1
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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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2
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Choudhary A, Ho TA. Confinement-induced clustering of H 2 and CO 2 gas molecules in hydrated nanopores. Phys Chem Chem Phys 2024; 26:10506-10514. [PMID: 38380805 DOI: 10.1039/d3cp06024a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2024]
Abstract
Gas molecule clustering within nanopores holds significance in the fields of nanofluidics, biology, gas adsorption/desorption, and geological gas storage. However, the intricate roles of nanoconfinement and surface chemistry that govern the formation of gas clusters remain inadequately explored. In this study, through free energy calculation in molecular simulations, we systematically compared the tendencies of H2 and CO2 molecules to aggregate within hydrated hydrophobic pyrophyllite and hydrophilic gibbsite nanopores. The results indicate that nanoconfinement enhances gas dimer formation in the nanopores, irrespective of surface chemistry. However, surface hydrophilicity prohibits the formation of gas clusters larger than dimers, while large gas clusters form easily in hydrophobic nanopores. Despite H2 and CO2 both being non-polar, the larger quadrupole moment of CO2 leads to a stronger preference for dimer/cluster formation compared to H2. Our results also indicate that gases prefer to enter the nanopores as individual molecules, but exit the nanopores as dimers/clusters. This investigation provides a mechanistic understanding of gas cluster formation within nanopores, which is relevant to various applications, including geological gas storage.
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Affiliation(s)
- Aditya Choudhary
- Geochemistry Department, Sandia National Laboratories, Albuquerque, NM 87185, USA.
| | - Tuan A Ho
- Geochemistry Department, Sandia National Laboratories, Albuquerque, NM 87185, USA.
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3
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Chen F, Kou Z, Jiang Z, Guo W, Liu X. Physical Limit of Nonlinear Brownian Oscillators in Quantum Trap. J Phys Chem Lett 2024; 15:1719-1725. [PMID: 38320267 DOI: 10.1021/acs.jpclett.3c03334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2024]
Abstract
Quantum trap, a quantum and thermal fluctuations-induced nonmonotonous potential, offers a chance to build up microscopic mechanical systems completely dominated by fluctuations. Here, we explore the physical limit of the effective damping ratio of the nonlinear Brownian oscillator in a quantum trap, set by the finite separation for avoiding molecular-scale effects on the trap potential and the surface confinement effect-induced diverging damping and random forces. The quasiharmonic approximations and Langevin dynamics simulations show that the lowest effective damping ratios of the suspended Au plate and Au sphere upon a Teflon coating of 10 nm can be ∼210 and ∼145, respectively, at room temperature. Perforation is proposed as an effective route to reduce the damping ratio (down to 6.4) by attenuating the surface confinement effect. An unexpected result due to the temperature dependences of dielectric function and viscosity of ethanol is a further reduced damping ratio at 400 K (1.3). The nonlinear Brownian oscillator in the quantum trap shows promise of probing near-boundary hydrodynamics at nanoscale.
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Affiliation(s)
- Fangyuan Chen
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control for Aerospace Structures, Nanjing University of Aeronautics and Astronautics, Nanjing, China 210016
| | - Zepu Kou
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control for Aerospace Structures, Nanjing University of Aeronautics and Astronautics, Nanjing, China 210016
| | - Zonghuiyi Jiang
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control for Aerospace Structures, Nanjing University of Aeronautics and Astronautics, Nanjing, China 210016
| | - Wanlin Guo
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control for Aerospace Structures, Nanjing University of Aeronautics and Astronautics, Nanjing, China 210016
| | - Xiaofei Liu
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control for Aerospace Structures, Nanjing University of Aeronautics and Astronautics, Nanjing, China 210016
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4
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Jiang Z, Chen F, Kou Z, Yin J, Liu X, Guo W. Large Casimir Flipping Torque in Quantum Trap. J Phys Chem B 2024; 128:350-357. [PMID: 38151461 DOI: 10.1021/acs.jpcb.3c06922] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2023]
Abstract
Casimir torque between parallel plates, a macroscopic quantum electrodynamics effect, is known to be induced by dielectric anisotropy and related to the rotational degree of freedom. We here reveal a different type of Casimir torque generated on a Au plate suspended in a quantum trap without recourse to materials anisotropy. As the Au plate deflects from the equilibrium plane with a nonzero flipping angle, the regions departing from and approaching the Teflon-coated Au substrate are subjected to attractive and repulsive Casimir forces, respectively, resulting in a restoring torque about the axis of flipping. For a quantum trap with an equilibrium separation of ∼10 nm, the stiffness per unit area of the Casimir flipping torque can be an order of magnitude larger than those of previously reported dielectric anisotropy-induced rotational torques at the same separation. The large Casimir flipping torque provides the possibility of designing a mechanical oscillator completely dominated by quantum and thermal fluctuations.
