1
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An R, Wu N, Gao Q, Dong Y, Laaksonen A, Shah FU, Ji X, Fuchs H. Integrative studies of ionic liquid interface layers: bridging experiments, theoretical models and simulations. NANOSCALE HORIZONS 2024; 9:506-535. [PMID: 38356335 DOI: 10.1039/d4nh00007b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2024]
Abstract
Ionic liquids (ILs) are a class of salts existing in the liquid state below 100 °C, possessing low volatility, high thermal stability as well as many highly attractive solvent and electrochemical capabilities, etc., making them highly tunable for a great variety of applications, such as lubricants, electrolytes, and soft functional materials. In many applications, ILs are first either physi- or chemisorbed on a solid surface to successively create more functional materials. The functions of ILs at solid surfaces can differ considerably from those of bulk ILs, mainly due to distinct interfacial layers with tunable structures resulting in new ionic liquid interface layer properties and enhanced performance. Due to an almost infinite number of possible combinations among the cations and anions to form ILs, the diversity of various solid surfaces, as well as different external conditions and stimuli, a detailed molecular-level understanding of their structure-property relationship is of utmost significance for a judicious design of IL-solid interfaces with appropriate properties for task-specific applications. Many experimental techniques, such as atomic force microscopy, surface force apparatus, and so on, have been used for studying the ion structuring of the IL interface layer. Molecular Dynamics simulations have been widely used to investigate the microscopic behavior of the IL interface layer. To interpret and clarify the IL structure and dynamics as well as to predict their properties, it is always beneficial to combine both experiments and simulations as close as possible. In another theoretical model development to bridge the structure and properties of the IL interface layer with performance, thermodynamic prediction & property modeling has been demonstrated as an effective tool to add the properties and function of the studied nanomaterials. Herein, we present recent findings from applying the multiscale triangle "experiment-simulation-thermodynamic modeling" in the studies of ion structuring of ILs in the vicinity of solid surfaces, as well as how it qualitatively and quantitatively correlates to the overall ILs properties, performance, and function. We introduce the most common techniques behind "experiment-simulation-thermodynamic modeling" and how they are applied for studying the IL interface layer structuring, and we highlight the possibilities of the IL interface layer structuring in applications such as lubrication and energy storage.
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Affiliation(s)
- Rong An
- Herbert Gleiter Institute of Nanoscience, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China.
| | - Nanhua Wu
- Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China
| | - Qingwei Gao
- College of Environmental and Chemical Engineering, Shanghai Key Laboratory of Materials Protection and Advanced Materials in Electric Power, Shanghai University of Electric Power, Shanghai 200090, China
| | - Yihui Dong
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Aatto Laaksonen
- Energy Engineering, Division of Energy Science, Luleå University of Technology, 97187 Luleå, Sweden.
- Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-10691 Stockholm, Sweden.
- Center of Advanced Research in Bionanoconjugates and Biopolymers, ''Petru Poni" Institute of Macromolecular Chemistry, Iasi 700469, Romania
- State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing 211816, China
| | - Faiz Ullah Shah
- Chemistry of Interfaces, Luleå University of Technology, 97187 Luleå, Sweden
| | - Xiaoyan Ji
- Energy Engineering, Division of Energy Science, Luleå University of Technology, 97187 Luleå, Sweden.
| | - Harald Fuchs
- Herbert Gleiter Institute of Nanoscience, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China.
- Center for Nanotechnology (CeNTech), Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany.
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2
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Hausen F. Relaxation Times of Ionic Liquids under Electrochemical Conditions Probed by Friction Force Microscopy. SMALL METHODS 2023; 7:e2300250. [PMID: 37551063 DOI: 10.1002/smtd.202300250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Revised: 07/14/2023] [Indexed: 08/09/2023]
Abstract
Ionic liquids (ILs) represent an important class of liquids considered for a broad range of applications such as lubrication, catalysis, or as electrolytes in batteries. It is well-known that in the case of charged surfaces, ILs form a pronounced layer structure that can be easily triggered by an externally applied electrode potential. Information about the time required to form a stable interface under varying electrode potentials is of utmost importance in many applications. For the first time, probing of relaxation times of ILs by friction force microscopy is demonstrated. The friction force is extremely sensitive to even subtle changes in the interfacial configuration of ILs. Various relaxation processes with different time scales are observed. A significant difference dependent on the direction of switching the applied potential, i.e., from a more cation-rich to a more anion-rich interface or vice versa, is found. Furthermore, variations in height immediately after the potential step and the presence of trace amounts of water are discussed as well.
