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Wijarnprecha K, Gregson C, Sillick M, Fuhrmann P, Sonwai S, Rousseau D. Temperature-dependent properties of fat in adipose tissue from pork, beef and lamb. Part 1: microstructural, thermal, and spectroscopic characterisation. Food Funct 2022; 13:7112-7122. [PMID: 35698889 DOI: 10.1039/d2fo00581f] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We investigated the temperature-dependent microstructure and thermal properties of back fat adipose tissue from pork, beef and lamb. Microstructural characterisation via electron, confocal and light microscopy showed that the back fats were structurally similar and consisted of fat dispersed as discrete units within a protein matrix akin to a closed cell foam. Differential scanning calorimetry showed distinct fat melting profiles for each of the tissues, which were ascribed to differences in fatty acid profile. Fat crystal organisation, melting and re-solidification signatures unique to each adipose tissue were found via X-ray diffraction and Raman spectroscopy. Overall, we found that the temperature-dependent microstructure of adipose fat was intricately linked to the fat phase melting behaviour, and importantly, to its protein matrix at elevated temperatures. Such understanding is necessary to provide the required insights to effectively replicate the functionality of adipose tissue using plant-based materials.
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Affiliation(s)
| | | | | | - Philipp Fuhrmann
- Department of Chemistry and Biology, Toronto Metropolitan University, Toronto, Canada.
| | - Sopark Sonwai
- Department of Food Technology, Silpakorn University, Thailand
| | - Dérick Rousseau
- Department of Chemistry and Biology, Toronto Metropolitan University, Toronto, Canada.
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2
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Ly TQ, Yang F, Baldelli S. In situ quantitative study of the phase transition in surfactant adsorption layers at the silica-water interface using total internal reflection Raman spectroscopy. Phys Chem Chem Phys 2021; 23:21701-21713. [PMID: 34581333 DOI: 10.1039/d1cp02645c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Dimethyldodecylamine N-oxide (DDAO), a unique type of surfactant, shows high surface activity with two distinct energy states at the buried hydrophilic silica/aqueous solution interface studied by total internal reflection (TIR) Raman spectroscopy combined with ratiometric and kinetic analysis. Different from other types of surfactant, i.e., ionic and nonionic, the adsorption of DDAO demonstrates a specific critical surface aggregation concentration (csac) at 0.15 mM gives a complete surface coverage of 6.6 ± 0.3 μmol m-2, much lower than the bulk critical micellization concentration (cmc) at the same conditions (csac ≈ 0.072 cmc). A phase transition of adsorbed layers from liquid crystalline as the intermediate state to the disordered liquid phase is spectroscopically and energetically analyzed. The adsorption of DDAO on silica surfaces is described quantitatively in a potential energy curve.
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Affiliation(s)
- Thong Q Ly
- Department of Chemistry, University of Houston, Houston, Texas 77204-5003, USA.
| | - Fangyuan Yang
- Department of Chemistry, University of Houston, Houston, Texas 77204-5003, USA.
| | - Steven Baldelli
- Department of Chemistry, University of Houston, Houston, Texas 77204-5003, USA.
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3
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Huo F, Ding J, Tong J, He H. Ionic liquid-air interface probed by sum frequency generation spectroscopy and molecular dynamics simulation: influence of alkyl chain length and anion volume. MOLECULAR SIMULATION 2021. [DOI: 10.1080/08927022.2021.1979539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Feng Huo
- Beijing Key Laboratory of Ionic Liquids Clean Process, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Jian Ding
- Beijing Key Laboratory of Ionic Liquids Clean Process, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, People’s Republic of China
- College of Chemical Engineering, China University of Petroleum, Beijing, People’s Republic of China
| | - Jiahuan Tong
- Beijing Key Laboratory of Ionic Liquids Clean Process, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Hongyan He
- Beijing Key Laboratory of Ionic Liquids Clean Process, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, People’s Republic of China
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4
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Góbi S, Reva I, Tarczay G, Fausto R. Amorphous and crystalline thioacetamide ice: Infrared spectra as a probe for temperature and structure. J Mol Struct 2020. [DOI: 10.1016/j.molstruc.2020.128719] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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5
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Yu Y, Fan W, Wang Y, Zhou X, Sun J, Liu S. Probe of Alcohol Structures in the Gas and Liquid States Using C⁻H Stretching Raman Spectroscopy. SENSORS (BASEL, SWITZERLAND) 2018; 18:E2061. [PMID: 29958405 PMCID: PMC6068699 DOI: 10.3390/s18072061] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/20/2018] [Revised: 06/22/2018] [Accepted: 06/26/2018] [Indexed: 01/16/2023]
Abstract
Vibrational spectroscopy is a powerful tool for probing molecular structures and dynamics since it offers a unique fingerprint that allows molecular identification. One of important aspects of applying vibrational spectroscopy is to develop the probes that can characterize the related properties of molecules such as the conformation and intermolecular interaction. Many examples of vibrational probes have appeared in the literature, including the azide group (⁻N₃), amide group (⁻CONH₂), nitrile groups (⁻CN), hydroxyl group (⁻OH), ⁻CH group and so on. Among these probes, the ⁻CH group is an excellent one since it is ubiquitous in organic and biological molecules and the C⁻H stretching vibrational spectrum is extraordinarily sensitive to the local molecular environment. However, one challenge encountered in the application of C⁻H probes arises from the difficulty in the accurate assignment due to spectral congestion in the C⁻H stretching region. In this paper, recent advances in the complete assignment of C⁻H stretching spectra of aliphatic alcohols and the utility of C⁻H vibration as a probe of the conformation and weak intermolecular interaction are outlined. These results fully demonstrated the potential of the ⁻CH chemical group as a molecular probe.
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Affiliation(s)
- Yuanqin Yu
- Department of Physics, Anhui University, Hefei 230601, China.
| | - Wei Fan
- Hefei National Laboratory for Physical Sciences at the Microscale, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China.
| | - Yuxi Wang
- Hefei National Laboratory for Physical Sciences at the Microscale, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China.
| | - Xiaoguo Zhou
- Hefei National Laboratory for Physical Sciences at the Microscale, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China.
| | - Jin Sun
- Department of Physics, Anhui University, Hefei 230601, China.
| | - Shilin Liu
- Hefei National Laboratory for Physical Sciences at the Microscale, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China.
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6
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Abstract
The temperature dependence of the low-frequency C-O bands in the IR spectrum of [(η4-norbornadiene)Fe(CO)3], reminiscent of signal coalescence in dynamic NMR, was interpreted by Grevels (in 1987) as chemical exchange due to very fast rotation of the diene group. Since then, there has been both support and objection to this interpretation. We discuss these various claims involving both one- and two-dimensional IR and, largely on the basis of new density functional theory calculations, furnish support for Grevels' original interpretation.
