, both at macroscopic and microscopic scales. In the case of air/water interfaces, particular attention has recently focused on water microdroplets, due to their distinctive chemical reactivity. However, the specific impact of curvature on the molecular properties of interfacial water and interfacial reactivity has so far remained elusive. Here, we use molecular dynamics simulations to determine the effect of curvature on a broad range of structural, dynamical, and thermodynamical properties of the interface. For a droplet, a flat interface, and a cavity, we successively examine the structure of the hydrogen-bond network and its relation to vibrational spectroscopy, the dynamics of water translation, rotation, and hydrogen-bond exchanges, and the thermodynamics of ion solvation and ion-pair dissociation. Our simulations show that curvature predominantly impacts the hydrogen-bond structure through the fraction of dangling OH groups and the dynamics of interfacial water molecules. In contrast, curvature has a limited effect on solvation and ion-pair dissociation thermodynamics. For water microdroplets, this suggests that the curvature alone cannot fully account for the distinctive reactivity measured in these systems, which are of great importance for catalysis and atmospheric chemistry.
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Affiliation(s)
- M de la Puente
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - D Laage
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
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11
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Limmer DT, Götz AW, Bertram TH, Nathanson GM. Molecular Insights into Chemical Reactions at Aqueous Aerosol Interfaces. Annu Rev Phys Chem 2024; 75:111-135. [PMID: 38360527 DOI: 10.1146/annurev-physchem-083122-121620] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2024]
Abstract
Atmospheric aerosols facilitate reactions between ambient gases and dissolved species. Here, we review our efforts to interrogate the uptake of these gases and the mechanisms of their reactions both theoretically and experimentally. We highlight the fascinating behavior of N2O5 in solutions ranging from pure water to complex mixtures, chosen because its aerosol-mediated reactions significantly impact global ozone, hydroxyl, and methane concentrations. As a hydrophobic, weakly soluble, and highly reactive species, N2O5 is a sensitive probe of the chemical and physical properties of aerosol interfaces. We employ contemporary theory to disentangle the fate of N2O5 as it approaches pure and salty water, starting with adsorption and ending with hydrolysis to HNO3, chlorination to ClNO2, or evaporation. Flow reactor and gas-liquid scattering experiments probe even greater complexity as added ions, organic molecules, and surfactants alter the interfacial composition and reaction rates. Together, we reveal a new perspective on multiphase chemistry in the atmosphere.
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Affiliation(s)
- David T Limmer
- Department of Chemistry, University of California, Berkeley, California, USA;
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
- Kavli Energy NanoScience Institute, Berkeley, California, USA
- Chemical Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Andreas W Götz
- San Diego Supercomputer Center, University of California San Diego, La Jolla, California, USA;
| | - Timothy H Bertram
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA; ,
| | - Gilbert M Nathanson
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA; ,
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12
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Sahoo CP, Panda DK, Bhargava BL. Computational insight into the effect of alkyl chain length in tetraalkylammonium-based deep eutectic solvents. J Mol Graph Model 2024; 128:108717. [PMID: 38281418 DOI: 10.1016/j.jmgm.2024.108717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Revised: 01/19/2024] [Accepted: 01/23/2024] [Indexed: 01/30/2024]
Abstract
The effect of the increase in the alkyl chain length of cation on the properties of deep eutectic solvents based on ethylene glycol has been investigated employing classical molecular dynamics simulations. The change in the structural and dynamic properties in both the bulk and liquid-vapor interface is explored through various analyses. The interaction between the anion and the ethylene glycol increases with an increase in the alkyl chain length of the cation, as observed in the increase of the lifetime of the hydrogen bond formed between the two. The terminal carbon atoms are found to be closer to each other when the cation changes from tetraethylammonium to tetrabutylammonium. The cations are located closer to the interface, and the association of the alkyl chains becomes more significant with increased alkyl chain length, decreasing the surface tension values.
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Affiliation(s)
- Chandan Prasad Sahoo
- School of Chemical Sciences, National Institute of Science Education & Research, An OCC of Homi Bhabha National Institute, P.O.: Jatni, Khurda, Odisha 752050, India
| | - Deepak Kumar Panda
- School of Chemical Sciences, National Institute of Science Education & Research, An OCC of Homi Bhabha National Institute, P.O.: Jatni, Khurda, Odisha 752050, India
| | - B L Bhargava
- School of Chemical Sciences, National Institute of Science Education & Research, An OCC of Homi Bhabha National Institute, P.O.: Jatni, Khurda, Odisha 752050, India.
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13
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Litman Y, Chiang KY, Seki T, Nagata Y, Bonn M. Surface stratification determines the interfacial water structure of simple electrolyte solutions. Nat Chem 2024; 16:644-650. [PMID: 38225269 PMCID: PMC10997511 DOI: 10.1038/s41557-023-01416-6] [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: 09/20/2022] [Accepted: 12/07/2023] [Indexed: 01/17/2024]
Abstract
The distribution of ions at the air/water interface plays a decisive role in many natural processes. Several studies have reported that larger ions tend to be surface-active, implying ions are located on top of the water surface, thereby inducing electric fields that determine the interfacial water structure. Here we challenge this view by combining surface-specific heterodyne-detected vibrational sum-frequency generation with neural network-assisted ab initio molecular dynamics simulations. Our results show that ions in typical electrolyte solutions are, in fact, located in a subsurface region, leading to a stratification of such interfaces into two distinctive water layers. The outermost surface is ion-depleted, and the subsurface layer is ion-enriched. This surface stratification is a key element in explaining the ion-induced water reorganization at the outermost air/water interface.
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Affiliation(s)
- Yair Litman
- Max Planck Institute for Polymer Research, Mainz, Germany.
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK.
| | | | - Takakazu Seki
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Yuki Nagata
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Mischa Bonn
- Max Planck Institute for Polymer Research, Mainz, Germany.
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14
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Cupp SS, Engle AE, Hardin AW, Lindberg GE. Identifying Local Interfaces. J Phys Chem B 2024; 128:1527-1534. [PMID: 38118072 DOI: 10.1021/acs.jpcb.3c06364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
While interfacial regions often occupy a relatively small portion of a system, physical and chemical processes often proceed differently within them. It is therefore useful to identify interfacial regions to answer many questions in physical chemistry. Thermodynamic phases are often described by their density and local structure; therefore, interfacial regions can then be defined as regions with densities and structures that deviate from the properties of the neighboring phases. Using this perspective of local density and structure around an atom, we describe a "directed search cone" method that has proved useful in identifying atoms that sit at the interface between two regions of a system. We call the set of atoms found to be sitting on the surface "leading atoms", and we construct an interface from these atoms that we call the "leading layer interface". We demonstrate the leading layer interface on solid-vacuum, liquid-vacuum, and liquid-vapor systems. In addition to presenting our method and example calculations, we discuss some observations of local density fluctuations that may be useful for the analysis of heterogeneous systems. Depending on the circumstances, there are various perspectives of an interface that may be insightful, and our leading layer interface will be useful in situations where the correlation between interfacial dynamics and local molecular composition is investigated.
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Affiliation(s)
- Shane S Cupp
- Department of Chemistry and Biochemistry, Northern Arizona University, Flagstaff, Arizona 86011, United States
- Department of Applied Physics and Materials Science, Northern Arizona University, Flagstaff, Arizona 86011, United States
| | - Anna E Engle
- Department of Astronomy and Planetary Science, Northern Arizona University, Flagstaff, Arizona 86011, United States
- Lowell Observatory, Flagstaff, Arizona 86001, United States
| | - Alex W Hardin
- Department of Applied Physics and Materials Science, Northern Arizona University, Flagstaff, Arizona 86011, United States
- MIRA, The Center for Materials Interfaces in Research and Applications, Northern Arizona University, Flagstaff, Arizona 86011, United States
| | - Gerrick E Lindberg
- Department of Chemistry and Biochemistry, Northern Arizona University, Flagstaff, Arizona 86011, United States
- Department of Astronomy and Planetary Science, Northern Arizona University, Flagstaff, Arizona 86011, United States
- MIRA, The Center for Materials Interfaces in Research and Applications, Northern Arizona University, Flagstaff, Arizona 86011, United States
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15
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Gale CD, Levinger NE. Predicting the Geometry of Core-Shell Structures: How a Shape Changes with Constant Added Thickness. J Phys Chem B 2024; 128:1317-1324. [PMID: 38288994 DOI: 10.1021/acs.jpcb.3c07652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
The core-shell assembly motif is ubiquitous in chemistry. While the most obvious examples are core/shell-type nanoparticles, many other examples exist. The shape of the core/shell constructs is poorly understood, making it impossible to separate chemical effects from geometric effects. Here, we create a model for the core/shell construct and develop proof for how the eccentricity is expected to change as a function of the shell. We find that the addition of a constant thickness shell always creates a relatively more spherical shape for all shapes covered by our model unless the shape is already spherical or has some underlying radial symmetry. We apply this work to simulated AOT reverse micelles and demonstrate that it is remarkably successful at explaining the observed shapes of the chemical systems. We identify the three specific cases where the model breaks down and how this impacts eccentricity.
