1
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Butman JL, Thomson RJ, Geiger FM. Unanticipated Hydrophobicity Increases of Squalene and Human Skin Oil Films Upon Ozone Exposure. J Phys Chem B 2022; 126:9417-9423. [PMID: 36331532 DOI: 10.1021/acs.jpcb.2c04849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The C-H and O-H oscillators on the surfaces of thin films of human-derived skin oil and squalene are probed under ambient conditions (300 K, 1 atm total pressure, 40% RH) using second-order vibrational spectroscopy and contact angle goniometry before and after exposure to ppb amounts of ozone. Skin oil and squalene are found to produce different vibrational sum frequency generation spectra in the C-H stretching region, while exposure to ozone results in surface spectra for both materials that is consistent with a loss of C-H oscillators. The measured contact angles show that the hydrophobicity of the films increases following exposure to ozone, consistent with the reduction in C═C···H2O ("πH") bonding interactions that is expected from C═C double bond loss due to ozonolysis and indicating that the polar functional groups formed point toward the films' interiors. Implications for heterogeneous indoor chemistry are discussed.
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Affiliation(s)
- Jana L Butman
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Regan J Thomson
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Franz M Geiger
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
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2
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Yamaguchi K, Kawaguchi D, Miyata N, Miyazaki T, Aoki H, Yamamoto S, Tanaka K. Kinetics of the interfacial curing reaction for an epoxy-amine mixture. Phys Chem Chem Phys 2022; 24:21578-21582. [PMID: 36093898 DOI: 10.1039/d2cp03394a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A better understanding of the chemical reaction between epoxy and amine compounds at a solid interface is crucial for the design and fabrication of materials with appropriate adhesive strength. Here, we examined the curing reaction kinetics of epoxy phenol novolac and 4,4'-diaminodiphenyl sulfone at the outermost interface using sum-frequency generation spectroscopy, and X-ray and neutron reflectivity in conjunction with a full atomistic molecular dynamics simulation. The reaction rate constant was much larger at the quartz interface than in the bulk. While the apparent activation energy at the quartz interface obtained from an Arrhenius plot was almost identical to the bulk value, the frequency factor at the quartz interface was greater than that in the bulk. These results could be explained in terms of the densification and orientation of reactants at the interface, facilitating the encounter of the reactants present.
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Affiliation(s)
- Ko Yamaguchi
- Department of Applied Chemistry, Kyushu University, Fukuoka, 819-0395, Japan.
| | - Daisuke Kawaguchi
- Department of Applied Chemistry, Kyushu University, Fukuoka, 819-0395, Japan. .,Center for Polymer Interface and Molecular Adhesion Science, Kyushu University, Fukuoka, 819-0395, Japan
| | - Noboru Miyata
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society, 162-1 Shirakata, Tokai, Naka, Ibaraki, 319-1106, Japan
| | - Tsukasa Miyazaki
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society, 162-1 Shirakata, Tokai, Naka, Ibaraki, 319-1106, Japan
| | - Hiroyuki Aoki
- Materials and Life Science Division, J-PARC Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai, Ibaraki, 319-1195, Japan.,Institute of Materials Structure Science, High Energy Accelerator Research Organization, 203-1 Shirakata, Tokai, Naka, Ibaraki, 319-1106, Japan
| | - Satoru Yamamoto
- Center for Polymer Interface and Molecular Adhesion Science, Kyushu University, Fukuoka, 819-0395, Japan
| | - Keiji Tanaka
- Department of Applied Chemistry, Kyushu University, Fukuoka, 819-0395, Japan. .,Center for Polymer Interface and Molecular Adhesion Science, Kyushu University, Fukuoka, 819-0395, Japan
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3
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von Domaros M, Liu Y, Butman JL, Perlt E, Geiger FM, Tobias DJ. Molecular Orientation at the Squalene/Air Interface from Sum Frequency Generation Spectroscopy and Atomistic Modeling. J Phys Chem B 2021; 125:3932-3941. [DOI: 10.1021/acs.jpcb.0c11158] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Michael von Domaros
- Department of Chemistry, University of California Irvine, Irvine, California 92697, United States
| | - Yangdongling Liu
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Jana L. Butman
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Eva Perlt
- Department of Chemistry, University of California Irvine, Irvine, California 92697, United States
| | - Franz M. Geiger
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Douglas J. Tobias
- Department of Chemistry, University of California Irvine, Irvine, California 92697, United States
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4
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Ngo D, He X, Luo H, Qu J, Kim SH. Competitive Adsorption of Lubricant Base Oil and Ionic Liquid Additives at Air/Liquid and Solid/Liquid Interfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:7582-7592. [PMID: 32482066 DOI: 10.1021/acs.langmuir.0c01197] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Oil-soluble ionic liquids (ILs) have been proved as effective additives in lubricant oils through tribological experiments and post-test analytical analyses. In this study, surface structures of lubricant base oil, oil-soluble ILs, and their mixtures at the air/liquid and solid/liquid interfaces have been studied using sum frequency generation (SFG) vibrational spectroscopy. At the air/base oil and air/IL interfaces, the alkyl chains of the studied compounds were shown to be conformationally disordered and their terminal methyl groups point outward at the liquid surface. The base oil dominates the air/(base oil + IL) interface due to its higher surface excess propensity and larger bulk concentration. At the solid (silica) surface, ILs adopt a structure with their charged headgroups in contact with the silica surface, while their alkyl chains are more conformationally ordered or packed compared to the air/IL interface. At the interface between silica and (base oil + IL) mixtures, ILs also preferentially adsorb to the silica surface with their layer structures somewhat different from those of ILs alone. These results showed that ILs can adsorb onto the solid surface even before tribological contacts are made. The insights obtained from this SFG study provide a better understanding of the role of ionic liquids in lubrication.
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Affiliation(s)
- Dien Ngo
- Department of Chemical Engineering and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Xin He
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Huimin Luo
- Energy and Transportation Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Jun Qu
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Seong H Kim
- Department of Chemical Engineering and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, United States
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5
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Matsuzaki K, Nihonyanagi S, Yamaguchi S, Nagata T, Tahara T. Quadrupolar mechanism for vibrational sum frequency generation at air/liquid interfaces: Theory and experiment. J Chem Phys 2019. [DOI: 10.1063/1.5088192] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Affiliation(s)
- Korenobu Matsuzaki
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
- Department of Chemistry, School of Science, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
| | - Satoshi Nihonyanagi
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
- Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
| | - Shoichi Yamaguchi
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
- Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
| | - Takashi Nagata
- Department of Chemistry, School of Science, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
| | - Tahei Tahara
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
- Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
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6
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Matsubara H, Aratono M. Unique Interfacial Phenomena on Macroscopic and Colloidal Scales Induced by Two-Dimensional Phase Transitions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:1989-2001. [PMID: 29925234 DOI: 10.1021/acs.langmuir.8b01203] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
This feature article addresses a variety of unique macroscopic-scale and colloidal-scale interfacial phenomena, such as wetting transitions of oil droplets into molecularly thin films, spontaneous merging and splitting of oil droplets at air-water interfaces, solid monolayer and bilayer formation in mixed cationic surfactant/alkane adsorbed films, switching of foam-film thickness, and oil-in-water emulsion stability. All of these phenomena can be observed using commercial cationic surfactants, liquid alkanes, and water.