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Affiliation(s)
- James J Turner
- School of Chemistry , University of Nottingham, University Park , Nottingham NG7 2RD , United Kingdom
| | - Michael Bühl
- School of Chemistry , University of St. Andrews , St. Andrews , Fife KY16 9ST , United Kingdom
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7
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DeBenedetti WJI, Li TL, Hines MA. Half-flat vs. atomically flat: Alkyl monolayers on morphologically controlled Si(100) and Si(111) have very similar structure, density, and chemical stability. J Chem Phys 2017; 146:052804. [PMID: 28178830 DOI: 10.1063/1.4963739] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Chemists have long preferred the Si(111) surface for chemical functionalization, as a simple aqueous etch can be used to produce ideal, atomically flat H/Si(111) surfaces for subsequent reactions. In contrast, industry-standard etches produce rough H/Si(100) surfaces terminated by nanohillocks. The recent discovery of an aqueous etch that produces morphologically controlled H/Si(100) surfaces with a near atomically flat or "half-flat" morphology challenges the assumption that Si(111) is an inherently preferable starting point for chemical functionalization. This study shows that alkyl functionalization of morphologically controlled, "half-flat" Si(100) surfaces by terminal alkenes produces dense, tightly packed monolayers that are essentially identical to those on atomically flat Si(111). The striking similarity between the infrared spectra on these two surfaces - in terms of absolute absorbance, line shape and position, and polarization dependence - strongly suggests that alkyl monolayers on morphologically controlled Si(111) and Si(100) have essentially identical structures. The principle difference between the two surfaces is the amount of residual H at the Si/organic interface, a difference that is dictated by the structure of the Si(100) surface. Alkyl monolayers on morphologically controlled Si(111) and Si(100) surfaces were shown to be equally resistant to harsh oxidants. As a result, there appears to be no chemical reason to prefer one surface over the other, at least for functionalization with terminal alkenes.
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Affiliation(s)
- William J I DeBenedetti
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
| | - Thomas L Li
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
| | - Melissa A Hines
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
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8
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Feng RJ, Li X, Zhang Z, Lu Z, Guo Y. Spectral assignment and orientational analysis in a vibrational sum frequency generation study of DPPC monolayers at the air/water interface. J Chem Phys 2016; 145:244707. [DOI: 10.1063/1.4972564] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Affiliation(s)
- Rong-Juan Feng
- Beijing National Laboratory for Molecular Sciences and State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xia Li
- Beijing National Laboratory for Molecular Sciences and State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhen Zhang
- Beijing National Laboratory for Molecular Sciences and State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Zhou Lu
- Beijing National Laboratory for Molecular Sciences and State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Yuan Guo
- Beijing National Laboratory for Molecular Sciences and State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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9
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Zoerb MC, Henderson JS, Glover SD, Lomont JP, Nguyen SC, Hill AD, Kubiak CP, Harris CB. Electron Dynamics and IR Peak Coalescence in Bridged Mixed Valence Dimers Studied by Ultrafast 2D-IR Spectroscopy. J Phys Chem B 2015. [DOI: 10.1021/acs.jpcb.5b06734] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Matthew C. Zoerb
- Department
of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Jane S. Henderson
- Department
of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, United States
| | - Starla D. Glover
- Department
of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, United States
| | - Justin P. Lomont
- Department
of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Son C. Nguyen
- Department
of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Adam D. Hill
- Department
of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Clifford P. Kubiak
- Department
of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, United States
| | - Charles B. Harris
- Department
of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
- Chemical
Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
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10
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Liljeblad JFD, Tyrode E, Thormann E, Dublanchet AC, Luengo G, Magnus Johnson C, Rutland MW. Self-assembly of long chain fatty acids: effect of a methyl branch. Phys Chem Chem Phys 2014; 16:17869-82. [DOI: 10.1039/c4cp00512k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The morphology and molecular conformation of monolayers of straight chain and methyl-branched fatty acids have been investigated by VSFS and AFM, revealing domains in the latter case, due to inverse micellar packing constraints.
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Affiliation(s)
- Jonathan F. D. Liljeblad
- School of Chemistry
- Division of Surface and Corrosion Science
- KTH Royal Institute of Technology
- SE-100 44 Stockholm, Sweden
| | - Eric Tyrode
- School of Chemistry
- Division of Surface and Corrosion Science
- KTH Royal Institute of Technology
- SE-100 44 Stockholm, Sweden
| | - Esben Thormann
- School of Chemistry
- Division of Surface and Corrosion Science
- KTH Royal Institute of Technology
- SE-100 44 Stockholm, Sweden
| | | | | | - C. Magnus Johnson
- School of Chemistry
- Division of Surface and Corrosion Science
- KTH Royal Institute of Technology
- SE-100 44 Stockholm, Sweden
| | - Mark W. Rutland
- School of Chemistry
- Division of Surface and Corrosion Science
- KTH Royal Institute of Technology
- SE-100 44 Stockholm, Sweden
- SP Technical Research Institute of Sweden
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11
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Hill AD, Zoerb MC, Nguyen SC, Lomont JP, Bowring MA, Harris CB. Determining equilibrium fluctuations using temperature-dependent 2D-IR. J Phys Chem B 2013; 117:15346-55. [PMID: 23844833 DOI: 10.1021/jp403791k] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
We demonstrate the capability of temperature-dependent 2D-IR to characterize sources of vibrational population transfer. In a model system of iron diene tricarbonyl "piano stool" complexes, this approach reveals symmetry breaking associated with equilibrium fluctuations and differentiates these from fluxional rearrangement. Tricarbonyl(1,3-butadiene)iron and tricarbonyl(1,5-cyclooctadiene)iron are shown to undergo intramolecular vibrational redistribution (IVR) coupled to the wagging motion of their carbonyl ligands. In the case of both molecules, these equilibrium fluctuations are distinguished from chemical exchange behaviors by their temperature dependence and arguments of molecular symmetry.
