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Boralkar TT, Bapat DU, Dalvi VH, Rossky PJ. A Molecular Expression for "Line Tension". Langmuir 2024; 40:10544-10550. [PMID: 38699991 DOI: 10.1021/acs.langmuir.4c00179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2024]
Abstract
"Line tension", a concept that features in an additional term to the Young's equation, was introduced to describe the size dependence of contact angles of nanodroplets on surfaces. Although this concept describes the observations in a succinct, elegant manner, theorists have long had misgivings about the physical interpretation of the phenomenon. Papers have been published that attempt to nail down its value, which is reportedly very small (∼10 pN) and evidently even the sign has been uncertain. Attempts to interpret it in a mechanical manner analogous to interfacial tension, i.e., due to the curvature of the three-phase contact line, have run into conceptual problems that require invocations of ever more complex models. In this work, we have used molecular simulations to systematically relate "line tension" to the additional free energy per unit length of the three-phase line and found no direct relation. However, when we rederived the Young's equation without ignoring the interfacial molecules, we found a physically satisfying explanation for the size dependence of the contact angle of nanodroplets without invoking the curvature of the three-phase contact line. The new model does not have the elegant form of the modified Young's equation, but each parameter in it has an unambiguous physical interpretation. An approximate form of this model, linearized in the inverse droplet radius, yields a quantity that is mathematically analogous to what is conventionally called "line tension", but unpacked at the molecular level, showing that it is unrelated to a restoring force associated with the curvature of the macroscopic three-phase contact line.
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Affiliation(s)
- Tejas T Boralkar
- Department of Chemical Engineering, Institute of Chemical Technology, Mumbai 400019, Maharashtra, India
| | - Deepak U Bapat
- Department of Chemical Engineering, Institute of Chemical Technology, Mumbai 400019, Maharashtra, India
| | - Vishwanath H Dalvi
- Department of Chemical Engineering, Institute of Chemical Technology, Mumbai 400019, Maharashtra, India
| | - Peter J Rossky
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, United States
- Department of Chemistry, Rice University, Houston, Texas 77005, United States
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2
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Volek TS, Armstrong ZT, Sowa JK, Wilson KS, Bohlmann Kunz M, Bera K, Koble M, Frontiera RR, Rossky PJ, Zanni MT, Roberts ST. Structural Disorder at the Edges of Rubrene Crystals Enhances Singlet Fission. J Phys Chem Lett 2023; 14:11497-11505. [PMID: 38088867 DOI: 10.1021/acs.jpclett.3c02845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
Materials that undergo singlet fission are of interest for their use in light-harvesting, photocatalysis, and quantum information science, but their ability to undergo fission can be sensitive to local variations in molecular packing. Herein we employ transient absorption microscopy, molecular dynamics simulations, and electronic structure calculations to interrogate how structures found at the edges of orthorhombic rubrene crystals impact singlet fission. Within a micrometer-scale spatial region at the edges of rubrene crystals, we find that the rate of singlet fission increases nearly 4-fold. This observation is consistent with formation of a region at crystal edges with reduced order that accelerates singlet fission by disrupting the symmetry found in rubrene's orthorhombic crystal structure. Our work demonstrates that structural distortions of singlet fission materials can be used to control fission in time and in space, potentially offering a means of controlling this process in light harvesting and quantum information applications.
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Affiliation(s)
- Tanner S Volek
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
- Center for Adopting Flaws as Features, Urbana, Illinois 61801, United States
| | - Zachary T Armstrong
- Center for Adopting Flaws as Features, Urbana, Illinois 61801, United States
- Department of Chemistry, University of Wisconsin Madison, Madison, Wisconsin 53706, United States
| | - Jakub K Sowa
- Center for Adopting Flaws as Features, Urbana, Illinois 61801, United States
- Department of Chemistry, Rice University, Houston, Texas 77005, United States
| | - Kelly S Wilson
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
- Center for Adopting Flaws as Features, Urbana, Illinois 61801, United States
| | - Miriam Bohlmann Kunz
- Center for Adopting Flaws as Features, Urbana, Illinois 61801, United States
- Department of Chemistry, University of Wisconsin Madison, Madison, Wisconsin 53706, United States
| | - Kajari Bera
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - MaKenna Koble
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Renee R Frontiera
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Peter J Rossky
- Center for Adopting Flaws as Features, Urbana, Illinois 61801, United States
- Department of Chemistry, Rice University, Houston, Texas 77005, United States
| | - Martin T Zanni
- Center for Adopting Flaws as Features, Urbana, Illinois 61801, United States
- Department of Chemistry, University of Wisconsin Madison, Madison, Wisconsin 53706, United States
| | - Sean T Roberts
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
- Center for Adopting Flaws as Features, Urbana, Illinois 61801, United States
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3
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Sowa JK, Roberts ST, Rossky PJ. Exploring Configurations of Nanocrystal Ligands Using Machine-Learned Force Fields. J Phys Chem Lett 2023; 14:7215-7222. [PMID: 37552568 DOI: 10.1021/acs.jpclett.3c01618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/10/2023]
Abstract
Semiconducting nanocrystals passivated with organic ligands have emerged as a powerful platform for light harvesting, light-driven chemical reactions, and sensing. Due to their complexity and size, little structural information is available from experiments, making these systems challenging to model computationally. Here, we develop a machine-learned force field trained on DFT data and use it to investigate the surface chemistry of a PbS nanocrystal interfaced with acetate ligands. In doing so, we go beyond considering individual local minimum energy geometries and, importantly, circumvent a precarious issue associated with the assumption of a single assigned atomic partial charge for each element in a nanocrystal, independent of its structural position. We demonstrate that the carboxylate ligands passivate the metal-rich surfaces by adopting a very wide range of "tilted-bridge" and "bridge" geometries and investigate the corresponding ligand IR spectrum. This work illustrates the potential of machine-learned force fields to transform computational modeling of these materials.