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Affiliation(s)
- Hiroki Matsubara
- Department of Chemistry, Faculty of Science , Kyushu University , Motooka 744 , Nishi-ku, Fukuoka 819-0395 , Japan
| | - Makoto Aratono
- Department of Chemistry, Faculty of Science , Kyushu University , Motooka 744 , Nishi-ku, Fukuoka 819-0395 , Japan
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7
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Kovacik F, Okur HI, Smolentsev N, Scheu R, Roke S. Hydration mediated interfacial transitions on mixed hydrophobic/hydrophilic nanodroplet interfaces. J Chem Phys 2018; 149:234704. [PMID: 30579299 DOI: 10.1063/1.5035161] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Interfacial phase transitions are of fundamental importance for climate, industry, and biological processes. In this work, we observe a hydration mediated surface transition in supercooled oil nanodroplets in aqueous solutions using second harmonic and sum frequency scattering techniques. Hexadecane nanodroplets dispersed in water freeze at a temperature of ∼15 °C below the melting point of the bulk alkane liquid. Addition of a trimethylammonium bromide (CXTA+) type surfactant with chain length equal to or longer than that of the alkane causes the bulk oil droplet freezing transition to be preceded by a structural interfacial transition that involves water, oil, and the surfactant. Upon cooling, the water loses some of its orientational order with respect to the surface normal, presumably by reorienting more parallel to the oil interface. This is followed by the surface oil and surfactant alkyl chains losing some of their flexibility, and this chain stretching induces alkyl chain ordering in the bulk of the alkane phase, which is then followed by the bulk transition occurring at a 3 °C lower temperature. This behavior is reminiscent of surface freezing observed in planar tertiary alkane/surfactant/water systems but differs distinctively in that it appears to be induced by the interfacial water and requires only a very small amount of surfactant.
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Affiliation(s)
- Filip Kovacik
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Halil I Okur
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Nikolay Smolentsev
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Rüdiger Scheu
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Sylvie Roke
- Laboratory for fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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8
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Haji-Akbari A, Debenedetti PG. Perspective: Surface freezing in water: A nexus of experiments and simulations. J Chem Phys 2017; 147:060901. [DOI: 10.1063/1.4985879] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Affiliation(s)
- Amir Haji-Akbari
- Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06520, USA
| | - Pablo G. Debenedetti
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08540, USA
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9
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Gao X, Huber P, Su Y, Zhao W, Wang D. Two-Step Freezing in Alkane Monolayers on Colloidal Silica Nanoparticles: From a Stretched-Liquid to an Interface-Frozen State. J Phys Chem B 2016; 120:7522-8. [PMID: 27386888 DOI: 10.1021/acs.jpcb.6b00119] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The crystallization behavior of an archetypical soft/hard hybrid nanocomposite, that is, an n-octadecane C18/SiO2-nanoparticle composite, was investigated by a combination of differential scanning calorimetry (DSC) and variable-temperature solid-state (13)C nuclear magnetic resonance (VT solid-state (13)C NMR) as a function of silica nanoparticles loading. Two latent heat peaks prior to bulk freezing, observed for composites with high silica loading, indicate that a sizable fraction of C18 molecules involve two phase transitions unknown from the bulk C18. Combined with the NMR measurements as well as experiments on alkanes and alkanols at planar amorphous silica surfaces reported in the literature, this phase behavior can be attributed to a transition toward a 2D liquid-like monolayer and subsequently a disorder-to-order transition upon cooling. The second transition results in the formation of a interface-frozen monolayer of alkane molecules with their molecular long axis parallel to the nanoparticles' surface normal. Upon heating, the inverse phase sequence was observed, however, with a sizable thermal hysteresis in accord with the characteristics of the first-order phase transition. A thermodynamic model considering a balance of interfacial bonding, chain stretching elasticity, and entropic effects quantitatively accounts for the observed behavior. Complementary synchrotron-based wide-angle X-ray diffraction (WAXD) experiments allow us to document the strong influence of this peculiar interfacial freezing behavior on the surrounding alkane melts and in particular the nucleation of a rotator phase absent in the bulk C18.
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Affiliation(s)
- Xia Gao
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China
| | - Patrick Huber
- Institute of Materials Physics and Technology, Hamburg University of Technology (TUHH) , Hamburg-Harburg, Eißendorfer Strasse 42, D-21073, Germany
| | - Yunlan Su
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China
| | - Weiwei Zhao
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China
| | - Dujin Wang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China
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10
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Smit WJ, Smolentsev N, Versluis J, Roke S, Bakker HJ. Freezing effects of oil-in-water emulsions studied by sum-frequency scattering spectroscopy. J Chem Phys 2016; 145:044706. [DOI: 10.1063/1.4959128] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Affiliation(s)
- W. J. Smit
- FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - N. Smolentsev
- Laboratory for Fundamental Biophotonics (LBP), Institute of Bioengineering (IBI), School of Engineering (STI), École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - J. Versluis
- FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - S. Roke
- Laboratory for Fundamental Biophotonics (LBP), Institute of Bioengineering (IBI), School of Engineering (STI), École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - H. J. Bakker
- FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
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11
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Zhu H, Dhinojwala A. Thermal Behavior of Long-Chain Alcohols on Sapphire Substrate. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:6306-6313. [PMID: 26010291 DOI: 10.1021/acs.langmuir.5b01330] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Structures of amphiphilic molecules at the liquid/solid and solid/solid interfaces are important in understanding lubrication, colloid stabilization, chromatography, and nucleation. Here, we have used interface-sensitive sum frequency generation (SFG) spectroscopy to characterize the interfacial structures of long-chain alcohols above and below the bulk melting temperature (Tm). The melting temperature of the ordered hexadecanol monolayer was measured to be around 30 °C above the bulk Tm, consistent with the transition temperature reported using X-ray reflectivity [ Phys. Rev. Lett. 2011 , 106 , 137801 ]. The disruption of hydrogen bonds between the sapphire and the alcohol hydroxyl groups was directly measured as a function of temperature. The strength of this hydrogen-bonding interaction, which explained the monolayer thermal stability above Tm, was calculated using the Badger-Bauer equation. Below Tm, the ordered self-assembled monolayer influenced the structure of the interfacial crystalline layer, and the transition from the ordered monolayer to the bulk crystalline phases (α rotator phase, β crystalline phase, and γ crystalline phase) resulted in packing frustrations at the interface.