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Affiliation(s)
- Zonghuiyi Jiang
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control for Aerospace Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
| | - Fangyuan Chen
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control for Aerospace Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
| | - Zepu Kou
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control for Aerospace Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
| | - Jun Yin
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control for Aerospace Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
| | - Xiaofei Liu
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control for Aerospace Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
| | - Wanlin Guo
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control for Aerospace Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
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5
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Dufils T, Schran C, Chen J, Geim AK, Fumagalli L, Michaelides A. Origin of dielectric polarization suppression in confined water from first principles. Chem Sci 2024; 15:516-527. [PMID: 38179530 PMCID: PMC10763014 DOI: 10.1039/d3sc04740g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Accepted: 11/23/2023] [Indexed: 01/06/2024] Open
Abstract
It has long been known that the dielectric constant of confined water should be different from that in bulk. Recent experiments have shown that it is vanishingly small, however the origin of the phenomenon remains unclear. Here we used ab initio molecular dynamics simulations (AIMD) and AIMD-trained machine-learning potentials to understand water's structure and electronic properties underpinning this effect. For the graphene and hexagonal boron-nitride substrates considered, we find that it originates in the spontaneous anti-parallel alignment of the water dipoles in the first two water layers near the solid interface. The interfacial layers exhibit net ferroelectric ordering, resulting in an overall anti-ferroelectric arrangement of confined water. Together with constrained hydrogen-bonding orientations, this leads to much reduced out-of-plane polarization. Furthermore, we directly contrast AIMD and simple classical force-field simulations, revealing important differences. This work offers insight into a property of water that is critical in modulating surface forces, the electric-double-layer formation and molecular solvation, and shows a way to compute it.
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Affiliation(s)
- T Dufils
- Department of Physics and Astronomy, University of Manchester Manchester M13 9PL UK
- National Graphene Institute, University of Manchester Manchester M13 9PL UK
| | - C Schran
- Cavendish Laboratory, Department of Physics, University of Cambridge Cambridge CB3 0HE UK
- Lennard-Jones Centre, University of Cambridge Trinity Ln Cambridge CB2 1TN UK
| | - J Chen
- School of Physics, Peking University Beijing 100871 China
| | - A K Geim
- Department of Physics and Astronomy, University of Manchester Manchester M13 9PL UK
- National Graphene Institute, University of Manchester Manchester M13 9PL UK
| | - L Fumagalli
- Department of Physics and Astronomy, University of Manchester Manchester M13 9PL UK
- National Graphene Institute, University of Manchester Manchester M13 9PL UK
| | - A Michaelides
- Lennard-Jones Centre, University of Cambridge Trinity Ln Cambridge CB2 1TN UK
- Yusuf Hamied Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK
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6
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Ruiz-Barragan S, Forbert H, Marx D. Anisotropic pressure effects on nanoconfined water within narrow graphene slit pores. Phys Chem Chem Phys 2023; 25:28119-28129. [PMID: 37818616 DOI: 10.1039/d3cp01687k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/12/2023]
Abstract
There is an increasing interest toward disclosing and explaining confinement effects on liquids, such as water or aqueous solutions, in slit pore setups. Particularly puzzling are the changes of physical and chemical properties in the nanoconfinement regime where no bulk-like water phase exists between the two interfacial water layers such that the density profile across the slit pore becomes highly stratified, ultimately leading to bilayer and monolayer water. These changes must be quantified with respect to some meaningful reference state of water, the most natural one being bulk water at the same pressure and temperature conditions. However, bulk water is a homogeneous liquid with isotropic properties, whereas water confined in slit pores is inhomogeneous, implying anisotropic properties as described by the perpendicular and parallel components of the respective tensors. In the case of pressure, the inhomogeneous nature of the setup results in a well-defined difference between the perpendicular and parallel pressure tensor components that is uniquely determined by the interfacial tension being a thermodynamic property. For bilayer water constrained in graphene slit pores that are only about 1 nm wide, we demonstrate that there exists a thermodynamic point where the pressure tensor of the inhomogeneous fluid, nanoconfined water, is effectively isotopic and the pressure is thus scalar as in the homogeneous fluid, bulk water. This specific point of vanishing effective interfacial tension is proposed to serve as a well-defined reference state to compare the properties of nanoconfined liquids to those of the corresponding bulk liquid at the same (isotropic) pressure and temperature conditions. In future work, this idea could be applied to assess confinement effects on chemical reactivity in aqueous solutions as well as to other nanoconfined liquids in other pores such as layered minerals.
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Affiliation(s)
- Sergi Ruiz-Barragan
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany.
| | - Harald Forbert
- Center for Solvation Science ZEMOS, Ruhr - Universität Bochum, 44780 Bochum, Germany
| | - Dominik Marx
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany.
