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An R, Laaksonen A, Wu M, Zhu Y, Shah FU, Lu X, Ji X. Atomic force microscopy probing interactions and microstructures of ionic liquids at solid surfaces. NANOSCALE 2022; 14:11098-11128. [PMID: 35876154 DOI: 10.1039/d2nr02812c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Ionic liquids (ILs) are room temperature molten salts that possess preeminent physicochemical properties and have shown great potential in many applications. However, the use of ILs in surface-dependent processes, e.g. energy storage, is hindered by the lack of a systematic understanding of the IL interfacial microstructure. ILs on the solid surface display rich ordering, arising from coulombic, van der Waals, solvophobic interactions, etc., all giving near-surface ILs distinct microstructures. Therefore, it is highly important to clarify the interactions of ILs with solid surfaces at the nanoscale to understand the microstructure and mechanism, providing quantitative structure-property relationships. Atomic force microscopy (AFM) opens a surface-sensitive way to probe the interaction force of ILs with solid surfaces in the layers from sub-nanometers to micrometers. Herein, this review showcases the recent progress of AFM in probing interactions and microstructures of ILs at solid interfaces, and the influence of IL characteristics, surface properties and external stimuli is thereafter discussed. Finally, a summary and perspectives are established, in which, the necessities of the quantification of IL-solid interactions at the molecular level, the development of in situ techniques closely coupled with AFM for probing IL-solid interfaces, and the combination of experiments and simulations are argued.
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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.
| | - 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
| | - Muqiu Wu
- Herbert Gleiter Institute of Nanoscience, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China.
| | - Yudan Zhu
- 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
| | - Xiaohua Lu
- State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing 211816, China
| | - Xiaoyan Ji
- Energy Engineering, Division of Energy Science, Luleå University of Technology, 97187 Luleå, Sweden.
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Zhang Y, Marlow JB, Millar W, Aman ZM, Silvester DS, Warr GG, Atkin R, Li H. Nanostructure, electrochemistry and potential-dependent lubricity of the catanionic surface-active ionic liquid [P 6,6,6,14] [AOT]. J Colloid Interface Sci 2022; 608:2120-2130. [PMID: 34752982 DOI: 10.1016/j.jcis.2021.10.120] [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: 09/12/2021] [Revised: 10/14/2021] [Accepted: 10/20/2021] [Indexed: 10/20/2022]
Abstract
HYPOTHESIS A catanionic surface-active ionic liquid (SAIL) trihexyltetradecylphosphonium 1,4-bis(2-ethylhexoxy)-1,4-dioxobutane-2-sulfonate ([P6,6,6,14] [AOT]) is nanostructured in the bulk and at the interface. The interfacial nanostructure and lubricity may be changed by applying a potential. EXPERIMENTS The bulk structure and viscosity have been investigated using small angle X-ray scattering (SAXS) and rheometry. The interfacial structure and lubricity as a function of potential have been investigated using atomic force microscopy (AFM). The electrochemistry has been investigated using cyclic voltammetry. FINDINGS [P6,6,6,14] [AOT] shows sponge-like bulk nanostructure with distinct interdigitation of cation-anion alkyl chains. Shear-thinning occurs at 293 K and below, but becomes less obvious on heating up to 313 K. Voltammetric analysis reveals that the electrochemical window of [P6,6,6,14] [AOT] on a gold micro disk electrode exceeds the potential range of the AFM experiments and that negligible redox activity occurs in this range. The interfacial layered structure of [P6,6,6,14] [AOT] is weaker than conventional ILs and SAILs, whereas lubricity is better, confirming the inverse correlation between the near-surface structure and lubricity. The adhesive forces of [P6,6,6,14] [AOT] are lower at -1.0 V than at open circuit potential and +1.0 V, likely due to reduced electrostatic interactions caused by shielding of charge centres via long alkyl chains.
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Affiliation(s)
- Yunxiao Zhang
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Joshua B Marlow
- School of Chemistry and Sydney Nano Institute, The University of Sydney, Sydney, NSW 2006, Australia
| | - Wade Millar
- School of Molecular and Life Sciences, Curtin University, GPO Box U1987, Perth 6845, Western Australia, Australia
| | - Zachary M Aman
- Fluid Science and Resources Division, School of Engineering, The University of Western Australia, Perth, Western Australia, Australia
| | - Debbie S Silvester
- School of Molecular and Life Sciences, Curtin University, GPO Box U1987, Perth 6845, Western Australia, Australia
| | - Gregory G Warr
- School of Chemistry and Sydney Nano Institute, The University of Sydney, Sydney, NSW 2006, Australia
| | - Rob Atkin
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, Australia.
| | - Hua Li
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, Australia; Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Perth, Western Australia, Australia.
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3
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Li H, Zhang Y, Jones S, Segalman R, Warr GG, Atkin R. Interfacial nanostructure and friction of a polymeric ionic liquid-ionic liquid mixture as a function of potential at Au(111) electrode interface. J Colloid Interface Sci 2022; 606:1170-1178. [PMID: 34487936 DOI: 10.1016/j.jcis.2021.08.067] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 08/09/2021] [Accepted: 08/09/2021] [Indexed: 11/28/2022]
Abstract
HYPOTHESIS The polymeric cations of polymeric ionic liquids (PILs) can adsorb from the bulk of a conventional ionic liquid (IL) to the Au(111) electrode interface and form a boundary layer. The interfacial properties of the PIL boundary layer may be tuned by potential. EXPERIMENTS Atomic force microscopy has been used to investigate the changes of surface morphology, normal and lateral forces of a 5 wt% PIL/IL mixture as a function of potential. FINDINGS Polymeric cations adsorb strongly to Au(111) and form a polymeric cation-enriched boundary layer at -1.0 V. This boundary layer binds less strongly to the surface at open circuit potential (OCP) and weakly at + 1.0 V. The polymeric cation chains are compressed at -1.0 V and OCP owing to electrical attractions with the electrode surface, but fully stretched at + 1.0 V due to electrical repulsions. The lateral forces of the 5 wt% PIL/IL mixture at -1.0 V and OCP are higher than at + 1.0 V as the polymeric cation-enriched boundary layer is rougher and has stronger interactions with the AFM probe; at + 1.0 V, the lateral force is low and comparable to pure conventional IL due to displacement of polymeric cations with conventional anions in the boundary layer.
