Surface structure evolution in a homologous series of ionic liquids

Haddad, Julia; Pontoni, Diego; Murphy, Bridget M.; Festersen, Sven; Runge, Benjamin; Magnussen, Olaf M.; Steinruck, Hans-Georg; Reichert, Harald; Ocko, Benjamin M.; Deutsch, Moshe

doi:10.1073/pnas.1716418115

Title: Surface structure evolution in a homologous series of ionic liquids

Journal Article · Mon Jan 22 00:00:00 EST 2018 · Proceedings of the National Academy of Sciences of the United States of America

DOI:https://doi.org/10.1073/pnas.1716418115· OSTI ID:1433970

Haddad, Julia ^[1];

^[2]; Murphy, Bridget M. ^[3]; Festersen, Sven ^[4]; Runge, Benjamin ^[4]; Magnussen, Olaf M. ^[3]; Steinruck, Hans-Georg ^[5]; Reichert, Harald ^[6]; Ocko, Benjamin M. ^[7];

^[1]

Bar-Ilan Univ., Ramat Gan (Israel). Physics Dept. Inst. of Nanotechnology and Advanced Materials
European Synchrotron Radiation Facility (ESRF), Grenoble (France). The European Synchrotron and Partnership for Soft Condensed Matter (PSCM)
Kiel Univ. (Germany). Inst. for Experimental and Applied Physics. Ruprecht Haensel Lab.
Kiel Univ. (Germany). Inst. for Experimental and Applied Physics
SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lab. (SSRL). Materials Science Division
European Synchrotron Radiation Facility (ESRF), Grenoble (France)
Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)

Interfaces of room temperature ionic liquids (RTILs) are important for both applications and basic science and are therefore intensely studied. However, the evolution of their interface structure with the cation’s alkyl chain length n from Coulomb to van der Waals interaction domination has not yet been studied for even a single broad homologous RTIL series. We present in this paper such a study of the liquid–air interface for n = 2 to 22, using angstrom-resolution X-ray methods. For n < 6, a typical “simple liquid” monotonic surface-normal electron density profile ρ e ( z ) is obtained, like those of water and organic solvents. For n > 6, increasingly more pronounced nanoscale self-segregation of the molecules’ charged moieties and apolar chains yields surface layering with alternating regions of headgroups and chains. The layering decays into the bulk over a few, to a few tens, of nanometers. The layering periods and decay lengths, their linear n dependence, and slopes are discussed within two models, one with partial-chain interdigitation and the other with liquid-like chains. No surface-parallel long-range order is found within the surface layer. For n = 22, a different surface phase is observed above melting. Finally, our results also impact general liquid-phase issues like supramolecular self-aggregation and bulk–surface structure relations.

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Research Organization:: Brookhaven National Laboratory (BNL), Upton, NY (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Basic Energy Sciences (BES); German Federal Ministry of Education and Research (BMBF); US-Israel Binational Science Foundation (BSF)

Grant/Contract Number:: SC0012704; 05k13fk2; 05k16fk1

OSTI ID:: 1433970

Report Number(s):: BNL-203505-2018-JAAM

Journal Information:: Proceedings of the National Academy of Sciences of the United States of America, Vol. 115, Issue 6; ISSN 0027-8424

Publisher:: National Academy of Sciences, Washington, DC (United States)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 38 works

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References (88)