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Affiliation(s)
- Adam D Hill
- Department of Chemistry, University of California , Berkeley, California 94720, United States
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12
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Yu Y, Wang Y, Lin K, Hu N, Zhou X, Liu S. Complete Raman Spectral Assignment of Methanol in the C–H Stretching Region. J Phys Chem A 2013; 117:4377-84. [DOI: 10.1021/jp400886y] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yuanqin Yu
- School of Physics and Material
Science, Anhui University, Hefei, Anhui
230039, China
- Hefei National
Laboratory for
Physical Sciences at the Microscale, Department of Chemical
Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yuxi Wang
- Hefei National
Laboratory for
Physical Sciences at the Microscale, Department of Chemical
Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Ke Lin
- Hefei National
Laboratory for
Physical Sciences at the Microscale, Department of Chemical
Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Naiyin Hu
- Hefei National
Laboratory for
Physical Sciences at the Microscale, Department of Chemical
Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Xiaoguo Zhou
- Hefei National
Laboratory for
Physical Sciences at the Microscale, Department of Chemical
Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Shilin Liu
- Hefei National
Laboratory for
Physical Sciences at the Microscale, Department of Chemical
Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
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13
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Watanabe K, Okajima H, Kato T, Hamaguchi HO. Rotational dynamics of solvated carbon dioxide studied by infrared, Raman, and time-resolved infrared spectroscopies and a molecular dynamics simulation. J Chem Phys 2012; 136:014508. [DOI: 10.1063/1.3671998] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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14
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Sharma A, Reva I, Fausto R, Hesse S, Xue Z, Suhm MA, Nayak SK, Sathishkumar R, Pal R, Guru Row TN. Conformation-Changing Aggregation in Hydroxyacetone: A Combined Low-Temperature FTIR, Jet, and Crystallographic Study. J Am Chem Soc 2011; 133:20194-207. [DOI: 10.1021/ja2030646] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Archna Sharma
- Department of Chemistry, University of Coimbra, Coimbra, Rua Larga 3004-535, Portugal
| | - Igor Reva
- Department of Chemistry, University of Coimbra, Coimbra, Rua Larga 3004-535, Portugal
| | - Rui Fausto
- Department of Chemistry, University of Coimbra, Coimbra, Rua Larga 3004-535, Portugal
| | - Susanne Hesse
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstrasse 6, D-37077 Göttingen, Germany
| | - Zhifeng Xue
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstrasse 6, D-37077 Göttingen, Germany
| | - Martin A. Suhm
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstrasse 6, D-37077 Göttingen, Germany
| | - Susanta K. Nayak
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore-560012, India
| | - Ranganthan Sathishkumar
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore-560012, India
| | - Rumpa Pal
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore-560012, India
| | - Tayur N. Guru Row
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore-560012, India
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15
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Bresson S, Rousseau D, Ghosh S, Marssi ME, Faivre V. Raman spectroscopy of the polymorphic forms and liquid state of cocoa butter. EUR J LIPID SCI TECH 2011. [DOI: 10.1002/ejlt.201100088] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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16
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Tang H, Sun S, Wu J, Wu P, Wan X. Conformational changes in novel thermotropic liquid crystalline polymer without conventional mesogens: A Raman spectroscopic investigation. POLYMER 2010. [DOI: 10.1016/j.polymer.2010.09.036] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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17
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Lee HH, Ruzele Z, Malysheva L, Onipko A, Gutés A, Björefors F, Valiokas R, Liedberg B. Long-chain alkylthiol assemblies containing buried in-plane stabilizing architectures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:13959-13971. [PMID: 19791763 DOI: 10.1021/la901668u] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A series of alkylthiol compounds were synthesized to study the formation and structure of complex self-assembled monolayers (SAMs) consisting of interchanging structural modules stabilized by intermolecular hydrogen bonds. The chemical structure of the synthesized compounds, HS(CH(2))(15)CONH(CH(2)CH(2)O)(6)CH(2)CONH-X, where X refers to the extended chains of either -(CH(2))(n)CH(3) or -(CD(2))(n)CD(3), with n = 0, 1, 7, 8, 15, was confirmed by NMR and elemental analysis. The formation of highly ordered, methyl-terminated SAMs on gold from diluted ethanolic solutions of these compounds was revealed using contact angle goniometry, null ellipsometry, cyclic voltammetry, and infrared reflection absorption spectroscopy. The experimental work was complemented with extensive DFT modeling of infrared spectra and molecular orientation. New assignments were introduced for both nondeuterated and deuterated compounds. The latter set of compounds also served as a convenient tool to resolve the packing, conformation, and orientation of the buried and extended modules within the SAM. Thus, it was shown that the lower alkyl portion together with the hexa(ethylene glycol) portion is stabilized by the two layers of lateral hydrogen bonding networks between the amide groups, and they provide a structurally robust support for the extended alkyls. The presented system can be considered to be an extension of the well-known alkyl SAM platform, enabling precise engineering of nanoscopic architectures on the length scale from a few to approximately 60 A for applications such as cell membrane mimetics, molecular nanolithography, and so forth.
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Affiliation(s)
- Hung-Hsun Lee
- Division of Molecular Physics, Department of Physics, Chemistry and Biology, Linköping University, 58183 Linköping, Sweden
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18
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Cao W, Tashiro K, Masunaga H, Sasaki S, Takata M. Relationship between Morphological Change and Crystalline Phase Transitions of Polyethylene−Poly(ethylene oxide) Diblock Copolymers. 3. Dependence of Morphological Transition Phenomena on the PE/PEO Segmental Lengths and Its Possible Origins. J Phys Chem B 2009; 113:8495-504. [DOI: 10.1021/jp901442a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Weiyu Cao
- Department of Future Industry-Oriented Basic Science and Materials, Toyota Technological Institute, Tempaku, Nagoya 468-8511, Japan, and Japan Synchrotron Radiation Research Institute, Kouto, Sayo, Hyogo 679-5198, Japan
| | - Kohji Tashiro
- Department of Future Industry-Oriented Basic Science and Materials, Toyota Technological Institute, Tempaku, Nagoya 468-8511, Japan, and Japan Synchrotron Radiation Research Institute, Kouto, Sayo, Hyogo 679-5198, Japan
| | - Hiroyasu Masunaga
- Department of Future Industry-Oriented Basic Science and Materials, Toyota Technological Institute, Tempaku, Nagoya 468-8511, Japan, and Japan Synchrotron Radiation Research Institute, Kouto, Sayo, Hyogo 679-5198, Japan
| | - Sono Sasaki
- Department of Future Industry-Oriented Basic Science and Materials, Toyota Technological Institute, Tempaku, Nagoya 468-8511, Japan, and Japan Synchrotron Radiation Research Institute, Kouto, Sayo, Hyogo 679-5198, Japan
| | - Masaki Takata
- Department of Future Industry-Oriented Basic Science and Materials, Toyota Technological Institute, Tempaku, Nagoya 468-8511, Japan, and Japan Synchrotron Radiation Research Institute, Kouto, Sayo, Hyogo 679-5198, Japan
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19
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Zhuang W, Hayashi T, Mukamel S. Kohärente mehrdimensionale Schwingungsspektroskopie von Biomolekülen: Konzepte, Simulationen und Herausforderungen. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200802644] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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20
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Santos CS, Baldelli S. Alkyl Chain Interaction at the Surface of Room Temperature Ionic Liquids: Systematic Variation of Alkyl Chain Length (R = C1−C4, C8) in both Cation and Anion of [RMIM][R−OSO3] by Sum Frequency Generation and Surface Tension. J Phys Chem B 2009; 113:923-33. [DOI: 10.1021/jp807924g] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Cherry S. Santos
- Department of Chemistry, University of Houston, Houston, Texas 77204-5003
| | - Steven Baldelli
- Department of Chemistry, University of Houston, Houston, Texas 77204-5003
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21
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Zhuang W, Hayashi T, Mukamel S. Coherent multidimensional vibrational spectroscopy of biomolecules: concepts, simulations, and challenges. Angew Chem Int Ed Engl 2009; 48:3750-81. [PMID: 19415637 PMCID: PMC3526115 DOI: 10.1002/anie.200802644] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The response of complex molecules to sequences of femtosecond infrared pulses provides a unique window into their structure, dynamics, and fluctuating environments. Herein we survey the basic principles of modern two-dimensional infrared (2DIR) spectroscopy, which analogous to those of multidimensional NMR spectroscopy. The perturbative approach for computing the nonlinear optical response of coupled localized chromophores is introduced and applied to the amide backbone transitions of proteins, liquid water, membrane lipids, and amyloid fibrils. The signals are analyzed using classical molecular dynamics simulations combined with an effective fluctuating Hamiltonian for coupled localized anharmonic vibrations whose dependence on the local electrostatic environment is parameterized by an ab initio map. Several simulation methods, (cumulant expansion of Gaussian fluctuation, quasiparticle scattering, the stochastic Liouville equations, direct numerical propagation) are surveyed. Chirality-induced techniques which dramatically enhance the resolution are demonstrated. Signatures of conformational and hydrogen-bonding fluctuations, protein folding, and chemical-exchange processes are discussed.