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Affiliation(s)
- Hua Li
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, Australia; Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Perth, Western Australia, Australia.
| | - Yunxiao Zhang
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, Australia
| | - Seamus Jones
- Department of Chemical Engineering and Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106, United States
| | - Rachel Segalman
- Department of Chemical Engineering and Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106, United States
| | - Gregory G Warr
- School of Chemistry and Sydney Nano Institute, The University of Sydney, NSW 2006, Australia
| | - Rob Atkin
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia, Australia.
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4
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Effect of Water and Salt on the Colloidal Stability of Latex Particles in Ionic Liquid Solutions. COLLOIDS AND INTERFACES 2021. [DOI: 10.3390/colloids6010002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The colloidal stability of sulfate (SL) and polyimidazolium-modified sulfate (SL-IP-2) latex particles was studied in an ionic liquid (IL) of ethylammonium nitrate (EAN) and its water mixtures. Aggregation rates were found to vary systematically as a function of the IL-to-water ratio. Repulsive electrostatic interactions between particles dominated at low IL concentrations, while they were significantly screened at intermediate IL concentrations, leading to destabilization of the dispersions. When the IL concentration was further increased, the aggregation of latex particles slowed down due to the increased viscosity and finally, a striking stabilization was observed in the IL-rich regime close to the pure IL solvent. The latter stabilization is due to the formation of IL layers at the interface between particles and IL, which induce repulsive oscillatory forces. The presence of the added salt in the system affected differently the structure of the interfaces around SL and SL-IP-2 particles. The sign of the charge and the composition of the particle surfaces were found to be the most important parameters affecting the colloidal stability. The nature of the counterions also plays an important role in the interfacial properties due to their influence on the structure of the IL surface layers. No evidence was observed for the presence of long-range electrostatic interactions between the particles in pure ILs. The results indicate that the presence of even low concentrations of water and salt in the system (as undesirable impurities) can strongly alter the interfacial structure and thus, the aggregation mechanism in particle IL dispersions.
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Li H, Niemann T, Ludwig R, Atkin R. Effect of Hydrogen Bonding between Ions of Like Charge on the Boundary Layer Friction of Hydroxy-Functionalized Ionic Liquids. J Phys Chem Lett 2020; 11:3905-3910. [PMID: 32338913 DOI: 10.1021/acs.jpclett.0c00689] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Atomic force microscopy has been used to measure the lubricity of a series of ionic liquids (ILs) at mica surfaces in the boundary friction regime. A previously unreported cation bilayer structure is detected at the IL-mica interface due to the formation of H-bonds between the hydroxy-functionalized cations [(c-c) H-bonds], which enhances the ordering of the ions in the boundary layer and improves the lubrication. The strength of the cation bilayer structure is controlled by altering the strength of (c-c) H-bonding via changes in the hydroxyalkyl chain length, the cation charge polarizability, and the coordination strength of the anions. This reveals a new means of controlling IL boundary nanostructure via H-bonding between ions of the same charge, which can impact diverse applications, including surface catalysis, particle stability, electrochemistry, etc.
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Affiliation(s)
- Hua Li
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia 6009, Australia
- Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Perth, Western Australia 6009, Australia
| | - Thomas Niemann
- Universität Rostock, Institut für Chemie, Abteilung für Physikalische Chemie, Dr.-Lorenz-Weg 2, 18059 Rostock, Germany
- Department LL&M, University of Rostock, Albert-Einstein-Strasse 25, 18059 Rostock, Germany
| | - Ralf Ludwig
- Universität Rostock, Institut für Chemie, Abteilung für Physikalische Chemie, Dr.-Lorenz-Weg 2, 18059 Rostock, Germany
- Department LL&M, University of Rostock, Albert-Einstein-Strasse 25, 18059 Rostock, Germany
- Leibniz-Institut für Katalyse an der Universität Rostock e.V., Albert-Einstein-Strasse 29a, 18059 Rostock, Germany
| | - Rob Atkin
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia 6009, Australia
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6
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Hjalmarsson N, Bergendal E, Wang YL, Munavirov B, Wallinder D, Glavatskih S, Aastrup T, Atkin R, Furó I, Rutland MW. Electro-Responsive Surface Composition and Kinetics of an Ionic Liquid in a Polar Oil. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:15692-15700. [PMID: 31581771 DOI: 10.1021/acs.langmuir.9b02119] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The quartz crystal microbalance (QCM) has been used to study how the interfacial layer of an ionic liquid dissolved in a polar oil at low weight percentages responds to changes in applied potential. The changes in surface composition at the QCM gold surface depend on both the magnitude and sign of the applied potential. The time-resolved response indicates that the relaxation kinetics are limited by the diffusion of ions in the interfacial region and not in the bulk, since there is no concentration dependence. The measured mass changes cannot be explained only in terms of simple ion exchange; the relative molecular volumes of the ions and the density changes in response to ion exclusion must be considered. The relaxation behavior of the potential between the electrodes upon disconnecting the applied potential is more complex than that observed for pure ionic liquids, but a measure of the surface charge can be extracted from the exponential decay when the rapid initial potential drop is accounted for. The adsorbed film at the gold surface consists predominantly of ionic liquid despite the low concentration, which is unsurprising given the surtactant-like structures of (some of) the ionic liquid ions. Changes in response to potential correspond to changes in the relative numbers of cations and anions, rather than a change in the oil composition. No evidence for an electric field induced change in viscosity is observed. This work shows conclusively that electric potentials can be used to control the surface composition, even in an oil-based system, and paves the way for other ion solvent studies.