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Affiliation(s)
- He Zhu
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
| | - Ali Dhinojwala
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
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12
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Mifflin AL, Velarde L, Ho J, Psciuk BT, Negre CFA, Ebben CJ, Upshur MA, Lu Z, Strick BL, Thomson RJ, Batista VS, Wang HF, Geiger FM. Accurate Line Shapes from Sub-1 cm–1 Resolution Sum Frequency Generation Vibrational Spectroscopy of α-Pinene at Room Temperature. J Phys Chem A 2015; 119:1292-302. [DOI: 10.1021/jp510700z] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Amanda L. Mifflin
- Department
of Chemistry, University of Puget Sound, Tacoma, Washington 98416, United States
| | - Luis Velarde
- William
R. Wiley
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Junming Ho
- Department
of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, United States
| | - Brian T. Psciuk
- Department
of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, United States
| | - Christian F. A. Negre
- Department
of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, United States
| | - Carlena J. Ebben
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Mary Alice Upshur
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Zhou Lu
- William
R. Wiley
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Benjamin L. Strick
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Regan J. Thomson
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Victor S. Batista
- Department
of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, United States
| | - Hong-Fei Wang
- William
R. Wiley
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Franz M. Geiger
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
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13
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Shrestha M, Zhang Y, Upshur MA, Liu P, Blair SL, Wang HF, Nizkorodov SA, Thomson RJ, Martin ST, Geiger FM. On Surface Order and Disorder of α-Pinene-Derived Secondary Organic Material. J Phys Chem A 2015; 119:4609-17. [DOI: 10.1021/jp510780e] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Mona Shrestha
- Department
of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Yue Zhang
- School of Engineering and Applied Sciences & Department of Earth and Planetary Sciences, Harvard University, 29 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Mary Alice Upshur
- Department
of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Pengfei Liu
- School of Engineering and Applied Sciences & Department of Earth and Planetary Sciences, Harvard University, 29 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Sandra L. Blair
- Department
of Chemistry, University of California, 1102 Natural Sciences 2, Irvine, California 92697, United States
| | - Hong-fei Wang
- Environmental
Molecular Sciences Laboratory, Pacific Northwest National Laboratory, 3335 Innovative Boulevard, Richland, Washington 99354, United States
| | - Sergey A. Nizkorodov
- Department
of Chemistry, University of California, 1102 Natural Sciences 2, Irvine, California 92697, United States
| | - Regan J. Thomson
- Department
of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Scot T. Martin
- School of Engineering and Applied Sciences & Department of Earth and Planetary Sciences, Harvard University, 29 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Franz M. Geiger
- Department
of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
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14
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Xu S, Xing S, Pei SS, Baldelli S. Sum Frequency Generation Spectroscopy Study of an Ionic Liquid at a Graphene-BaF2 (111) Interface. J Phys Chem B 2014; 118:5203-10. [DOI: 10.1021/jp502500u] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Siyun Xu
- Department
of Chemistry, University of Houston, Houston, Texas 77204-5003, United States
| | - Sirui Xing
- Department
of Electrical and Computer Engineering, University of Houston, Houston, Texas 77204-5003, United States
- Center
for Advanced Materials, University of Houston, Houston, Texas 77204-5003, United States
| | - Shin-Shem Pei
- Department
of Electrical and Computer Engineering, University of Houston, Houston, Texas 77204-5003, United States
- Center
for Advanced Materials, University of Houston, Houston, Texas 77204-5003, United States
| | - Steven Baldelli
- Department
of Chemistry, University of Houston, Houston, Texas 77204-5003, United States
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15
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Kumar MV, Prasad SK, Rao DSS, Mukherjee PK. Competition between anisometric and aliphatic entities: an unusual phase sequence with the induction of a phase in an n-alkane-liquid crystal binary system. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:4465-4473. [PMID: 24678973 DOI: 10.1021/la500367y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In this work, we demonstrate two important features that arise out of introducing a liquid-crystalline (LC) compound into the rotator phase matrix and the consequent competition between the anisometric segments of the LC moieties and the aliphatic units. First, we show that the change in the structural character of the mixed medium depends on which of the entities forms the minority concentration: in the case of this being the alkane, the two components of the binary system are nanophase segregated, whereas if the LC molecules are present in a small concentration, then the layered structure merely gets roughened without any segregation. The second and more significant result of the calorimetric and X-ray experiments, at low LC concentrations, is the induction of a rotator phase that leads to unusual phase sequence not reported hitherto. Possible scenarios for the molecular arrangement are discussed. A Landau model is also presented that explains some of the observed features.