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Affiliation(s)
- Christopher D Gale
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Nancy E Levinger
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
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16
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Devlin SW, Bernal F, Riffe EJ, Wilson KR, Saykally RJ. Spiers Memorial Lecture: Water at interfaces. Faraday Discuss 2024; 249:9-37. [PMID: 37795954 DOI: 10.1039/d3fd00147d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/06/2023]
Abstract
In this article we discuss current issues in the context of the four chosen subtopics for the meeting: dynamics and nano-rheology of interfacial water, electrified/charged aqueous interfaces, ice interfaces, and soft matter/water interfaces. We emphasize current advances in both theory and experiment, as well as important practical manifestations and areas of unresolved controversy.
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Affiliation(s)
- Shane W Devlin
- Department of Chemistry, University of California, Berkeley, CA 94720, USA.
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
| | - Franky Bernal
- Department of Chemistry, University of California, Berkeley, CA 94720, USA.
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
| | - Erika J Riffe
- Department of Chemistry, University of California, Berkeley, CA 94720, USA.
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
| | - Kevin R Wilson
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
| | - Richard J Saykally
- Department of Chemistry, University of California, Berkeley, CA 94720, USA.
- Chemical Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
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17
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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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18
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Jiao S, Robinson Brown DC, Shell MS. Relationships between Water's Structure and Solute Affinity at Polypeptoid Brush Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:761-771. [PMID: 38118078 DOI: 10.1021/acs.langmuir.3c02971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
Excellent antifouling surfaces are generally thought to create a tightly bound layer of water that resists solute adsorption, and highly hydrophilic surfaces such as those with zwitterionic functionalities are of significant current interest as antifoulant strategies. However, despite significant proofs-of-concept, we still lack a fundamental understanding of how the nanoscopic structure of this hydration layer translates to reduced fouling, how surface chemistry can be tuned to achieve antifouling through hydration water, and why, in particular, zwitterionic surfaces seem so promising. Here, we use molecular dynamics simulations and free energy calculations to investigate the molecular relationships among surface chemistry, hydration water structure, and surface-solute affinity across a variety of surface-decorated chemistries. Specifically, we consider polypeptoid-decorated surfaces that display well-known experimental antifouling capabilities and that can be synthesized sequence specifically, with precise backbone positioning of, e.g., charged groups. Through simulations, we calculate the affinities of a range of small solutes to polypeptoid brush surfaces of varied side-chain chemistries. We then demonstrate that measures of the structure of surface hydration water in response to a particular surface chemistry signal solute-surface affinity; specifically, we find that zwitterionic chemistries produce solute-surface repulsion through highly coordinated hydration water while suppressing tetrahedral structuring around the solute, in contrast to uncharged surfaces that show solute-surface affinity. Based on the relationship of this structural perturbation to the affinity of small-molecule solutes, we propose a molecular mechanism by which zwitterionic surface chemistries enhance solute repulsion, with broader implications for the design of antifouling surfaces.
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Affiliation(s)
- Sally Jiao
- Department of Chemical Engineering, University of California, Santa Barbara, California 93106, United States
| | - Dennis C Robinson Brown
- Department of Chemical Engineering, University of California, Santa Barbara, California 93106, United States
| | - M Scott Shell
- Department of Chemical Engineering, University of California, Santa Barbara, California 93106, United States
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19
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Zhang X, Arges CG, Kumar R. Computational Investigations of the Water Structure at the α-Al 2O 3(0001)-Water Interface. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2023; 127:15600-15610. [PMID: 37593231 PMCID: PMC10428097 DOI: 10.1021/acs.jpcc.3c03243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 07/03/2023] [Indexed: 08/19/2023]
Abstract
The α-Al2O3(0001)-water interface is investigated using ab initio molecular dynamics (AIMD) simulations. The spectral signatures of the vibrational sum frequency generation (vSFG) spectra of OH stretching mode for water molecules at the interface are related to the interfacial water orientation, hydrogen bond network, and water dissociation process at different water/alumina interfaces. Significant differences are found between alumina surfaces at different hydroxylation levels, namely, Al-terminated and O-terminated α-Al2O3(0001). By calculating the vibrational sum frequency generation spectrum and its imaginary component from AIMD results, the structure of interfacial waters as well as the termination of alumina slab are related to the spectral signatures of vSFG data.
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Affiliation(s)
- Xiaoliu Zhang
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803-1804, United
States
| | - Christopher G. Arges
- Department
of Chemical Engineering, Pennsylvania State
University, University Park, Pennsylvania 16802, United States
| | - Revati Kumar
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803-1804, United
States
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20
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Marks SM, Vicars Z, Thosar AU, Patel AJ. Characterizing Surface Ice-Philicity Using Molecular Simulations and Enhanced Sampling. J Phys Chem B 2023. [PMID: 37378637 DOI: 10.1021/acs.jpcb.3c01627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/29/2023]
Abstract
The formation of ice, which plays an important role in diverse contexts ranging from cryopreservation to atmospheric science, is often mediated by solid surfaces. Although surfaces that interact favorably with ice (relative to liquid water) can facilitate ice formation by lowering nucleation barriers, the molecular characteristics that confer icephilicity to a surface are complex and incompletely understood. To address this challenge, here we introduce a robust and computationally efficient method for characterizing surface ice-philicity that combines molecular simulations and enhanced sampling techniques to quantify the free energetic cost of increasing surface-ice contact at the expense of surface-water contact. Using this method to characterize the ice-philicity of a family of model surfaces that are lattice matched with ice but vary in their polarity, we find that the nonpolar surfaces are moderately ice-phobic, whereas the polar surfaces are highly ice-philic. In contrast, for surfaces that display no complementarity to the ice lattice, we find that ice-philicity is independent of surface polarity and that both nonpolar and polar surfaces are moderately ice-phobic. Our work thus provides a prescription for quantitatively characterizing surface ice-philicity and sheds light on how ice-philicity is influenced by lattice matching and polarity.
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Affiliation(s)
- Sean M Marks
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Zachariah Vicars
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Aniket U Thosar
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Amish J Patel
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
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21
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Konstantinovsky D, Yan ECY, Hammes-Schiffer S. Characterizing Interfaces by Voronoi Tessellation. J Phys Chem Lett 2023; 14:5260-5266. [PMID: 37265175 PMCID: PMC10344600 DOI: 10.1021/acs.jpclett.3c01159] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The chemistry of interfaces differs markedly from that of the bulk. Calculation of interfacial properties depends strongly on the definition of the interface, which can lead to ambiguous results that vary between studies. There is a need for a method that can explicitly define the interfaces and boundaries in molecular systems. Voronoi tessellation offers an attractive solution to this problem through its ability to determine neighbors among specified groups of atoms. Here we discuss three cases where Voronoi tessellation combined with modeling of vibrational sum frequency generation (SFG) spectroscopy yields relevant insights: the breakdown of the air-water interface into clear and intuitive molecular layers, the study of the hydration shell in biological systems, and the acceleration of difficult spectral calculations where intermolecular vibrational couplings dominate. The utility of Voronoi tessellation has broad applications that extend beyond any single type of spectroscopy or system.