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Affiliation(s)
| | | | | | | | | | - Sergei Glavatskih
- Department of Electrical Energy, Metals, Mechanical Constructions and Systems , Ghent University , B-9000 , Ghent , Belgium
| | | | - Rob Atkin
- School of Molecular Sciences , University of Western Australia , 6009 Perth , Australia
| | | | - Mark W Rutland
- Surfaces, Processes and Formulation , RISE Research Institutes of Sweden , SE-50115 Stockholm , Sweden
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7
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Anomalous Interfacial Structuring of a Non-Halogenated Ionic Liquid: Effect of Substrate and Temperature. COLLOIDS AND INTERFACES 2018. [DOI: 10.3390/colloids2040060] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We investigate the interfacial properties of the non-halogenated ionic liquid (IL), trihexyl(tetradecyl)phosphonium bis(mandelato)borate, [P6,6,6,14][BMB], in proximity to solid surfaces, by means of surface force measurement. The system consists of sharp atomic force microscopy (AFM) tips interacting with solid surfaces of mica, silica, and gold. We find that the force response has a monotonic form, from which a characteristic steric decay length can be extracted. The decay length is comparable with the size of the ions, suggesting that a layer is formed on the surface, but that it is diffuse. The long alkyl chains of the cation, the large size of the anion, as well as crowding of the cations at the surface of negatively charged mica, are all factors which are likely to oppose the interfacial stratification which has, hitherto, been considered a characteristic of ionic liquids. The variation in the decay length also reveals differences in the layer composition at different surfaces, which can be related to their surface charge. This, in turn, allows the conclusion that silica has a low surface charge in this aprotic ionic liquid. Furthermore, the effect of temperature has been investigated. Elevating the temperature to 40 °C causes negligible changes in the interaction. At 80 °C and 120 °C, we observe a layering artefact which precludes further analysis, and we present the underlying instrumental origin of this rather universal artefact.
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8
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Safinejad R, Mehdipour N, Eslami H. Atomistic reverse nonequilibrium molecular dynamics simulation of the viscosity of ionic liquid 1-n-butyl 3-methylimidazolium bis(trifluoromethylsulfonyl)imide [bmim][Tf 2N]. Phys Chem Chem Phys 2018; 20:21544-21551. [PMID: 30094445 DOI: 10.1039/c8cp02393j] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The shear viscosity of room-temperature ionic liquid (IL) 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [bmim][Tf2N] is calculated over a temperature range 298-353 K, using the reverse nonequilibrium molecular dynamics simulation technique. The results of this work show that while the use of equilibrium molecular dynamics simulation techniques might be inefficient for viscosity calculations of ILs, the reverse nonequilibrium molecular dynamics technique is an efficient tool for this purpose. Our findings indicate that the shear rate for crossover from the Newtonian plateau to the shear thinning regime, corresponds to the relaxation time for the slowest microscopic scale motions, i.e., exchange of counterions in an ion's solvation shell (ion-pair relaxation time). The closeness of the time scales and activation energies for zero-shear-rate viscosities to the relaxation times and the corresponding activation energies for ion-pair formation/rupture, connects macroscopic dynamic properties with local atomic-level motions of the IL. The calculated viscosity coefficients and relaxation times for reorientations of the cation and anion as well as their corresponding activation energies are in very good agreement with experimental data.
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Affiliation(s)
- Rouhollah Safinejad
- Department of Chemistry, College of Sciences, Persian Gulf University, Boushehr 75168, Iran.
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9
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Roohi H, Ghauri K, Salehi R. Non-covalent green functionalization of boron nitride nanotubes with tunable aryl alkyl ionic liquids: A quantum chemical approach. J Mol Liq 2017. [DOI: 10.1016/j.molliq.2017.08.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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10
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Rutland MW. Chemical physics of electroactive materials: concluding remarks. Faraday Discuss 2017; 199:615-630. [PMID: 28675400 DOI: 10.1039/c7fd00176b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
It is an honour to be charged with providing the concluding remarks for a Faraday Discussion. As many have remarked before, it is nonetheless a prodigious task, and what follows is necessarily a personal, and probably perverse, view of a watershed event in the Chemical Physics of Electroactive materials. The spirit of the conference was captured in a single sentence during the meeting itself."It is the nexus between rheology, electrochemistry, colloid science and energy storage". The current scientific climate is increasingly dominated by a limited number of global challenges, and there is thus a tendency for research to resemble a football match played by 6 year olds, where everyone on the field chases the (funding) ball instead of playing to their "discipline". It is thus reassuring to see how the application of rigorous chemical physics is leading to ingenious new solutions for both energy storage and harvesting, via, for example, nanoactuation, electrowetting, ionic materials and nanoplasmonics. In fact, the same language of chemical physics allows seamless transition between applications as diverse as mechano-electric energy generation, active moisture transport and plasmonic shutters - even the origins of life were addressed in the context of electro-autocatalysis!
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Affiliation(s)
- Mark W Rutland
- KTH Royal Institute of Technology, Surface and Corrosion Science, Drottning Kristinas väg 51, Stockholm 10044, Sweden. and RISE Research Institutes of Sweden AB, Chemistry Materials and Surfaces, Drottning Kristinas väg 45, Stockholm 11486, Sweden
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11
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Gebbie MA, Smith AM, Dobbs HA, Lee AA, Warr GG, Banquy X, Valtiner M, Rutland MW, Israelachvili JN, Perkin S, Atkin R. Long range electrostatic forces in ionic liquids. Chem Commun (Camb) 2017; 53:1214-1224. [DOI: 10.1039/c6cc08820a] [Citation(s) in RCA: 231] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Experimental evidence for long range surface forces in ionic liquids is collated and examined, key outstanding questions are identified, and possible mechanisms underpinning these long range forces are explored.