Interfacial Restructuring of Ionic Liquids Determined by Sum-Frequency Generation Spectroscopy and X-Ray Reflectivity Jeon, Yoonnam; Sung, Jaeho; Bu, Wei The Journal of Physical Chemistry C, Vol. 112, Issue 49 https://doi.org/10.1021/jp807873j	journal	November 2008
Multiscale Studies on Ionic Liquids Dong, Kun; Liu, Xiaomin; Dong, Haifeng Chemical Reviews, Vol. 117, Issue 10 https://doi.org/10.1021/acs.chemrev.6b00776	journal	February 2017
Effect of the Chain Length on the Structure of Ionic Liquids: from Spatial Heterogeneity to Ionic Liquid Crystals Ji, Yumeng; Shi, Rui; Wang, Yanting The Journal of Physical Chemistry B, Vol. 117, Issue 4 https://doi.org/10.1021/jp310231f	journal	January 2013
Structural Signal of a Dynamic Glass Transition Chattopadhyay, Sudeshna; Uysal, Ahmet; Stripe, Benjamin Physical Review Letters, Vol. 103, Issue 17 https://doi.org/10.1103/PhysRevLett.103.175701	journal	October 2009
Small angle neutron scattering from 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids ([Cnmim][PF6], n=4, 6, and 8) Hardacre, Christopher; Holbrey, John D.; Mullan, Claire L. The Journal of Chemical Physics, Vol. 133, Issue 7 https://doi.org/10.1063/1.3473825	journal	August 2010
Local Order in Liquid n -Alkanes: Evidence from Raman Spectroscopic Study Brambilla, Luigi; Zerbi, Giuseppe Macromolecules, Vol. 38, Issue 8 https://doi.org/10.1021/ma047390k	journal	April 2005
Solid-liquid interfaces of ionic liquid solutions—Interfacial layering and bulk correlations Mezger, Markus; Roth, Roland; Schröder, Heiko The Journal of Chemical Physics, Vol. 142, Issue 16 https://doi.org/10.1063/1.4918742	journal	April 2015
Structure and Aggregation in the 1-Alkyl-3-Methylimidazolium Bis(trifluoromethylsulfonyl)imide Ionic Liquid Homologous Series Shimizu, Karina; Bernardes, Carlos E. S.; Canongia Lopes, José N. The Journal of Physical Chemistry B, Vol. 118, Issue 2 https://doi.org/10.1021/jp409987d	journal	January 2014
High-Accuracy Vapor Pressure Data of the Extended [C _n C ₁ im][Ntf ₂ ] Ionic Liquid Series: Trend Changes and Structural Shifts Rocha, Marisa A. A.; Lima, Carlos F. R. A. C.; Gomes, Lígia R. The Journal of Physical Chemistry B, Vol. 115, Issue 37 https://doi.org/10.1021/jp2049316	journal	September 2011
Temperature Dependence of Multilayering at the Free Surface of Ionic Liquids Probed by X-ray Reflectivity Measurements Nishi, Naoya; Uruga, Tomoya; Tanida, Hajime Langmuir, Vol. 27, Issue 12 https://doi.org/10.1021/la200252z	journal	June 2011
Liquid Surfaces and Interfaces: Synchrotron X-ray Methods Pershan, Peter S.; Schlossman, Mark https://doi.org/10.1017/CBO9781139045872	book	September 2012
Ionic liquid crystals based on 1-alkyl-3-methylimidazolium cations and perfluorinated sulfonylimide anions Li, Ting; Xu, Fei; Shi, Wei Chemical Physics Letters, Vol. 628 https://doi.org/10.1016/j.cplett.2015.04.003	journal	May 2015
Structural characteristics of alkylimidazolium-based salts containing fluoroanions Matsumoto, Kazuhiko; Hagiwara, Rika Journal of Fluorine Chemistry, Vol. 128, Issue 4 https://doi.org/10.1016/j.jfluchem.2006.10.016	journal	April 2007
Unique Spatial Heterogeneity in Ionic Liquids Wang, Yanting; Voth, Gregory A. Journal of the American Chemical Society, Vol. 127, Issue 35 https://doi.org/10.1021/ja053796g	journal	September 2005
Ionic Liquids in Synthesis Wasserscheid, Peter; Welton, Thomas https://doi.org/10.1002/3527600701	book	November 2002
Ionic Liquids at Electrified Interfaces Fedorov, Maxim V.; Kornyshev, Alexei A. Chemical Reviews, Vol. 114, Issue 5 https://doi.org/10.1021/cr400374x	journal	March 2014