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Affiliation(s)
- Daniel Konstantinovsky
- Department of Chemistry, Yale University, New Haven, CT, USA 06511
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA 06511
| | - Elsa C. Y. Yan
- Department of Chemistry, Yale University, New Haven, CT, USA 06511
| | - Sharon Hammes-Schiffer
- Department of Chemistry, Yale University, New Haven, CT, USA 06511
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA 06511
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22
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Phan A, Stamatakis M, Koh CA, Striolo A. Microscopic insights on clathrate hydrate growth from non-equilibrium molecular dynamics simulations. J Colloid Interface Sci 2023; 649:185-193. [PMID: 37348338 DOI: 10.1016/j.jcis.2023.06.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2023] [Revised: 05/03/2023] [Accepted: 06/06/2023] [Indexed: 06/24/2023]
Abstract
Clathrate hydrates form and grow at interfaces. Understanding the relevant molecular processes is crucial for developing hydrate-based technologies. Many computational studies focus on hydrate growth within the aqueous phase using the 'direct coexistence method', which is limited in its ability to investigate hydrate film growth at hydrocarbon-water interfaces. To overcome this shortcoming, a new simulation setup is presented here, which allows us to study the growth of a methane hydrate nucleus in a system where oil-water, hydrate-water, and hydrate-oil interfaces are all simultaneously present, thereby mimicking experimental setups. Using this setup, hydrate growth is studied here under the influence of two additives, a polyvinylcaprolactam oligomer and sodium dodecyl sulfate, at varying concentrations. Our results confirm that hydrate films grow along the oil-water interface, in general agreement with visual experimental observations; growth, albeit slower, also occurs at the hydrate-water interface, the interface most often interrogated via simulations. The results obtained demonstrate that the additives present within curved interfaces control the solubility of methane in the aqueous phase, which correlates with hydrate growth rate. Building on our simulation insights, we suggest that by combining data for the potential of mean force profile for methane transport across the oil-water interface and for the average free energy required to perturb a flat interface, it is possible to predict the performance of additives used to control hydrate growth. These insights could be helpful to achieve optimal methane storage in hydrates, one of many applications which are attracting significant fundamental and applied interests.
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Affiliation(s)
- Anh Phan
- School of Chemistry and Chemical Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, UK.
| | - Michail Stamatakis
- Department of Chemical Engineering, University College London, London WC1E 7JE, UK
| | - Carolyn A Koh
- Center for Hydrate Research, Chemical & Biological Engineering Department, Colorado School of Mines, Golden, CO 80401, United States
| | - Alberto Striolo
- Department of Chemical Engineering, University College London, London WC1E 7JE, UK; School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, OK 73019, United States.
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23
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McFegan L, Juhász Á, Márton P, Hórvölgyi Z, Jedlovszky-Hajdu A, Hantal G, Jedlovszky P. Surface Affinity of Tetramethylammonium Iodide in Aqueous Solutions: A Combined Experimental and Computer Simulation Study. J Phys Chem B 2023. [PMID: 37276239 DOI: 10.1021/acs.jpcb.3c01370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The surface affinity of tetramethylammonium iodide (TMAI) in aqueous solutions is investigated by surface tension measurements and molecular dynamics computer simulations. Experiments, performed in the entire composition range of solubility using the pendant drop method with two different setups, clearly reveal that TMAI is a weakly capillary active salt. Computer simulations performed with the AMBER force field reproduce the experimental data very well, while two other major force fields (i.e., CHARMM and OPLS) can still reproduce the experimental trend qualitatively; however, even qualitative reproduction of the experimental trend requires scaling down the ion charges according to the Leontyev-Stuchebrukhov correction. On the other hand, the GROMOS force field fails in reproducing the experimentally confirmed capillary activity of TMAI. Molecular dynamics simulation results show that, among the two ions, iodide has a clearly larger surface affinity than tetramethylammonium (TMA+). Further, the adsorption of the I- anions is strictly limited to the first molecular layer beneath the liquid-vapor interface, which is followed by several layers of their depletion. On the other hand, the net negative charge of the surface layer, caused by the excess amount of I- with respect to TMA+, is compensated by a diffuse layer of adsorbed TMA+ cations, extending to or beyond the fourth molecular layer beneath the liquid surface.
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Affiliation(s)
- Louisa McFegan
- Faculty of Chemical Technology and Biotechnology, Budapest University of Technology and Economics, Szt. Gellért tér 4, H-1111 Budapest, Hungary
| | | | - Péter Márton
- Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, Budafoki út 8, H-1111 Budapest, Hungary
| | - Zoltán Hórvölgyi
- Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, Budafoki út 8, H-1111 Budapest, Hungary
| | | | - György Hantal
- Institute of Physics and Materials Science, University of Natural Resources and Life Sciences, Peter Jordan Straße 82, A-1190 Vienna, Austria
| | - Pál Jedlovszky
- Department of Chemistry, Eszterházy Károly Catholic University, Leányka utca 6, H-3300 Eger, Hungary
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24
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Hantal G, Jedlovszky P, Sega M. Local structure of liquid/vapour interfaces approaching the critical point. SOFT MATTER 2023; 19:3773-3782. [PMID: 37098698 DOI: 10.1039/d3sm00176h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Investigating the structure of fluid interfaces at high temperatures is a particularly delicate task that requires effective ways of discriminating liquid from vapour and identifying the location of the liquid phase boundary, thereby allowing to distinguish intrinsic from capillary fluctuations. Several numerical approaches require introducing a coarse-graining length scale, often heuristically chosen to be the molecular size, to determine the location of the liquid phase boundary. Here, we propose an alternative rationale for choosing this coarse-graining length scale; we require the average position of the local liquid phase dividing surface to match its flat, macroscopic counterpart. We show that this approach provides additional insight into the structure of the liquid/vapour interface, suggesting the presence of another length scale beyond the bulk correlation one that plays an important role in determining the interface structure.
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Affiliation(s)
- György Hantal
- Institute of Physics and Materials Science, University of Natural Resources and Life Sciences, Peter Jordan Strasse 82, A-1190 Vienna, Austria
| | - Pál Jedlovszky
- Department of Chemistry, Eszterhazy Karoly University, Leanyka utca 6, H-3300 Eger, Hungary
| | - Marcello Sega
- Department of Chemical Engineering, University College London, London WC1E 7JE, UK.
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25
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Lemay AC, Sontarp EJ, Martinez D, Maruri P, Mohammed R, Neapole R, Wiese M, Willemsen JAR, Bourg IC. Molecular Dynamics Simulation Prediction of the Partitioning Constants ( KH, Kiw, Kia) of 82 Legacy and Emerging Organic Contaminants at the Water-Air Interface. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:6296-6308. [PMID: 37014786 DOI: 10.1021/acs.est.3c00267] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
The tendency of organic contaminants (OCs) to partition between different phases is a key set of properties that underlie their human and ecological health impacts and the success of remediation efforts. A significant challenge associated with these efforts is the need for accurate partitioning data for an ever-expanding list of OCs and breakdown products. All-atom molecular dynamics (MD) simulations have the potential to help generate these data, but existing studies have applied these techniques only to a limited variety of OCs. Here, we use established MD simulation approaches to examine the partitioning of 82 OCs, including many compounds of critical concern, at the water-air interface. Our predictions of the Henry's law constant (KH) and interfacial adsorption coefficients (Kiw, Kia) correlate strongly with experimental results, indicating that MD simulations can be used to predict KH, Kiw, and Kia values with mean absolute deviations of 1.1, 0.3, and 0.3 logarithmic units after correcting for systematic bias, respectively. A library of MD simulation input files for the examined OCs is provided to facilitate future investigations of the partitioning of these compounds in the presence of other phases.
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Affiliation(s)
- Amélie C Lemay
- Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Ethan J Sontarp
- Department of Geosciences, Princeton University, Princeton, New Jersey 08544, United States
| | - Daniela Martinez
- Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Philip Maruri
- Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Raneem Mohammed
- Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Ryan Neapole
- Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Morgan Wiese
- Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Jennifer A R Willemsen
- Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Ian C Bourg
- Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, United States
- High Meadows Environmental Institute, Princeton University, Princeton, New Jersey 08544, United States
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26
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Dupuy R, Filser J, Richter C, Buttersack T, Trinter F, Gholami S, Seidel R, Nicolas C, Bozek J, Egger D, Oberhofer H, Thürmer S, Hergenhahn U, Reuter K, Winter B, Bluhm H. Ångstrom-Depth Resolution with Chemical Specificity at the Liquid-Vapor Interface. PHYSICAL REVIEW LETTERS 2023; 130:156901. [PMID: 37115858 DOI: 10.1103/physrevlett.130.156901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 02/22/2023] [Indexed: 06/19/2023]
Abstract
The determination of depth profiles across interfaces is of primary importance in many scientific and technological areas. Photoemission spectroscopy is in principle well suited for this purpose, yet a quantitative implementation for investigations of liquid-vapor interfaces is hindered by the lack of understanding of electron-scattering processes in liquids. Previous studies have shown, however, that core-level photoelectron angular distributions (PADs) are altered by depth-dependent elastic electron scattering and can, thus, reveal information on the depth distribution of species across the interface. Here, we explore this concept further and show that the experimental anisotropy parameter characterizing the PAD scales linearly with the average distance of atoms along the surface normal obtained by molecular dynamics simulations. This behavior can be accounted for in the low-collision-number regime. We also show that results for different atomic species can be compared on the same length scale. We demonstrate that atoms separated by about 1 Å along the surface normal can be clearly distinguished with this method, achieving excellent depth resolution.