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7
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Borgis D, Laage D, Belloni L, Jeanmairet G. Dielectric response of confined water films from a classical density functional theory perspective. Chem Sci 2023; 14:11141-11150. [PMID: 37860645 PMCID: PMC10583706 DOI: 10.1039/d3sc01267k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Accepted: 08/21/2023] [Indexed: 10/21/2023] Open
Abstract
We re-examine the problem of the dielectric response of highly polar liquids such as water in confinement between two walls using simple two-variable density functional theory involving number and polarisation densities. In the longitudinal polarisation case where a perturbing field is applied perpendicularly to the walls, we show that the notion of the local dielectric constant, although ill-defined at a microscopic level, makes sense when coarse-graining over the typical size of a particle is introduced. The approach makes it possible to study the effective dielectric response of thin liquid films of various thicknesses in connection with the recent experiments of Fumagalli et al., [Science, 2018, 360, 1339-1342], and to discuss the notion of the interfacial dielectric constant. We argue that the observed properties as a function of slab dimensions, in particular the very low dielectric constants of the order of 2-3 measured for thin slabs of ∼1 nm thickness do not highlight any special properties of water but can be recovered for a generic polar solvent having similar particle size and the same high dielectric constant. Regarding the transverse polarisation case where the perturbing field is parallel to the walls, the associated effective dielectric constant as a function of slab dimensions reaches bulk-like values at much shorter widths than in the longitudinal case. In both cases, we find an oscillatory behaviour for slab thicknesses in the one nanometer range due to packing effects.
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Affiliation(s)
- Daniel Borgis
- Maison de la Simulation, CNRS-CEA-Université Paris-Saclay UAR 3441 91191 Gif-sur-Yvette France
- PASTEUR, Département de chimie, École Normale Supérieure, PSL University, Sorbonne Université, CNRS 75005 Paris France
| | - Damien Laage
- PASTEUR, Département de chimie, École Normale Supérieure, PSL University, Sorbonne Université, CNRS 75005 Paris France
| | - Luc Belloni
- Université Paris-Saclay, CEA, CNRS, NIMBE 91191 Gif-sur-Yvette France
| | - Guillaume Jeanmairet
- Sorbonne Université, CNRS, Physico-Chimie des Électrolytes et Nanosystèmes Interfaciaux, PHENIX F-75005 Paris France
- Réseau sur le Stockage Électrochimique de l'Énergie (RS2E), FR CNRS 3459 80039 Amiens Cedex France
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8
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Batsanov SS, Gavrilkin SM, Dan’kin DA, Batsanov AS, Kurakov AV, Shatalova TB, Kulikova IM. Transparent Colloids of Detonation Nanodiamond: Physical, Chemical and Biological Properties. MATERIALS (BASEL, SWITZERLAND) 2023; 16:6227. [PMID: 37763505 PMCID: PMC10532683 DOI: 10.3390/ma16186227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 08/24/2023] [Accepted: 09/13/2023] [Indexed: 09/29/2023]
Abstract
Aqueous suspensions (colloids) containing detonation nano-diamond (DND) feature in most applications of DND and are an indispensable stage of its production; therefore, the interaction of DND with water is actively studied. However, insufficient attention has been paid to the unique physico-chemical and biological properties of transparent colloids with low DND content (≤0.1%), which are the subject of this review. Thus, such colloids possess giant dielectric permittivity which shows peculiar temperature dependence, as well as quasi-periodic fluctuations during slow evaporation or dilution. In these colloids, DND interacts with water and air to form cottonwool-like fibers comprising living micro-organisms (fungi and bacteria) and DND particles, with elevated nitrogen content due to fixation of atmospheric N2. Prolonged contact between these solutions and air lead to the formation of ammonium nitrate, sometimes forming macroscopic crystals. The latter was also formed during prolonged oxidation of fungi in aqueous DND colloids. The possible mechanism of N2 fixation is discussed, which can be attributable to the high reactivity of DND.
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Affiliation(s)
- Stepan S. Batsanov
- National Research Institute for Physical-Technical Measurements, Mendeleevo 141570, Russia;
| | - Sergey M. Gavrilkin
- National Research Institute for Physical-Technical Measurements, Mendeleevo 141570, Russia;
| | - Dmitry A. Dan’kin
- Fritsch Laboratory Instruments, Moscow Branch, Moscow 115093, Russia;
| | | | | | | | - Inna M. Kulikova
- Institute of Mineralogy, Geochemistry and Crystalchemistry of Rare Elements, Moscow 121357, Russia;
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9
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Pivnic K, de Souza JP, Kornyshev AA, Urbakh M, Bazant MZ. Orientational Ordering in Nano-confined Polar Liquids. NANO LETTERS 2023. [PMID: 37285463 DOI: 10.1021/acs.nanolett.3c00927] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Water and other polar liquids exhibit nanoscale structuring near charged interfaces. When a polar liquid is confined between two charged surfaces, the interfacial solvent layers begin to overlap, resulting in solvation forces. Here, we perform molecular dynamics simulations of polar liquids with different dielectric constants and molecular shapes and sizes confined between charged surfaces, demonstrating strong orientational ordering in the nanoconfined liquids. To rationalize the observed structures, we apply a coarse-grained continuum theory that captures the orientational ordering and solvation forces of those liquids. Our findings reveal the subtle behavior of different nanoconfined polar liquids and establish a simple law for the decay length of the interfacial orientations of the solvents, which depends on their molecular size and polarity. These insights shed light on the nature of solvation forces, which are important in colloid and membrane science, scanning probe microscopy, and nano-electrochemistry.