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Affiliation(s)
- Jakub K Sowa
- Department of Chemistry, Rice University, Houston, Texas 77005, United States
- Center for Adapting Flaws into Features, Rice University, Houston, Texas 77005, United States
| | - Sean T Roberts
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
- Center for Adapting Flaws into Features, Rice University, Houston, Texas 77005, United States
| | - Peter J Rossky
- Department of Chemistry, Rice University, Houston, Texas 77005, United States
- Center for Adapting Flaws into Features, Rice University, Houston, Texas 77005, United States
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4
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Sowa JK, Allen TC, Rossky PJ. Accumulation and ordering of P3HT oligomers at the liquid-vapor interface with implications for thin-film morphology. Phys Chem Chem Phys 2023; 25:20808-20816. [PMID: 37493614 DOI: 10.1039/d3cp02718j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2023]
Abstract
The morphology of semiconducting polymer thin films is known to have a profound effect on their opto-electronic properties. Although considerable efforts have been made to control and understand the processes which influence the structures of these systems, it remains largely unclear what physical factors determine the arrangement of polymer chains in spin-cast films. Here, we investigate the role that the liquid-vapor interfaces in chlorobenzene solutions of poly(3-hexylthiophene) [P3HT] play in the conformational geometries adopted by the polymers. Using all-atom molecular dynamics (MD), and supported by toy-model simulations, we demonstrate that, with increasing concentration, P3HT oligomers in solution exhibit a strong propensity for the liquid-vapor interface. Due to the differential solubility of the backbone and side chains of the oligomers, in the vicinity of this interface, hexyl chains and the thiophene rings, have a clear orientational preference with respect to the liquid surface. At high concentrations, we additionally establish a substantial degree of inter-oligomer alignment and thiophene ring stacking near the interface. Our results broadly concur with the limited existing experimental evidence and we suggest that the interfacial structure can act as a template for film structure. We argue that the differences in solvent affinity of the side chain and backbone moieties are the driving force for the anisotropic orientations of the polymers near the interface. This finer grained description contrasts with the usual monolithic characterization of polymer units. Since this phenomenon can be controlled by concurrent chemical design and the choice of solvents, this work establishes a fabrication principle which may be useful to develop more highly functional polymer films.
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Affiliation(s)
- Jakub K Sowa
- Department of Chemistry, Rice University, Houston, TX 77005, USA.
| | - Thomas C Allen
- Department of Chemistry, Rice University, Houston, TX 77005, USA.
| | - Peter J Rossky
- Department of Chemistry, Rice University, Houston, TX 77005, USA.
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5
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Fan D, Bajgiran SR, Samghabadi FS, Dutta C, Gillett E, Rossky PJ, Conrad JC, Marciel AB, Landes CF. Imaging Heterogeneous 3D Dynamics of Individual Solutes in a Polyelectrolyte Brush. Langmuir 2023. [PMID: 37290000 DOI: 10.1021/acs.langmuir.3c00868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Understanding molecular transport in polyelectrolyte brushes (PEBs) is crucial for applications such as separations, drug delivery, anti-fouling, and biosensors, where structural features of the polymer control intermolecular interactions. The complex structure and local heterogeneity of PEBs, while theoretically predicted, are not easily accessed with conventional experimental methods. In this work, we use 3D single-molecule tracking to understand transport behavior within a cationic poly(2-(N,N-dimethylamino)ethyl acrylate) (PDMAEA) brush using an anionic dye, Alexa Fluor 546, as the probe. The analysis is done by a parallelized, unbiased 3D tracking algorithm. Our results explicitly demonstrate that spatial heterogeneity within the brush manifests as heterogeneity of single-molecule displacements. Two distinct populations of probe motion are identified, with anticorrelated axial and lateral transport confinement, which we believe to correspond to intra- vs inter-chain probe motion.