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Affiliation(s)
- R Dupuy
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, LCPMR, F-75005 Paris Cedex 05, France
| | - J Filser
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - C Richter
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - T Buttersack
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - F Trinter
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
- Institut für Kernphysik, Goethe-Universität Frankfurt am Main, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany
| | - S Gholami
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - R Seidel
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
| | - C Nicolas
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP 48 91192, Gif-sur-Yvette Cedex, France
| | - J Bozek
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP 48 91192, Gif-sur-Yvette Cedex, France
| | - D Egger
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - H Oberhofer
- Department of Physics, University of Bayreuth, 95440 Bayreuth, Germany
| | - S Thürmer
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto 606-8502, Japan
| | - U Hergenhahn
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - K Reuter
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - B Winter
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - H Bluhm
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
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27
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Zhang H, Sundaresan S, Webb MA. Molecular Dynamics Investigation of Nanoscale Hydrophobicity of Polymer Surfaces: What Makes Water Wet? J Phys Chem B 2023. [PMID: 37043668 DOI: 10.1021/acs.jpcb.3c00616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Abstract
The wettability of a polymer surface─related to its hydrophobicity or tendency to repel water─can be crucial for determining its utility, such as for a coating or a purification membrane. While wettability is commonly associated with the macroscopic measurement of a contact angle between surface, water, and air, the molecular physics that underlie these macroscopic observations are not fully known, and anticipating the relative behavior of different polymers is challenging. To address this gap in molecular-level understanding, we use molecular dynamics simulations to investigate and contrast interactions of water with six chemically distinct polymers: polytetrafluoroethylene, polyethylene, polyvinyl chloride, poly(methyl methacrylate), Nylon-66, and poly(vinyl alcohol). We show that several prospective quantitative metrics for hydrophobicity agree well with experimental contact angles. Moreover, the behavior of water in proximity to these polymer surfaces can be distinguished with analysis of interfacial water dynamics, extent of hydrogen bonding, and molecular orientation─even when macroscopic measures of hydrophobicity are similar. The predominant factor dictating wettability is found to be the extent of hydrogen bonding between polymer and water, but the precise manifestation of hydrogen bonding and its impact on surface water structure varies. In the absence of hydrogen bonding, other molecular interactions and polymer mechanics control hydrophobic ordering. These results provide new insights into how polymer chemistry specifically impacts water-polymer interactions and translates to surface hydrophobicity. Such factors may facilitate the design or processing of polymer surfaces to achieve targeted wetting behavior, and presented analyses can be useful in studying the interfacial physics of other systems.
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Affiliation(s)
- Hang Zhang
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Sankaran Sundaresan
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Michael A Webb
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
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28
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Subasinghege Don V, Kim L, David R, Nauman JA, Kumar R. Adsorption Studies at the Graphene Oxide-Liquid Interface: A Molecular Dynamics Study. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2023; 127:5920-5930. [PMID: 37025926 PMCID: PMC10069394 DOI: 10.1021/acs.jpcc.2c07080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 03/08/2023] [Indexed: 06/19/2023]
Abstract
The adsorption of organic aromatic molecules, namely aniline, onto graphene oxide is investigated using molecular simulations. The effect of the oxidation level of the graphene oxide sheet as well as the presence of two different halide salts, sodium chloride and sodium iodide, were examined. The aniline molecule in the more-reduced graphene oxide case, in the absence of added salt, showed a slightly greater affinity for the graphene oxide-water interface as compared to the oxidized form. The presence of the iodide ion increased the affinity of the aniline molecule in the reduced case but had the opposite effect for the more-oxidized form. The effect of oxidation and added salt on the interfacial water layer was also examined.
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Affiliation(s)
- Visal Subasinghege Don
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803-1804, United States
| | - Lukas Kim
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803-1804, United States
| | - Rolf David
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803-1804, United States
| | - Julia A. Nauman
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803-1804, United States
| | - Revati Kumar
- Department
of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803-1804, United States
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29
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Donkor ED, Laio A, Hassanali A. Do Machine-Learning Atomic Descriptors and Order Parameters Tell the Same Story? The Case of Liquid Water. J Chem Theory Comput 2023. [PMID: 36920997 DOI: 10.1021/acs.jctc.2c01205] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
Abstract
Machine-learning (ML) has become a key workhorse in molecular simulations. Building an ML model in this context involves encoding the information on chemical environments using local atomic descriptors. In this work, we focus on the Smooth Overlap of Atomic Positions (SOAP) and their application in studying the properties of liquid water both in the bulk and at the hydrophobic air-water interface. By using a statistical test aimed at assessing the relative information content of different distance measures defined on the same data space, we investigate if these descriptors provide the same information as some of the common order parameters that are used to characterize local water structure such as hydrogen bonding, density, or tetrahedrality to name a few. Our analysis suggests that the ML description and the standard order parameters of the local water structure are not equivalent. In particular, a combination of these order parameters probing local water environments can predict SOAP similarity only approximately, and vice versa, the environments that are similar according to SOAP are not necessarily similar according to the standard order parameters. We also elucidate the role of some of the metaparameters in the SOAP definition in encoding chemical information.
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Affiliation(s)
- Edward Danquah Donkor
- The Abdus Salam International Center for Theoretical Physics (ICTP), Strada Costiera 11, 34151 Trieste, Italy.,Scuola Internazionale Superiore di Studi Avanzati (SISSA), via Bonomea 265, 34136 Trieste, Italy
| | - Alessandro Laio
- Scuola Internazionale Superiore di Studi Avanzati (SISSA), via Bonomea 265, 34136 Trieste, Italy
| | - Ali Hassanali
- The Abdus Salam International Center for Theoretical Physics (ICTP), Strada Costiera 11, 34151 Trieste, Italy
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30
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Shin S, Willard AP. Quantifying the Molecular Polarization Response of Liquid Water Interfaces at Heterogeneously Charged Surfaces. J Chem Theory Comput 2023; 19:1843-1852. [PMID: 36866865 DOI: 10.1021/acs.jctc.2c01256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Abstract
The hydration shells of proteins mediate interactions, such as small molecule binding, that are vital to their biological function or in some cases their dysfunction. However, even when the structure of a protein is known, the properties of its hydration environment cannot be easily predicted due to the complex interplay between protein surface heterogeneity and the collective structure of water's hydrogen bonding network. This manuscript presents a theoretical study of the influence of surface charge heterogeneity on the polarization response of the liquid water interface. We focus our attention on classical point charge models of water, where the polarization response is limited to molecular reorientation. We introduce a new computational method for analyzing simulation data that is capable of quantifying water's collective polarization response and determining the effective surface charge distribution of hydrated surfaces over atomistic length scales. To illustrate the utility of this method, we present the results of molecular dynamics simulations of liquid water in contact with a heterogeneous model surface and the CheY protein.
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Affiliation(s)
- Sucheol Shin
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.,Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Adam P Willard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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31
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Ge P, Zhang L, Lei H. Machine learning assisted coarse-grained molecular dynamics modeling of meso-scale interfacial fluids. J Chem Phys 2023; 158:064104. [PMID: 36792498 DOI: 10.1063/5.0131567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
A hallmark of meso-scale interfacial fluids is the multi-faceted, scale-dependent interfacial energy, which often manifests different characteristics across the molecular and continuum scale. The multi-scale nature imposes a challenge to construct reliable coarse-grained (CG) models, where the CG potential function needs to faithfully encode the many-body interactions arising from the unresolved atomistic interactions and account for the heterogeneous density distributions across the interface. We construct the CG models of both single- and two-component polymeric fluid systems based on the recently developed deep coarse-grained potential [Zhang et al., J. Chem. Phys. 149, 034101 (2018)] scheme, where each polymer molecule is modeled as a CG particle. By only using the training samples of the instantaneous force under the thermal equilibrium state, the constructed CG models can accurately reproduce both the probability density function of the void formation in bulk and the spectrum of the capillary wave across the fluid interface. More importantly, the CG models accurately predict the volume-to-area scaling transition for the apolar solvation energy, illustrating the effectiveness to probe the meso-scale collective behaviors encoded with molecular-level fidelity.