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Affiliation(s)
- Florian Hausen
- Forschungszentrum Jülich, Institute of Energy and Climate Research, IEK-9, 52425, Jülich, Germany
- RWTH Aachen University, Institute of Physical Chemistry, 52074, Aachen, Germany
- INM-Leibniz Institute for New Materials, Campus D2 2, 66123, Saarbrücken, Germany
- Jülich-Aachen Research Alliance, Section: JARA-Energy, 52425, Jülich, Germany
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3
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Bresme F, Kornyshev AA, Perkin S, Urbakh M. Electrotunable friction with ionic liquid lubricants. NATURE MATERIALS 2022; 21:848-858. [PMID: 35761059 DOI: 10.1038/s41563-022-01273-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 05/02/2022] [Indexed: 06/15/2023]
Abstract
Room-temperature ionic liquids and their mixtures with organic solvents as lubricants open a route to control lubricity at the nanoscale via electrical polarization of the sliding surfaces. Electronanotribology is an emerging field that has a potential to realize in situ control of friction-that is, turning the friction on and off on demand. However, fulfilling its promise needs more research. Here we provide an overview of this emerging research area, from its birth to the current state, reviewing the main achievements in non-equilibrium molecular dynamics simulations and experiments using atomic force microscopes and surface force apparatus. We also present a discussion of the challenges that need to be solved for future applications of electrotunable friction.
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Affiliation(s)
- Fernando Bresme
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, London, UK.
| | - Alexei A Kornyshev
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, London, UK.
| | - Susan Perkin
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, UK.
| | - Michael Urbakh
- Department of Physical Chemistry, School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences, and The Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv, Israel.
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4
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de Souza JP, Pivnic K, Bazant MZ, Urbakh M, Kornyshev AA. Structural Forces in Ionic Liquids: The Role of Ionic Size Asymmetry. J Phys Chem B 2022; 126:1242-1253. [PMID: 35134297 PMCID: PMC9007453 DOI: 10.1021/acs.jpcb.1c09441] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 01/04/2022] [Indexed: 11/29/2022]
Abstract
Ionic liquids (ILs) are charged fluids composed of anions and cations of different size and shape. The ordering of charge and density in ILs confined between charged interfaces underlies numerous applications of IL electrolytes. Here, we analyze the screening behavior and the resulting structural forces of a representative IL confined between two charge-varied plates. Using both molecular dynamics simulations and a continuum theory, we contrast the screening features of a more-realistic asymmetric system and a less-realistic symmetric one. The ionic size asymmetry plays a nontrivial role in charge screening, affecting both the ionic density profiles and the disjoining pressure distance dependence. Ionic systems with size asymmetry are stronger coupled systems, and this manifests itself both in their response to the electrode polarization and spontaneous structure formation at the interface. Analytical expressions for decay lengths of the disjoining pressure are obtained in agreement with the pressure profiles computed from molecular dynamics simulations.
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Affiliation(s)
- J. Pedro de Souza
- Department
of Chemical Engineering, Massachusetts Institute
of Technology, Cambridge, Massachusetts 02139, United States
| | - Karina Pivnic
- 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
| | - Michael Urbakh
- School
of Chemistry, The Sackler Center for Computational Molecular and Materials
Science, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Alexei A. Kornyshev
- Department
of Chemistry, Molecular Sciences Research Hub, Imperial College London, London, W12 0BZ 2AZ, United Kingdom
- Thomas
Young Centre for Theory and Simulation of Materials, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom
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5
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Wang YL, Li B, Sarman S, Mocci F, Lu ZY, Yuan J, Laaksonen A, Fayer MD. Microstructural and Dynamical Heterogeneities in Ionic Liquids. Chem Rev 2020; 120:5798-5877. [PMID: 32292036 PMCID: PMC7349628 DOI: 10.1021/acs.chemrev.9b00693] [Citation(s) in RCA: 192] [Impact Index Per Article: 48.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Indexed: 12/11/2022]
Abstract
Ionic liquids (ILs) are a special category of molten salts solely composed of ions with varied molecular symmetry and charge delocalization. The versatility in combining varied cation-anion moieties and in functionalizing ions with different atoms and molecular groups contributes to their peculiar interactions ranging from weak isotropic associations to strong, specific, and anisotropic forces. A delicate interplay among intra- and intermolecular interactions facilitates the formation of heterogeneous microstructures and liquid morphologies, which further contributes to their striking dynamical properties. Microstructural and dynamical heterogeneities of ILs lead to their multifaceted properties described by an inherent designer feature, which makes ILs important candidates for novel solvents, electrolytes, and functional materials in academia and industrial applications. Due to a massive number of combinations of ion pairs with ion species having distinct molecular structures and IL mixtures containing varied molecular solvents, a comprehensive understanding of their hierarchical structural and dynamical quantities is of great significance for a rational selection of ILs with appropriate properties and thereafter advancing their macroscopic functionalities in applications. In this review, we comprehensively trace recent advances in understanding delicate interplay of strong and weak interactions that underpin their complex phase behaviors with a particular emphasis on understanding heterogeneous microstructures and dynamics of ILs in bulk liquids, in mixtures with cosolvents, and in interfacial regions.