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Affiliation(s)
- Karina Pivnic
- School of Chemistry, The Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv 6997801, Israel
| | - J Pedro de Souza
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Alexei A Kornyshev
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, W12 0BZ 2AZ London, United Kingdom
- Thomas Young Centre for Theory and Simulation of Materials, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Michael Urbakh
- School of Chemistry, The Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Martin Z Bazant
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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10
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Das B, Ruiz-Barragan S, Marx D. Deciphering the Properties of Nanoconfined Aqueous Solutions by Vibrational Sum Frequency Generation Spectroscopy. J Phys Chem Lett 2023; 14:1208-1213. [PMID: 36716226 PMCID: PMC9923734 DOI: 10.1021/acs.jpclett.2c03409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Accepted: 12/21/2022] [Indexed: 06/18/2023]
Abstract
When confined between walls at nanometer distances, water exhibits surprisingly different properties with reference to bare interfacial water. Based on computer simulations, we demonstrate how vibrational sum frequency generation (VSFG) spectroscopy can be used-even with very mild symmetry breaking-to discriminate multilayer water in wide slit pores from both bilayer and monolayer water confined within molecularly narrow pores. Applying the technique, the VSFG lineshapes of monolayer, bilayer, and multilayer water are found to differ in characteristic ways, which is explained by their distinct density stratifications giving rise to different H-bonding patterns in the respective solvation layers.
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Affiliation(s)
- Banshi Das
- Lehrstuhl
für Theoretische Chemie, Ruhr-Universität
Bochum, 44780Bochum, Germany
| | - Sergi Ruiz-Barragan
- Lehrstuhl
für Theoretische Chemie, Ruhr-Universität
Bochum, 44780Bochum, Germany
- Departament
de Fisica, Universitat Politecnica de Catalunya, Rambla Sant Nebridi 22, 08222 Terrassa, Barcelona, Spain
| | - Dominik Marx
- Lehrstuhl
für Theoretische Chemie, Ruhr-Universität
Bochum, 44780Bochum, Germany
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11
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Deißenbeck F, Wippermann S. Dielectric Properties of Nanoconfined Water from Ab Initio Thermopotentiostat Molecular Dynamics. J Chem Theory Comput 2023; 19:1035-1043. [PMID: 36705611 PMCID: PMC9933428 DOI: 10.1021/acs.jctc.2c00959] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We discuss how to include our recently proposed thermopotentiostat technique [Deissenbeck et al. Phys. Rev. Lett. 2021, 126, 136803] into any existing ab initio molecular dynamics (AIMD) package. Using thermopotentiostat AIMD simulations in the canonical NVTΦ ensemble at a constant electrode potential, we compute the polarization bound charge and dielectric response of interfacial water from first principles.
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Affiliation(s)
- Florian Deißenbeck
- Max-Planck-Institut
für Eisenforschung GmbH, Max-Planck-Straße 1, 40237 Düsseldorf, Germany
| | - Stefan Wippermann
- Max-Planck-Institut
für Eisenforschung GmbH, Max-Planck-Straße 1, 40237 Düsseldorf, Germany,Philipps-Universität
Marburg, Renthof 5, 35032 Marburg, Germany,E-mail:
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12
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Majumdar J, Dasgupta S, Mandal S, Moid M, Jain M, Maiti PK. Does twist angle affect the properties of water confined inside twisted bilayer graphene? J Chem Phys 2023; 158:034501. [PMID: 36681635 DOI: 10.1063/5.0139256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Graphene nanoslit pores are used for nanofluidic devices, such as, in water desalination, ion-selective channels, ionic transistors, sensing, molecular sieving, blue energy harvesting, and protein sequencing. It is a strenuous task to prepare nanofluidic devices, because a small misalignment leads to a significant alteration in various properties of the devices. Here, we focus on the rotational misalignment between two parallel graphene sheets. Using molecular dynamics simulation, we probe the structure and dynamics of monolayer water confined inside graphene nanochannels for a range of commensurate twist angles. With SPC/E and TIP4P/2005 water models, our simulations reveal the independence of the equilibrium number density- n ∼ 13 nm-2 for SPC/E and n ∼ 11.5 nm-2 for TIP4P/2005- across twists. Based on the respective densities of the water models, the structure and dielectric constant are invariant of twist angles. The confined water structure at this density shows square ice ordering for SPC/E water only. TIP4P/2005 shows ordering at the vicinity of a critical density (n ∼ 12.5 nm-2). The average perpendicular dielectric constant of the confined water remains anomalously low (∼2 for SPC/E and ∼6 for TIP4P/2005) for the studied twist angles. We find that the friction coefficient of confined water molecules varies for small twist angles, while becoming independent for twists greater than 5.1°. Our results indicate that a small, angular misalignment will not impair the dielectric properties of monolayer water within a graphene slit-pore, but can significantly influence its dynamics.