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Affiliation(s)
- Matthew A. Gebbie
- Geballe Laboratory for Advanced Materials
- Stanford University
- Stanford
- USA
| | - Alexander M. Smith
- Department of Chemistry
- Physical & Theoretical Chemistry Laboratory
- University of Oxford
- Oxford
- UK
| | - Howard A. Dobbs
- Department of Chemical Engineering
- University of California
- Santa Barbara
- UK
| | - Alpha A. Lee
- School of Engineering and Applied Sciences
- Harvard University
- Cambridge
- USA
| | - Gregory G. Warr
- School of Chemistry
- F11
- The University of Sydney
- NSW 2006
- Australia
| | - Xavier Banquy
- Faculty of Pharmacy
- Universite de Montreal
- Montreal
- Canada
| | - Markus Valtiner
- Interface Chemistry and Surface Engineering
- Max Planck Institut fur Eisenforschung GmbH
- Dusseldorf
- Germany
| | - Mark W. Rutland
- Surface and Corrosion Science
- KTH Royal Institute of Technology
- SE-10044 Stockholm
- Sweden
- SP Chemistry Materials and Surfaces
| | | | - Susan Perkin
- Department of Chemistry
- Physical & Theoretical Chemistry Laboratory
- University of Oxford
- Oxford
- UK
| | - Rob Atkin
- Priority Research Centre for Advanced Fluid Interfaces
- Newcastle Institute for Energy and Resources
- The University of Newcastle
- Australia
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12
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Hjalmarsson N, Atkin R, Rutland MW. Switchable long-range double layer force observed in a protic ionic liquid. Chem Commun (Camb) 2017; 53:647-650. [DOI: 10.1039/c6cc07396d] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A repulsive double layer force has been measured for ethylammonium nitrate (EAN) at 373 K and 393 K, which is absent at lower temperatures.
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Affiliation(s)
- N. Hjalmarsson
- Surface and Corrosion Science
- KTH Royal Institute of Technology
- SE-10044 Stockholm
- Sweden
| | - R. Atkin
- Priority Research Centre for Advanced Fluids and Interfaces
- The University of Newcastle
- Callaghan
- Australia
| | - M. W. Rutland
- Surface and Corrosion Science
- KTH Royal Institute of Technology
- SE-10044 Stockholm
- Sweden
- Chemistry, Materials and Surfaces
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13
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Hjalmarsson N, Atkin R, Rutland MW. Is the boundary layer of an ionic liquid equally lubricating at higher temperature? Phys Chem Chem Phys 2016; 18:9232-9. [PMID: 26976694 DOI: 10.1039/c5cp05837f] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Atomic force microscopy has been used to study the effect of temperature on normal forces and friction for the room temperature ionic liquid (IL) ethylammonium nitrate (EAN), confined between mica and a silica colloid probe at 25 °C, 50 °C, and 80 °C. Force curves revealed a strong fluid dynamic influence at room temperature, which was greatly reduced at elevated temperatures due to the reduced liquid viscosity. A fluid dynamic analysis reveals that bulk viscosity is manifested at large separation but that EAN displays a nonzero slip, indicating a region of different viscosity near the surface. At high temperatures, the reduction in fluid dynamic force reveals step-like force curves, similar to those found at room temperature using much lower scan rates. The ionic liquid boundary layer remains adsorbed to the solid surface even at high temperature, which provides a mechanism for lubrication when fluid dynamic lubrication is strongly reduced. The friction data reveals a decrease in absolute friction force with increasing temperature, which is associated with increased thermal motion and reduced viscosity of the near surface layers but, consistent with the normal force data, boundary layer lubrication was unaffected. The implications for ILs as lubricants are discussed in terms of the behaviour of this well characterised system.
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Affiliation(s)
- Nicklas Hjalmarsson
- Surface and Corrosion Science, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden.
| | - Rob Atkin
- Priority Research Centre for Advanced Fluids and Interfaces, The University of Newcastle, Callaghan, NSW 2308, Australia
| | - Mark W Rutland
- Surface and Corrosion Science, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden. and Chemistry, Materials and Surfaces, SP Technical Research Institute Sweden, SE-11428 Stockholm, Sweden
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14
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Murphy T, Callear SK, Yepuri N, Shimizu K, Watanabe M, Canongia Lopes JN, Darwish T, Warr GG, Atkin R. Bulk nanostructure of the prototypical ‘good’ and ‘poor’ solvate ionic liquids [Li(G4)][TFSI] and [Li(G4)][NO3]. Phys Chem Chem Phys 2016; 18:17224-36. [DOI: 10.1039/c6cp00176a] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The bulk nanostructures of a prototypical ‘good’ solvate ionic liquid (SIL) and ‘poor’ SIL have been examined using neutron diffraction and empirical potential structure refinement (EPSR) simulated fits.
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Affiliation(s)
- Thomas Murphy
- Priority Research Centre for Advanced Fluids and Interfaces
- Newcastle Institute for Energy & Resources
- University of Newcastle
- Callaghan
- Australia
| | | | - Nageshwar Yepuri
- National Deuteration Facility
- Australian Nuclear Science and Technology Organisation
- Kirrawee DC
- Australia
| | - Karina Shimizu
- Centro de Química Estrutural
- Instituto Superior Técnico
- Universidade de Lisboa
- 1049 001 Lisboa
- Portugal
| | - Masayoshi Watanabe
- Department of Chemistry and Biotechnology
- Yokohama National University
- Yokohama 240-8501
- Japan
| | - José N. Canongia Lopes
- Centro de Química Estrutural
- Instituto Superior Técnico
- Universidade de Lisboa
- 1049 001 Lisboa
- Portugal
| | - Tamim Darwish
- National Deuteration Facility
- Australian Nuclear Science and Technology Organisation
- Kirrawee DC
- Australia
| | | | - Rob Atkin
- Priority Research Centre for Advanced Fluids and Interfaces
- Newcastle Institute for Energy & Resources
- University of Newcastle
- Callaghan
- Australia
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15
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Cooper PK, Li H, Rutland MW, Webber GB, Atkin R. Tribotronic control of friction in oil-based lubricants with ionic liquid additives. Phys Chem Chem Phys 2016; 18:23657-62. [PMID: 27511143 DOI: 10.1039/c6cp04405k] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Atomic force microscopy (AFM) reveals that tribotronic control of friction using an external potential applied to a gold surface is possible for ionic liquid (IL) concentrations as low as 5 mol% in hexadecane.