Surface Tensions for the 1-Alkyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide Ionic Liquids Carvalho, Pedro J.; Freire, Mara G.; Marrucho, Isabel M. Journal of Chemical & Engineering Data, Vol. 53, Issue 6 https://doi.org/10.1021/je800069z	journal	June 2008
Long-range electrostatic screening in ionic liquids Gebbie, Matthew A.; Dobbs, Howard A.; Valtiner, Markus Proceedings of the National Academy of Sciences, Vol. 112, Issue 24 https://doi.org/10.1073/pnas.1508366112	journal	May 2015
Nanoscale heterogeneity in alkyl-methylimidazolium bromide ionic liquids Aoun, Bachir; Goldbach, Andreas; González, Miguel A. The Journal of Chemical Physics, Vol. 134, Issue 10 https://doi.org/10.1063/1.3563540	journal	March 2011
Vapor pressures of 1,3-dialkylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids with long alkyl chains Rocha, Marisa A. A.; Coutinho, João A. P.; Santos, Luís M. N. B. F. The Journal of Chemical Physics, Vol. 141, Issue 13 https://doi.org/10.1063/1.4896704	journal	October 2014
Ionic Liquid–Vacuum Interfaces Probed by Reactive Atom Scattering: Influence of Alkyl Chain Length and Anion Volume Tesa-Serrate, Maria A.; Marshall, Brooks C.; Smoll, Eric J. The Journal of Physical Chemistry C, Vol. 119, Issue 10 https://doi.org/10.1021/jp5126238	journal	February 2015
The effect of lithium salt doping on the nanostructure of ionic liquids Aguilera, Luis; Völkner, Johannes; Labrador, Ana Physical Chemistry Chemical Physics, Vol. 17, Issue 40 https://doi.org/10.1039/C5CP03825A	journal	January 2015
Structure of ionic liquids of 1-alkyl-3-methylimidazolium cations: A systematic computer simulation study Urahata, Sérgio M.; Ribeiro, Mauro C. C. The Journal of Chemical Physics, Vol. 120, Issue 4 https://doi.org/10.1063/1.1635356	journal	January 2004
Mixtures of ionic liquids Niedermeyer, Heiko; Hallett, Jason P.; Villar-Garcia, Ignacio J. Chemical Society Reviews, Vol. 41, Issue 23 https://doi.org/10.1039/c2cs35177c	journal	January 2012
X-Ray Reflectivity Measurements of Surface Layering in Liquid Mercury Magnussen, O. M.; Ocko, B. M.; Regan, M. J. Physical Review Letters, Vol. 74, Issue 22 https://doi.org/10.1103/PhysRevLett.74.4444	journal	May 1995
Small-Angle X-ray Scattering Studies of Liquid Crystalline 1-Alkyl-3-methylimidazolium Salts Bradley, A. E.; Hardacre, C.; Holbrey, J. D. Chemistry of Materials, Vol. 14, Issue 2 https://doi.org/10.1021/cm010542v	journal	February 2002
Ionic Liquids in Synthesis Laali, Kenneth K. Synthesis, Vol. 2003, Issue 11 https://doi.org/10.1055/s-2003-40869	journal	August 2003
Cation Alkyl Side Chain Length and Symmetry Effects on the Surface Tension of Ionic Liquids Almeida, Hugo F. D.; Freire, Mara G.; Fernandes, Ana M. Langmuir, Vol. 30, Issue 22 https://doi.org/10.1021/la501308q	journal	May 2014
Thermally excited capillary waves at vapor/liquid interfaces of water–alcohol mixtures Vaknin, David; Bu, Wei; Sung, Jaeho Journal of Physics: Condensed Matter, Vol. 21, Issue 11 https://doi.org/10.1088/0953-8984/21/11/115105	journal	February 2009
Surface structures of binary mixtures of imidazolium-based ionic liquids using high-resolution Rutherford backscattering spectroscopy and time of flight secondary ion mass spectroscopy Nakajima, Kaoru; Miyashita, Motoki; Suzuki, Motofumi The Journal of Chemical Physics, Vol. 139, Issue 22 https://doi.org/10.1063/1.4838376	journal	December 2013