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Affiliation(s)
- Jeet Majumdar
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Subhadeep Dasgupta
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Soham Mandal
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Mohd Moid
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Manish Jain
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Prabal K Maiti
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560012, India
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13
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Nanoconfinement facilitates reactions of carbon dioxide in supercritical water. Nat Commun 2022; 13:5932. [PMID: 36209274 PMCID: PMC9547913 DOI: 10.1038/s41467-022-33696-w] [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: 03/31/2022] [Accepted: 09/27/2022] [Indexed: 11/08/2022] Open
Abstract
The reactions of CO2 in water under extreme pressure-temperature conditions are of great importance to the carbon storage and transport below Earth’s surface, which substantially affect the carbon budget in the atmosphere. Previous studies focus on the CO2(aq) solutions in the bulk phase, but underground aqueous solutions are often confined to the nanoscale, and nanoconfinement and solid-liquid interfaces may substantially affect chemical speciation and reaction mechanisms, which are poorly known on the molecular scale. Here, we apply extensive ab initio molecular dynamics simulations to study aqueous carbon solutions nanoconfined by graphene and stishovite (SiO2) at 10 GPa and 1000 ~ 1400 K. We find that CO2(aq) reacts more in nanoconfinement than in bulk. The stishovite-water interface makes the solutions more acidic, which shifts the chemical equilibria, and the interface chemistry also significantly affects the reaction mechanisms. Our findings suggest that CO2(aq) in deep Earth is more active than previously thought, and confining CO2 and water in nanopores may enhance the efficiency of mineral carbonation. Aqueous CO2 under nanoconfinement is of great importance to the carbon storage and transport in Earth. Here, the authors apply ab initio molecular dynamics simulations to study the effects of confinement and interfaces, and show that that CO(aq) reacts more in nanoconfinement than in bulk.
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14
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Muñoz-Santiburcio D. Accurate diffusion coefficients of the excess proton and hydroxide in water via extensive ab initio simulations with different schemes. J Chem Phys 2022; 157:024504. [PMID: 35840376 DOI: 10.1063/5.0093958] [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
Despite its simple molecular formula, obtaining an accurate in silico description of water is far from straightforward. Many of its very peculiar properties are quite elusive, and in particular, obtaining good estimations of the diffusion coefficients of the solvated proton and hydroxide at a reasonable computational cost has been an unsolved challenge until now. Here, I present extensive results of several unusually long ab initio molecular dynamics (MD) simulations employing different combinations of the Born-Oppenheimer and second-generation Car-Parrinello MD propagation methods with different ensembles (NVE and NVT) and thermostats, which show that these methods together with the RPBE-D3 functional provide a very accurate estimation of the diffusion coefficients of the solvated H3O+ and OH- ions, together with an extremely accurate description of several properties of neutral water (such as the structure of the liquid and its diffusion and shear viscosity coefficients). In addition, I show that the estimations of DH3O+ and DOH- depend dramatically on the simulation length, being necessary to reach timescales in the order of hundreds of picoseconds to obtain reliable results.
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Affiliation(s)
- Daniel Muñoz-Santiburcio
- CIC nanoGUNE BRTA, Tolosa Hiribidea 76, 20018 San Sebastián, Spain and Instituto de Fusión Nuclear "Guillermo Velarde," Universidad Politécnica de Madrid, C/ José Gutiérrez Abascal 2, 28006 Madrid, Spain
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15
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de Souza JP, Kornyshev AA, Bazant MZ. Polar liquids at charged interfaces: A dipolar shell theory. J Chem Phys 2022; 156:244705. [PMID: 35778078 DOI: 10.1063/5.0096439] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The structure of polar liquids and electrolytic solutions, such as water and aqueous electrolytes, at interfaces underlies numerous phenomena in physics, chemistry, biology, and engineering. In this work, we develop a continuum theory that captures the essential features of dielectric screening by polar liquids at charged interfaces, including decaying spatial oscillations in charge and mass, starting from the molecular properties of the solvent. The theory predicts an anisotropic dielectric tensor of interfacial polar liquids previously studied in molecular dynamics simulations. We explore the effect of the interfacial polar liquid properties on the capacitance of the electrode/electrolyte interface and on hydration forces between two plane-parallel polarized surfaces. In the linear response approximation, we obtain simple formulas for the characteristic decay lengths of molecular and ionic profiles at the interface.