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Affiliation(s)
- M Vijay Kumar
- Centre for Soft Matter Research, Jalahalli, Bangalore 560 013, India
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16
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Takiue T, Shimasaki M, Tsuura M, Sakamoto H, Matsubara H, Aratono M. Surface Freezing and Molecular Miscibility of Binary Alkane–Alkane and Fluoroalkane–Alkane Liquid Mixtures. J Phys Chem B 2014; 118:1519-26. [DOI: 10.1021/jp406431m] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Takanori Takiue
- Department
of Chemistry, Faculty of Sciences, Kyushu University, Hakozaki
6-10-1, Higashi-ku, Fukuoka 812-8581, Japan
| | - Mayuko Shimasaki
- Department
of Chemistry, Faculty of Sciences, Kyushu University, Hakozaki
6-10-1, Higashi-ku, Fukuoka 812-8581, Japan
| | - Miyako Tsuura
- Department
of Chemistry, Faculty of Sciences, Kyushu University, Hakozaki
6-10-1, Higashi-ku, Fukuoka 812-8581, Japan
| | - Hiroyasu Sakamoto
- Department
of Visual Communication Design, Faculty of Design, Kyushu University, Fukuoka 815-8540, Japan
| | - Hiroki Matsubara
- Department
of Chemistry, Faculty of Sciences, Kyushu University, Hakozaki
6-10-1, Higashi-ku, Fukuoka 812-8581, Japan
| | - Makoto Aratono
- Department
of Chemistry, Faculty of Sciences, Kyushu University, Hakozaki
6-10-1, Higashi-ku, Fukuoka 812-8581, Japan
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17
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Shrestha M, Zhang Y, Ebben CJ, Martin ST, Geiger FM. Vibrational sum frequency generation spectroscopy of secondary organic material produced by condensational growth from α-pinene ozonolysis. J Phys Chem A 2013; 117:8427-36. [PMID: 23876044 DOI: 10.1021/jp405065d] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Secondary organic material (SOM) was produced in a flow tube from α-pinene ozonolysis, and collected particles were analyzed spectroscopically via a nonlinear coherent vibrational spectroscopic technique, namely sum frequency generation (SFG). The SOM precursor α-pinene was injected into the flow tube reactor at concentrations ranging from 0.125 ± 0.01 ppm to 100 ± 3 ppm. The oxidant ozone was varied from 0.15 ± 0.02 to 194 ± 2 ppm. The residence time was 38 ± 1 s. The integrated particle number concentrations, studied using a scanning mobility particle sizer (SMPS), varied from no particles produced up to (1.26 ± 0.02) × 10(7) cm(-3) for the matrix of reaction conditions. The mode diameters of the aerosols increased from 7.7 nm (geometric standard deviation (gsd), 1.0) all the way to 333.8 nm (gsd, 1.9). The corresponding volume concentrations were as high as (3.0 ± 0.1) × 10(14) nm(3) cm(-3). The size distributions indicated access to different particle growth stages, namely condensation, coagulation, or combination of both, depending on reaction conditions. For filter collection and subsequent spectral analysis, reaction conditions were selected that gave a mode diameter of 63 ± 3 nm and 93 ± 3 nm, respectively, and an associated mass concentration of 12 ± 2 μg m(-3) and (1.2 ± 0.1) × 10(3) μg m(-3) for an assumed density of 1200 kg m(-3). Teflon filters loaded with 24 ng to 20 μg of SOM were analyzed by SFG. The SFG spectra obtained from particles formed under condensational and coagulative growth conditions were found to be quite similar, indicating that the distribution of SFG-active C-H oscillators is similar for particles prepared under both conditions. The spectral features of these flow-tube particles agreed with those prepared in an earlier study that employed the Harvard Environmental Chamber. The SFG intensity was found to increase linearly with the number of particles, consistent with what is expected from SFG signal production from particles, while it decreased at higher mass loadings of 10 and 20 μg, consistent with the notion that SFG probes the top surface of the SOM material following the complete coverage of the filter. The linear increase in SFG intensity with particle density also supports the notion that the average number of SFG active oscillators per particle is constant for a given particle size, that the particles are present on the collection filters in a random array, and that the particles are not coalesced. The limit of detection of SFG intensity was established as 24 ng of mass on the filter, corresponding to a calculated density of about 100 particles in the laser spot. As established herein, the technique is applicable for detecting low particle number or mass concentrations in ambient air. The related implication is that SFG is useful for short collection times and would therefore provide increased temporal resolution in a locally evolving atmospheric environment.
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Affiliation(s)
- Mona Shrestha
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA
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18
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Fu D, Su Y, Gao X, Liu Y, Wang D. Confined crystallization of n-hexadecane located inside microcapsules or outside submicrometer silica nanospheres: a comparison study. J Phys Chem B 2013; 117:6323-9. [PMID: 23617564 DOI: 10.1021/jp4021849] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Crystallization and phase transition behaviors of n-hexadecane (n-C16H34, abbreviated as C16) confined in microcapsules and n-alkane/SiO2 nanosphere composites have been investigated by the combination of differential scanning calorimetry (DSC) and temperature-dependent X-ray diffraction (XRD). As evident from the DSC measurement, the surface freezing phenomenon of C16 is enhanced in both the microcapsules and SiO2 nanosphere composites because the surface-to-volume ratio is dramatically enlarged in both kinds of confinement. It is revealed from the XRD results that the novel solid-solid phase transition is observed only in the microencapsulated C16, which crystallizes into a stable triclinic phase via a mestastable rotator phase (RI). For the C16/SiO2 composite, however, no novel rotator phase emerges during the cooling process, and C16 crystallizes into a stable triclinic phase directly from the liquid state. Heterogeneous nucleation induced by the surface freezing phase is dominant in the microencapsulated sample and contributes to the emergence of the novel rotator phase, whereas heterogeneous nucleation induced by foreign crystallization nuclei dominates the C16/SiO2 composite, leading to phase transition behaviors similar to those of bulk C16.
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Affiliation(s)
- Dongsheng Fu
- Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
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19
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Hernandez DA, Domínguez H. Structural and thermodynamic behavior of alkane chains at the liquid/vapor interface. J Chem Phys 2013; 138:134702. [DOI: 10.1063/1.4798346] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
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20
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21
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Backus EHG, Bonn D, Cantin S, Roke S, Bonn M. Laser-heating-induced displacement of surfactants on the water surface. J Phys Chem B 2012; 116:2703-12. [PMID: 22324652 DOI: 10.1021/jp2074545] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report a combined vibrational sum-frequency generation (SFG) spectroscopy, Brewster angle microscopy (BAM), and ellipsometry study of different surfactants on water as a function of surfactant density. Vibrational SFG spectra of surfactants on the water surface in a Langmuir trough have been measured in both the surfactant CH and the water OH stretch regions. At low densities, the SFG signal generated at the surface in the presence of the surfactant is indistinguishable from the SFG signal generated at the clean water-air interface. When the surfactant density increases, i.e., upon compressing the monolayer, a very sudden increase in the SFG signal in both the CH and OH spectral regions is observed. For higher laser fluences, this stepwise increase occurs at increasingly higher surfactant densities. Since BAM shows that surfactant molecules are clearly present at these low densities, we conclude that at low surfactant density the laser beam displaces relatively high-density domains with surfactants in the liquid expanded phase out of the region of the laser focus. This is a consequence of the thermal gradient induced by local heating of the water phase with the monolayer on top due to repetitive laser excitation at 1 kHz. It can be circumvented by using a rotating trough. In this manner, the sampled surface area can be refreshed, allowing artifact-free vibrational SFG spectra to be measured down to the very lowest surfactant densities. In ellipsometry experiments, a similar step can be noticed, which, however, is of a different nature; i.e., it is not related to heating (the laser fluence is very low and the light nonresonant) but to a molecular transition. The occurrence of the step in ellipsometry as a function of area per molecule depends critically on the preparation of the monolayer. By giving the molecules time and space to relax during the preparation of the monolayer, this step could also be eliminated.