Molecular scale structure and dynamics at an ionic liquid/electrode interface Reichert, Peter; Kjær, Kasper Skov; Brandt van Driel, Tim Faraday Discussions, Vol. 206 https://doi.org/10.1039/C7FD00171A	journal	January 2018
Modern Room Temperature Ionic Liquids, a Simple Guide to Understanding Their Structure and How It May Relate to Dynamics Araque, Juan C.; Hettige, Jeevapani J.; Margulis, Claudio J. The Journal of Physical Chemistry B, Vol. 119, Issue 40 https://doi.org/10.1021/acs.jpcb.5b05506	journal	August 2015
What is the Origin of the Prepeak in the X-ray Scattering of Imidazolium-Based Room-Temperature Ionic Liquids? Annapureddy, Harsha V. R.; Kashyap, Hemant K.; De Biase, Pablo M. The Journal of Physical Chemistry B, Vol. 114, Issue 50 https://doi.org/10.1021/jp108545z	journal	December 2010
Quantized Layer Growth at Liquid-Crystal Surfaces Ocko, B. M.; Braslau, A.; Pershan, P. S. Physical Review Letters, Vol. 57, Issue 7 https://doi.org/10.1103/PhysRevLett.57.923.5	journal	August 1986
Alkyl Chain Length and Temperature Effects on Structural Properties of Pyrrolidinium-Based Ionic Liquids: A Combined Atomistic Simulation and Small-Angle X-ray Scattering Study Li, Song; Bañuelos, José Leobardo; Guo, Jianchang The Journal of Physical Chemistry Letters, Vol. 3, Issue 1 https://doi.org/10.1021/jz2013209	journal	December 2011
Structure and phase transitions in Langmuir monolayers Kaganer, Vladimir M.; Möhwald, Helmuth; Dutta, Pulak Reviews of Modern Physics, Vol. 71, Issue 3 https://doi.org/10.1103/RevModPhys.71.779	journal	April 1999
Structure of protic (HCnImNTf2, n=0–12) and aprotic (C1CnImNTf2, n=1–12) imidazolium ionic liquids: A vibrational spectroscopic study Moschovi, Anastasia Maria; Dracopoulos, Vassileios Journal of Molecular Liquids, Vol. 210 https://doi.org/10.1016/j.molliq.2015.06.035	journal	October 2015
Morphology of 1-alkyl-3-methylimidazolium hexafluorophosphate room temperature ionic liquids Triolo, Alessandro; Russina, Olga; Fazio, Barbara Chemical Physics Letters, Vol. 457, Issue 4-6 https://doi.org/10.1016/j.cplett.2008.04.027	journal	May 2008
Alkylimidazolium Based Ionic Liquids: Impact of Cation Symmetry on Their Nanoscale Structural Organization Rocha, Marisa A. A.; Neves, Catarina M. S. S.; Freire, Mara G. The Journal of Physical Chemistry B, Vol. 117, Issue 37 https://doi.org/10.1021/jp406374a	journal	September 2013
First example of interdigitated U-shape benzimidazolium ionic liquid crystals Lee, Kwang Ming; Lee, Ching Kuan; Lin, Ivan J. B. Chemical Communications, Issue 9 https://doi.org/10.1039/a608517b	journal	January 1997
Structural Study at the Gas-Liquid Interface of 1-Alkyl-3-Methylimidazolium Alkylsulfates Using Surface Potential Measurements Martinez, Imee Su; Santos, Cherry; Baldelli, Steven ChemPhysChem, Vol. 13, Issue 7 https://doi.org/10.1002/cphc.201100985	journal	April 2012
Accounting for the Unique, Doubly Dual Nature of Ionic Liquids from a Molecular Thermodynamic and Modeling Standpoint Rebelo, Luís Paulo N.; Lopes, José N. Canongia; Esperança, José M. S. S. Accounts of Chemical Research, Vol. 40, Issue 11 https://doi.org/10.1021/ar7000556	journal	November 2007
New insight into the nanostructure of ionic liquids: a small angle X-ray scattering (SAXS) study on liquid tri-alkyl-methyl-ammonium bis(trifluoromethanesulfonyl)amides and their mixtures Pott, Tanja; Méléard, Philippe Physical Chemistry Chemical Physics, Vol. 11, Issue 26 https://doi.org/10.1039/b901582e	journal	January 2009
Surface Nanocrystallization of an Ionic Liquid Jeon, Yoonnam; Vaknin, David; Bu, Wei Physical Review Letters, Vol. 108, Issue 5 https://doi.org/10.1103/PhysRevLett.108.055502	journal	January 2012