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Affiliation(s)
- Wei Zhuang
- Department of Chemistry, University of California at Irvine, CA 92697-2025, USA
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22
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Johansson TP, Leach GW. A Low Temperature Phase Transition in Langmuir-Blodgett Films. J Phys Chem B 2008; 112:13823-33. [DOI: 10.1021/jp806226e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Thomas P. Johansson
- Laboratory for Advanced Spectroscopy and Imaging Research, 4D LABS and Department of Chemistry, Simon Fraser University, Burnaby, B.C., V5A 1S6 Canada
| | - Gary W. Leach
- Laboratory for Advanced Spectroscopy and Imaging Research, 4D LABS and Department of Chemistry, Simon Fraser University, Burnaby, B.C., V5A 1S6 Canada
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23
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D'Andrea TM, Zhang X, Jochnowitz EB, Lindeman TG, Simpson CJSM, David DE, Curtiss TJ, Morris JR, Ellison GB. Oxidation of Organic Films by Beams of Hydroxyl Radicals. J Phys Chem B 2007; 112:535-44. [DOI: 10.1021/jp7096108] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Timothy M. D'Andrea
- Department of Chemistry & Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109-8099, Institute for Physical Chemistry, University of Basel, Klingelbergstrasse 19, CH-4056 Basel, Switzerland, Department of Chemistry, Colorado College, Colorado Springs, Colorado 80903-3298, Physical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, United Kingdom,
| | - Xu Zhang
- Department of Chemistry & Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109-8099, Institute for Physical Chemistry, University of Basel, Klingelbergstrasse 19, CH-4056 Basel, Switzerland, Department of Chemistry, Colorado College, Colorado Springs, Colorado 80903-3298, Physical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, United Kingdom,
| | - Evan B. Jochnowitz
- Department of Chemistry & Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109-8099, Institute for Physical Chemistry, University of Basel, Klingelbergstrasse 19, CH-4056 Basel, Switzerland, Department of Chemistry, Colorado College, Colorado Springs, Colorado 80903-3298, Physical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, United Kingdom,
| | - T. G. Lindeman
- Department of Chemistry & Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109-8099, Institute for Physical Chemistry, University of Basel, Klingelbergstrasse 19, CH-4056 Basel, Switzerland, Department of Chemistry, Colorado College, Colorado Springs, Colorado 80903-3298, Physical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, United Kingdom,
| | - C. J. S. M. Simpson
- Department of Chemistry & Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109-8099, Institute for Physical Chemistry, University of Basel, Klingelbergstrasse 19, CH-4056 Basel, Switzerland, Department of Chemistry, Colorado College, Colorado Springs, Colorado 80903-3298, Physical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, United Kingdom,
| | - Donald E. David
- Department of Chemistry & Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109-8099, Institute for Physical Chemistry, University of Basel, Klingelbergstrasse 19, CH-4056 Basel, Switzerland, Department of Chemistry, Colorado College, Colorado Springs, Colorado 80903-3298, Physical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, United Kingdom,
| | - Thomas J. Curtiss
- Department of Chemistry & Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109-8099, Institute for Physical Chemistry, University of Basel, Klingelbergstrasse 19, CH-4056 Basel, Switzerland, Department of Chemistry, Colorado College, Colorado Springs, Colorado 80903-3298, Physical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, United Kingdom,
| | - John R. Morris
- Department of Chemistry & Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109-8099, Institute for Physical Chemistry, University of Basel, Klingelbergstrasse 19, CH-4056 Basel, Switzerland, Department of Chemistry, Colorado College, Colorado Springs, Colorado 80903-3298, Physical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, United Kingdom,
| | - G. Barney Ellison
- Department of Chemistry & Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109-8099, Institute for Physical Chemistry, University of Basel, Klingelbergstrasse 19, CH-4056 Basel, Switzerland, Department of Chemistry, Colorado College, Colorado Springs, Colorado 80903-3298, Physical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, United Kingdom,
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24
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Greenfield MS, Vold RL, Vold RR. Deuterium spin relaxation and guest motion in the n-nonadecane/urea clathrate. Mol Phys 2007. [DOI: 10.1080/00268978900100131] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Michael S. Greenfield
- a Department of Chemistry , University of California, San Diego , Las Jolla , California , 92093 , U.S.A
- b Department of Chemistry , University of California, Los Angeles , Los Angeles , California , 90024 , U.S.A
| | - Robert L. Vold
- a Department of Chemistry , University of California, San Diego , Las Jolla , California , 92093 , U.S.A
| | - Regitze R. Vold
- a Department of Chemistry , University of California, San Diego , Las Jolla , California , 92093 , U.S.A
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25
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Mohanambe L, Vasudevan S. Aromatic Molecules in Restricted Geometries: Pyrene Excimer Formation in an Anchored Bilayer. J Phys Chem B 2006; 110:14345-54. [PMID: 16854141 DOI: 10.1021/jp061695e] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The galleries of an anionic clay, Mg-Al Layered Double Hydroxide (Mg-Al LDH) have been functionalized by intercalating the anionic surfactant do-decyl sulfate. Within the galleries, the alkyl chains of the surfactant adopt a bilayer structure with the sulfate headgroup anchored to the inorganic sheet. Pyrene molecules have been solubilized in the anchored bilayer by partitioning from polar solvents. The presence of pyrene molecules induces conformational disorder in the alkyl chains of the bilayer and more importantly inhibits the rotational disordering motion of the sulfate headgroup. Pyrene fluorescence indicates formation of excimers whose intensity increases with concentration of solubilized pyrene indicating that they are mobile. Pyrene solubilized in the anchored bilayer exhibits unusual phenomena; on evacuation the excimer band disappear but reappears on releasing vacuum. It is shown that this behavior arises due to the loss of water of hydration of the headgroup on evacuation and as a consequence the pyrene moves into the less polar interior of the bilayer where it is immobile and can no longer diffuse and form excimers. The motion of pyrene into the interior of the bilayer creates free space near the surfactant chain termini, which manifests in the disappearance of the methyl-rocking mode of the ordered (-tt) end-chain conformer in the Raman spectra.
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Affiliation(s)
- L Mohanambe
- Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India
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26
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True NS. Evidence of conformational exchange averaging in the thermal rotational spectrum of ethyl cyanoformate. J Phys Chem A 2006; 110:7364-74. [PMID: 16759124 DOI: 10.1021/jp060481u] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The Stark modulated low resolution microwave spectrum of ethyl cyanoformate between 21.5 and 24.0 GHz at 210, 300, and 358 K, which shows the J + 1 <-- J = 8 <-- 7 bands of three species, is compared to simulations based on electronic structure calculations at the MP2/6-311++G theory level. Calculations at this theory level reproduce the relative energies of the syn-anti and syn-gauche conformers, obtained in a previous study, and indicate that the barrier to conformer exchange is approximately 360 cm(-1) higher in energy than the syn-anti minimum. Simulated spectra of the eigenstates of the calculated O-ethyl torsional potential function reproduce the relative intensities and shapes of the lower and higher frequency bands which correspond to transitions of the syn-anti and syn-gauche conformers, respectively, but fail to reproduce the intense center band in the experimental spectra. A model incorporating exchange averaging reproduces the intensity of the center band and its temperature dependence. These simulations indicate that a large fraction of the thermal population at all three temperatures undergoes conformational exchange with an average energy specific rate constant, <k(E)>, of approximately 25 GHz. This model can explain anomalies present in rotational spectra of many other compounds composed of mixtures of conformers.