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Affiliation(s)
- Ellen H G Backus
- FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
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22
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Hsu PY, Dhinojwala A. Contact of oil with solid surfaces in aqueous media probed using sum frequency generation spectroscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:2567-73. [PMID: 22206274 DOI: 10.1021/la203228t] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
We have studied the interface between hexadecane droplets and sapphire substrates in water using infrared-visible sum frequency generation spectroscopy (SFG). At high pH and above the isoelectric point of the sapphire substrate, the hexadecane drop is repelled due to electrostatic forces. The SFG measurements are consistent with the observation that a thick layer of water is present between the oil and the sapphire substrate. Below the isoelectric point of the sapphire substrate, the hexadecane drops stick to the sapphire surface. Surprisingly, the SFG results show the presence of a thin layer of water between hexadecane drop and the sapphire substrate. At this contact interface, we observe contributions to the SFG signal from both the hexadecane/water and water/sapphire interfaces. The reasons for the presence of a thin water layer with adhesive contact can be explained due to weaker repulsive double layer and the attractive van der Waals interactions.
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Affiliation(s)
- Ping Yuan Hsu
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
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23
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Buchbinder AM, Ray NA, Lu J, Van Duyne RP, Stair PC, Weitz E, Geiger FM. Displacement of hexanol by the hexanoic acid overoxidation product in alcohol oxidation on a model supported palladium nanoparticle catalyst. J Am Chem Soc 2011; 133:17816-23. [PMID: 21919461 DOI: 10.1021/ja2067274] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
This work characterizes the adsorption, structure, and binding mechanism of oxygenated organic species from cyclohexane solution at the liquid/solid interface of optically flat alumina-supported palladium nanoparticle surfaces prepared by atomic layer deposition (ALD). The surface-specific nonlinear optical vibrational spectroscopy, sum-frequency generation (SFG), was used as a probe for adsorption and interfacial molecular structure. 1-Hexanoic acid is an overoxidation product and possible catalyst poison for the aerobic heterogeneous oxidation of 1-hexanol at the liquid/solid interface of Pd/Al(2)O(3) catalysts. Single component and competitive adsorption experiments show that 1-hexanoic acid adsorbs to both ALD-prepared alumina surfaces and alumina surfaces with palladium nanoparticles, that were also prepared by ALD, more strongly than does 1-hexanol. Furthermore, 1-hexanoic acid adsorbs with conformational order on ALD-prepared alumina surfaces, but on surfaces with palladium particles the adsorbates exhibit relative disorder at low surface coverage and become more ordered, on average, at higher surface coverage. Although significant differences in binding constant were not observed between surfaces with and without palladium nanoparticles, the palladium particles play an apparent role in controlling adsorbate structures. The disordered adsorption of 1-hexanoic acid most likely occurs on the alumina support, and probably results from modification of binding sites on the alumina, adjacent to the particles. In addition to providing insight on the possibility of catalyst poisoning by the overoxidation product and characterizing changes in its structure that result in only small adsorption energy changes, this work represents a step toward using surface science techniques that bridge the complexity gap between fundamental studies and realistic catalyst models.
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Affiliation(s)
- Avram M Buchbinder
- Department of Chemistry, Center for Catalysis and Surface Science, Northwestern University, Evanston, Illinois 60208, USA
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24
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Rivera CA, Fourkas JT. Reexamining the interpretation of vibrational sum-frequency generation spectra. INT REV PHYS CHEM 2011. [DOI: 10.1080/0144235x.2011.641263] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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25
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Liu Y, Yang DQ, Nie HY, Lau WM, Yang J. Study of a hydrogen-bombardment process for molecular cross-linking within thin films. J Chem Phys 2011; 134:074704. [DOI: 10.1063/1.3554430] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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26
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XIE R, SONG Y, WAN L, YUAN H, LI P, XIAO X, LIU L, YE S, LEI S, WANG L. Two-Dimensional Polymerization and Reaction at the Solid/Liquid Interface: Scanning Tunneling Microscopy Study. ANAL SCI 2011; 27:129-38. [DOI: 10.2116/analsci.27.129] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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27
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Fu D, Su Y, Xie B, Zhu H, Liu G, Wang D. Phase change materials of n-alkane-containing microcapsules: observation of coexistence of ordered and rotator phases. Phys Chem Chem Phys 2011; 13:2021-6. [DOI: 10.1039/c0cp01173h] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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28
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Fu D, Liu Y, Liu G, Su Y, Wang D. Confined crystallization of binary n-alkane mixtures: stabilization of a new rotator phase by enhanced surface freezing and weakened intermolecular interactions. Phys Chem Chem Phys 2011; 13:15031-6. [DOI: 10.1039/c1cp21281h] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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29
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Sung W, Seok S, Kim D, Tian CS, Shen YR. Sum-frequency spectroscopic study of Langmuir monolayers of lipids having oppositely charged headgroups. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:18266-18272. [PMID: 20977244 DOI: 10.1021/la103129z] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Sum-frequency vibrational spectroscopy, with the help of surface pressure-area (π-A) isotherm, was used to study lipid Langmuir monolayers composed of molecules with positively and negatively charged headgroups as well as a 1:1 neutral mixture of the two. The spectral profiles of the CH(x) stretch vibrations are similar for all monolayers in the liquid-condensed (LC) phase. They suggest a monolayer structure of closely packed alkyl chains that are nearly all-trans and well oriented along the surface normal. In the liquid-expanded (LE) phase, the spectra of all monolayers appear characteristic of loosely packed chains with significant gauche defects. The OH stretch spectra of interfacial water for both positively and negatively charged monolayers are significantly enhanced in comparison with a neutral water interface, but the phase measurement of SFVS indicates that OH in the two cases points toward the bulk and the interface, respectively. The enhancement results mainly from surface-field-induced polar ordering of interfacial water molecules. For a charge-neutral monolayer composed of an equal number of positively and negatively charged lipid molecules, no such enhancement is observed. This mixed monolayer exhibits a wide range of LC/LE coexistence region extended to very low surface pressure and its CH(x) spectral profile in the coexistence region resembles that of the LC phase. This result suggests that in the LC/LE coexistence region, the mixed monolayer consists of coexisting LC and LE patches in which oppositely charged lipid molecules are homogeneously mixed and dispersed.