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Affiliation(s)
- Pei Ge
- Department of Computational Mathematics, Science and Engineering, Michigan State University, East Lansing, Michigan 48824, USA
| | | | - Huan Lei
- Department of Computational Mathematics, Science and Engineering, Michigan State University, East Lansing, Michigan 48824, USA
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32
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Chen W, Sanders SE, Özdamar B, Louaas D, Brigiano FS, Pezzotti S, Petersen PB, Gaigeot MP. On the Trail of Molecular Hydrophilicity and Hydrophobicity at Aqueous Interfaces. J Phys Chem Lett 2023; 14:1301-1309. [PMID: 36724059 DOI: 10.1021/acs.jpclett.2c03300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Uncovering microscopic hydrophilicity and hydrophobicity at heterogeneous aqueous interfaces is essential as it dictates physico/chemical properties such as wetting, the electrical double layer, and reactivity. Several molecular and spectroscopic descriptors were proposed, but a major limitation is the lack of connections between them. Here, we combine density functional theory-based MD simulations (DFT-MD) and SFG spectroscopy to explore how interfacial water responds in contact with self-assembled monolayers (SAM) of tunable hydrophilicity. We introduce a microscopic metric to track the transition from hydrophobic to hydrophilic interfaces. This metric combines the H/V descriptor, a structural descriptor based on the preferential orientation within the water network in the topmost binding interfacial layer (BIL) and spectroscopic fingerprints of H-bonded and dangling OH groups of water carried by BIL-resolved SFG spectra. This metric builds a bridge between molecular descriptors of hydrophilicity/hydrophobicity and spectroscopically measured quantities and provides a recipe to quantitatively or qualitatively interpret experimental SFG signals.
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Affiliation(s)
- Wanlin Chen
- Université Paris-Saclay, Université Evry, CNRS, LAMBE UMR8587, 91025Evry-Courcouronnes, France
| | - Stephanie E Sanders
- Department of Chemistry and Biochemistry, Ruhr University Bochum, 44801Bochum, Germany
| | - Burak Özdamar
- Université Paris-Saclay, Université Evry, CNRS, LAMBE UMR8587, 91025Evry-Courcouronnes, France
| | - Dorian Louaas
- Université Paris-Saclay, Université Evry, CNRS, LAMBE UMR8587, 91025Evry-Courcouronnes, France
| | - Flavio Siro Brigiano
- Université Paris-Saclay, Université Evry, CNRS, LAMBE UMR8587, 91025Evry-Courcouronnes, France
- Laboratoire de Chimie Théorique, Sorbonne Université, UMR 7616 CNRS, 4 Place Jussieu, 75005Paris, France
| | - Simone Pezzotti
- Université Paris-Saclay, Université Evry, CNRS, LAMBE UMR8587, 91025Evry-Courcouronnes, France
- Department of Physical Chemistry II, Ruhr University Bochum, D-44801Bochum, Germany
| | - Poul B Petersen
- Department of Chemistry and Biochemistry, Ruhr University Bochum, 44801Bochum, Germany
| | - Marie-Pierre Gaigeot
- Université Paris-Saclay, Université Evry, CNRS, LAMBE UMR8587, 91025Evry-Courcouronnes, France
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33
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Salehi SM, Pezzella M, Willard A, Meuwly M, Karplus M. Water dynamics around T 0 vs R 4 of hemoglobin from local hydrophobicity analysis. J Chem Phys 2023; 158:025101. [PMID: 36641390 DOI: 10.1063/5.0129990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The local hydration around tetrameric hemoglobin (Hb) in its T0 and R4 conformational substates is analyzed based on molecular dynamics simulations. Analysis of the local hydrophobicity (LH) for all residues at the α1β2 and α2β1 interfaces, responsible for the quaternary T → R transition, which is encoded in the Monod-Wyman-Changeux model, as well as comparison with earlier computations of the solvent accessible surface area, makes clear that the two quantities measure different aspects of hydration. Local hydrophobicity quantifies the presence and structure of water molecules at the interface, whereas "buried surface" reports on the available space for solvent. For simulations with Hb frozen in its T0 and R4 states, the correlation coefficient between LH and buried surface is 0.36 and 0.44, respectively, but it increases considerably if the 95% confidence interval is used. The LH with Hb frozen and flexible changes little for most residues at the interfaces but is significantly altered for a few select ones: Thr41α, Tyr42α, Tyr140α, Trp37β, Glu101β (for T0) and Thr38α, Tyr42α, Tyr140α (for R4). The number of water molecules at the interface is found to increase by ∼25% for T0 → R4, which is consistent with earlier measurements. Since hydration is found to be essential to protein function, it is clear that hydration also plays an essential role in allostery.
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Affiliation(s)
- Seyedeh Maryam Salehi
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
| | - Marco Pezzella
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
| | - Adam Willard
- Department of Chemistry MIT, Cambridge, Massachusetts 02139, USA
| | - Markus Meuwly
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
| | - Martin Karplus
- Department of Chemistry, Harvard University, Cambridge, Massachusetts 02138, USA
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34
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Hao H, Adams EM, Funke S, Schwaab G, Havenith M, Head-Gordon T. Highly Altered State of Proton Transport in Acid Pools in Charged Reverse Micelles. J Am Chem Soc 2023; 145:1826-1834. [PMID: 36633459 PMCID: PMC9881006 DOI: 10.1021/jacs.2c11331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Transport mechanisms of solvated protons of 1 M HCl acid pools, confined within reverse micelles (RMs) containing the negatively charged surfactant sodium bis(2-ethylhexyl) sulfosuccinate (NaAOT) or the positively charged cetyltrimethylammonium bromide (CTABr), are analyzed with reactive force field simulations to interpret dynamical signatures from TeraHertz absorption and dielectric relaxation spectroscopy. We find that the forward proton hopping events for NaAOT are further suppressed compared to a nonionic RM, while the Grotthuss mechanism ceases altogether for CTABr. We attribute the sluggish proton dynamics for both charged RMs as due to headgroup and counterion charges that expel hydronium and chloride ions from the interface and into the bulk interior, thereby increasing the pH of the acid pools relative to the nonionic RM. For charged NaAOT and CTABr RMs, the localization of hydronium near a counterion or conjugate base reduces the Eigen and Zundel configurations that enable forward hopping. Thus, localized oscillatory hopping dominates, an effect that is most extreme for CTABr in which the proton residence time increases dramatically such that even oscillatory hopping is slow.
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Affiliation(s)
- Hongxia Hao
- Kenneth
S. Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California, Berkeley, California94720, United States
| | - Ellen M. Adams
- Cluster
of Excellence Physics of Life, Technische
Universität Dresden, 01307Dresden, Germany,Helmholtz-Zentrum
Dresden-Rossendorf, Institute of Resource
Ecology, 01328Dresden, Germany
| | - Sarah Funke
- Lehrstuhl
für Physkalische Chemie II, Ruhr
Universität Bochum, 44801Bochum, Germany
| | - Gerhard Schwaab
- Lehrstuhl
für Physkalische Chemie II, Ruhr
Universität Bochum, 44801Bochum, Germany
| | - Martina Havenith
- Lehrstuhl
für Physkalische Chemie II, Ruhr
Universität Bochum, 44801Bochum, Germany
| | - Teresa Head-Gordon
- Kenneth
S. Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California, Berkeley, California94720, United States,Department
of Bioengineering, Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California94720, United States,Chemical
Sciences Division, Lawrence Berkeley National
Laboratory, Berkeley, California94720, United States,
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35
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Becker MR, Loche P, Netz RR. Electrokinetic, electrochemical, and electrostatic surface potentials of the pristine water liquid-vapor interface. J Chem Phys 2022; 157:240902. [PMID: 36586978 DOI: 10.1063/5.0127869] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Although conceptually simple, the air-water interface displays rich behavior and is subject to intense experimental and theoretical investigations. Different definitions of the electrostatic surface potential as well as different calculation methods, each relevant for distinct experimental scenarios, lead to widely varying potential magnitudes and sometimes even different signs. Based on quantum-chemical density-functional-theory molecular dynamics (DFT-MD) simulations, different surface potentials are evaluated and compared to force-field (FF) MD simulations. As well explained in the literature, the laterally averaged electrostatic surface potential, accessible to electron holography, is dominated by the trace of the water molecular quadrupole moment, and using DFT-MD amounts to +4.35 V inside the water phase, very different from results obtained with FF water models which yield negative values of the order of -0.4 to -0.6 V. Thus, when predicting potentials within water molecules, as relevant for photoelectron spectroscopy and non-linear interface-specific spectroscopy, DFT simulations should be used. The electrochemical surface potential, relevant for ion transfer reactions and ion surface adsorption, is much smaller, less than 200 mV in magnitude, and depends specifically on the ion radius. Charge transfer between interfacial water molecules leads to a sizable surface potential as well. However, when probing electrokinetics by explicitly applying a lateral electric field in DFT-MD simulations, the electrokinetic ζ-potential turns out to be negligible, in agreement with predictions using continuous hydrodynamic models. Thus, interfacial polarization charges from intermolecular charge transfer do not lead to significant electrokinetic mobility at the pristine vapor-liquid water interface, even assuming these transfer charges are mobile in an external electric field.