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Affiliation(s)
- Yong-Lei Wang
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Bin Li
- School
of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, P. R. China
| | - Sten Sarman
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Francesca Mocci
- Department
of Chemical and Geological Sciences, University
of Cagliari, I-09042 Monserrato, Italy
| | - Zhong-Yuan Lu
- State
Key Laboratory of Supramolecular Structure and Materials, Institute
of Theoretical Chemistry, Jilin University, Changchun 130021, P. R. China
| | - Jiayin Yuan
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Aatto Laaksonen
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
- State
Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing 210009, P. R. China
- Centre of
Advanced Research in Bionanoconjugates and Biopolymers, Petru Poni Institute of Macromolecular Chemistry Aleea Grigore Ghica-Voda, 41A, 700487 Iasi, Romania
- Department
of Engineering Sciences and Mathematics, Division of Energy Science, Luleå University of Technology, SE-97187 Luleå, Sweden
| | - Michael D. Fayer
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
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6
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Park S, McDaniel JG. Interference of electrical double layers: Confinement effects on structure, dynamics, and screening of ionic liquids. J Chem Phys 2020; 152:074709. [DOI: 10.1063/1.5144260] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Affiliation(s)
- Suehyun Park
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA
| | - Jesse G. McDaniel
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA
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7
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Weiss H, Cheng HW, Mars J, Li H, Merola C, Renner FU, Honkimäki V, Valtiner M, Mezger M. Structure and Dynamics of Confined Liquids: Challenges and Perspectives for the X-ray Surface Forces Apparatus. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:16679-16692. [PMID: 31614087 PMCID: PMC6933819 DOI: 10.1021/acs.langmuir.9b01215] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 10/15/2019] [Indexed: 05/21/2023]
Abstract
The molecular-scale structure and dynamics of confined liquids has increasingly gained relevance for applications in nanotechnology. Thus, a detailed knowledge of the structure of confined liquids on molecular length scales is of great interest for fundamental and applied sciences. To study confined structures under dynamic conditions, we constructed an in situ X-ray surface forces apparatus (X-SFA). This novel device can create a precisely controlled slit-pore confinement down to dimensions on the 10 nm scale by using a cylinder-on-flat geometry for the first time. Complementary structural information can be obtained by simultaneous force measurements and X-ray scattering experiments. The in-plane structure of liquids parallel to the slit pore and density profiles perpendicular to the confining interfaces are studied by X-ray scattering and reflectivity. The normal load between the opposing interfaces can be modulated to study the structural dynamics of confined liquids. The confinement gap distance is tracked simultaneously with nanometer precision by analyzing optical interference fringes of equal chromatic order. Relaxation processes can be studied by driving the system out of equilibrium by shear stress or compression/decompression cycles of the slit pore. The capability of the new device is demonstrated on the liquid crystal 4'-octyl-4-cyano-biphenyl (8CB) in its smectic A (SmA) mesophase. Its molecular-scale structure and orientation confined in 100 nm to 1.7 μm slit pores was studied under static and dynamic nonequilibrium conditions.