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Affiliation(s)
- Nancy S True
- Department of Chemistry, The University of California, One Shields Avenue, Davis, California 95616, USA.
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27
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Rivera-Rubero S, Baldelli S. Surface Characterization of 1-Butyl-3-methylimidazolium Br-, I-, PF6-, BF4-, (CF3SO2)2N-, SCN-, CH3SO3-, CH3SO4-, and (CN)2N- Ionic Liquids by Sum Frequency Generation. J Phys Chem B 2006; 110:4756-65. [PMID: 16526712 DOI: 10.1021/jp0563989] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sum frequency generation spectroscopy, SFG, was used for the surface characterization at the gas-liquid interface of the 1-butyl-3-methylimidazolium cation combined with the following anions: Br-, I-, PF6-, BF4-, (CF3SO2)2N- (imide), SCN-, CH3SO3- (MeSO3), CH3SO4- (MS), and (CN)2N- (DCN). The SFG spectra obtained for the different ionic liquids were similar independent of the anion selected; therefore, a comprehensive analysis for the surface characterization of the ionic liquids' cation was focused only on the PF6- and Br- anion combinations. For an accurate identification of the vibrational modes observed, FT-IR and Raman spectroscopy in combination with isotopic labeling with deuterium and polarized Raman spectroscopy was used. The cation orientation was determined by analysis of polarization-dependent SFG spectra. For a compound dried in a vacuum to < or = 2 x 10(-5) Torr, the cation appears to be oriented with the ring laying flat along the surface plane and the butyl chain projecting into the gas phase independent of the anion identity.
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28
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Hauchard C, Pépin C, Rowntree P. Fe(CO)5 thin films adsorbed on Au(111) and on self-assembled organic monolayers: I. Structure. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:9154-65. [PMID: 16171346 DOI: 10.1021/la050593x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The adsorption of Fe(CO)(5) onto Au(111)/mica and C(4), C(8), C(12), and C(16) SAMs/Au(111)/mica surfaces has been studied using infrared spectroscopy to elucidate the coverage-dependent structures of these films and the intermolecular couplings that determine the form of the spectra. For all substrates, the first layer is composed of molecules physisorbed with one axial and two equatorial carbonyl groups directed toward the substrate; subsequent layers are preferentially oriented with the C(3) molecular axis aligned perpendicular to the substrate (i.e., one axial carbonyl group directed toward the substrate). The axial vibrational band systematically shifts to higher frequencies with increasing surface coverage because of the effects of intermolecular coupling of the quasiparallel transition dipole moments. The strong effects of dipolar coupling are also witnessed by the trends of the band positions when the distance to the image plane is systematically varied using highly organized self-assembled organic substrates; no band shifts are observed when dilute Fe(CO)(5) is embedded in Xe matrixes under identical experimental conditions. The as-deposited films are structurally stable below 125 K on Au(111)/mica surfaces and below 100 K on the organic self-assembled monolayers. The instability of the films above these temperatures demonstrates that the as-adsorbed films do not form thermodynamically well-defined phases but are structurally metastable. The results presented herein and in the companion paper provide a consistent framework to interpret the spectroscopy of these systems that resolves outstanding issues concerning these films and provides a structural model that explains the dynamic properties of these films during exposure to low-energy electron beams.
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Affiliation(s)
- Christelle Hauchard
- Département de Chimie, Université de Sherbrooke, Centre for the Self-Assembled Chemical Systems, Sherbrooke, Québec J1K 2R1, Canada
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29
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Orendorff CJ, Pemberton JE. Alkylsilane-Based Stationary Phases via a Displaceable Surface Template Approach: Synthesis, Characterization, and Chromatographic Performance. Anal Chem 2005; 77:6069-77. [PMID: 16159143 DOI: 10.1021/ac0511795] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A method is presented for the preparation of silica-based alkylsilane stationary phases using octanol as a displaceable surface template to control the rate of alkylsilane condensation with the silica surface, and thereby, the resulting alkylsilane surface coverage. This method improves upon conventional preparation schemes by allowing alkylsilane stationary phases of systematically varying surface coverage to be prepared from a single reaction mixture and a single precursor molecule without rigorous control of water content of the solution or of the silica. Octadecylsilane stationary phases ranging in surface coverage from approximately 3.5 to 6.0 micromol/m(2) were synthesized using one set of experimental conditions with variation of only the octadecylsilane/octanol ratio. The conformational order of the octadecylsilane alkyl chains was assessed using Raman spectroscopy and was found to increase with increasing surface coverage in a manner similar to stationary phases prepared by conventional routes. As chromatographic stationary phases in microbore columns for the reversed-phase separation of monosubstituted aromatic compounds, the performance of these materials is comparable to or better than that of commercially available octadecylsilane stationary phases under identical chromatographic conditions. Furthermore, the high-density stationary phases (>3.5 micromol/m(2)) prepared by this route exhibit geometric shape selectivity comparable to or better than that reported earlier for high-density octadecylsilane stationary phases prepared using conventional methods.
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Affiliation(s)
- Christopher J Orendorff
- Department of Chemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, USA
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30
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Watanabe D, Hamaguchi HO. Ion association dynamics in aqueous solutions of sulfate salts as studied by Raman band shape analysis. J Chem Phys 2005; 123:34508. [PMID: 16080745 DOI: 10.1063/1.1931660] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A new perspective is shown on the interaction between the sulfate ion and its counter cation in aqueous solutions. We propose the dynamic exchange model of ion association instead of the conventional static equilibrium model. The concentration dependence of the Raman band shape of the totally symmetric (a(1)) SO stretch mode of the sulfate ion is investigated systematically for four sulfate ions, MgSO(4), (NH(4))(2)SO(4), K(2)SO(4), and Li(2)SO(4). The concentration dependence of the a(1) Raman band shape in the MgSO(4) system is successfully reproduced by the analysis based on the dynamic exchange model. As a result, quantitative information about the extremely dynamic nature of the ion association has been obtained: the mean time between associations is a few picoseconds and the mean lifetime of association is several hundred femtoseconds.