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Affiliation(s)
- J Pedro de Souza
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Alexei A Kornyshev
- Department of Chemistry and Thomas Young Centre for Theory and Simulation of Materials, Imperial College London, Molecular Sciences Research Hub, White City Campus, London W12 0BZ, United Kingdom
| | - Martin Z Bazant
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
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16
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Papadopoulou E, Zavadlav J, Podgornik R, Praprotnik M, Koumoutsakos P. Tuning the Dielectric Response of Water in Nanoconfinement through Surface Wettability. ACS NANO 2021; 15:20311-20318. [PMID: 34813279 DOI: 10.1021/acsnano.1c08512] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The tunable polarity of water can be exploited in emerging technologies including catalysis, gas storage, and green chemistry. Recent experimental and theoretical studies have shown that water can be rendered into an effectively apolar solvent under nanoconfinement. We furthermore demonstrate, through molecular simulations, that the static dielectric constant of water can be modified by changing the wettability of the confining material. We find the out-of-plane dielectric response to be highly sensitive to the level of confinement and can be reduced up to 40× , in accordance with experimental data. By altering the surface wettability from superhydrophilic to superhydrophobic, we observe a 36% increase for the out-of-plane and a 31% decrease for the in-plane dielectric constants. Our findings demonstrate the feasibility of tunable water polarity, a phenomenon with great potential for scientific and technological impact.
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Affiliation(s)
- Ermioni Papadopoulou
- Computational Science and Engineering Laboratory, ETH-Zurich, Clausiusstrasse 33, CH-8092 Zurich, Switzerland
| | - Julija Zavadlav
- Professorship of Multiscale Modeling of Fluid Materials, TUM School of Engineering and Design, Technical University of Munich, Boltzmannstrasse 15, DE-85748 Garching near Munich, Germany
| | - Rudolf Podgornik
- School of Physical Sciences and Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
- Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, SI-1000 Ljubljana, Slovenia
- CAS Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Wenzhou Institute of the University of Chinese Academy of Sciences, Wenzhou, Zhejiang 325000, China
| | - Matej Praprotnik
- Laboratory for Molecular Modeling, National Institute of Chemistry, Hajdrihova 19, SI-1001 Ljubljana, Slovenia
- Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, SI-1000 Ljubljana, Slovenia
| | - Petros Koumoutsakos
- Computational Science and Engineering Laboratory, ETH-Zurich, Clausiusstrasse 33, CH-8092 Zurich, Switzerland
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
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17
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Olivieri JF, Laage D, Hynes JT. A Model Electron Transfer Reaction in Confined Aqueous Solution. Chemphyschem 2021; 22:2247-2255. [PMID: 34427964 DOI: 10.1002/cphc.202100351] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 08/24/2021] [Indexed: 11/09/2022]
Abstract
Liquid water confined within nanometer-sized channels exhibits a strongly reduced local dielectric constant perpendicular to the wall, especially at the interface, and this has been suggested to induce faster electron transfer kinetics at the interface than in the bulk. We study a model electron transfer reaction in aqueous solution confined between graphene sheets with classical molecular dynamics. We show that the solvent reorganization energy is reduced at the interface compared to the bulk, which explains the larger rate constant. However, this facilitated solvent reorganization is due to the partial desolvation by the graphene sheet of the ions involved in the electron transfer and not to a local dielectric constant reduction effect.
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Affiliation(s)
- Jean-François Olivieri
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005, Paris, France
| | - Damien Laage
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005, Paris, France
| | - James T Hynes
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005, Paris, France.,Department of Chemistry, University of Colorado, Boulder, CO 80309, USA
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18
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Abstract
The thermodynamic stability of water next to graphitic surfaces is of fundamental interest, as it underlies several natural phenomena and important industrial processes. It is commonly assumed that water wets graphite more than graphene due to increased, favorable van der Waals interactions between the interfacial water molecules with multiple carbon sheets. Here, we employed extensive computer simulations and analysis of the molecular correlation functions to show that the interfacial water thermodynamics is in fact dominated by surface entropy. We show that on graphite, destabilization of the interfacial hydrogen bond network leads to an overcompensating increase in population of low frequency translational and librational modes, which is ultimately responsible for the increased interfacial stability compared to graphene. The spectroscopic signature of this effect is an enhancement of the modes near 100 and 300 cm-1. This subtle interplay between entropy and surface binding may have important consideration for interpretations of various phenomena, including the hydrophobic effect.
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Affiliation(s)
- Tod A Pascal
- ATLAS Materials Physics Laboratory, Department of NanoEngineering and Chemical Engineering, University of California San Diego, La Jolla, California 92093, United States
- Materials Science and Engineering, University of California San Diego, La Jolla, California 92093, United States
| | - William A Goddard
- Materials and Process Simulation Center, California Institute of Technology, Pasadena, California 91125, United States
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19
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Abstract
It has long been anticipated that dielectric constants of polar liquids are reduced in the interfacial layer. Recent experiments and computer simulations support these expectations. A strong reduction of the dielectric constant is found in the direction perpendicular to a planar substrate, while the parallel response is bulk-like. This Perspective highlights recent theoretical calculations and simulations with an eye on relating them to properties observable in the laboratory. The average interface dielectric constant computed from simulations connects to thin films experiments, but this cannot be extended to screening of charges. In contrast to dielectric theories where a single dielectric constant gauges both the polarization energy and screening, these two signatures of dielectric polarization diverge on the molecular scale. The reduction of the dielectric constant of water in thin films is currently viewed as a combined effect of geometric confinement imposed by the substrate and the reconstruction of water hydrogen bonds in the surface layer.
