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Zhao Y, Stratt RM. Measuring order in disordered systems and disorder in ordered systems: Random matrix theory for isotropic and nematic liquid crystals and its perspective on pseudo-nematic domains. J Chem Phys 2018; 148:204501. [PMID: 29865812 DOI: 10.1063/1.5024678] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Surprisingly long-ranged intermolecular correlations begin to appear in isotropic (orientationally disordered) phases of liquid crystal forming molecules when the temperature or density starts to close in on the boundary with the nematic (ordered) phase. Indeed, the presence of slowly relaxing, strongly orientationally correlated, sets of molecules under putatively disordered conditions ("pseudo-nematic domains") has been apparent for some time from light-scattering and optical-Kerr experiments. Still, a fully microscopic characterization of these domains has been lacking. We illustrate in this paper how pseudo-nematic domains can be studied in even relatively small computer simulations by looking for order-parameter tensor fluctuations much larger than one would expect from random matrix theory. To develop this idea, we show that random matrix theory offers an exact description of how the probability distribution for liquid-crystal order parameter tensors converges to its macroscopic-system limit. We then illustrate how domain properties can be inferred from finite-size-induced deviations from these random matrix predictions. A straightforward generalization of time-independent random matrix theory also allows us to prove that the analogous random matrix predictions for the time dependence of the order-parameter tensor are similarly exact in the macroscopic limit, and that relaxation behavior of the domains can be seen in the breakdown of the finite-size scaling required by that random-matrix theory.
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Affiliation(s)
- Yan Zhao
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA
| | - Richard M Stratt
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA
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2
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Kiefer LM, Kubarych KJ. Solvent exchange in preformed photocatalyst-donor precursor complexes determines efficiency. Chem Sci 2018; 9:1527-1533. [PMID: 29675196 PMCID: PMC5887230 DOI: 10.1039/c7sc04533f] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 12/20/2017] [Indexed: 11/21/2022] Open
Abstract
In homogeneous photocatalytic reduction of CO2, it is widely assumed that the primary electron transfer from the sacrificial donor to the catalyst is diffusion controlled, thus little attention has been paid to optimizing this step. We present spectroscopic evidence that the precursor complex is preformed, driven by preferential solvation, and two-dimensional infrared spectroscopy reveals triethanolamine (donor)/tetrahydrofuran (solvent) exchange in the photocatalyst's solvation shell, reaching greatest magnitude at the known optimal concentration (∼20% v/v TEOA in THF) for catalytically reducing CO2 to CO. Transient infrared absorption shows the appearance of the singly reduced catalyst on an ultrafast (<70 ps) time scale, consistent with non-diffusion controlled electron transfer within the preformed precursor complex. Identification of preferential catalyst-cosolvent interactions suggests a revised paradigm for the primary electron transfer, while illuminating the pivotal importance of solvent exchange in determining the overall efficiency of the photocycle.
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Affiliation(s)
- Laura M Kiefer
- Department of Chemistry , University of Michigan , Ann Arbor , MI 48109 , USA .
| | - Kevin J Kubarych
- Department of Chemistry , University of Michigan , Ann Arbor , MI 48109 , USA .
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3
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Panda MR, Koley S, Mishra K, Ghosh S. Probing of Reorganization Dynamics within the Different Phases of Themotropic Liquid Crystals. ChemistrySelect 2018. [DOI: 10.1002/slct.201702944] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Manas Ranjan Panda
- School of Chemical Sciences; National Institute of Science Education and Research, HBNI; Khurda - 752050, Odisha India
| | - Somnath Koley
- School of Chemical Sciences; National Institute of Science Education and Research, HBNI; Khurda - 752050, Odisha India
| | - Krishna Mishra
- School of Chemical Sciences; National Institute of Science Education and Research, HBNI; Khurda - 752050, Odisha India
| | - Subhadip Ghosh
- School of Chemical Sciences; National Institute of Science Education and Research, HBNI; Khurda - 752050, Odisha India
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4
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Thomaz JE, Bailey HE, Fayer MD. The influence of mesoscopic confinement on the dynamics of imidazolium-based room temperature ionic liquids in polyether sulfone membranes. J Chem Phys 2017; 147:194502. [DOI: 10.1063/1.5003036] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Joseph E. Thomaz
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Heather E. Bailey
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Michael D. Fayer
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
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5
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Kraack JP. Ultrafast structural molecular dynamics investigated with 2D infrared spectroscopy methods. Top Curr Chem (Cham) 2017; 375:86. [PMID: 29071445 DOI: 10.1007/s41061-017-0172-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 10/02/2017] [Indexed: 12/23/2022]
Abstract
Ultrafast, multi-dimensional infrared (IR) spectroscopy has been advanced in recent years to a versatile analytical tool with a broad range of applications to elucidate molecular structure on ultrafast timescales, and it can be used for samples in a many different environments. Following a short and general introduction on the benefits of 2D IR spectroscopy, the first part of this chapter contains a brief discussion on basic descriptions and conceptual considerations of 2D IR spectroscopy. Outstanding classical applications of 2D IR are used afterwards to highlight the strengths and basic applicability of the method. This includes the identification of vibrational coupling in molecules, characterization of spectral diffusion dynamics, chemical exchange of chemical bond formation and breaking, as well as dynamics of intra- and intermolecular energy transfer for molecules in bulk solution and thin films. In the second part, several important, recently developed variants and new applications of 2D IR spectroscopy are introduced. These methods focus on (i) applications to molecules under two- and three-dimensional confinement, (ii) the combination of 2D IR with electrochemistry, (iii) ultrafast 2D IR in conjunction with diffraction-limited microscopy, (iv) several variants of non-equilibrium 2D IR spectroscopy such as transient 2D IR and 3D IR, and (v) extensions of the pump and probe spectral regions for multi-dimensional vibrational spectroscopy towards mixed vibrational-electronic spectroscopies. In light of these examples, the important open scientific and conceptual questions with regard to intra- and intermolecular dynamics are highlighted. Such questions can be tackled with the existing arsenal of experimental variants of 2D IR spectroscopy to promote the understanding of fundamentally new aspects in chemistry, biology and materials science. The final part of the chapter introduces several concepts of currently performed technical developments, which aim at exploiting 2D IR spectroscopy as an analytical tool. Such developments embrace the combination of 2D IR spectroscopy and plasmonic spectroscopy for ultrasensitive analytics, merging 2D IR spectroscopy with ultra-high-resolution microscopy (nanoscopy), future variants of transient 2D IR methods, or 2D IR in conjunction with microfluidics. It is expected that these techniques will allow for groundbreaking research in many new areas of natural sciences.