Densities and Derived Thermodynamic Properties of Ionic Liquids. 3. Phosphonium-Based Ionic Liquids over an Extended Pressure Range Esperança, José M. S. S.; Guedes, Henrique J. R.; Blesic, Marijana Journal of Chemical & Engineering Data, Vol. 51, Issue 1 https://doi.org/10.1021/je050358g	journal	January 2006
Surface structure of imidazolium-based ionic liquids: Quantitative comparison between simulations and high-resolution RBS measurements Nakajima, Kaoru; Nakanishi, Shunto; Lísal, Martin The Journal of Chemical Physics, Vol. 144, Issue 11 https://doi.org/10.1063/1.4943887	journal	March 2016
Intrinsic profiles and the structure of liquid surfaces Tarazona, P.; Chacón, E.; Bresme, F. Journal of Physics: Condensed Matter, Vol. 24, Issue 28 https://doi.org/10.1088/0953-8984/24/28/284123	journal	June 2012
Structure and Nanostructure in Ionic Liquids Hayes, Robert; Warr, Gregory G.; Atkin, Rob Chemical Reviews, Vol. 115, Issue 13 https://doi.org/10.1021/cr500411q	journal	June 2015
Surface freezing in chain molecules: Normal alkanes Ocko, B. M.; Wu, X. Z.; Sirota, E. B. Physical Review E, Vol. 55, Issue 3 https://doi.org/10.1103/PhysRevE.55.3164	journal	March 1997
Structure of the Ethylammonium Nitrate Surface: An X-ray Reflectivity and Vibrational Sum Frequency Spectroscopy Study Niga, Petru; Wakeham, Deborah; Nelson, Andrew Langmuir, Vol. 26, Issue 11 https://doi.org/10.1021/la904697g	journal	June 2010
Layering at Free Liquid Surfaces Chacón, E.; Reinaldo-Falagán, M.; Tarazona, P. The American Physical Society https://doi.org/10.17877/de290r-11117	text	January 2001
Photoelectron Spectroscopy of Ionic Liquid-Based Interfaces Lovelock, Kevin R. J.; Villar-Garcia, Ignacio J.; Maier, Florian Chemical Reviews, Vol. 110, Issue 9 https://doi.org/10.1021/cr100114t	journal	September 2010
Experimental evidences for molecular origin of low- Q peak in neutron/x-ray scattering of 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ionic liquids Fujii, Kenta; Kanzaki, Ryo; Takamuku, Toshiyuki The Journal of Chemical Physics, Vol. 135, Issue 24 https://doi.org/10.1063/1.3672097	journal	December 2011
Molecular Layering of Fluorinated Ionic Liquids at a Charged Sapphire (0001) Surface Mezger, M.; Schroder, H.; Reichert, H. Science, Vol. 322, Issue 5900 https://doi.org/10.1126/science.1164502	journal	October 2008
Observation of Surface Layering in a Nonmetallic Liquid Mo, Haiding; Evmenenko, Guennadi; Kewalramani, Sumit Physical Review Letters, Vol. 96, Issue 9 https://doi.org/10.1103/PhysRevLett.96.096107	journal	March 2006
Mesoscopic Structural Heterogeneities in Room-Temperature Ionic Liquids Russina, Olga; Triolo, Alessandro; Gontrani, Lorenzo The Journal of Physical Chemistry Letters, Vol. 3, Issue 1 https://doi.org/10.1021/jz201349z	journal	December 2011
Demixing Transition in a Quasi-Two-Dimensional Surface-Frozen Layer Sloutskin, E.; Gang, O.; Kraack, H. Physical Review Letters, Vol. 89, Issue 6 https://doi.org/10.1103/PhysRevLett.89.065501	journal	July 2002
Assessing the Dispersive and Electrostatic Components of the Cohesive Energy of Ionic Liquids Using Molecular Dynamics Simulations and Molar Refraction Data Shimizu, Karina; Tariq, Mohammad; Gomes, Margarida F. Costa The Journal of Physical Chemistry B, Vol. 114, Issue 17 https://doi.org/10.1021/jp101910c	journal	May 2010
Surface layering and melting in an ionic liquid studied by resonant soft X-ray reflectivity Mezger, M.; Ocko, B. M.; Reichert, H. Proceedings of the National Academy of Sciences, Vol. 110, Issue 10 https://doi.org/10.1073/pnas.1211749110	journal	February 2013