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Affiliation(s)
- P. K. Cooper
- Priority Research Centre for Advanced Fluids and Interfaces
- Newcastle Institute for Energy and Resources
- University of Newcastle
- Callaghan
- Australia
| | - H. Li
- Priority Research Centre for Advanced Fluids and Interfaces
- Newcastle Institute for Energy and Resources
- University of Newcastle
- Callaghan
- Australia
| | - M. W. Rutland
- KTH Royal Institute of Technology
- School of Chemical Science and Engineering
- Department of Chemistry
- SE-100 44 Stockholm
- Sweden
| | - G. B. Webber
- Priority Research Centre for Advanced Fluids and Interfaces
- Newcastle Institute for Energy and Resources
- University of Newcastle
- Callaghan
- Australia
| | - R. Atkin
- Priority Research Centre for Advanced Fluids and Interfaces
- Newcastle Institute for Energy and Resources
- University of Newcastle
- Callaghan
- Australia
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16
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Murphy T, Hayes R, Imberti S, Warr GG, Atkin R. Ionic liquid nanostructure enables alcohol self assembly. Phys Chem Chem Phys 2016; 18:12797-809. [DOI: 10.1039/c6cp01739h] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Weakly structured solutions are formed from mixtures of one or more amphiphiles and a polar solvent (usually water), and often contain additional organic components.
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Affiliation(s)
- Thomas Murphy
- Priority Research Centre for Advanced Fluids and Interfaces
- Newcastle Institute for Energy & Resources
- University of Newcastle
- Callaghan
- Australia
| | - Robert Hayes
- Priority Research Centre for Advanced Fluids and Interfaces
- Newcastle Institute for Energy & Resources
- University of Newcastle
- Callaghan
- Australia
| | | | | | - Rob Atkin
- Priority Research Centre for Advanced Fluids and Interfaces
- Newcastle Institute for Energy & Resources
- University of Newcastle
- Callaghan
- Australia
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17
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Begić S, Li H, Atkin R, Hollenkamp AF, Howlett PC. A comparative AFM study of the interfacial nanostructure in imidazolium or pyrrolidinium ionic liquid electrolytes for zinc electrochemical systems. Phys Chem Chem Phys 2016; 18:29337-29347. [DOI: 10.1039/c6cp04299f] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
AFM measurements show that the electrochemical performance of zinc based ionic liquid electrolytes is controlled by ion arrangements at the electrode surface.
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Affiliation(s)
- Srđan Begić
- ARC Centre of Excellence for Electromaterials Science (ACES)
- Institute for Frontier Materials (IFM)
- Deakin University Burwood Campus
- Burwood
- Australia
| | - Hua Li
- Priority Research Centre for Advanced Fluids and Interfaces
- The University of Newcastle
- Callaghan
- Australia
| | - Rob Atkin
- Priority Research Centre for Advanced Fluids and Interfaces
- The University of Newcastle
- Callaghan
- Australia
| | | | - Patrick C. Howlett
- ARC Centre of Excellence for Electromaterials Science (ACES)
- Institute for Frontier Materials (IFM)
- Deakin University Burwood Campus
- Burwood
- Australia
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18
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Murphy T, Callear SK, Warr GG, Atkin R. Dissolved chloride markedly changes the nanostructure of the protic ionic liquids propylammonium and ethanolammonium nitrate. Phys Chem Chem Phys 2016; 18:17169-82. [DOI: 10.1039/c5cp06947e] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The bulk nanostructure of 15 mol% propylammonium chloride (PACl) dissolved in propylammonium nitrate (PAN) and 15 mol% ethanolammonium chloride (EtACl) in ethanolammonium nitrate (EtAN) has been determined using neutron diffraction with empirical potential structure refinement fits.
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Affiliation(s)
- Thomas Murphy
- Priority Research Centre for Advanced Fluids and Interfaces
- The University of Newcastle
- Callaghan
- Australia
| | | | | | - Rob Atkin
- Priority Research Centre for Advanced Fluids and Interfaces
- The University of Newcastle
- Callaghan
- Australia
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19
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Li H, Somers AE, Howlett PC, Rutland MW, Forsyth M, Atkin R. Addition of low concentrations of an ionic liquid to a base oil reduces friction over multiple length scales: a combined nano- and macrotribology investigation. Phys Chem Chem Phys 2016; 18:6541-7. [DOI: 10.1039/c5cp07061a] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The efficacy of ionic liquids (ILs) as lubricant additives to a model base oil has been probed at the nanoscale and macroscale as a function of IL concentration using the same materials.
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Affiliation(s)
- Hua Li
- Priority Research Centre for Advanced Fluids and Interfaces
- The University of Newcastle
- Callaghan
- Australia
| | | | | | - Mark W. Rutland
- School of Chemical Science and Engineering
- KTH Royal Institute of Technology
- SE100 44, Sweden
- Chemistry
- Materials and Surfaces
| | - Maria Forsyth
- Institute for Frontier Materials
- Deakin University
- Geelong
- Australia
| | - Rob Atkin
- Priority Research Centre for Advanced Fluids and Interfaces
- The University of Newcastle
- Callaghan
- Australia
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20
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Abdulbari HA, Oluwasoga Akindoyo E, Mahmood WK. Renewable Resource-Based Lubricating Greases from Natural and Synthetic Sources: Insights and Future Challenges. CHEMBIOENG REVIEWS 2015. [DOI: 10.1002/cben.201500006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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21
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Greaves TL, Drummond CJ. Protic Ionic Liquids: Evolving Structure-Property Relationships and Expanding Applications. Chem Rev 2015; 115:11379-448. [PMID: 26426209 DOI: 10.1021/acs.chemrev.5b00158] [Citation(s) in RCA: 498] [Impact Index Per Article: 55.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Tamar L Greaves
- School of Applied Sciences, College of Science, Engineering and Health, RMIT University , GPO Box 2476, Melbourne, Victoria 3001, Australia
| | - Calum J Drummond
- School of Applied Sciences, College of Science, Engineering and Health, RMIT University , GPO Box 2476, Melbourne, Victoria 3001, Australia
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22
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Álvarez-Asencio R, Wallqvist V, Kjellin M, Rutland MW, Camacho A, Nordgren N, Luengo GS. Nanomechanical properties of human skin and introduction of a novel hair indenter. J Mech Behav Biomed Mater 2015; 54:185-93. [PMID: 26469630 DOI: 10.1016/j.jmbbm.2015.09.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Revised: 09/01/2015] [Accepted: 09/14/2015] [Indexed: 11/18/2022]
Abstract
The mechanical resistance of the stratum corneum, the outermost layer of skin, to deformation has been evaluated at different length scales using Atomic Force Microscopy. Nanomechanical surface mapping was first conducted using a sharp silicon tip and revealed that Young׳s modulus of the stratum corneum varied over the surface with a mean value of about 0.4GPa. Force indentation measurements showed permanent deformation of the skin surface only at high applied loads (above 4µN). The latter effect was further demonstrated using nanomechanical imaging in which the obtained depth profiles clearly illustrate the effects of increased normal force on the elastic/plastic surface deformation. Force measurements utilizing the single hair fiber probe supported the nanoindentation results of the stratum corneum being highly elastic at the nanoscale, but revealed that the lateral scale of the deformation determines the effective elastic modulus.This result resolves the fact that the reported values in the literature vary greatly and will help to understand the biophysics of the interaction of razor cut hairs that curl back during growth and interact with the skin.