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Affiliation(s)
- Dmitry V Matyushov
- School of Molecular Sciences and Department of Physics, Arizona State University, PO Box 871504, Tempe, Arizona 85287-1504, United States
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20
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Majumdar J, Moid M, Dasgupta C, Maiti PK. Dielectric Profile and Electromelting of a Monolayer of Water Confined in Graphene Slit Pore. J Phys Chem B 2021; 125:6670-6680. [PMID: 34107687 DOI: 10.1021/acs.jpcb.1c02266] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A monolayer of water confined between two parallel graphene sheets exists in many different phases and exhibits fascinating dielectric properties that have been studied in experiments. In this work, we use molecular dynamics simulations to study how the dielectric properties of a confined monolayer of water is affected by its structure. We consider six of the popular nonpolarizable water models-SPC/E, SPC/Fw, TIP3P, TIP3P_M (modified), TIP4P-2005, and TIP4P-2005f-and find that the in-plane structure of the water molecules at ambient temperature and pressure is strongly dependent on the water model: all the 3-point water models considered here show square ice formation, whereas no such structural ordering is observed for the 4-point water models. This allows us to investigate the role of the in-plane structure of the water monolayer on its dielectric profile. Our simulations show an anomalous perpendicular dielectric constant compared to the bulk, and the models that do not exhibit ice formation show very different dielectric response along the channel width compared to models that exhibit square ice formation. We also demonstrate the occurrence of electromelting of the in-plane ordered water under the application of a perpendicular electric field and find that the critical field for electromelting strongly depends on the water model. Together, we have shown the dependence of confined water properties on the different water structures that it may take when sandwiched between bilayer graphene. These remarkable properties of confined water can be exploited in various nanofluidic devices, artificial ion channels, and molecular sieving.
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Affiliation(s)
- Jeet Majumdar
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Mohd Moid
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560012, India
| | - Chandan Dasgupta
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560012, India.,International Centre for Theoretical Sciences, Bangalore 560089, India
| | - Prabal K Maiti
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560012, India
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21
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Muñoz-Santiburcio D, Marx D. Confinement-Controlled Aqueous Chemistry within Nanometric Slit Pores. Chem Rev 2021; 121:6293-6320. [PMID: 34006106 DOI: 10.1021/acs.chemrev.0c01292] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
In this Focus Review, we put the spotlight on very recent insights into the fascinating world of wet chemistry in the realm offered by nanoconfinement of water in mechanically rather rigid and chemically inert planar slit pores wherein only monolayer and bilayer water lamellae can be hosted. We review the effect of confinement on different aspects such as hydrogen bonding, ion diffusion, and charge defect migration of H+(aq) and OH-(aq) in nanoconfined water depending on slit pore width. A particular focus is put on the strongly modulated local dielectric properties as quantified in terms of anisotropic polarization fluctuations across such extremely confined water films and their putative effects on chemical reactions therein. The stunning findings disclosed only recently extend wet chemistry in particular and solvation science in general toward extreme molecular confinement conditions.
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Affiliation(s)
- Daniel Muñoz-Santiburcio
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany.,CIC nanoGUNE BRTA, Tolosa Hiribidea 76, 20018 San Sebastián, Spain
| | - Dominik Marx
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany
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22
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Olivieri JF, Hynes JT, Laage D. Confined Water's Dielectric Constant Reduction Is Due to the Surrounding Low Dielectric Media and Not to Interfacial Molecular Ordering. J Phys Chem Lett 2021; 12:4319-4326. [PMID: 33914550 DOI: 10.1021/acs.jpclett.1c00447] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Liquid water confined within nanometer-sized channels exhibits a surprisingly low dielectric constant along the direction orthogonal to the channel walls. This is typically assumed to result from a pronounced heterogeneity across the sample: the dielectric constant would be bulk-like everywhere except at the interface, where it would be dramatically reduced by strong restrictions on interfacial molecules. Here we study the dielectric properties of water confined within graphene slit channels via classical molecular dynamics simulations. We show that the permittivity reduction is not due to any important alignment of interfacial water molecules, but instead to the long-ranged anisotropic dipole correlations combined with an excluded-volume effect of the low-dielectric confining material. The bulk permittivity is gradually recovered only over several nanometers due to the impact of long-range electrostatics, rather than structural features. This has important consequences for the control of, e.g., ion transport and chemical reactivity in nanoscopic channels and droplets.