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Affiliation(s)
| | - Philip Loche
- Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | - Roland R Netz
- Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
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36
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Das B, Chandra A. Vibrational Sum Frequency Generation Spectra of Water-Vapor Interfaces Covered by Alcohols: Effects of Surface Coverage and Coupling between Oscillators. Chemphyschem 2022; 24:e202200604. [PMID: 36537178 DOI: 10.1002/cphc.202200604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Revised: 12/18/2022] [Accepted: 12/20/2022] [Indexed: 12/24/2022]
Abstract
The present study deals with the effects of varying coverage of water surface by alcohols on the vibrational sum frequency generation (VSFG) spectrum of interfacial water. We have considered two different alcohols: Tertiary butyl alcohol (TBA) whose alkyl part is fully branched and stearyl alcohol (STA) which has a long linear alkyl chain with larger hydrophobic surface area than that of TBA. With increase of the alcohol concentration, the hydrogen bonded OH stretch region of the VSFG spectrum is found to change following a regular trend for the STA-water system, whereas non-monotonic variation of the VSFG spectrum is observed for the TBA-water system which can be correlated with the presence of very different interactions of TBA molecules at different concentrations. On increasing the concentration of TBA, the hydrophobic groups get more tilted towards the water phase and significant hydrophobic interactions are introduced at higher concentrations. Whereas, for STA, there is a gradual increase in the hydrophilic interaction. Because of stacking interactions between the long chain alkyl groups, the hydrophobic parts stay outward from the water phase at higher concentrations and a regular change in the VSFG spectrum is observed. We have also presented a computationally efficient scheme to calculate the VSFG spectrum of interfacial systems for coupled oscillators which is expected to be beneficial for the treatment of coupling where the interfacial system size is inherently large.
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Affiliation(s)
- Banshi Das
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Amalendu Chandra
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India, 208016
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37
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Heindel JP, Hao H, LaCour RA, Head-Gordon T. Spontaneous Formation of Hydrogen Peroxide in Water Microdroplets. J Phys Chem Lett 2022; 13:10035-10041. [PMID: 36264238 DOI: 10.1021/acs.jpclett.2c01721] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
There is accumulating evidence that many chemical reactions are accelerated by several orders of magnitude in micrometer-sized aqueous or organic liquid droplets compared to their corresponding bulk liquid phase. However, the molecular origin of the enhanced rates remains unclear as in the case of spontaneous appearance of 1 μM hydrogen peroxide in water microdroplets. In this Letter, we consider the range of ionization energies and whether interfacial electric fields of a microdroplet can feasibly overcome the high energy step from hydroxide ions (OH-) to hydroxyl radicals (OH•) in a primary H2O2 mechanism. We find that the vertical ionization energies (VIEs) of partially solvated OH- ions are greatly lowered relative to the average VIE in the bulk liquid, unlike the case of the Cl- anion which shows no reduction in the VIEs regardless of solvation environment. Overall reduced hydrogen-bonding and undercoordination of OH- are structural features that are more readily present at the air-water interface, where the energy scale for ionization can be matched by statistically probable electric field values.
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Affiliation(s)
- Joseph P Heindel
- Kenneth S. Pitzer Theory Center and Department of Chemistry, University of California, Berkeley, California94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California94720, United States
| | - Hongxia Hao
- Kenneth S. Pitzer Theory Center and Department of Chemistry, University of California, Berkeley, California94720, United States
| | - R Allen LaCour
- Kenneth S. Pitzer Theory Center and Department of Chemistry, University of California, Berkeley, California94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California94720, United States
| | - Teresa Head-Gordon
- Kenneth S. Pitzer Theory Center and Department of Chemistry, University of California, Berkeley, California94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California94720, United States
- Departments of Bioengineering and Chemical and Biomolecular EngineeringUniversity of California, Berkeley, California94720, United States
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38
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Yen TH, Chen YL. Analysis of Gas Nanoclusters in Water Using All-Atom Molecular Dynamics. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:13195-13205. [PMID: 36255233 DOI: 10.1021/acs.langmuir.2c02042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The Young-Laplace equation suggests that nanosized gas clusters would dissolve under the effects of perturbation. The fact that nanobubbles are observed raises questions as to the mechanism underlying their stability. In the current study, we used all-atom molecular dynamics simulations to investigate the gas-water interfacial properties of gas clusters. We employed the instantaneous coarse-graining method to define the fluctuating boundaries and analyze the deformation of gas clusters. Fourier transform analysis of the cluster morphology revealed that the radius and morphology deformation variations exhibit power law relationships with the vibrational frequency, indicating that the surface energy dissipated through morphology variations. Increasing pressure in the liquid region was found to alter the network of water molecules at the interface, whereas increasing pressure in the gas region did not exhibit this effect. The overall gas concentration was oversaturated and proportional to the gas density inside the clusters. However, the result of comparison with Henry's law reveals that the gas pressure at the interface reduced by the interfacial effects is much lower than that inside the gas region, thus reducing the demanding degree of oversaturation. Originating from the interfacial charge allocation, the magnitude of the electrostatic stress is greater than that of the gas pressure inside the cluster. However, the magnitude of the reversed tension induced by electrostatic stress is far below the value of interfacial tension. The potential of mean force (PMF) profiles revealed that a barrier potential at the interface hindered gas particles from escaping the cluster. Several effects contribute to stabilizing the gas clusters in water, including high-frequency morphological deformation, electrostatic stress, reduced interfacial tension, and gas oversaturation conditions. Our results suggest that gas clusters can exist in water under gas oversaturation conditions in the absence of hydrophobic contaminants or pinning charges at interfaces.
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Affiliation(s)
- Tsu-Hsu Yen
- Department of Marine Science, R.O.C. Naval Academy, Zuoying, Kaohsiung, Taiwan, R.O.C.813
| | - Yeng-Long Chen
- Institute of Physics, Academia Sinica, Taipei, Taiwan, R.O.C.11529
- Department of Chemical Engineering, National Tsing-Hua University, Hsinchu, Taiwan, R.O.C30013
- Physics Division, National Center for Theoretical Sciences, Taipei, Taiwan, R.O.C10617
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39
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Hao H, Ruiz Pestana L, Qian J, Liu M, Xu Q, Head‐Gordon T. Chemical transformations and transport phenomena at interfaces. WIRES COMPUTATIONAL MOLECULAR SCIENCE 2022. [DOI: 10.1002/wcms.1639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Hongxia Hao
- Kenneth S. Pitzer Theory Center and Department of Chemistry University of California Berkeley California USA
- Chemical Sciences Division Lawrence Berkeley National Laboratory Berkeley California USA
| | - Luis Ruiz Pestana
- Department of Civil and Architectural Engineering University of Miami Coral Gables Florida USA
| | - Jin Qian
- Chemical Sciences Division Lawrence Berkeley National Laboratory Berkeley California USA
| | - Meili Liu
- Department of Civil and Architectural Engineering University of Miami Coral Gables Florida USA
| | - Qiang Xu
- Chemical Sciences Division Lawrence Berkeley National Laboratory Berkeley California USA
| | - Teresa Head‐Gordon
- Kenneth S. Pitzer Theory Center and Department of Chemistry University of California Berkeley California USA
- Chemical Sciences Division Lawrence Berkeley National Laboratory Berkeley California USA
- Department of Bioengineering and Chemical and Biomolecular Engineering University of California Berkeley California USA
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40
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Zhou Y, Lopez GE, Giovambattista N. Anomalous properties in the potential energy landscape of a monatomic liquid across the liquid-gas and liquid-liquid phase transitions. J Chem Phys 2022; 157:124502. [PMID: 36182441 PMCID: PMC9525132 DOI: 10.1063/5.0106923] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 08/26/2022] [Indexed: 11/14/2022] Open
Abstract
As a liquid approaches the gas state, the properties of the potential energy landscape (PEL) sampled by the system become anomalous. Specifically, (i) the mechanically stable local minima of the PEL [inherent structures (IS)] can exhibit cavitation above the so-called Sastry volume, vS, before the liquid enters the gas phase. In addition, (ii) the pressure of the liquid at the sampled IS [i.e., the PEL equation of state, PIS(v)] develops a spinodal-like minimum at vS. We perform molecular dynamics simulations of a monatomic water-like liquid and verify that points (i) and (ii) hold at high temperatures. However, at low temperatures, cavitation in the liquid and the corresponding IS occurs simultaneously and a Sastry volume cannot be defined. Remarkably, at intermediate/high temperatures, the IS of the liquid can exhibit crystallization, i.e., the liquid regularly visits the regions of the PEL that belong to the crystal state. The model liquid considered also exhibits a liquid-liquid phase transition (LLPT) between a low-density and a high-density liquid (LDL and HDL). By studying the behavior of PIS(v) during the LLPT, we identify a Sastry volume for both LDL and HDL. The HDL Sastry volume marks the onset above which IS are heterogeneous (composed of LDL and HDL particles), analogous to points (i) and (ii) above. However, the relationship between the LDL Sastry volume and the onset of heterogeneous IS is less evident. We conclude by presenting a thermodynamic argument that can explain the behavior of the PEL equation of state PIS(v) across both the liquid-gas phase transition and LLPT.