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Affiliation(s)
- Dongyu Fan
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, United States
| | - Shahryar Ramezani Bajgiran
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, United States
| | - Farshad Safi Samghabadi
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Chayan Dutta
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States
| | - Emil Gillett
- Department of Chemistry, Rice University, Houston, Texas 77005, United States
| | - Peter J Rossky
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, United States
- Department of Chemistry, Rice University, Houston, Texas 77005, United States
- Smalley Curl Institute, Rice University, Houston, Texas 77005, United States
| | - Jacinta C Conrad
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Amanda B Marciel
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, United States
| | - Christy F Landes
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, United States
- Department of Chemistry, Rice University, Houston, Texas 77005, United States
- Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77005, United States
- Smalley Curl Institute, Rice University, Houston, Texas 77005, United States
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6
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Cadena DM, Sowa JK, Cotton DE, Wight CD, Hoffman CL, Wagner HR, Boette JT, Raulerson EK, Iverson BL, Rossky PJ, Roberts ST. Aggregation of Charge Acceptors on Nanocrystal Surfaces Alters Rates of Photoinduced Electron Transfer. J Am Chem Soc 2022; 144:22676-22688. [PMID: 36450151 DOI: 10.1021/jacs.2c09758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Semiconductor nanocrystals (NCs) interfaced with molecular ligands that function as charge and energy acceptors are an emerging platform for the design of light-harvesting, photon-upconverting, and photocatalytic materials. However, NC systems explored for these applications often feature high concentrations of bound acceptor ligands, which can lead to ligand-ligand interactions that may alter each system's ability to undergo charge and energy transfer. Here, we demonstrate that aggregation of acceptor ligands impacts the rate of photoinduced NC-to-ligand charge transfer between lead(II) sulfide (PbS) NCs and perylenediimide (PDI) electron acceptors. As the concentration of PDI acceptors is increased, we find the average electron transfer rate from PbS to PDI ligands decreases by nearly an order of magnitude. The electron transfer rate slowdown with increasing PDI concentration correlates strongly with the appearance of PDI aggregates in steady-state absorption spectra. Electronic structure calculations and molecular dynamics (MD) simulations suggest PDI aggregation slows the rate of electron transfer by reducing orbital overlap between PbS charge donors and PDI charge acceptors. While we find aggregation slows electron transfer in this system, the computational models we employ predict ligand aggregation could also be used to speed electron transfer by producing delocalized states that exhibit improved NC-molecule electronic coupling and energy alignment with NC conduction band states. Our results demonstrate that ligand aggregation can alter rates of photoinduced electron transfer between NCs and organic acceptor ligands and should be considered when designing hybrid NC:molecule systems for charge separation.
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Affiliation(s)
- Danielle M Cadena
- Department of Chemistry, The University of Texas at Austin, Austin, Texas78712, United States.,Center for Adapting Flaws into Features, Rice University, Houston, Texas77251, United States
| | - Jakub K Sowa
- Center for Adapting Flaws into Features, Rice University, Houston, Texas77251, United States.,Department of Chemistry, Rice University, Houston, Texas77251, United States
| | - Daniel E Cotton
- Department of Chemistry, The University of Texas at Austin, Austin, Texas78712, United States
| | - Christopher D Wight
- Department of Chemistry, The University of Texas at Austin, Austin, Texas78712, United States
| | - Cole L Hoffman
- Department of Chemistry, The University of Texas at Austin, Austin, Texas78712, United States
| | - Holden R Wagner
- Department of Chemistry, The University of Texas at Austin, Austin, Texas78712, United States
| | - Jessica T Boette
- Department of Chemistry, The University of Texas at Austin, Austin, Texas78712, United States
| | - Emily K Raulerson
- Department of Chemistry, The University of Texas at Austin, Austin, Texas78712, United States
| | - Brent L Iverson
- Department of Chemistry, The University of Texas at Austin, Austin, Texas78712, United States
| | - Peter J Rossky
- Center for Adapting Flaws into Features, Rice University, Houston, Texas77251, United States.,Department of Chemistry, Rice University, Houston, Texas77251, United States
| | - Sean T Roberts
- Department of Chemistry, The University of Texas at Austin, Austin, Texas78712, United States.,Center for Adapting Flaws into Features, Rice University, Houston, Texas77251, United States
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7
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Gao J, Rossky PJ. The Age of Direct Chemical Dynamics. Acc Chem Res 2022; 55:471-472. [PMID: 35164506 DOI: 10.1021/acs.accounts.2c00021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jiali Gao
- Shenzhen Bay Laboratory
- University of Minnesota
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8
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Misiura A, Shen H, Tauzin L, Dutta C, Bishop LDC, Carrejo NC, Zepeda O J, Ramezani S, Moringo NA, Marciel AB, Rossky PJ, Landes CF. Single-Molecule Dynamics Reflect IgG Conformational Changes Associated with Ion-Exchange Chromatography. Anal Chem 2021; 93:11200-11207. [PMID: 34346671 DOI: 10.1021/acs.analchem.1c01799] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Conformational changes of antibodies and other biologics can decrease the effectiveness of pharmaceutical separations. Hence, a detailed mechanistic picture of antibody-stationary phase interactions that occur during ion-exchange chromatography (IEX) can provide critical insights. This work examines antibody conformational changes and how they perturb antibody motion and affect ensemble elution profiles. We combine IEX, three-dimensional single-protein tracking, and circular dichroism spectroscopy to investigate conformational changes of a model antibody, immunoglobulin G (IgG), as it interacts with the stationary phase as a function of salt conditions. The results indicate that the absence of salt enhances electrostatic attraction between IgG and the stationary phase, promotes surface-induced unfolding, slows IgG motion, and decreases elution from the column. Our results reveal previously unreported details of antibody structural changes and their influence on macroscale elution profiles.