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Affiliation(s)
- Henning Weiss
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Hsiu-Wei Cheng
- Institute
of Applied Physics, Vienna Institute of
Technology, Wiedner Hauptstrasse 8-10/E134, 1040 Wien, Austria
| | - Julian Mars
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55128 Mainz, Germany
| | - Hailong Li
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Claudia Merola
- Institute
of Applied Physics, Vienna Institute of
Technology, Wiedner Hauptstrasse 8-10/E134, 1040 Wien, Austria
| | - Frank Uwe Renner
- Institute
for Materials Research, Hasselt University, 3590 Diepenbeek, Belgium
| | - Veijo Honkimäki
- ESRF-European
Synchrotron Radiation Facility, Avenue des Martyrs 71, 38043 Grenoble, Cedex 9, France
| | - Markus Valtiner
- Institute
of Applied Physics, Vienna Institute of
Technology, Wiedner Hauptstrasse 8-10/E134, 1040 Wien, Austria
- Max-Planck-Institut
für Eisenforschung GmbH, Max-Planck-Strasse 1, 40237 Düsseldorf, Germany
| | - Markus Mezger
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55128 Mainz, Germany
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8
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Boinovich LB. Boundary layers and surface forces in pure nonaqueous liquids. Curr Opin Colloid Interface Sci 2019. [DOI: 10.1016/j.cocis.2019.10.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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9
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Pivnic K, Bresme F, Kornyshev AA, Urbakh M. Structural Forces in Mixtures of Ionic Liquids with Organic Solvents. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:15410-15420. [PMID: 31657581 DOI: 10.1021/acs.langmuir.9b02121] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Using molecular dynamics simulations, we study the impact of electrode charging and addition of solvent (acetonitrile, ACN) on structural forces of the BMIM PF6 ionic liquid (IL) confined by surfaces at nanometer separations. We establish relationships between the structural forces and the microscopic structure of the confined liquid. Depending on the structural arrangements of cations and anions across the nanofilm, the load-induced squeeze-out of liquid layers occurs via one-layer or bilayer steps. The cations confined between charged plates orient with their aliphatic chain perpendicular to the surface planes and link two adjacent IL layers. These structures facilitate the squeeze-out of single layers. For both pure IL and IL-ACN mixtures, we observe a strong dependence of nanofilm structure on the surface charge density, which affects the simulated pressure-displacement curves. Addition of solvent to the IL modifies the layering in the confined film. At high electrode charges and high dilution of IL (below 10% molar fraction), the layered structure of the nanofilm is less well defined. We predict a change in the squeeze-out mechanism under pressure, from a discontinuous squeeze-out (for high IL concentrations) to an almost continuous one (for low IL concentrations). Importantly, our simulations show that charged electrodes are coated with ions even at low IL concentrations. These ion-rich layers adjacent to the charged plate surfaces are not squeezed out even under very high normal pressures of ∼5 GPa. Hence, we demonstrate the high performance of IL-solvent mixtures to protect surfaces from wear and to provide lubrication at high loads.
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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
| | - Fernando Bresme
- 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
| | - 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
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Han M, Espinosa-Marzal RM. Influence of Water on Structure, Dynamics, and Electrostatics of Hydrophilic and Hydrophobic Ionic Liquids in Charged and Hydrophilic Confinement between Mica Surfaces. ACS APPLIED MATERIALS & INTERFACES 2019; 11:33465-33477. [PMID: 31408307 DOI: 10.1021/acsami.9b10923] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Water is ubiquitous in the environment and is the origin for operational constraints in ionic-liquid based electrolytes for supercapacitors. In this study, the influence of water on the interfacial behavior of hydrophilic (1-ethyl-3-methylimidazolium ethylsulfate, abbr. [EMIM][EtSO4]) and hydrophobic (1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, abbr. [EMIM][FAP] and [EMIM][TFSI], respectively) ionic liquids (ILs) confined between mica surfaces was investigated at separations precisely modulated by a surface force apparatus and at controlled relative humidity between 0% and 50% RH. Diffusion experiments revealed that water spontaneously invades the nanoconfined ILs above a certain humidity threshold and that the confined hydrophobic IL is completely replaced by water at sufficiently high environmental humidity (∼45% here) as a result of surface-induced phase separation. This behavior is expected to be universal for other ILs that are not fully miscible with water when they are confined in hydrophilic nanopores of a few nanometers in width. The effect of environmental humidity on interfacial structure, dynamics, and electrostatics was studied via dynamic force measurements. In the dry state, several layers of ions are immobilized on the mica surface, and the effective viscosity increases by up to 2 orders of magnitude with a decrease in film thickness from ∼10 to ∼3 nm. Based on recent work, it is proposed that nanoconfinement enhances the anion-cation association in highly concentrated electrolytes, thereby justifying the loss of fluidity of the ILs. When phase separation is excluded, water is intercalated in the layered structure of the three ILs, and it leads to a change of the layer thickness compared to the dry state. Furthermore, our results reveal that interfacial water prevents ions from being immobilized on the surface and facilitates the outflow of both hydrophilic and hydrophobic ILs by reducing their effective viscosity in the order [EMIM][FAP] < [EMIM][TFSI] < [EMIM][EtSO4]. The underlying mechanisms are evaluated by considering the roles of water in enhancing ion dissociation through screening of electrostatic interactions and solvation of the selected ILs to different extents. The discussed experimental observations support the recent discoveries made by molecular dynamic simulations and neutron scattering studies that using hydrophilic ILs coupled with water as cosolvent could lead to the enhanced power density of IL-based supercapacitors, and therefore, that water-in-(hydrophilic) ILs is a direction worth exploring as electrolytes for supercapacitors.