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Affiliation(s)
- Woongmo Sung
- Department of Physics, Sogang University, Seoul 121-742, Korea
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30
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Buchbinder AM, Weitz E, Geiger FM. When the Solute Becomes the Solvent: Orientation, Ordering, and Structure of Binary Mixtures of 1-Hexanol and Cyclohexane over the (0001) α-Al2O3 Surface. J Am Chem Soc 2010; 132:14661-8. [DOI: 10.1021/ja1068504] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Avram M. Buchbinder
- Department of Chemistry and the Institute for Catalysis in Energy Processes, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208
| | - Eric Weitz
- Department of Chemistry and the Institute for Catalysis in Energy Processes, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208
| | - Franz M. Geiger
- Department of Chemistry and the Institute for Catalysis in Energy Processes, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208
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31
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Freezing transition of wetting film of tetradecane on tetradecyltrimethylammonium bromide solutions. Colloid Polym Sci 2010. [DOI: 10.1007/s00396-010-2258-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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32
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Brindza MR, Ding F, Fourkas JT, Walker RA. n-alkane adsorption to polar silica surfaces. J Chem Phys 2010; 132:114701. [DOI: 10.1063/1.3336727] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
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33
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SMITH P, LYNDEN-BELL RM, EARNSHAW JC, SMITH W. The surface-ordered phase of liquid heptadecane: a simulation study. Mol Phys 2009. [DOI: 10.1080/00268979909482957] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- P. SMITH
- a Atomistic Simulation Group and Irish Centre for Colloid Science , School of Mathematics and Physics, The Queen's University , Belfast , BT7 1NN , UK
| | - R. M. LYNDEN-BELL
- a Atomistic Simulation Group and Irish Centre for Colloid Science , School of Mathematics and Physics, The Queen's University , Belfast , BT7 1NN , UK
| | - J. C. EARNSHAW
- b Department of Pure and Applied Physics , The Queen's University , Belfast , BT7 1NN , UK
| | - W. SMITH
- c CCLRC, Daresbury, Laboratory Daresbury , Warrington , WA4 4AD , UK
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34
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Waring C, Bagot PAJ, Räisänen MT, Costen ML, McKendrick KG. Dynamics of the Reaction of O(3P) Atoms with Alkylthiol Self-assembled Monolayers. J Phys Chem A 2009; 113:4320-9. [DOI: 10.1021/jp8109868] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Carla Waring
- School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K. and School of Chemistry, University of St. Andrews, St. Andrews, Fife KY16 9ST, U.K
| | - Paul A. J. Bagot
- School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K. and School of Chemistry, University of St. Andrews, St. Andrews, Fife KY16 9ST, U.K
| | - Minna T. Räisänen
- School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K. and School of Chemistry, University of St. Andrews, St. Andrews, Fife KY16 9ST, U.K
| | - Matthew L. Costen
- School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K. and School of Chemistry, University of St. Andrews, St. Andrews, Fife KY16 9ST, U.K
| | - Kenneth G. McKendrick
- School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K. and School of Chemistry, University of St. Andrews, St. Andrews, Fife KY16 9ST, U.K
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35
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Matsubara H, Ohtomi E, Aratono M, Bain CD. Wetting and Freezing of Hexadecane on an Aqueous Surfactant Solution: Triple Point in a 2-D film. J Phys Chem B 2008; 112:11664-8. [DOI: 10.1021/jp802108v] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- H. Matsubara
- Department of Chemistry, University of Durham, South Road, Durham, DH1 3LE, United Kingdom and Department of Chemistry, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan
| | - E. Ohtomi
- Department of Chemistry, University of Durham, South Road, Durham, DH1 3LE, United Kingdom and Department of Chemistry, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan
| | - M. Aratono
- Department of Chemistry, University of Durham, South Road, Durham, DH1 3LE, United Kingdom and Department of Chemistry, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan
| | - Colin D. Bain
- Department of Chemistry, University of Durham, South Road, Durham, DH1 3LE, United Kingdom and Department of Chemistry, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan
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36
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Paso K, Kompalla T, Aske N, Sjöblom J. A Quartz Crystal Microbalance Characterization of Metal‐Oil Interfaces and Interactions with Wax Molecules. J DISPER SCI TECHNOL 2008. [DOI: 10.1080/01932690701757915] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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37
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Bredenbeck J, Ghosh A, Smits M, Bonn M. Ultrafast two dimensional-infrared spectroscopy of a molecular monolayer. J Am Chem Soc 2008; 130:2152-3. [PMID: 18225904 DOI: 10.1021/ja710099c] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Jens Bredenbeck
- FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ, Amsterdam, The Netherlands.
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38
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Hearn JD, Smith GD. Ozonolysis of Mixed Oleic Acid/n-Docosane Particles: The Roles of Phase, Morphology, and Metastable States. J Phys Chem A 2007; 111:11059-65. [DOI: 10.1021/jp0755701] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- John D. Hearn
- Department of Chemistry, The University of Georgia, Athens, Georgia 30602
| | - Geoffrey D. Smith
- Department of Chemistry, The University of Georgia, Athens, Georgia 30602
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39
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Wilkinson KM, Qunfang L, Bain CD. Freezing transitions in mixed surfactant/alkane monolayers at the air-solution interface. SOFT MATTER 2006; 2:66-76. [PMID: 32646096 DOI: 10.1039/b511561b] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Mixed monolayers at the air-water interface of the cationic surfactant, hexadecyltrimethylammonium bromide (CTAB), with alkanes show a first-order freezing transition as a function of temperature. Sum-frequency spectra and ellipsometric measurements are consistent with a structure in which the high-temperature phase is liquid-like and the low-temperature phase has all-, upright chains. There are strong structural similarities between the low-temperature phase in the mixed monolayers and frozen monolayers at the alkane-air and alkane-CTAB solution interfaces. The difference between the surface freezing point and the freezing point of the bulk alkane ranges from 1 °C for alkane chain length = 17, to 28 °C for = 11. Surface freezing is more favourable in mixed monolayers at the air-water interface than at the bulk alkane-water interface for the same surfactant concentration. Long-chain alkanes do not wet water, but it is postulated that if they did, they would also show surface freezing analogously to alkanes on silica. The surfactant plays the dual role of enhancing wetting and surface freezing of the alkane on water.
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Affiliation(s)
- Katherine M Wilkinson
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, UKOX1 3TA.
| | - Lei Qunfang
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, UKOX1 3TA.
| | - Colin D Bain
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, UKOX1 3TA.
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40
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Esenturk O, Walker RA. Surface vibrational structure at alkane liquid/vapor interfaces. J Chem Phys 2006; 125:174701. [PMID: 17100455 DOI: 10.1063/1.2356858] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Broadband vibrational sum frequency spectroscopy (VSFS) has been used to examine the surface structure of alkane liquid/vapor interfaces. The alkanes range in length from n-nonane (C(9)H(20)) to n-heptadecane (C(17)H(36)), and all liquids except heptadecane are studied at temperatures well above their bulk (and surface) freezing temperatures. Intensities of vibrational bands in the CH stretching region acquired under different polarization conditions show systematic, chain length dependent changes. Data provide clear evidence of methyl group segregation at the liquid/vapor interface, but two different models of alkane chain structure can predict chain length dependent changes in band intensities. Each model leads to a different interpretation of the extent to which different chain segments contribute to the anisotropic interfacial region. One model postulates that changes in vibrational band intensities arise solely from a reduced surface coverage of methyl groups as alkane chain length increases. The additional methylene groups at the surface must be randomly distributed and make no net contribution to the observed VSF spectra. The second model considers a simple statistical distribution of methyl and methylene groups populating a three dimensional, interfacial lattice. This statistical picture implies that the VSF signal arises from a region extending several functional groups into the bulk liquid, and that the growing fraction of methylene groups in longer chain alkanes bears responsibility for the observed spectral changes. The data and resulting interpretations provide clear benchmarks for emerging theories of molecular structure and organization at liquid surfaces, especially for liquids lacking strong polar ordering.