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Affiliation(s)
- Jean-François Olivieri
- PASTEUR, Department of Chemistry, École normale supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - James T Hynes
- PASTEUR, Department of Chemistry, École normale supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
- Department of Chemistry, University of Colorado, Boulder, Colorado 80309, United States
| | - Damien Laage
- PASTEUR, Department of Chemistry, École normale supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
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23
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Deißenbeck F, Freysoldt C, Todorova M, Neugebauer J, Wippermann S. Dielectric Properties of Nanoconfined Water: A Canonical Thermopotentiostat Approach. PHYSICAL REVIEW LETTERS 2021; 126:136803. [PMID: 33861101 DOI: 10.1103/physrevlett.126.136803] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 08/14/2020] [Accepted: 02/26/2021] [Indexed: 06/12/2023]
Abstract
We introduce a novel approach to sample the canonical ensemble at constant temperature and applied electric potential. Our approach can be straightforwardly implemented into any density-functional theory code. Using thermopotentiostat molecular dynamics simulations allows us to compute the dielectric constant of nanoconfined water without any assumptions for the dielectric volume. Compared to the commonly used approach of calculating dielectric properties from polarization fluctuations, our thermopotentiostat technique reduces the required computational time by 2 orders of magnitude.
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Affiliation(s)
- F Deißenbeck
- Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237Düsseldorf, Germany
| | - C Freysoldt
- Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237Düsseldorf, Germany
| | - M Todorova
- Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237Düsseldorf, Germany
| | - J Neugebauer
- Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237Düsseldorf, Germany
| | - S Wippermann
- Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237Düsseldorf, Germany
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24
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Hamid I, Jalali H, Peeters FM, Neek-Amal M. Abnormal in-plane permittivity and ferroelectricity of confined water: From sub-nanometer channels to bulk. J Chem Phys 2021; 154:114503. [PMID: 33752365 DOI: 10.1063/5.0038359] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Dielectric properties of nano-confined water are important in several areas of science, i.e., it is relevant in the dielectric double layer that exists in practically all heterogeneous fluid-based systems. Molecular dynamics simulations are used to predict the in-plane dielectric properties of confined water in planar channels of width ranging from sub-nanometer to bulk. Because of suppressed rotational degrees of freedom near the confining walls, the dipole of the water molecules tends to be aligned parallel to the walls, which results in a strongly enhanced in-plane dielectric constant (ε∥) reaching values of about 120 for channels with height 8 Å < h < 10 Å. With the increase in the width of the channel, we predict that ε∥ decreases nonlinearly and reaches the bulk value for h > 70 Å. A stratified continuum model is proposed that reproduces the h > 10 Å dependence of ε∥. For sub-nanometer height channels, abnormal behavior of ε∥ is found with two orders of magnitude reduction of ε∥ around h ∼ 7.5 Å, which is attributed to the formation of a particular ice phase that exhibits long-time (∼μs) stable ferroelectricity. This is of particular importance for the understanding of the influence of confined water on the functioning of biological systems.
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Affiliation(s)
- Ilyar Hamid
- Department of Physics, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium
| | - Hossein Jalali
- Department of Physics, University of Zanjan, 45195-313 Zanjan, Iran
| | - Francois M Peeters
- Department of Physics, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium
| | - Mehdi Neek-Amal
- Department of Physics, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium
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25
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Loche P, Ayaz C, Wolde-Kidan A, Schlaich A, Netz RR. Universal and Nonuniversal Aspects of Electrostatics in Aqueous Nanoconfinement. J Phys Chem B 2020; 124:4365-4371. [PMID: 32364728 DOI: 10.1021/acs.jpcb.0c01967] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dielectric water properties, which significantly change in confinement, determine electrostatic interactions and thereby influence all molecular forces and chemical reactions. We present comparative simulations of water between graphene sheets, decanol monolayers, and phospholipid and glycolipid bilayers. Generally, dielectric profiles strongly differ in perpendicular and parallel surface directions and for large surface separation decay to the bulk value 1-2 nm away from the surface. Polar surface groups enhance the local interfacial dielectric response and for phospholipid bilayers induce a giant parallel contribution. A mapping on a box model with asymptotically determined effective water layer widths demonstrates that the perpendicular effective dielectric constant for all systems decreases for confinement below a nanometer, while the parallel one stays rather constant. The confinement-dependent perpendicular effective dielectric constant for graphene is in agreement with experimental data only if the effective water layer width is suitably adjusted. The interactions between two charges at small separation depend on the product of parallel and perpendicular effective water dielectric components; for large separation the interactions depend on the confining medium. For metallic confining media the interactions at large separation decay exponentially with a decay length that depends on the ratio of the effective parallel and perpendicular water dielectric components.
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Affiliation(s)
- Philip Loche
- Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | - Cihan Ayaz
- Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | | | | | - Roland R Netz
- Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
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