Mixing ionic liquids – “simple mixtures” or “double salts”? Chatel, Gregory; Pereira, Jorge F. B.; Debbeti, Varun Green Chemistry, Vol. 16, Issue 4 https://doi.org/10.1039/c3gc41389f	journal	January 2014
Self-Consistent Interpretation of the 2D Structure of the Liquid ${Au}_{82} {Si}_{18}$ Surface: Bending Rigidity and the Debye-Waller Effect Mechler, S.; Pershan, P. S.; Yahel, E. Physical Review Letters, Vol. 105, Issue 18 https://doi.org/10.1103/PhysRevLett.105.186101	journal	October 2010
Insights into the interplay between molecular structure and diffusional motion in 1-alkyl-3-methylimidazolium ionic liquids: a combined PFG NMR and X-ray scattering study Martinelli, A.; Maréchal, M.; Östlund, Å. Physical Chemistry Chemical Physics, Vol. 15, Issue 15 https://doi.org/10.1039/c3cp00097d	journal	January 2013
Thermally excited capillary waves at vapor/liquid interfaces of water-alcohol mixtures Vaknin, David; Bu, Wei; Sung, Jaeho arXiv https://doi.org/10.48550/arxiv.0904.2412	text	January 2009
Bilayer order in a polycarbazole-conjugated polymer Lu, Xinhui; Hlaing, Htay; Germack, David S. Nature Communications, Vol. 3, Issue 1 https://doi.org/10.1038/ncomms1790	journal	January 2012
Influence of the ionic liquid/gas surface on ionic liquid chemistry Lovelock, Kevin R. J. Physical Chemistry Chemical Physics, Vol. 14, Issue 15 https://doi.org/10.1039/c2cp23851a	journal	January 2012
Morphology and intermolecular dynamics of 1-alkyl-3-methylimidazolium bis{(trifluoromethane)sulfonyl}amide ionic liquids: structural and dynamic evidence of nanoscale segregation Russina, Olga; Triolo, Alessandro; Gontrani, Lorenzo Journal of Physics: Condensed Matter, Vol. 21, Issue 42 https://doi.org/10.1088/0953-8984/21/42/424121	journal	September 2009
X-ray reflectivity study of thermal capillary waves on liquid surfaces Ocko, B. M.; Wu, X. Z.; Sirota, E. B. Physical Review Letters, Vol. 72, Issue 2 https://doi.org/10.1103/PhysRevLett.72.242	journal	January 1994
IR and X-ray Study of Polymorphism in 1-Alkyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imides Paulechka, Y. U.; Kabo, G. J.; Blokhin, A. V. The Journal of Physical Chemistry B, Vol. 113, Issue 28 https://doi.org/10.1021/jp903702c	journal	July 2009
Surface induced smectic order in ionic liquids – an X-ray reflectivity study of [C ₂₂ C ₁ im] ⁺ [NTf ₂ ] ⁻ Mars, Julian; Hou, Binyang; Weiss, Henning Physical Chemistry Chemical Physics, Vol. 19, Issue 39 https://doi.org/10.1039/C7CP04852A	journal	January 2017
Surface Layering in Ionic Liquids: An X-ray Reflectivity Study Sloutskin, Eli; Ocko, Benjamin M.; Tamam, Lilach Journal of the American Chemical Society, Vol. 127, Issue 21 https://doi.org/10.1021/ja0509679	journal	June 2005
Mesoscopic Correlation Functions in Heterogeneous Ionic Liquids Weiss, Henning; Mars, Julian; Li, Hailong The Journal of Physical Chemistry B, Vol. 121, Issue 3 https://doi.org/10.1021/acs.jpcb.6b11220	journal	January 2017
Bulk and Liquid–Vapor Interface of Pyrrolidinium-Based Ionic Liquids: A Molecular Simulation Study Paredes, Xavier; Fernández, Josefa; Pádua, Agílio A. H. The Journal of Physical Chemistry B, Vol. 118, Issue 3 https://doi.org/10.1021/jp406651f	journal	January 2014
The ionic liquid–vacuum outer atomic surface: a low-energy ion scattering study Villar-Garcia, Ignacio J.; Fearn, Sarah; De Gregorio, Gilbert F. Chem. Sci., Vol. 5, Issue 11 https://doi.org/10.1039/C4SC00640B	journal	January 2014