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Affiliation(s)
- Okan Esenturk
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
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41
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Clarke ML, Chen C, Wang J, Chen Z. Molecular level structures of poly(n-alkyl methacrylate)s with different side chain lengths at the polymer/air and polymer/water interfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:8800-6. [PMID: 17014120 DOI: 10.1021/la061386f] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Sum frequency generation (SFG) vibrational spectroscopy has been successfully applied to study molecular structures of several poly(n-alkyl methacrylate)s (PAMAs) with different side chain lengths at the PAMA/air and PAMA/water interfaces. We have observed that the ester side chains from all PAMAs always dominate the interface, but the orientation information of the methyl end group on the side chains varies, depending on the length of the side chain. The contributions from methylene groups on the side chains have been evaluated, and the surface structures have been related to the surface tension of these polymers. Different water restructuring behaviors have been observed for different PAMAs. This phenomenon and its reversibility are strongly dependent on the glass transition temperature of each polymer, which is influenced by the side chain length. Detailed data fitting and analysis has been discussed.
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Affiliation(s)
- Matthew L Clarke
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
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42
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Zhang WK, Wang HF, Zheng DS. Quantitative measurement and interpretation of optical second harmonic generation from molecular interfaces. Phys Chem Chem Phys 2006; 8:4041-52. [PMID: 17028693 DOI: 10.1039/b608005g] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Second harmonic generation (SHG) has been proven a uniquely effective technique in the investigation of molecular structure and conformations, as well as dynamics of molecular interfaces. The ability to apply SHG to molecular interface studies depends on the ability to abstract quantitative information from the measurable quantities in the actual SHG experiments. In this review, we try to assess recent developments in the SHG experimental methodologies towards quantitative analysis of the nonlinear optical properties of the achiral molecular interfaces with rotational isotropy along the interface normal. These developments include the methodology for orientational analysis of the SHG experimental data, the experimental approaches for more accurate SHG measurements, and a novel treatment of the symmetry properties of the molecular polarizability tensors in association with the experimentally measurable quantities. In the end, the recent developments on the problem of surface versus bulk contribution in SHG surface studies is discussed. These developments can put SHG on a more solid foundation for molecular interface studies, and to pave the way for better understanding and application of SHG surface studies in general.
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Affiliation(s)
- Wen-kai Zhang
- State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, ZhongGuanCun, Beijing, China100080
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43
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Köhler SPK, Reed SK, Westacott RE, McKendrick KG. Molecular Dynamics Study to Identify the Reactive Sites of a Liquid Squalane Surface. J Phys Chem B 2006; 110:11717-24. [PMID: 16800468 DOI: 10.1021/jp060431p] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Molecular dynamics simulations of liquid squalane, C30H62, were performed, focusing in particular on the liquid-vacuum interface. These theoretical studies were aimed at identifying potentially reactive sites on the surface, knowledge of which is important for a number of inelastic and reactive scattering experiments. A united atom force field (Martin, M. G.; Siepmann, J. I. J. Phys. Chem. B 1999, 103, 4508-4517) was used, and the simulations were analyzed with respect to their interfacial properties. A modest but clearly identifiable preference for methyl groups to protrude into the vacuum has been found at lower temperatures. This effect decreases when going to higher temperatures. Additional simulations tracking the flight paths of projectiles directed at a number of randomly chosen surfaces extracted from the molecular dynamics simulations were performed. The geometrical parameters for these calculations were chosen to imitate a typical abstraction reaction, such as the reaction between ground-state oxygen atoms and hydrocarbons. Despite the preference for methyl groups to protrude further into the vacuum, Monte Carlo tracking simulations suggest, on geometric grounds, that primary and secondary hydrogen atoms are roughly equally likely to react with incoming gas-phase atoms. These geometric simulations also indicate that a substantial fraction of the scattered products is likely to undergo at least one secondary collision with hydrocarbon side chains. These results help to interpret the outcome of previous measurements of the internal and external energy distribution of the gas-phase OH products of the interfacial reaction between oxygen atoms and liquid squalane.
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Affiliation(s)
- Sven P K Köhler
- School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom
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44
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Tyrode E, Johnson CM, Kumpulainen A, Rutland MW, Claesson PM. Hydration State of Nonionic Surfactant Monolayers at the Liquid/Vapor Interface: Structure Determination by Vibrational Sum Frequency Spectroscopy. J Am Chem Soc 2005; 127:16848-59. [PMID: 16316231 DOI: 10.1021/ja053289z] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The OH stretching region of water molecules in the vicinity of nonionic surfactant monolayers has been investigated using vibrational sum frequency spectroscopy (VSFS) under the polarization combinations ssp, ppp, and sps. The surface sensitivity of the VSFS technique has allowed targeting the few water molecules present at the surface with a net orientation and, in particular, the hydration shell around alcohol, sugar, and poly(ethylene oxide) headgroups. Dramatic differences in the hydration shell of the uncharged headgroups were observed, both in comparison to each another and in comparison to the pure water surface. The water molecules around the rigid glucoside and maltoside sugar rings were found to form strong hydrogen bonds, similar to those observed in tetrahedrally coordinated water in ice. In the case of the poly(ethylene oxide) surfactant monolayer a significant ordering of both strongly and weakly hydrogen bonded water was observed. Moreover, a band common to all the surfactants studied, clearly detected at relatively high frequencies in the polarization combinations ppp and sps, was assigned to water species located in proximity to the surfactant hydrocarbon tail phase, with both hydrogen atoms free from hydrogen bonds. An orientational analysis provided additional information on the water species responsible for this band.
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Affiliation(s)
- Eric Tyrode
- Department of Chemistry, Surface Chemistry, Royal Institute of Technology, Stockholm, Sweden
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45
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Nanjundiah K, Dhinojwala A. Confinement-induced ordering of alkanes between an elastomer and a solid surface. PHYSICAL REVIEW LETTERS 2005; 95:154301. [PMID: 16241729 DOI: 10.1103/physrevlett.95.154301] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2005] [Indexed: 05/05/2023]
Abstract
We have studied the molecular structure of liquid alkanes confined between a flexible elastomeric poly(dimethyl siloxane) lens and a rigid sapphire substrate using surface-sensitive infrared-visible sum frequency generation spectroscopy. The reduction in the gauche defects suggests ordering of liquid alkanes under confinement. The cooling of confined liquid below the freezing temperature leads to crystallization with alkane molecules lying on the substrate with the symmetry axis parallel to the surface normal. This structure is very different from the bulk alkane crystals next to sapphire or air interfaces.