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Affiliation(s)
- Anastasiia Misiura
- Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, United States
| | - Hao Shen
- Department of Chemistry and Biochemistry, Kent State University, 800 E Summit Street, Kent, Ohio 44240, United States
| | - Lawrence Tauzin
- Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, United States
| | - Chayan Dutta
- Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, United States
| | - Logan D C Bishop
- Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, United States
| | - Nicole C Carrejo
- Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, United States
| | - Jorge Zepeda O
- Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, Texas 77005, United States
| | - Shahryar Ramezani
- Chemical and Biomolecular Engineering, Rice University, 6100 Main Street, Houston, Texas 77005, United States
| | - Nicholas A Moringo
- Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, United States
| | - Amanda B Marciel
- Chemical and Biomolecular Engineering, Rice University, 6100 Main Street, Houston, Texas 77005, United States
| | - Peter J Rossky
- Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, United States.,Chemical and Biomolecular Engineering, Rice University, 6100 Main Street, Houston, Texas 77005, United States.,Smalley-Curl Institute, Rice University, 6100 Main Street, Houston, Texas 77005, United States
| | - Christy F Landes
- Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, United States.,Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, Texas 77005, United States.,Chemical and Biomolecular Engineering, Rice University, 6100 Main Street, Houston, Texas 77005, United States.,Smalley-Curl Institute, Rice University, 6100 Main Street, Houston, Texas 77005, United States
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9
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Rossky PJ. An Autobiographical History of Peter J. Rossky. J Phys Chem B 2020; 124:10594-10597. [DOI: 10.1021/acs.jpcb.0c09811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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10
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Affiliation(s)
- Pablo E. Videla
- Departamento de Química Inorgánica Analítica y Química-Física e INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina
| | - Peter J. Rossky
- Department of Chemistry, Rice University, Houston, Texas 77251-1892, USA
| | - D. Laria
- Departamento de Química Inorgánica Analítica y Química-Física e INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina
- Departamento de Física de la Materia Condensada, Comisión Nacional de Energía Atómica, Avenida Libertador 8250, 1429 Buenos Aires, Argentina
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11
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Raithel D, Simine L, Pickel S, Schötz K, Panzer F, Baderschneider S, Schiefer D, Lohwasser R, Köhler J, Thelakkat M, Sommer M, Köhler A, Rossky PJ, Hildner R. Direct observation of backbone planarization via side-chain alignment in single bulky-substituted polythiophenes. Proc Natl Acad Sci U S A 2018; 115:2699-2704. [PMID: 29483262 PMCID: PMC5856543 DOI: 10.1073/pnas.1719303115] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The backbone conformation of conjugated polymers affects, to a large extent, their optical and electronic properties. The usually flexible substituents provide solubility and influence the packing behavior of conjugated polymers in films or in bad solvents. However, the role of the side chains in determining and potentially controlling the backbone conformation, and thus the optical and electronic properties on the single polymer level, is currently under debate. Here, we investigate directly the impact of the side chains by studying the bulky-substituted poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT) and the common poly(3-hexylthiophene) (P3HT), both with a defined molecular weight and high regioregularity, using low-temperature single-chain photoluminescence (PL) spectroscopy and quantum-classical simulations. Surprisingly, the optical transition energy of PDOPT is significantly (∼2,000 cm-1 or 0.25 eV) red-shifted relative to P3HT despite a higher static and dynamic disorder in the former. We ascribe this red shift to a side-chain induced backbone planarization in PDOPT, supported by temperature-dependent ensemble PL spectroscopy. Our atomistic simulations reveal that the bulkier 2,5-dioctylphenyl side chains of PDOPT adopt a clear secondary helical structural motif and thus protect conjugation, i.e., enforce backbone planarity, whereas, for P3HT, this is not the case. These different degrees of planarity in both thiophenes do not result in different conjugation lengths, which we found to be similar. It is rather the stronger electronic coupling between the repeating units in the more planar PDOPT which gives rise to the observed spectral red shift as well as to a reduced calculated electron-hole polarization.