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Affiliation(s)
- Jan Philip Kraack
- Department of Chemistry, University of Zürich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
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6
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Bailey HE, Wang YL, Fayer MD. Impact of Hydrogen Bonding on the Dynamics and Structure of Protic Ionic Liquid/Water Binary Mixtures. J Phys Chem B 2017; 121:8564-8576. [DOI: 10.1021/acs.jpcb.7b06376] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Heather E. Bailey
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Yong-Lei Wang
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Michael D. Fayer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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7
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Hoffman DJ, Sokolowsky KP, Fayer MD. Direct observation of dynamic crossover in fragile molecular glass formers with 2D IR vibrational echo spectroscopy. J Chem Phys 2017; 146:124505. [DOI: 10.1063/1.4978852] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- David J. Hoffman
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | | | - Michael D. Fayer
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
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8
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Frechette L, Stratt RM. The inherent dynamics of isotropic- and nematic-phase liquid crystals. J Chem Phys 2017; 144:234505. [PMID: 27334177 DOI: 10.1063/1.4953618] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The geodesic (shortest) pathways through the potential energy landscape of a liquid can be thought of as defining what its dynamics would be if thermal noise were removed, revealing what we have called the "inherent dynamics" of the liquid. We show how these inherent paths can be located for a model liquid crystal former, showing, in the process, how the molecular mechanisms of translation and reorientation compare in the isotropic and nematic phases of these systems. These mechanisms turn out to favor the preservation of local orientational order even under macroscopically isotropic conditions (a finding consistent with the experimental observation of pseudonematic domains in these cases), but disfavor the maintenance of macroscopic orientational order, even in the nematic phase. While the most efficient nematic pathways that maintain nematic order are indeed shorter than those that do not, it is apparently difficult for the system to locate these paths, suggesting that molecular motion in liquid-crystal formers is dynamically frustrated, and reinforcing the sense that there are strong analogies between liquid crystals and supercooled liquids.
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Affiliation(s)
- Layne Frechette
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA
| | - Richard M Stratt
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA
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Kraack JP, Hamm P. Surface-Sensitive and Surface-Specific Ultrafast Two-Dimensional Vibrational Spectroscopy. Chem Rev 2016; 117:10623-10664. [DOI: 10.1021/acs.chemrev.6b00437] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Jan Philip Kraack
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Peter Hamm
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
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10
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Tamimi A, Bailey HE, Fayer MD. Alkyl Chain Length Dependence of the Dynamics and Structure in the Ionic Regions of Room-Temperature Ionic Liquids. J Phys Chem B 2016; 120:7488-501. [DOI: 10.1021/acs.jpcb.6b05397] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Amr Tamimi
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Heather E. Bailey
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Michael D. Fayer
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
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11
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Sokolowsky KP, Bailey HE, Hoffman DJ, Andersen HC, Fayer MD. Critical Slowing of Density Fluctuations Approaching the Isotropic–Nematic Transition in Liquid Crystals: 2D IR Measurements and Mode Coupling Theory. J Phys Chem B 2016; 120:7003-15. [DOI: 10.1021/acs.jpcb.6b04997] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Heather E. Bailey
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| | - David J. Hoffman
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Hans C. Andersen
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Michael D. Fayer
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
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12
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Giammanco CH, Kramer PL, Yamada SA, Nishida J, Tamimi A, Fayer MD. Carbon dioxide in an ionic liquid: Structural and rotational dynamics. J Chem Phys 2016; 144:104506. [DOI: 10.1063/1.4943390] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Chiara H. Giammanco
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Patrick L. Kramer
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Steven A. Yamada
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Jun Nishida
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Amr Tamimi
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Michael D. Fayer
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
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13
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Kramer PL, Nishida J, Fayer MD. Separation of experimental 2D IR frequency-frequency correlation functions into structural and reorientation-induced contributions. J Chem Phys 2015; 143:124505. [DOI: 10.1063/1.4931402] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Patrick L. Kramer
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Jun Nishida
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Michael D. Fayer
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
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14
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Kramer PL, Nishida J, Giammanco CH, Tamimi A, Fayer MD. Observation and theory of reorientation-induced spectral diffusion in polarization-selective 2D IR spectroscopy. J Chem Phys 2015; 142:184505. [DOI: 10.1063/1.4920949] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Patrick L. Kramer
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Jun Nishida
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Chiara H. Giammanco
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Amr Tamimi
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Michael D. Fayer
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
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