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Affiliation(s)
- Mengwei Han
- University of Illinois at Urbana-Champaign , 205 North Matthews Avenue , Urbana , Illinois 61801 , United States
| | - Rosa M Espinosa-Marzal
- University of Illinois at Urbana-Champaign , 205 North Matthews Avenue , Urbana , Illinois 61801 , United States
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11
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Qu C, Liu B, Ma M, Zheng Q. Design and optimization of the diamagnetic lateral force calibration method. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:113704. [PMID: 30501302 DOI: 10.1063/1.5041854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2018] [Accepted: 10/18/2018] [Indexed: 06/09/2023]
Abstract
The lateral force calibration is a key procedure for applications of atomic force microscopes. Among different calibration methods, the diamagnetic lateral force calibration (DLFC) method has been widely used due to its ease of use as well as being able to estimate the cross talk conversion factor and achieve very small stiffness. The lateral stiffness of the system is the only parameter in the DLFC method; however, its dependence on the properties and parameters of the DLFC system remains unexplored. In this paper, a theoretical formulation of such dependence is developed and experimentally verified. These results provide a guidance to design and optimize future DLFC systems with better applicability and precision in calibrations. As an example, we optimized a DLFC system such that it is robust against normal load, which is previously assumed impossible.
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Affiliation(s)
- Cangyu Qu
- Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
| | - Bingtong Liu
- Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084, China
| | - Ming Ma
- Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084, China
| | - Quanshui Zheng
- Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
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12
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Pilkington GA, Harris K, Bergendal E, Reddy AB, Palsson GK, Vorobiev A, Antzutkin ON, Glavatskih S, Rutland MW. Electro-responsivity of ionic liquid boundary layers in a polar solvent revealed by neutron reflectance. J Chem Phys 2018; 148:193806. [DOI: 10.1063/1.5001551] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Affiliation(s)
- Georgia A. Pilkington
- Surface and Corrosion Science, Department of Chemistry, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Kathryn Harris
- System and Component Design, Department of Machine Design, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Erik Bergendal
- Surface and Corrosion Science, Department of Chemistry, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Akepati Bhaskar Reddy
- System and Component Design, Department of Machine Design, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Gunnar K. Palsson
- Department of Physics and Astronomy, Division of Materials Physics, Uppsala University, Uppsala, Sweden
| | - Alexei Vorobiev
- Department of Physics and Astronomy, Division of Materials Physics, Uppsala University, Uppsala, Sweden
| | | | - Sergei Glavatskih
- System and Component Design, Department of Machine Design, KTH Royal Institute of Technology, Stockholm, Sweden
- Department of Electrical Energy, Systems and Automation, Ghent University, Ghent, Belgium
| | - Mark W. Rutland
- Surface and Corrosion Science, Department of Chemistry, KTH Royal Institute of Technology, Stockholm, Sweden
- Surfaces, Processes and Formulation, RISE Research Institutes of Sweden, Stockholm, Sweden
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13
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Abstract
The application of ionic liquids as lubricants has attracted substantial interest over the past decade and this has produced a rich literature. The aim of this review is to summarize the main findings about frictional behavior of ionic liquids in the boundary lubrication regime. We first recall why the unusual properties of ionic liquids make them very promising lubricants, and the molecular mechanisms at the origin of their lubricating behavior. We then point out the main challenges to be overcome in order to optimise ionic liquid lubricant performance for common applications. We finally discuss their use in the context of electroactive lubrication.
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