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Affiliation(s)
- Daisuke Watanabe
- Department of Chemistry, School of Science, The University of Tokyo, Bunkyo-ku, Japan
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31
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Lu R, Gan W, Wu BH, Zhang Z, Guo Y, Wang HF. C−H Stretching Vibrations of Methyl, Methylene and Methine Groups at the Vapor/Alcohol (n = 1−8) Interfaces. J Phys Chem B 2005; 109:14118-29. [PMID: 16852773 DOI: 10.1021/jp051565q] [Citation(s) in RCA: 218] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In IR and Raman spectral studies, the congestion of the vibrational modes in the C-H stretching region between 2800 and 3000 cm(-1) has complicated spectral assignment, conformational analysis, and structural and dynamics studies, even with quite a few of the simplest molecules. To resolve these issues, polarized spectra measurement on a well aligned sample is generally required. Because the liquid interface is generally ordered and molecularly thin, and sum frequency generation vibrational spectroscopy (SFG-VS) is an intrinsically coherent polarization spectroscopy, SFG-VS can be used for discerning details in vibrational spectra of the interfacial molecules. Here we show that, from systematic molecular symmetry and SFG-VS polarization analysis, a set of polarization selection rules could be developed for explicit assignment of the SFG vibrational spectra of the C-H stretching modes. These polarization selection rules helped assignment of the SFG-VS spectra of vapor/alcohol (n = 1-8) interfaces with unprecedented details. Previous approach on assignment of these spectra relied on IR and Raman spectral assignment, and they were not able to give such detailed assignment of the SFG vibrational spectra. Sometimes inappropriate assignment was made, and consequently misleading conclusions on interfacial structure, conformation and even dynamics were reached. With these polarization rules in addition to knowledge from IR and Raman studies, new structural information and understanding of the molecular interactions at these interfaces were obtained, and some new spectral features for the C-H stretching modes were also identified. Generally speaking, these new features can be applied to IR and Raman spectroscopic studies in the condensed phase. Therefore, the advancement on vibrational spectra assignment may find broad applications in the related fields using IR and Raman as vibrational spectroscopic tools.
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Affiliation(s)
- Rong Lu
- State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, the Chinese Academy of Sciences, Beijing, P.R. China, 100080
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32
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Wang * HF, Gan † ‡ W, Lu † ‡ § R, Rao † ‡ ¶ Y, Wu † BH. Quantitative spectral and orientational analysis in surface sum frequency generation vibrational spectroscopy (SFG-VS). INT REV PHYS CHEM 2005. [DOI: 10.1080/01442350500225894] [Citation(s) in RCA: 508] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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33
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Orendorff CJ, Pemberton JE. Raman spectroscopic study of the conformational order of octadecylsilane stationary phases: effects of electrolyte and pH. Anal Bioanal Chem 2005; 382:691-7. [PMID: 15770468 DOI: 10.1007/s00216-005-3133-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2004] [Revised: 01/11/2005] [Accepted: 01/19/2005] [Indexed: 11/28/2022]
Abstract
This study investigates effects of the electrolyte, of acidic and basic compounds, and of pH on the rotational and conformational order of octadecylsilane stationary phases with surface coverages of 3.09 and 6.45 micromol/m(2). Both phases exhibit an increase in alkyl chain rotational and conformational order in 5-200 mM aqueous electrolyte solutions relative to water. These stationary phases are effectively "salted-out" of aqueous electrolyte solutions, thereby causing alkyl chain intermolecular interactions to increase with a concomitant increase in alkyl chain order. Although the presence of acidic and basic compounds generally has no effect on the conformational order of either stationary phase as a function of pH, the higher coverage stationary phase does exhibit pH-dependent changes in aqueous solutions of benzoic acid. At pH values below the pK(a) of benzoic acid, the conformational order of this stationary phase is unchanged relative to that observed in the same pH solution in the absence of benzoic acid. In light of independent evidence that such monosubstituted aromatics interact with the octadecylsilane stationary phase under these conditions, the absence of a measurable effect on alkyl chain order for these conditions is attributed to benzoic acid self-association at the stationary phase-mobile phase interface. In contrast, at pH values above the pK(a) of benzoic acid, slight disordering of the alkyl chains is observed and is attributed to repulsive interactions between retained benzoate anions.
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Affiliation(s)
- Christopher J Orendorff
- Department of Chemistry, University of Arizona, 1306 East University Boulevard, Tucson, AZ 85721, USA
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34
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Park SH, Lee CE. Layered Copper Hydroxide n-Alkylsulfonate Salts: Synthesis, Characterization, and Magnetic Behaviors in Relation to the Basal Spacing. J Phys Chem B 2004; 109:1118-24. [PMID: 16851069 DOI: 10.1021/jp046902u] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A series of hybrid inorganic-organic copper(II) hydroxy n-alkylsulfonate with a triangular lattice, Cu(2)(OH)(3)(C(n)H(2)(n)(+1)SO(3)) (n = 6, 8, 10), are prepared by anion exchange, starting from copper hydroxy nitrate Cu(2)(OH)(3)NO(3). These compounds show a layered structure as determined by X-ray diffraction, with interlayer distances of 14.3-34.8 A in alternation with interdigitated bilayer packing. Magnetic properties have been investigated by means of dc and ac measurements. All the compounds show similar metamagnet behaviors, with a Neel temperature of about 11 K. A subtle difference in the ac magnetic susceptibility among the compounds is understood by the existence of hydrogen bonding between the sulfonate headgroup and the hydroxide anion. A detailed molecular structure of the alkyl chains incorporated to the inorganic copper hydroxide layer is also discussed from the FTIR data.
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Affiliation(s)
- Seong-Hun Park
- Institute for Nano Science and Department of Physics, Korea University, Seoul 136-701, Korea
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35
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Jansen TLC, Zhuang W, Mukamel S. Stochastic Liouville equation simulation of multidimensional vibrational line shapes of trialanine. J Chem Phys 2004; 121:10577-98. [PMID: 15549941 DOI: 10.1063/1.1807824] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The line shapes detected in coherent femtosecond vibrational spectroscopies contain direct signatures of peptide conformational fluctuations through their effect on vibrational frequencies and intermode couplings. These effects are simulated in trialanine using a Green's function solution of a stochastic Liouville equation constructed for four collective bath coordinates (two Ramachandran angles affecting the mode couplings and two diagonal energies). We find that fluctuations of the Ramachandran angles which hardly affect the linear absorption can be effectively probed by two-dimensional spectra. The signal generated at k(1)+k(2)-k(3) is particularly sensitive to such fluctuations.
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36
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Cherney DP, Conboy JC, Harris JM. Optical-trapping Raman microscopy detection of single unilamellar lipid vesicles. Anal Chem 2004; 75:6621-8. [PMID: 14640737 DOI: 10.1021/ac034838r] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Raman spectra of individual unilamellar phospholipid vesicles ( approximately 0.6 microm in size) have been acquired by optical-trapping confocal Raman microscopy over the 900-3200-cm(-)(1) region. Raman scattering from the phospholipid bilayer of a single, trapped liposome could be detected, along with molecular species trapped within the vesicle. The Raman spectra of vesicles prepared from four different phosphatidylcholine lipids, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), could be readily distinguished by evaluating differences in the skeletal C-C and C-H stretching modes of the acyl hydrocarbon tails. These differences correlate with changes in lipid organization for different gel to liquid-crystal transition temperatures (T(m)): 41, 24, 7, and -20 degrees C for DPPC, DMPC, DLPC, and DOPC, respectively. The spectra could be acquired on the same trapped vesicle for several hours, which allowed the permeability of the bilayer to be investigated by monitoring the leakage of perchlorate anions from the vesicle. Vesicles prepared from pure DPPC or DOPC, with gel to liquid-crystal transition temperatures well above and well below room temperature, exhibited no detectable anion transfer. DLPC and DMPC vesicles permitted rapid ion transfer across the bilayer. The lengths of hydrocarbon tails were shorter in these two lipids, which could indicate that shorter chains lower the hydrophobic barrier of a membrane to ion transport. While the DMPC chains were longer than DLPC with a correspondingly higher T(m), the temperature of the experiment corresponds to the T(m) of DMPC, and domain boundaries between gel and liquid-crystal phases could contribute to high membrane permeability.