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Affiliation(s)
- Rubén Álvarez-Asencio
- KTH Royal Institute of Technology, School of Chemical Science and Engineering, Department of Chemistry, SE-100 44 Stockholm, Sweden; Institute for Advanced Studies, IMDEA Nanoscience, c/Faraday 9, Campus Cantoblanco, 28049 Madrid, Spain
| | - Viveca Wallqvist
- SP Technical Research Institute of Sweden, SP Chemistry, Materials and Surfaces, SE-114 86 Stockholm, Sweden
| | - Mikael Kjellin
- SP Technical Research Institute of Sweden, SP Chemistry, Materials and Surfaces, SE-114 86 Stockholm, Sweden
| | - Mark W Rutland
- KTH Royal Institute of Technology, School of Chemical Science and Engineering, Department of Chemistry, SE-100 44 Stockholm, Sweden; SP Technical Research Institute of Sweden, SP Chemistry, Materials and Surfaces, SE-114 86 Stockholm, Sweden
| | | | - Niklas Nordgren
- SP Technical Research Institute of Sweden, SP Chemistry, Materials and Surfaces, SE-114 86 Stockholm, Sweden.
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23
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Affiliation(s)
- Robert Hayes
- Discipline
of Chemistry, The University of Newcastle, NSW 2308, Callaghan, Australia
| | - Gregory G. Warr
- School
of Chemistry, The University of Sydney, NSW 2006, Sydney, Australia
| | - Rob Atkin
- Discipline
of Chemistry, The University of Newcastle, NSW 2308, Callaghan, Australia
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24
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Harris KL, Pitenis AA, Sawyer WG, Krick BA, Blackman GS, Kasprzak DJ, Junk CP. PTFE Tribology and the Role of Mechanochemistry in the Development of Protective Surface Films. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b00452] [Citation(s) in RCA: 173] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | | | | | - Brandon A. Krick
- Department
of Mechanical Engineering and Mechanics Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Gregory S. Blackman
- Experimental
Station E500/2604B, DuPont Central Research and Development, 200
Powder Mill Road, P.O. Box 8352 Wilmington, Delaware 19803, United States
| | - Daniel J. Kasprzak
- Experimental
Station E500/2604B, DuPont Central Research and Development, 200
Powder Mill Road, P.O. Box 8352 Wilmington, Delaware 19803, United States
| | - Christopher P. Junk
- Experimental
Station E500/2604B, DuPont Central Research and Development, 200
Powder Mill Road, P.O. Box 8352 Wilmington, Delaware 19803, United States
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25
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Sweeney J, Webber GB, Atkin R. Near surface properties of mixtures of propylammonium nitrate with n-alkanols 2. Nanotribology and fluid dynamics. Phys Chem Chem Phys 2015; 17:26629-37. [DOI: 10.1039/c5cp04787k] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Colloid probe friction force microscopy (FFM) has been used to study the lubricity of propylammonium nitrate (PAN) mixed with n-alkanols confined between sliding silica and mica surfaces.
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Affiliation(s)
- James Sweeney
- Centre for Advanced Particle Processing and Transport
- Newcastle Institute for Energy and Resources
- The University of Newcastle
- Callaghan
- Australia
| | - Grant B. Webber
- Centre for Advanced Particle Processing and Transport
- Newcastle Institute for Energy and Resources
- The University of Newcastle
- Callaghan
- Australia
| | - Rob Atkin
- Centre for Advanced Particle Processing and Transport
- Newcastle Institute for Energy and Resources
- The University of Newcastle
- Callaghan
- Australia
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26
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Chen Z, Greaves TL, Caruso RA, Drummond CJ. Amphiphile Micelle Structures in the Protic Ionic Liquid Ethylammonium Nitrate and Water. J Phys Chem B 2014; 119:179-91. [DOI: 10.1021/jp509557z] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Zhengfei Chen
- Particulate
Fluids Processing Centre (PFPC), School of Chemistry, The University of Melbourne, Melbourne, Victoria 3010, Australia
- CSIRO Materials Science and Engineering, Bag
10, Clayton South MDC, Victoria 3169, Australia
| | - Tamar L. Greaves
- CSIRO Materials Science and Engineering, Bag
10, Clayton South MDC, Victoria 3169, Australia
- School
of Applied Sciences, College of Science, Engineering and Health, RMIT University, GPO
Box 2476, Melbourne, Victoria 3001, Australia
| | - Rachel A. Caruso
- Particulate
Fluids Processing Centre (PFPC), School of Chemistry, The University of Melbourne, Melbourne, Victoria 3010, Australia
- CSIRO Materials Science and Engineering, Bag
10, Clayton South MDC, Victoria 3169, Australia
| | - Calum J. Drummond
- CSIRO Materials Science and Engineering, Bag
10, Clayton South MDC, Victoria 3169, Australia
- School
of Applied Sciences, College of Science, Engineering and Health, RMIT University, GPO
Box 2476, Melbourne, Victoria 3001, Australia
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27
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Li H, Cooper PK, Somers AE, Rutland MW, Howlett PC, Forsyth M, Atkin R. Ionic Liquid Adsorption and Nanotribology at the Silica-Oil Interface: Hundred-Fold Dilution in Oil Lubricates as Effectively as the Pure Ionic Liquid. J Phys Chem Lett 2014; 5:4095-4099. [PMID: 26278938 DOI: 10.1021/jz5021422] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The remarkable physical properties of ionic liquids (ILs) make them potentially excellent lubricants. One of the challenges for using ILs as lubricants is their high cost. In this article, atomic force microscopy (AFM) nanotribology measurements reveal that a 1 mol % solution of IL dissolved in an oil lubricates the silica surface as effectively as the pure IL. The adsorption isotherm shows that the IL surface excess need only be approximately half of the saturation value to prevent surface contact and effectively lubricate the sliding surfaces. Using ILs in this way makes them viable for large-scale applications.