X-ray optics for liquid surface/interface spectrometers Honkimäki, V.; Reichert, H.; Okasinski, J. S. Journal of Synchrotron Radiation, Vol. 13, Issue 6 https://doi.org/10.1107/S0909049506031438	journal	October 2006
A novel X-ray diffractometer for studies of liquid–liquid interfaces Murphy, Bridget M.; Greve, Matthais; Runge, Benjamin Journal of Synchrotron Radiation, Vol. 21, Issue 1 https://doi.org/10.1107/S1600577513026192	journal	November 2013
Troika II: a versatile beamline for the study of liquid and solid interfaces Smilgies, Detlef-M.; Boudet, Nathalie; Struth, Bernd Journal of Synchrotron Radiation, Vol. 12, Issue 3 https://doi.org/10.1107/S0909049505000361	journal	April 2005
High-temperature surface tension and density measurements of 1-alkyl-3-methylimidazolium bistriflamide ionic liquids Tariq, Mohammad; Serro, Ana P.; Mata, José L. Fluid Phase Equilibria, Vol. 294, Issue 1-2 https://doi.org/10.1016/j.fluid.2010.02.020	journal	July 2010
Probing the protic ionic liquid surface using X-ray reflectivity Wakeham, Deborah; Nelson, Andrew; Warr, Gregory G. Physical Chemistry Chemical Physics, Vol. 13, Issue 46 https://doi.org/10.1039/c1cp22351h	journal	January 2011
Ionic Liquids: Dissecting the Enthalpies of Vaporization Köddermann, Thorsten; Paschek, Dietmar; Ludwig, Ralf ChemPhysChem, Vol. 9, Issue 4 https://doi.org/10.1002/cphc.200700814	journal	March 2008
O( ³ P) Atoms as a Probe of Surface Ordering in 1-Alkyl-3-methylimidazolium-Based Ionic Liquids Waring, Carla; Bagot, Paul A. J.; Slattery, John M. The Journal of Physical Chemistry Letters, Vol. 1, Issue 1 https://doi.org/10.1021/jz900247y	journal	November 2009
X-Ray reflectometry studies on the effect of water on the surface structure of [C4mpyr][NTf2] ionic liquid Lauw, Y.; Horne, M. D.; Rodopoulos, T. Physical Chemistry Chemical Physics, Vol. 11, Issue 48 https://doi.org/10.1039/b916046a	journal	January 2009
Molecular Organization of Liquid n-Octanol: An X-ray Diffraction Analysis Franks, N. P.; Abraham, M. H.; Lieb, W. R. Journal of Pharmaceutical Sciences, Vol. 82, Issue 5 https://doi.org/10.1002/jps.2600820507	journal	May 1993
Making Sense of Enthalpy of Vaporization Trends for Ionic Liquids: New Experimental and Simulation Data Show a Simple Linear Relationship and Help Reconcile Previous Data Verevkin, Sergey P.; Zaitsau, Dzmitry H.; Emel’yanenko, Vladimir N. The Journal of Physical Chemistry B, Vol. 117, Issue 21 https://doi.org/10.1021/jp311429r	journal	May 2013
Layering at Free Liquid Surfaces Chacón, E.; Reinaldo-Falagán, M.; Velasco, E. Physical Review Letters, Vol. 87, Issue 16 https://doi.org/10.1103/PhysRevLett.87.166101	journal	September 2001
What is the Origin of the Prepeak in the X-ray Scattering of Imidazolium-Based Room-Temperature Ionic Liquids? Annapureddy, Harsha V. R.; Kashyap, Hemant K.; De Biase, Pablo M. The Journal of Physical Chemistry B, Vol. 115, Issue 30 https://doi.org/10.1021/jp205051t	journal	July 2011
Quantized layer growth at liquid-crystal surfaces Ocko, B. M.; Braslau, A.; Pershan, P. S. Physical Review Letters, Vol. 57, Issue 1 https://doi.org/10.1103/physrevlett.57.94	journal	July 1986
Double-Layer in Ionic Liquids: Paradigm Change? Kornyshev, Alexei A. The Journal of Physical Chemistry B, Vol. 111, Issue 20 https://doi.org/10.1021/jp067857o	journal	May 2007
Applications of ionic liquids in the chemical industry Plechkova, Natalia V.; Seddon, Kenneth R. Chem. Soc. Rev., Vol. 37, Issue 1 https://doi.org/10.1039/B006677J	journal	January 2008

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