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Affiliation(s)
- Kumar Nanjundiah
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325, USA
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46
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Sloutskin E, Bain CD, Ocko BM, Deutsch M. Surface freezing of chain molecules at the liquid–liquid and liquid–air interfaces. Faraday Discuss 2005; 129:339-52; discussion 353-66. [PMID: 15715317 DOI: 10.1039/b405969g] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Surface freezing (SF) is the formation of a crystalline monolayer at the free surface of a melt at a temperature Ts, a few degrees above the bulk freezing temperature, Tb. This effect, i.e. Ts > Tb, common to many chain molecules, is in a marked contrast with the surface melting effect, i.e. Ts < or = Tb, shown by almost all other materials. Depending on chain length, n, the SF layer shows a variety of phases, in some cases tuneable by bulk additives. The SF behaviour of binary mixtures of different-length alkanes and alcohols is governed by the relative chain length mismatch, /delta n/n/2, yielding a quasi-"universal" behaviour for the freezing of both bulk and surface. While SF at the liquid air interface was studied rather extensively, Lei and Bain (Phys. Rev. Lett., 2004, 94, 176103) have shown only very recently that interfacial freezing (IF) can be induced also at the water: tetradecane interface by adding the ionic surfactant CTAB to the water phase. We present measurements of the interfacial tension of the water: hexadecane interface, as a function of temperature and the ionic surfactant STAB, revealing IF at a STAB-concentration-dependent temperature Ti > Tb. The measurements indicate that a single frozen monolayer is formed, with a temperature-existence range of up to 10 degrees C, much larger than the 1.2 degrees C found for SF at the free surface of the melt. We also find a new effect, where the IF allows tuning of the interfacial tension between the two bulk phases to zero for a range of temperatures, deltaT = Tmix - Tb < or = Ti - Tb by cooling the system below Ti. We discuss qualitatively the factors stabilizing the frozen layer and their variation from the liquid-air to the liquid-liquid interfaces. The surfactant concentration dependence of Ti is also discussed and a tentative theoretical explanation is suggested.
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Affiliation(s)
- Eli Sloutskin
- Physics Department, Bar-Ilan University, Ramat-Gan 52900, Israel
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47
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Nickolov ZS, Wang X, Miller JD. Liquid/air interfacial structure of alcohol-octyl hydroxamic acid mixtures: a study by sum-frequency spectroscopy. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2004; 60:2711-2717. [PMID: 15350903 DOI: 10.1016/j.saa.2003.12.046] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2003] [Accepted: 12/19/2003] [Indexed: 05/24/2023]
Abstract
The molecular structure of the liquid/air interfaces of 1-octanol, 1-decanol, n-decane and the branched decyl alcohol EXXAL 10 has been studied by sum-frequency spectroscopy (SFS) in the C-H stretching vibrational region. The data suggest that the interfaces consist of ordered molecules with closely packed alkyl tails, in close to all-trans conformation with some gauche defects. The degree of surface ordering for the branched alcohol is much higher than for octanol and decanol. When octyl hydroxamic acid (OHA) is dissolved in 1-octanol it increases the gauche conformational defects in the interfacial chains, possibly due to mixing with the surface alcohol molecules and disrupting their ordering. In contrast, we suggest that when octyl hydroxamic acid is dissolved in EXXAL 10, the surface ordering of the alcohol chains does not change. We put forward the hypothesis that the appearance of new bands, belonging to the asymmetric methylene group vibrations and to the asymmetric methyl modes in the SF spectra of the mixture suggests that the surface OHA molecules are arranged with their hydrocarbon tails tilted very close to the interface.
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Affiliation(s)
- Zh S Nickolov
- Department of Metallurgical Engineering, University of Utah, 135 S. 1460 E., Room 412, Salt Lake City, UT 84112-0114, UK
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48
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Esenturk O, Walker RA. Surface Structure at Hexadecane and Halo-hexadecane Liquid/Vapor Interfaces. J Phys Chem B 2004. [DOI: 10.1021/jp047984p] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Okan Esenturk
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742
| | - Robert A. Walker
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742
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49
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Lu R, Gan W, Wu BH, Chen H, Wang HF. Vibrational Polarization Spectroscopy of CH Stretching Modes of the Methylene Group at the Vapor/Liquid Interfaces with Sum Frequency Generation. J Phys Chem B 2004. [DOI: 10.1021/jp036674o] [Citation(s) in RCA: 190] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rong Lu
- State Key Laboratory of Molecular Reaction Dynamics, Center for Molecular Sciences, Institute of Chemistry, the Chinese Academy of Sciences, Beijing, P. R. China 100080
| | - Wei Gan
- State Key Laboratory of Molecular Reaction Dynamics, Center for Molecular Sciences, Institute of Chemistry, the Chinese Academy of Sciences, Beijing, P. R. China 100080
| | - Bao-hua Wu
- State Key Laboratory of Molecular Reaction Dynamics, Center for Molecular Sciences, Institute of Chemistry, the Chinese Academy of Sciences, Beijing, P. R. China 100080
| | - Hua Chen
- State Key Laboratory of Molecular Reaction Dynamics, Center for Molecular Sciences, Institute of Chemistry, the Chinese Academy of Sciences, Beijing, P. R. China 100080
| | - Hong-fei Wang
- State Key Laboratory of Molecular Reaction Dynamics, Center for Molecular Sciences, Institute of Chemistry, the Chinese Academy of Sciences, Beijing, P. R. China 100080
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50
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Lei Q, Bain CD. Surfactant-induced surface freezing at the alkane-water interface. PHYSICAL REVIEW LETTERS 2004; 92:176103. [PMID: 15169172 DOI: 10.1103/physrevlett.92.176103] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2003] [Indexed: 05/24/2023]
Abstract
Long-chain alkanes exhibit surface freezing at the alkane-air but not the alkane-water interface. Ellipsometry and surface tensiometry are used to show that a simple cationic surfactant, hexadecyltrimethylammonium bromide (CTAB), can induce surface freezing at the tetradecane-water interface even when present in mole fractions as low as 0.1. The surface-freezing temperature T(s) is a linear function of the interfacial excess of CTAB. The excess surface entropy below T(s), S(sigma)=-0.76+/-0.02 mJ K-1 m(-2), is consistent with a rotator phase. Ellipsometry provides strong evidence for a frozen monolayer in which the chains are oriented near the surface normal.
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Affiliation(s)
- Qunfang Lei
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, United Kingdom
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