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Affiliation(s)
- Hua Li
- †Centre for Advanced Particle Processing and Transport, The University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Peter K Cooper
- †Centre for Advanced Particle Processing and Transport, The University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Anthony E Somers
- ‡ARC Centre of Excellence for Electromaterials Science, Institute for Frontier Materials, Deakin University, 221 Burwood Highway, Burwood, Victoria 3125, Australia
| | - Mark W Rutland
- §School of Chemical Science and Engineering, KTH Royal Institute of Technology, Stockholm SE100 44, Sweden
- ⊥Chemistry, Materials and Surfaces, SP Technical Research Institute of Sweden, Stockholm SE100 44, Sweden
| | - Patrick C Howlett
- ‡ARC Centre of Excellence for Electromaterials Science, Institute for Frontier Materials, Deakin University, 221 Burwood Highway, Burwood, Victoria 3125, Australia
| | - Maria Forsyth
- ‡ARC Centre of Excellence for Electromaterials Science, Institute for Frontier Materials, Deakin University, 221 Burwood Highway, Burwood, Victoria 3125, Australia
| | - Rob Atkin
- †Centre for Advanced Particle Processing and Transport, The University of Newcastle, Callaghan, New South Wales 2308, Australia
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28
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29
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Li H, Wood RJ, Endres F, Atkin R. Influence of alkyl chain length and anion species on ionic liquid structure at the graphite interface as a function of applied potential. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:284115. [PMID: 24920055 DOI: 10.1088/0953-8984/26/28/284115] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Atomic force microscopy (AFM) force measurements elucidate the effect of cation alkyl chain length and the anion species on ionic liquid (IL) interfacial structure at highly ordered pyrolytic graphite (HOPG) surfaces as a function of potential. Three ILs are examined: 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIM] FAP), 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([EMIM] FAP), and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM] TFSA). The step-wise force-distance profiles indicate the ILs adopt a multilayered morphology near the surface. When the surface is biased positively or negatively versus Pt quasireference electrode, both the number of steps, and the force required to rupture each step increase, indicating stronger interfacial structure. At all potentials, push-through forces for [HMIM] FAP are the highest, because the long alkyl chain results in strong cohesive interactions between cations, leading to well-formed layers that resist the AFM tip. The most layers are observed for [EMIM] FAP, because the C2 chains are relatively rigid and the dimensions of the cation and anion are similar, facilitating neat packing. [EMIM] TFSA has the smallest push-through forces and fewest layers, and thus the weakest interfacial structure. Surface-tip attractive forces are measured for all ILs. At the same potential, the attractions are the strongest for [EMIM] TFSA and the weakest for [HMIM] FAP because the interfacial layers are better formed for the longer alkyl chain cation. This means interfacial forces are stronger, which masks the weak attractive forces.
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Affiliation(s)
- Hua Li
- Centre for Advanced Particle Processing and Transport, The University of Newcastle, Callaghan, NSW 2308, Australia
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30
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Sweeney J, Webber GB, Rutland MW, Atkin R. Effect of ion structure on nanoscale friction in protic ionic liquids. Phys Chem Chem Phys 2014; 16:16651-8. [DOI: 10.1039/c4cp02320j] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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31
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Chen Y, Wang H, Wang J. Effects of Alkyl Chain Length and Solvents on Thermodynamic Dissociation Constants of the Ionic Liquids with One Carboxyl Group in the Alkyl Chain of Imidazolium Cations. J Phys Chem B 2014; 118:4630-5. [DOI: 10.1021/jp501731j] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yuehua Chen
- Collaborative Innovation
Center of Henan Province for Green Manufacturing of Fine Chemicals,
Key Laboratory of Green Chemical Media and Reactions, Ministry of
Education, School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, Henan 453007, People’s Republic of China
| | - Huiyong Wang
- Collaborative Innovation
Center of Henan Province for Green Manufacturing of Fine Chemicals,
Key Laboratory of Green Chemical Media and Reactions, Ministry of
Education, School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, Henan 453007, People’s Republic of China
| | - Jianji Wang
- Collaborative Innovation
Center of Henan Province for Green Manufacturing of Fine Chemicals,
Key Laboratory of Green Chemical Media and Reactions, Ministry of
Education, School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, Henan 453007, People’s Republic of China
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32
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Smith J, Webber GB, Warr GG, Atkin R. Silica particle stability and settling in protic ionic liquids. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:1506-1513. [PMID: 24450614 DOI: 10.1021/la403978b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Silica particle suspensions of 10 wt % have been investigated in the protic ionic liquids (ILs) ethylammonium nitrate (EAN), ethanolammonium nitrate (EtAN), propylammonium nitrate (PAN), and dimethylethylammonium formate (DMEAF). Static and dynamic light scattering reveal that single particles coexist in dynamic equilibrium with flocculated networks at room temperature. These types of systems are classified as weakly flocculated and are quite rare. As weakly flocculated systems generally exist only within a narrow range of conditions, the effect of temperature was probed. When temperature is increased, the thermal motion of suspended particles increases, favoring dispersion, but in ILs suspensions, heating reduces the stabilizing effect of the interfacial structure of the IL. When subjected to a small increase in temperature, particle suspensions in ILs become unstable, indicated by the absence of a peak corresponding to single particles in the light scattering data. For EAN and DMEAF, further increasing temperatures above 40 °C returns the systems to a weakly flocculated state in which thermal energy is sufficient to break particles away from aggregates. Weakly flocculated suspensions in EAN and EtAN settle more rapidly than predicted by the Stokes equation, as the particles spend a significant portion of time in large, rapidly settling flocs. Surprisingly, suspensions in PAN and DMEAF settle slower than predicted. Oscillatory rheology indicates that these suspensions are viscoelastic, due to a persistent, long-range structure in the suspension that slows settling. In aggregated systems, settling is very rapid.