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Affiliation(s)
- Dominic Raithel
- Experimental Physics IV, University of Bayreuth, 95440 Bayreuth, Germany
| | - Lena Simine
- Department of Chemistry, Rice University, Houston, TX 77005
| | - Sebastian Pickel
- Experimental Physics IV, University of Bayreuth, 95440 Bayreuth, Germany
| | - Konstantin Schötz
- Experimental Physics II, University of Bayreuth, 95440 Bayreuth, Germany
| | - Fabian Panzer
- Experimental Physics II, University of Bayreuth, 95440 Bayreuth, Germany
| | | | - Daniel Schiefer
- Institute of Macromolecular Chemistry, University of Freiburg, 79104 Freiburg, Germany
| | - Ruth Lohwasser
- Applied Functional Polymers, University of Bayreuth, 95440 Bayreuth, Germany
| | - Jürgen Köhler
- Experimental Physics IV, University of Bayreuth, 95440 Bayreuth, Germany
- Bayreuth Institute of Macromolecular Research, University of Bayreuth, 95440 Bayreuth, Germany
| | - Mukundan Thelakkat
- Applied Functional Polymers, University of Bayreuth, 95440 Bayreuth, Germany
| | - Michael Sommer
- Institute of Macromolecular Chemistry, University of Freiburg, 79104 Freiburg, Germany
| | - Anna Köhler
- Experimental Physics II, University of Bayreuth, 95440 Bayreuth, Germany
- Bayreuth Institute of Macromolecular Research, University of Bayreuth, 95440 Bayreuth, Germany
| | - Peter J Rossky
- Department of Chemistry, Rice University, Houston, TX 77005
| | - Richard Hildner
- Experimental Physics IV, University of Bayreuth, 95440 Bayreuth, Germany;
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12
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Videla PE, Rossky PJ, Laria D. Isotopic equilibria in aqueous clusters at low temperatures: Insights from the MB-pol many-body potential. J Chem Phys 2018; 148:084303. [DOI: 10.1063/1.5019377] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Affiliation(s)
- Pablo E. Videla
- Departamento de Química Inorgánica Analítica y Química-Física e INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina
| | - Peter J. Rossky
- Department of Chemistry, Rice University, Houston, Texas 77005-1892, USA
| | - Daniel Laria
- Departamento de Química Inorgánica Analítica y Química-Física e INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina
- Departamento de Física de la Materia Condensada, Comisión Nacional de Energía Atómica, Avenida Libertador 8250, 1429 Buenos Aires, Argentina
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13
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Simine L, Lammert H, Sun L, Onuchic JN, Rossky PJ. Fluorescent Proteins Detect Host Structural Rearrangements via Electrostatic Mechanism. J Am Chem Soc 2018; 140:1203-1206. [PMID: 29328673 DOI: 10.1021/jacs.7b10851] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The rational design of genetically encoded fluorescent biosensors, which can detect rearrangements of target proteins via interdomain allostery, is hindered by the absence of mechanistic understanding of the underlying photophysics. Here, we focus on the modulation of fluorescence by mechanical perturbation in a popular biological probe: enhanced Green Fluorescent Protein (eGFP). Using a combination of molecular dynamics (MD) simulations and quantum chemistry, and a set of physically motivated assumptions, we construct a map of fluorescence quantum yield as a function of a 2D electric field imposed by the protein environment on the fluorophore. This map is transferable between Tsien's Class 2 GFP's, and it allows one to estimate the shifts in fluorescence intensity due to mechanical perturbations directly from MD simulations. We use it in combination with steered MD simulations to put forward a hypothesis for the mechanism of a genetically encoded voltage probe (ArcLight) whose mechanism is currently under debate.
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Affiliation(s)
- Lena Simine
- Departments of Chemistry, and ‡Physics, and §the Center for Theoretical Biological Physics, Rice University , Houston, Texas 77030, United States
| | - Heiko Lammert
- Departments of Chemistry, and ‡Physics, and §the Center for Theoretical Biological Physics, Rice University , Houston, Texas 77030, United States
| | - Li Sun
- Departments of Chemistry, and ‡Physics, and §the Center for Theoretical Biological Physics, Rice University , Houston, Texas 77030, United States
| | - José N Onuchic
- Departments of Chemistry, and ‡Physics, and §the Center for Theoretical Biological Physics, Rice University , Houston, Texas 77030, United States
| | - Peter J Rossky
- Departments of Chemistry, and ‡Physics, and §the Center for Theoretical Biological Physics, Rice University , Houston, Texas 77030, United States
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14
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Abstract
An ongoing controversy about water cluster anions concerns the electron-binding motif, whether the charge center is localized at the surface or within the cluster interior. Here, mixed quantum-classical dynamics simulations have been carried out for a wide range of cluster sizes (n ≤ 1000) for (H2O)n- and (D2O)n-, based on a nonequilibrium first-order rate constant approach. The computed data are in good general agreement with time-resolved photoelectron imaging results (n ≤ 200). The analysis reveals that, for surface state electrons, the cluster size dependence of the excited state electronic energy gap and the magnitude of the nonadiabatic couplings have compensating influences on the excited state lifetimes: the excited state lifetime for surface states reaches a minimum for n ∼ 150 and then increases for larger clusters. It is concluded that the electron resides in a surface-localized motif in all of these measured clusters, dominating at least up to n = 200.