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41
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Sinha I, Cramer SM, Ashbaugh HS, Garde S. Connecting Non-Gaussian Water Density Fluctuations to the Lengthscale Dependent Crossover in Hydrophobic Hydration. J Phys Chem B 2022; 126:7604-7614. [PMID: 36154059 DOI: 10.1021/acs.jpcb.2c04990] [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
We connect density fluctuations in liquid water to lengthscale dependent crossover in hydrophobic hydration. Specifically, we employ indirect umbrella sampling (INDUS) simulations to characterize density fluctuations in observation volumes of various sizes and shapes in water and as a function of temperature and salt concentration. Consistent with previous observations, density fluctuations are Gaussian in small molecular scale volumes, but they display non-Gaussian "low-density fat tails" in larger volumes. These non-Gaussian tails are indicative of the proximity of water to its liquid to vapor phase transition and have implications on biomolecular interactions and function. We show that the onset of non-Gaussian fluctuations in large volumes is accompanied by the formation of a cavity in the observation volume. We develop a model that uses the physics of cavity-water interface formation as a key ingredient and show that it captures the nature of non-Gaussian density fluctuations over a broad region in water and in salt solutions. We discuss the limitations of this model in the very low density region of the distribution. Our calculations provide new insights into the origins of non-Gaussian density fluctuations in water and their connections to lengthscale dependent crossover in hydrophobic hydration.
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Affiliation(s)
- Imee Sinha
- Howard P. Isermann Department of Chemical and Biological Engineering and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180, United States
| | - Steven M Cramer
- Howard P. Isermann Department of Chemical and Biological Engineering and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180, United States
| | - Henry S Ashbaugh
- Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70123, United States
| | - Shekhar Garde
- Howard P. Isermann Department of Chemical and Biological Engineering and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180, United States
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42
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Jami L, Zemb T, Casas J, Dufrêche JF. Individual adsorption of low volatility pheromones: Amphiphilic molecules on a clean water-air interface. J Chem Phys 2022; 157:094708. [PMID: 36075737 DOI: 10.1063/5.0110264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Environmental conditions can alter olfactory scent and chemical communication among biological species. In particular, odorant molecules interact with aerosols. Thermodynamics variables governing the adsorption from air to water surface of bombykol, the most studied pheromone, and of three derivative molecules, bombykal, bombykoic acid, and bombykyle acetate, are computed by steered and un-biased molecular dynamics in order to compare the role of their polar head group on adsorption on aqueous aerosols. When adsorbed, the molecule center of mass stands at about 1.2 Å from the interface and oscillates on the same length scale, trapped in an energy well. Gibbs energy of adsorption and desorption time of bombykol are found to be 9.2 kBT and 59 µs, respectively. The following ordering between the molecules is observed, reading from the more to the least adsorbed: bombykoic acid > bombykol > bombykoic acetate > bombykal. It originates from a complex interplay of entropy and enthalpy. The entropy and enthalpy of adsorption are discussed in the light of structural arrangement, H-bonding, and hydrophilic tail positioning of the molecules at the interface. Our results show that, when dispersed in the air, pheromones adsorb on aqueous aerosols. However, the individual residence time is quite short on pure water surfaces. Aerosols can, therefore, only have a decisive influence on chemical communication through collective effects or through their chemical composition that is generally more complex than that of a pure water surface.
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Affiliation(s)
- L Jami
- Institut de Recherche sur la Biologie de l'Insecte, UMR 7261, CNRS-Université de Tours, Tours, France
| | - T Zemb
- ICSM, CEA, CNRS, ENSCM, Univ. Montpellier, Marcoule, France
| | - J Casas
- Institut de Recherche sur la Biologie de l'Insecte, UMR 7261, CNRS-Université de Tours, Tours, France
| | - J-F Dufrêche
- ICSM, CEA, CNRS, ENSCM, Univ. Montpellier, Marcoule, France
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43
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Chiang KY, Seki T, Yu CC, Ohto T, Hunger J, Bonn M, Nagata Y. The dielectric function profile across the water interface through surface-specific vibrational spectroscopy and simulations. Proc Natl Acad Sci U S A 2022; 119:e2204156119. [PMID: 36037357 PMCID: PMC9457560 DOI: 10.1073/pnas.2204156119] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 07/25/2022] [Indexed: 11/18/2022] Open
Abstract
The dielectric properties of interfacial water on subnanometer length scales govern chemical reactions, carrier transfer, and ion transport at interfaces. Yet, the nature of the interfacial dielectric function has remained under debate as it is challenging to access the interfacial dielectric with subnanometer resolution. Here we use the vibrational response of interfacial water molecules probed using surface-specific sum-frequency generation (SFG) spectra to obtain exquisite depth resolution. Different responses originate from water molecules at different depths and report back on the local interfacial dielectric environment via their spectral amplitudes. From experimental and simulated SFG spectra at the air/water interface, we find that the interfacial dielectric constant changes drastically across an ∼1 Å thin interfacial water region. The strong gradient of the interfacial dielectric constant leads, at charged planar interfaces, to the formation of an electric triple layer that goes beyond the standard double-layer model.
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Affiliation(s)
- Kuo-Yang Chiang
- Molecular Spectroscopy Department, Max Planck Institute for Polymer Research, 55128 Mainz, Germany
| | - Takakazu Seki
- Molecular Spectroscopy Department, Max Planck Institute for Polymer Research, 55128 Mainz, Germany
| | - Chun-Chieh Yu
- Molecular Spectroscopy Department, Max Planck Institute for Polymer Research, 55128 Mainz, Germany
| | - Tatsuhiko Ohto
- Division of Frontier Materials Science, Graduate School of Engineering Science, Osaka University, Toyonaka 60-8531, Japan
| | - Johannes Hunger
- Molecular Spectroscopy Department, Max Planck Institute for Polymer Research, 55128 Mainz, Germany
| | - Mischa Bonn
- Molecular Spectroscopy Department, Max Planck Institute for Polymer Research, 55128 Mainz, Germany
| | - Yuki Nagata
- Molecular Spectroscopy Department, Max Planck Institute for Polymer Research, 55128 Mainz, Germany
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44
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Benjamin I. Structure, Thermodynamics, and Dynamics of Thiocyanate Ion Adsorption and Transfer across the Water/Toluene Interface. J Phys Chem B 2022; 126:5706-5714. [PMID: 35861680 DOI: 10.1021/acs.jpcb.2c03956] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Molecular dynamics simulations are used to examine in detail the structure, thermodynamics, and dynamics involve in the adsorption and transfer of the thiocyanate ion (SCN-) across the water/toluene interface. Free energy, hydration structure, and several dynamical properties as a function of the ion location along the interface normal are calculated and contrasted with recent experiments. The free energy profile exhibits a local minimum near the interface corresponding to adsorption free energy relative to bulk water of -6 kJ/mol, in reasonable agreement with experiments. The simulations provide insight into the water surface fluctuations that are coupled to the ion transfer, demonstrating formation of water finger-like structures assisting the transfer process.