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Affiliation(s)
- Jacob Smith
- Priority Research Centre for Advanced Particle Processing and Transport, The University of Newcastle , Callaghan, NSW 2308, Australia
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33
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Murphy T, Hayes R, Imberti S, Warr GG, Atkin R. Nanostructure of an ionic liquid–glycerol mixture. Phys Chem Chem Phys 2014; 16:13182-90. [DOI: 10.1039/c4cp01570c] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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34
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Eder SJ, Vernes A, Betz G. On the Derjaguin offset in boundary-lubricated nanotribological systems. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:13760-13772. [PMID: 24164715 DOI: 10.1021/la4026443] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We performed molecular dynamics simulations of boundary-lubricated sliding, varying the boundary lubricant type, its molecular surface coverage, the substrate roughness, and the load. The resulting load versus friction behavior was then analyzed to study how changes in lubricant type, coverage, and roughness affect the extrapolated friction force at zero load, the so-called Derjaguin offset. A smooth-particle-based evaluation method by the authors, applied here for the first time to visualize the sliding interface between the two layers of boundary lubricant, allowed the definition and calculation of a dimensionless normalized sliding resistance area, which was then related to the Derjaguin offset. This relationship excellently reflects the molecular surface coverage, which determines the physical condition of the lubricant, and can differentiate between some lubricant-specific frictional properties.
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Affiliation(s)
- Stefan J Eder
- Austrian Center of Competence for Tribology , Viktor-Kaplan-Straße 2, 2700 Wiener Neustadt, Austria
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35
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Nalam PC, Ramakrishna SN, Espinosa-Marzal RM, Spencer ND. Exploring lubrication regimes at the nanoscale: nanotribological characterization of silica and polymer brushes in viscous solvents. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:10149-10158. [PMID: 23859353 DOI: 10.1021/la402148b] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Nanotribological properties of silica surfaces, with and without adsorbed, brushlike copolymers of poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) and poly(L-lysine)-graft-dextran (PLL-g-dextran) have been investigated in aqueous viscous solvent mixtures by means of colloid-probe lateral force microscopy. Lateral forces for PEG/dextran brushes have been measured as a function of shear velocity in aqueous mixtures of glycerol and ethylene glycol (EG), which are highly miscible with water, but are poor solvents for hydrophilic PEG and dextran chains. Prior to the friction measurements on polymer brushes, a nanoscale Stribeck curve was obtained on a bare silica surface in the selected aqueous cosolvent mixtures. The Stribeck curve for bare surfaces indicates the existence of a surface-solvating thin film due to the adsorption of hydrated ions, preventing direct silica-silica contact in the boundary-lubrication regime. A clear transition to the hydrodynamic regime is seen at high speeds for solvents with higher viscosities. The polymer brushes, however, show a shear-thinning effect with increasing shear speed and a combined influence of polymer film and solvent viscosity on the measured friction forces. The formation of an interfacial fluid-film is shown to shift the hydrodynamic regime of hydrated brushes to a lower value of Uη. The correlation between the structural configuration and the corresponding frictional properties of the polymer brushes upon changing solvent quality is discussed.
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Affiliation(s)
- Prathima C Nalam
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, 8093 Zurich, Switzerland
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36
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Guo D, Li J, Chang L, Luo J. Measurement of the friction between single polystyrene nanospheres and silicon surface using atomic force microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:6920-5. [PMID: 23725519 DOI: 10.1021/la400984d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
In the present work, the individual nanoparticles have been manipulated on a silicon surface, using atomic force microscope (AFM) techniques. As a model system, near-spherical polystyrene nanoparticles with radii from 28.85 nm to 228.2 nm were deposited on a nanosmooth silicon wafer. Experiments demonstrated that when the normal force is above a threshold load, nanoparticles could steadily be pushed by the tip of the AFM along the defined pathway. The tests allow us to quantitatively study the interfacial friction between the nanoparticle and the surface. It was found that the friction could be affected by various factors such as the load, the particle size, and the surface treatment. The results showed that the friction between particles and substrate is proportional to the two-third power of the radius, which is in agreement with the Hertzian theory. It can also be seen that the ratio between the kinetic and the static friction was slightly changed from 0.3 to 0.6, depending on the size of the particles. However, the value of the ratio was little affected by other factors such as the particles' location, the tip normal force and the surface modification. The results provided new insights into the intriguing friction phenomenon on the nanoscale.
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Affiliation(s)
- Dan Guo
- State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China.
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37
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Segura JJ, Elbourne A, Wanless EJ, Warr GG, Voïtchovsky K, Atkin R. Adsorbed and near surface structure of ionic liquids at a solid interface. Phys Chem Chem Phys 2013; 15:3320-8. [DOI: 10.1039/c3cp44163f] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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38
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Li H, Rutland MW, Atkin R. Ionic liquid lubrication: influence of ion structure, surface potential and sliding velocity. Phys Chem Chem Phys 2013; 15:14616-23. [DOI: 10.1039/c3cp52638k] [Citation(s) in RCA: 126] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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