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Affiliation(s)
- Daniel Borgis
- Pôle de Chimie Théorique, UMR-CNRS PASTEUR, Ecole Normale Supérieure, 24, rue Lhomond, 75231 Paris Cedex 05, France
| | - Peter J Rossky
- Department of Chemistry, Rice University , P.O. Box 1892, MS-60, Houston, Texas 77251-1892, United States
| | - László Turi
- Department of Physical Chemistry, ELTE Eötvös Loránd University , Budapest 112, P.O. Box 32, H-1518 Budapest, Hungary
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15
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Abstract
The optoelectronic properties of amorphous conjugated polymers are sensitive to the details of the conformational disorder, and spectroscopy provides the means for structural characterization of the fragments of the chain that interact with light-"chromophores". A faithful interpretation of spectroscopic conformational signatures, however, presents a theoretical challenge. Here we investigate the relationship between the ground-state optical gaps, the properties of the excited states, and the structural features of chromophores of a single molecule poly(3-hexyl)-thiophene (P3HT) using quantum-classical atomistic simulations. Our results demonstrate that chromophoric disorder arises through the interplay between excited-state delocalization and electron-hole polarization, controlled by the torsional disorder introduced by side chains. Within this conceptual framework, we predict and explain the counterintuitive spectral behavior of P3HT, a red-shifted absorption, despite shortening of chromophores, with increasing temperature. This discussion introduces the concept of disorder-induced separation of charges in amorphous conjugated polymers.
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Affiliation(s)
- Lena Simine
- Department of Chemistry, Rice University , Houston, Texas 77005, United States
| | - Peter J Rossky
- Department of Chemistry, Rice University , Houston, Texas 77005, United States
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16
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Affiliation(s)
- Pablo E. Videla
- Departamento de Química Inorgánica Analítica y Química-Física e INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina
| | - Peter J. Rossky
- Department of Chemistry, Rice University, Houston, Texas 77251-1892, USA
| | - D. Laria
- Departamento de Química Inorgánica Analítica y Química-Física e INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina
- Departamento de Física de la Materia Condensada, Comisión Nacional de Energía Atómica, Avenida Libertador 8250, 1429 Buenos Aires, Argentina
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17
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Hu Z, Willard AP, Ono RJ, Bielawski CW, Rossky PJ, Vanden Bout DA. An insight into non-emissive excited states in conjugated polymers. Nat Commun 2015; 6:8246. [PMID: 26391514 PMCID: PMC4595598 DOI: 10.1038/ncomms9246] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2014] [Accepted: 08/03/2015] [Indexed: 11/25/2022] Open
Abstract
Conjugated polymers in the solid state usually exhibit low fluorescence quantum yields, which limit their applications in many areas such as light-emitting diodes. Despite considerable research efforts, the underlying mechanism still remains controversial and elusive. Here, the nature and properties of excited states in the archetypal polythiophene are investigated via aggregates suspended in solvents with different dielectric constants (ɛ). In relatively polar solvents (ɛ>∼ 3), the aggregates exhibit a low fluorescence quantum yield (QY) of 2–5%, similar to bulk films, however, in relatively nonpolar solvents (ɛ<∼ 3) they demonstrate much higher fluorescence QY up to 20–30%. A series of mixed quantum-classical atomistic simulations illustrate that dielectric induced stabilization of nonradiative charge-transfer (CT) type states can lead to similar drastic reduction in fluorescence QY as seen experimentally. Fluorescence lifetime measurement reveals that the CT-type states exist as a competitive channel of the formation of emissive exciton-type states. Conjugated polymers in thin films exhibit low fluorescence quantum yields, but the mechanism is still unclear. Here, Hu et al. show the trade-off between charge transfer and emissive exciton states, whilst the former can be suppressed via dielectric-induced stabilization for large fluorescence quantum yields.