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Affiliation(s)
- Daniel P Cherney
- Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850, USA
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37
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Doyle AW, Fick J, Himmelhaus M, Eck W, Graziani I, Prudovsky I, Grunze M, Maciag T, Neivandt DJ. Protein deformation of lipid hybrid bilayer membranes studied by sum frequency generation vibrational spectroscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:8961-8965. [PMID: 15461473 DOI: 10.1021/la0484220] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Structural deformations of lipid hybrid bilayer membranes induced by signal peptideless (SPL) proteins have been studied for the first time using the inherently surface specific nonlinear optical technique of sum frequency generation vibrational spectroscopy. Specifically, deformations of 1,2-distearoylphosphatidylglycerol(DSPG) membranes induced by interaction with FGF-1, a SPL protein which is released asa function of cellular stress through a nonclassical pathway, have been investigated. FGF-1 was found to induce lipid alkyl chain deformations in previously highly ordered DSPG membranes at the extremely low concentration of 1 nM at 60 degrees C. The deformation process was shown to exhibit a degree of reversibility upon removal of the protein by rinsing with buffer solution.
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38
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Electrochemical, neutron reflectivity and in situ PM-FT-IRRAS studies of a monolayer of n-octadecanol at a Au(111) electrode surface. Electrochim Acta 2004. [DOI: 10.1016/j.electacta.2004.02.051] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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39
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Garand É, Picard JF, Rowntree P. Inter- and Intramolecular Temperature-Dependent Vibrational Perturbations of Alkanethiol Self-Assembled Monolayers. J Phys Chem B 2004. [DOI: 10.1021/jp031273u] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Étienne Garand
- Département de chimie, Université de Sherbrooke, Sherbrooke, Québec, Canada J1K 2R1
| | - Jean-François Picard
- Département de chimie, Université de Sherbrooke, Sherbrooke, Québec, Canada J1K 2R1
| | - Paul Rowntree
- Département de chimie, Université de Sherbrooke, Sherbrooke, Québec, Canada J1K 2R1
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40
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Ji N, Shen YR. Sum frequency vibrational spectroscopy of leucine molecules adsorbed at air–water interface. J Chem Phys 2004; 120:7107-12. [PMID: 15267614 DOI: 10.1063/1.1669375] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Sum frequency vibrational spectroscopy was used to study adsorption of leucine molecules at air-water interface from solutions with different concentrations and pH values. The surface density and the orientation of the isopropyl head group of the adsorbed leucine molecules could be deduced from the measurements. It was found that the orientation depends on the surface density, but only weakly on bulk pH value at the saturated surface density. The vibrational spectra of the interfacial water molecules appeared to be strongly affected by the charge state of the adsorbed leucine molecules. Enhancement and inversion of polar orientation of interfacial water molecules by surface charges or field controllable by the bulk pH value were observed.
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Affiliation(s)
- Na Ji
- Department of Physics, University of California at Berkeley, 94720, USA
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41
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Gorce JP, Spells SJ, Zeng XB, Ungar G. Infrared Active Methyl Group Vibrations in Tetratetracontane: A Probe for Chain End Organization and Crystal Structure. J Phys Chem B 2004. [DOI: 10.1021/jp030794e] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jean-Philippe Gorce
- Materials Research Institute, Sheffield Hallam University, City Campus, Sheffield S1 1WB, United Kingdom, and Department of Engineering Materials, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - Stephen. J. Spells
- Materials Research Institute, Sheffield Hallam University, City Campus, Sheffield S1 1WB, United Kingdom, and Department of Engineering Materials, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - Xiang-Bing Zeng
- Materials Research Institute, Sheffield Hallam University, City Campus, Sheffield S1 1WB, United Kingdom, and Department of Engineering Materials, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - Goran Ungar
- Materials Research Institute, Sheffield Hallam University, City Campus, Sheffield S1 1WB, United Kingdom, and Department of Engineering Materials, University of Sheffield, Sheffield S1 3JD, United Kingdom
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42
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Sando GM, Spears KG. Density Functional Theory Studies of the Co(Cp)2|V(CO)6 Radical-Pair System. J Phys Chem A 2004. [DOI: 10.1021/jp036383f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gerald M. Sando
- Northwestern University, Department of Chemistry, 2145 Sheridan Road, Evanston, Illinois 60208-3113
| | - Kenneth G. Spears
- Northwestern University, Department of Chemistry, 2145 Sheridan Road, Evanston, Illinois 60208-3113
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43
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Choi HJ, Han SW, Lee SJ, Kim K. Structure and thermal behavior of a layered silver hydroxyalkanecarboxylate. J Colloid Interface Sci 2003; 264:458-66. [PMID: 16256665 DOI: 10.1016/s0021-9797(03)00413-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2002] [Accepted: 04/15/2003] [Indexed: 11/17/2022]
Abstract
The structure and thermal behavior of silver 16-hydroxyhexadecanoate (Ag-HHDA) have been investigated by using various analytical tools. The X-ray diffraction pattern was composed of a series of peaks that could be indexed to (0k0) reflections of a layered structure. Diffuse reflectance infrared Fourier transform spectroscopy revealed that the alkyl chains in Ag-HHDA as prepared were in an all-trans conformational state. Upon heating the sample, noticeable structural changes took place particularly in two temperature regions. The first structural change occurring at approximately 380 K was a partially irreversible one in which the binding state of carboxylate to silver converted from bridging into unidentate. A second dramatic structural change occurring at approximately 480 K was a totally irreversible process that could be associated with the decomposition of Ag-HHDA. All of these thermal characteristics of Ag-HHDA are comparable to those of silver stearate (Ag-STA). Separately, we have endeavored without success to intercalate polar molecules into the OH-group terminated layers in Ag-HHDA; the exfoliation of Ag-HHDA in various polar solvents was also unsuccessful. This is indicative of the presence of a rather stronger H-bond in Ag-HHDA, but the comparable thermal characteristics of Ag-HHDA and Ag-STA dictate that the thermal behavior of silver alkanoate is determined exclusively by the silver-to-carboxylate group interaction. This is in sharp contrast to the case of two-dimensional self-assembled monolayers for which the terminal functionalities play a crucial role in determining the structure and thermal stability of entire monolayers.
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Affiliation(s)
- Hyouk Jin Choi
- Laboratory of Intelligent Interfaces, School of Chemistry and Molecular Engineering and Center for Molecular Catalysis, Seoul National University, Seoul 151-742, South Korea
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44
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Orendorff CJ, Ducey MW, Pemberton JE, Sander LC. Structure−Function Relationships in High-Density Octadecylsilane Stationary Phases by Raman Spectroscopy. 3. Effects of Self-Associating Solvents. Anal Chem 2003; 75:3360-8. [PMID: 14570185 DOI: 10.1021/ac020638o] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Raman spectroscopy is used to examine the subtle effects of polar, hydrogen-bonding solvents; temperature; and the surface grafting method (surface- or solution-polymerized) on alkyl chain rotational and conformational order in a series of high-density octadecylsilane stationary phases ranging in surface coverage from 3.09 to 6.45 micromol/m2. Rotational and conformational order is assessed using the intensity ratio of the antisymmetric to symmetric v(CH2) modes as well as the frequencies at which these Raman bands are observed. Alkyl rotational and conformational order decreases with decreasing surface coverage in these polar solvents, consistent with the behavior of these materials in air. For homogeneously distributed, high surface coverage materials, these polar solvents induce rotational ordering that is proposed to be due to the self-association of these solvents through hydrogen bonding or other dipole interactions at the alkylsilane-solvent interface. From these observations, molecular pictures of these solvent-stationary-phase interfaces are proposed in which solvent interaction with the stationary phase occurs primarily at the distal methyl group of the alkyl chains.