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Affiliation(s)
- Ilan Benjamin
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States
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45
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Odendahl NL, Geissler PL. Local Ice-like Structure at the Liquid Water Surface. J Am Chem Soc 2022; 144:11178-11188. [PMID: 35696525 DOI: 10.1021/jacs.2c01827] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Experiments and computer simulations have established that liquid water's surfaces can deviate in important ways from familiar bulk behavior. Even in the simplest case of an air-water interface, distinctive layering, orientational biases, and hydrogen bond arrangements have been reported, but an overarching picture of their origins and relationships has been incomplete. Here we show that a broad set of such observations can be understood through an analogy with the basal face of crystalline ice. Using simulations, we demonstrate a number of structural similarities between water and ice surfaces, suggesting the presence of domains at the air-water interface with ice-like features that persist over 2-3 molecular diameters. Most prominent is a shared characteristic layering of molecular density and orientation perpendicular to the interface. Lateral correlations of hydrogen bond network geometry point to structural similarities in the parallel direction as well. Our results bolster and significantly extend previous conceptions of ice-like structure at the liquid's boundary and suggest that the much-discussed quasi-liquid layer on ice evolves subtly above the melting point into a quasi-ice layer at the surface of liquid water.
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Affiliation(s)
- Nathan L Odendahl
- Department of Chemistry, University of California, Berkeley, California 94720, United States.,Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Phillip L Geissler
- Department of Chemistry, University of California, Berkeley, California 94720, United States.,Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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46
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Yu CC, Seki T, Wang Y, Bonn M, Nagata Y. Polarization-Dependent Sum-Frequency Generation Spectroscopy for Ångstrom-Scale Depth Profiling of Molecules at Interfaces. PHYSICAL REVIEW LETTERS 2022; 128:226001. [PMID: 35714258 DOI: 10.1103/physrevlett.128.226001] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 02/28/2022] [Accepted: 04/08/2022] [Indexed: 06/15/2023]
Abstract
The three-dimensional spatial distribution of molecules at soft matter interfaces is crucial for processes ranging from membrane biophysics to atmospheric chemistry. While several techniques can access surface composition, obtaining information on the depth distribution is challenging. We develop a noninvasive, polarization-resolved, surface-specific sum-frequency generation spectroscopy providing quantitative depth information. We demonstrate the technique on formic acid molecules at the air-water interface. With increasing molar fraction from 2.5% to 10%, the formic acid molecules shift, on average, ∼0.9 Å into the bulk. The consistency with the simulation data manifests that the technique allows for probing the Ångstrom-scale depth profile.
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Affiliation(s)
- Chun-Chieh Yu
- Molecular Spectroscopy Department, Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Takakazu Seki
- Molecular Spectroscopy Department, Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Yongkang Wang
- Molecular Spectroscopy Department, Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Mischa Bonn
- Molecular Spectroscopy Department, Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
| | - Yuki Nagata
- Molecular Spectroscopy Department, Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
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47
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Singh H, Sharma S. Hydration of Linear Alkanes is Governed by the Small Length-Scale Hydrophobic Effect. J Chem Theory Comput 2022; 18:3805-3813. [PMID: 35648114 DOI: 10.1021/acs.jctc.2c00219] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Length-scale dependence of the hydrophobic effect is well understood for apolar spherical solutes: for small solutes (diameter, d ≲ 0.8 nm), the hydration free energy is entropically driven, while for larger solutes (d ≳ 2 nm), it is enthalpically driven. The nature of the hydrophobic effect in the case of anisotropic molecules such as linear alkanes is not understood yet. In this work, we have calculated the hydration free energy of linear alkanes going from methane to octadecane and of a spherical decane droplet of d ≈ 3 nm using molecular simulations. We show that the hydration free energies of alkanes, irrespective of their size, are governed by the small length-scale hydrophobic effect. That is, unlike the case of large spherical solutes, the hydration free energies of linear alkanes are entropically driven.
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Affiliation(s)
- Himanshu Singh
- Department of Chemical and Biomolecular Engineering, Ohio University, Athens, Ohio 45701, United States
| | - Sumit Sharma
- Department of Chemical and Biomolecular Engineering, Ohio University, Athens, Ohio 45701, United States
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48
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The Effects of Flexibility on dsDNA–dsDNA Interactions. Life (Basel) 2022; 12:life12050699. [PMID: 35629366 PMCID: PMC9147707 DOI: 10.3390/life12050699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 05/02/2022] [Accepted: 05/06/2022] [Indexed: 11/29/2022] Open
Abstract
A detailed understanding of the physical mechanism of ion-mediated dsDNA interactions is important in biological functions such as DNA packaging and homologous pairing. We report the potential of mean force (PMF) or the effective solvent mediated interactions between two parallel identical dsDNAs as a function of interhelical separation in 0.15 M NaCl solution. Here, we study the influence of flexibility of dsDNAs on the effective interactions by comparing PMFs between rigid models and flexible ones. The role of flexibility of dsDNA pairs in their association is elucidated by studying the energetic properties of Na+ ions as well as the fluctuations of ions around dsDNAs. The introduction of flexibility of dsDNAs softens the vdW contact wall and induces more counterion fluctuations around dsDNAs. In addition, flexibility facilitates the Na+ ions dynamics affecting their distribution. The results quantify the extent of attraction influenced by dsDNA flexibility and further emphasize the importance of non-continuum solvation approaches.
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49
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Rahman MR, Shen L, Ewen JP, Dini D, Smith ER. The Intrinsic Fragility of the Liquid-Vapor Interface: A Stress Network Perspective. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:4669-4679. [PMID: 35385282 PMCID: PMC9022435 DOI: 10.1021/acs.langmuir.2c00201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 03/24/2022] [Indexed: 05/25/2023]
Abstract
The evolution of the liquid-vapor interface of a Lennard-Jones fluid is examined with molecular dynamics simulations using the intrinsic sampling method. Results suggest clear damping of the intrinsic profiles with increasing temperature. Investigating the surface stress distribution, we have identified a linear variation of the space-filling nature (fractal dimension) of the stress clusters at the intrinsic surface with increasing surface tension or, equivalently, with decreasing temperature. A percolation analysis of these stress networks indicates that the stress field is more disjointed at higher temperatures. This leads to more fragile (or poorly connected) interfaces which result in a reduction in surface tension.
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Affiliation(s)
- Muhammad Rizwanur Rahman
- Department
of Mechanical Engineering, Imperial College
London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Li Shen
- Department
of Mechanical Engineering, Imperial College
London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - James P. Ewen
- Department
of Mechanical Engineering, Imperial College
London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Daniele Dini
- Department
of Mechanical Engineering, Imperial College
London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - E. R. Smith
- Department
of Mechanical and Aerospace Engineering, Brunel University London, Uxbridge UB8 3PH, United Kingdom
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50
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Gasparotto P, Fitzner M, Cox SJ, Sosso GC, Michaelides A. How do interfaces alter the dynamics of supercooled water? NANOSCALE 2022; 14:4254-4262. [PMID: 35244128 DOI: 10.1039/d2nr00387b] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The structure of liquid water in the proximity of an interface can deviate significantly from that of bulk water, with surface-induced structural perturbations typically converging to bulk values at about ∼1 nm from the interface. While these structural changes are well established it is, in contrast, less clear how an interface perturbs the dynamics of water molecules within the liquid. Here, through an extensive set of molecular dynamics simulations of supercooled bulk and interfacial water films and nano-droplets, we observe the formation of persistent, spatially extended dynamical domains in which the average mobility varies as a function of the distance from the interface. This is in stark contrast with the dynamical heterogeneity observed in bulk water, where these domains average out spatially over time. We also find that the dynamical response of water to an interface depends critically on the nature of the interface and on the choice of interface definition. Overall these results reveal a richness in the dynamics of interfacial water that opens up the prospect of tuning the dynamical response of water through specific modifications of the interface structure or confining material.
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Affiliation(s)
- Piero Gasparotto
- Scientific Computing Division, Paul Scherrer Institute, Villigen 5232, Switzerland.
| | - Martin Fitzner
- Thomas Young Centre, London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1E 6BT, UK
| | - Stephen James Cox
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
| | - Gabriele Cesare Sosso
- Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
| | - Angelos Michaelides
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
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