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Affiliation(s)
- Zhongjian Hu
- Center for Nano- and Molecular Science and Technology, Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
| | - Adam P Willard
- Center for Nano- and Molecular Science and Technology, Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
| | - Robert J Ono
- Center for Nano- and Molecular Science and Technology, Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
| | - Christopher W Bielawski
- Center for Nano- and Molecular Science and Technology, Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
| | - Peter J Rossky
- Center for Nano- and Molecular Science and Technology, Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
| | - David A Vanden Bout
- Center for Nano- and Molecular Science and Technology, Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
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18
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Wang C, Angelella M, Doyle SJ, Lytwak LA, Rossky PJ, Holliday BJ, Tauber MJ. Resonance Raman Spectroscopy of the T1 Triplet Excited State of Oligothiophenes. J Phys Chem Lett 2015; 6:3521-3527. [PMID: 26291623 DOI: 10.1021/acs.jpclett.5b01410] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The characterization of triplet excited states is essential for research on organic photovoltaics and singlet fission. We report resonance Raman spectra of two triplet oligothiophenes with n-alkyl substituents, a tetramer and hexamer. The spectra of the triplets are more complex than the ground state, and we find that density functional theory calculations are a useful starting point for characterizing the bands. The spectra of triplet tetrathiophene and hexathiophene differ significantly from one another. This observation is consistent with a T1 excitation that is delocalized over at least five rings in long oligomers. Bands in the 500-800 cm(-1) region are greatly diminished for an aggregated sample of hexathiophene, likely caused by fast electronic dephasing. These experiments highlight the potential of resonance Raman spectroscopy to unequivocally detect and characterize triplets in thiophene materials. The vibrational spectra can also serve as rigorous standards for evaluating computational methods for excited-state molecules.
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Affiliation(s)
- Chen Wang
- Department of Chemistry & Biochemistry, University of California at San Diego , La Jolla, California 92093, United States
| | - Maria Angelella
- Department of Chemistry & Biochemistry, University of California at San Diego , La Jolla, California 92093, United States
| | - Samantha J Doyle
- Department of Chemistry & Biochemistry, University of California at San Diego , La Jolla, California 92093, United States
| | - Lauren A Lytwak
- Department of Chemistry, The University of Texas at Austin , Austin, Texas 78712, United States
| | - Peter J Rossky
- Department of Chemistry, Rice University , Houston, Texas 77251, United States
| | - Bradley J Holliday
- Department of Chemistry, The University of Texas at Austin , Austin, Texas 78712, United States
| | - Michael J Tauber
- Department of Chemistry & Biochemistry, University of California at San Diego , La Jolla, California 92093, United States
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19
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Affiliation(s)
- Pablo E. Videla
- Departamento
de Química Inorgánica Analítica y Química-Física
e INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina
| | - Peter J. Rossky
- Department
of Chemistry, Rice University, Houston, Texas 77005-1892, United States
| | - Daniel Laria
- Departamento
de Química Inorgánica Analítica y Química-Física
e INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina
- Departamento
de Física de la Materia Condensada, Comisión Nacional de Energía Atómica, Avenida Libertador 8250, 1429 Buenos Aires, Argentina
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20
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Worley BC, Kim S, Park S, Rossky PJ, Akinwande D, Dodabalapur A. Dramatic vapor-phase modulation of the characteristics of graphene field-effect transistors. Phys Chem Chem Phys 2015; 17:18426-30. [PMID: 26107384 DOI: 10.1039/c5cp01888a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Here we report on dramatic and favorable changes to the operating characteristics in monolayer graphene field-effect transistors (FETs) exposed to vapor-phase, polar organic molecules in ambient. These changes include significant reduction of the Dirac voltage, accompanied by both an increase in electron and hole mobility, μ, and a decrease in residual carrier density, N0, to < 3 × 10(11) cm(-2). In contrast to graphene FET modulation with various liquid- and solid-phase dielectric media present in the literature, we attribute these changes to screening by polar vapor-phase molecules of fields induced by charged impurities and defects, n(imp), in or near the active layer. The magnitude of the changes produced in the graphene FET parameters scales remarkably well with the dipole moment of the delivered molecules. These effects are reversible, a unique advantage of working in the vapor phase. The changes observed upon polar molecule delivery are analogous to those produced by depositing and annealing fluoropolymer coatings on graphene that have been reported previously, and we attribute these changes to similar charge screening or neutralization phenomena.