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45
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Berg O, Klenerman D. Vibrational spectroscopy of mechanically compressed monolayers. J Am Chem Soc 2003; 125:5493-500. [PMID: 12720464 DOI: 10.1021/ja027128w] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sum-frequency spectroscopy has been used to investigate the behavior of self-assembled monolayers in a solid-solid contact. Various alkanethiol layers on gold were observed before, during, and after compression to 660 MPa against a sapphire counterface. Well-ordered layers that differ only in the length of their alkane tails (C(8) versus C(18)) behave similarly. In contrast, defective and partly melted monolayers are more sensitive to stress than are their well-ordered analogues, and they are more prone to irreversible changes. In all cases, the intensity of methyl C-H stretching modes decreases with applied pressure, indicating a loss of net orientational order among the terminal methyl groups. The magnitude of this effect in well-ordered layers can be compared with the theoretical sensitivity of the resonant sum-frequency signal to molecular orientation. On these grounds, an increased population of terminal gauche conformers is identified as the disordering mechanism under pressure.
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Affiliation(s)
- Otto Berg
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
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46
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Barman S, Venkataraman NV, Vasudevan S, Seshadri R. Phase Transitions in the Anchored Organic Bilayers of Long-Chain Alkylammonium Lead Iodides (CnH2n+1NH3)2PbI4; n = 12, 16, 18. J Phys Chem B 2003. [DOI: 10.1021/jp026879h] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- S. Barman
- Solid State and Structural Chemistry Unit and Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore-560012, India
| | - N. V. Venkataraman
- Solid State and Structural Chemistry Unit and Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore-560012, India
| | - S. Vasudevan
- Solid State and Structural Chemistry Unit and Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore-560012, India
| | - Ram Seshadri
- Solid State and Structural Chemistry Unit and Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore-560012, India
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47
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Ducey MW, Orendorff CJ, Pemberton JE, Sander LC. Structure-function relationships in high-density octadecylsilane stationary phases by Raman spectroscopy. 1. Effects of temperature, surface coverage, and preparation procedure. Anal Chem 2002; 74:5576-84. [PMID: 12433091 DOI: 10.1021/ac0203488] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Raman spectroscopy is used to examine the effects of temperature, surface coverage, nature of the alkylsilane precursor (octadecyltrichlorosilane, methyloctadecyldichlorosilane, or dimethyloctadecylchlorosilane), and surface grafting method (surface or solution polymerized) on alkyl chain conformational order in a series of high-density octadecylsilane stationary phases ranging in surface coverage from 3.09 to 6.45 micromol/m2. Conformational order is assessed using the intensity ratio of the antisymmetric and symmetric v(CH2) modes as well as the frequency at which these Raman bands are observed. Conformational order increases with surface coverage. Temperature-induced surface phase changes are observed between 258 and 343 K for this homologous series of stationary phases that are demonstrated to adhere to the Clapeyron equation for a simple first-order transition. Phase changes are discussed in terms of variation of the molar enthalpy, molar entropy, and molar volume of the stationary phase, all of which depend on surface coverage. For the limited range of systems investigated, a correlation between stationary-phase preparation (surface versus solution polymerized and nature of the silane precursor) and extent of alkyl chain order is not clearly observed.Instead, akyl chain order is largely dependent on bonding density. A molecular picture of temperature-induced disorder in octadecylsilane stationary phases is proposed, with disorder originating at the distal carbon and propagating toward the proximal carbon.
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Affiliation(s)
- Michael W Ducey
- Department of Chemistry, University of Arizona, Tucson 85721, USA
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48
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Orendorff CJ, Ducey MW, Pemberton JE. Quantitative Correlation of Raman Spectral Indicators in Determining Conformational Order in Alkyl Chains. J Phys Chem A 2002; 106:6991-6998. [DOI: 10.1021/jp014311n] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Christopher J. Orendorff
- University of Arizona, Department of Chemistry, 1306 East University Blvd., Tucson, Arizona 85721
| | - Michael W. Ducey
- University of Arizona, Department of Chemistry, 1306 East University Blvd., Tucson, Arizona 85721
| | - Jeanne E. Pemberton
- University of Arizona, Department of Chemistry, 1306 East University Blvd., Tucson, Arizona 85721
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49
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Lee SJ, Han SW, Choi HJ, Kim K. Structure and Thermal Behavior of a Layered Silver Carboxylate. J Phys Chem B 2002. [DOI: 10.1021/jp0132937] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Seung Joon Lee
- Laboratory of Intelligent Interfaces, School of Chemistry and Molecular Engineering and Center for Molecular Catalysis, Seoul National University, Seoul 151-742, Korea
| | - Sang Woo Han
- Laboratory of Intelligent Interfaces, School of Chemistry and Molecular Engineering and Center for Molecular Catalysis, Seoul National University, Seoul 151-742, Korea
| | - Hyouk Jin Choi
- Laboratory of Intelligent Interfaces, School of Chemistry and Molecular Engineering and Center for Molecular Catalysis, Seoul National University, Seoul 151-742, Korea
| | - Kwan Kim
- Laboratory of Intelligent Interfaces, School of Chemistry and Molecular Engineering and Center for Molecular Catalysis, Seoul National University, Seoul 151-742, Korea
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50
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Pemberton JE, Ho M, Orendorff CJ, Ducey MW. Raman spectroscopy of octadecylsilane stationary phase conformational order. Effect of solvent. J Chromatogr A 2001; 913:243-52. [PMID: 11355819 DOI: 10.1016/s0021-9673(01)00569-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The effect of solvent on the conformation of alkyl chains of two octadecysilane-based stationary phases is probed using Raman spectroscopy. Spectral data indicate that the alkyl chains of commercially available polymeric and monomeric solid-phase extraction stationary phases are disordered to a varying extent by solvents of different polarity. For the polymeric octadecylsilane stationary phase, the polar solvents water, acetonitrile, methanol, acetone and isopropanol have little impact on the conformational order of the octadecylsilane bonded phase relative to air. However, the alkyl portion of this stationary phase is substantially disordered in the low-polarity solvents tetrahydrofuran, chloroform, benzene, toluene and hexane. The monomeric octadecylsilane stationary phase is less susceptible to disordering by solvents, although more disorder in the less polar solvents is also observed for this system. These results are interpreted in terms of the local surface bonding density and interchain spacing of these two stationary phases, and the ability of the solvent to penetrate the chains as a function of polarity. The results clearly demonstrate the ability of Raman spectroscopy to precisely indicate subtle changes in conformational order of alkylsilane stationary phases.
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Affiliation(s)
- J E Pemberton
- Department of Chemistry, University of Arizona, Tucson 85721, USA.
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