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Affiliation(s)
- Barrett C Worley
- Microelectronics Research Center, The University of Texas at Austin, Austin, TX 78758, USA
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21
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Smith KKG, Poulsen JA, Nyman G, Cunsolo A, Rossky PJ. Application of a new ensemble conserving quantum dynamics simulation algorithm to liquid para-hydrogen and ortho-deuterium. J Chem Phys 2015; 142:244113. [DOI: 10.1063/1.4922888] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Kyle K. G. Smith
- Institute for Computational Engineering and Sciences and Department of Chemistry,University of Texas at Austin, Austin, Texas 78712, USA
| | - Jens Aage Poulsen
- Physical Chemistry, Department of Chemistry and Molecular Biology, University of Gothenburg, SE 41296 Gothenburg, Sweden
| | - Gunnar Nyman
- Physical Chemistry, Department of Chemistry and Molecular Biology, University of Gothenburg, SE 41296 Gothenburg, Sweden
| | - Alessandro Cunsolo
- Photon Sciences Directorate, Brookhaven National Laboratory, P.O. Box 5000, Upton, New York 11973, USA
| | - Peter J. Rossky
- Department of Chemistry, Rice University, Houston, Texas 77251, USA
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22
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Smith KKG, Poulsen JA, Nyman G, Rossky PJ. A new class of ensemble conserving algorithms for approximate quantum dynamics: Theoretical formulation and model problems. J Chem Phys 2015; 142:244112. [DOI: 10.1063/1.4922887] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Kyle K. G. Smith
- Institute for Computational Engineering and Sciences and Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA
| | - Jens Aage Poulsen
- Physical Chemistry, Department of Chemistry and Molecular Biology, University of Gothenburg, SE 41296 Gothenburg, Sweden
| | - Gunnar Nyman
- Physical Chemistry, Department of Chemistry and Molecular Biology, University of Gothenburg, SE 41296 Gothenburg, Sweden
| | - Peter J. Rossky
- Department of Chemistry, Rice University, Houston, Texas 77251, USA
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23
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Omar AK, Hanson B, Haws RT, Hu Z, Vanden Bout DA, Rossky PJ, Ganesan V. Aggregation behavior of rod-coil-rod triblock copolymers in a coil-selective solvent. J Phys Chem B 2014; 119:330-7. [PMID: 25513935 DOI: 10.1021/jp509016c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Recent experiments have reported that the self-assembly of conjugated polymers mimicking rod-coil-rod triblock copolymers (BCPs) in selective solvents exhibits unique aggregate morphologies. However, the nature of the arrangement of the polymers within the aggregates and the spatial organization of the aggregates remain an unresolved issue. We report the results of coarse-grained Langevin dynamics simulations, which investigated the self-assembly behavior of rod-coil-rod BCPs in a coil-selective solvent. We observe a rapid formation of cylindrically shaped multichain clusters. The initial stages of formation of the aggregates was seen to be independent of the strength of the solvent selectivity. However, for higher solvent selectivities, the clusters were seen to merge into larger units at later stages. A reduction in rod to coil block ratio was observed to decrease the size and number of clusters. In the limit of a highly concentrated solution, we observe the formation of a networked system of distinct clusters, which however retain the cylindrical arrangement observed at lower polymer concentrations.
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Affiliation(s)
- Ahmad K Omar
- Department of Chemical Engineering and ‡Department of Chemistry, University of Texas at Austin , Austin, Texas 78712, United States
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24
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Hu Z, Adachi T, Haws R, Shuang B, Ono RJ, Bielawski CW, Landes CF, Rossky PJ, Vanden Bout DA. Excitonic Energy Migration in Conjugated Polymers: The Critical Role of Interchain Morphology. J Am Chem Soc 2014; 136:16023-31. [DOI: 10.1021/ja508112k] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Zhongjian Hu
- Center
for Nano and Molecular Science and Technology, Department of Chemistry, University of Texas, Austin, Texas 78712, United States
| | - Takuji Adachi
- Center
for Nano and Molecular Science and Technology, Department of Chemistry, University of Texas, Austin, Texas 78712, United States
| | - Ryan Haws
- Center
for Nano and Molecular Science and Technology, Department of Chemistry, University of Texas, Austin, Texas 78712, United States
| | - Bo Shuang
- Department
of Chemistry, Rice University, Houston, Texas 77251, United States
| | - Robert J. Ono
- Center
for Nano and Molecular Science and Technology, Department of Chemistry, University of Texas, Austin, Texas 78712, United States
| | - Christopher W. Bielawski
- Center
for Nano and Molecular Science and Technology, Department of Chemistry, University of Texas, Austin, Texas 78712, United States
| | - Christy F. Landes
- Department
of Chemistry, Rice University, Houston, Texas 77251, United States
| | - Peter J. Rossky
- Center
for Nano and Molecular Science and Technology, Department of Chemistry, University of Texas, Austin, Texas 78712, United States
| | - David A. Vanden Bout
- Center
for Nano and Molecular Science and Technology, Department of Chemistry, University of Texas, Austin, Texas 78712, United States
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25
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Abstract
Using ring polymer molecular dynamics simulations, we examine equilibrium and dynamical characteristics of solid-like, aqueous clusters that combine isotopic mixtures of HDO dilute in H2O, at temperatures intermediate between 50 and 175 K. In particular, we focus attention on the relative thermodynamic stabilities of the two isotopes at dangling hydrogen bond sites. The water octamer is analyzed as a reference system. For this aggregate, decreasing temperature yields a gradual stabilization of the light isotope at dangling sites in molecules acting as single-donor-double-acceptors of hydrogen bonds. At T ∼ 50 K, the imbalance between the corresponding quantum kinetic energies leads to a free energy difference between dangling and hydrogen bonded sites of the order of ∼2kBT. Similar free energy differences were found at dangling sites in Nw = 50 water clusters. The extent of the H/D segregation can be adequately monitored by modifications in the peak intensity of the high frequency shoulder of the stretching band of the infrared spectrum. These signals, in turn, represent a potential experimental signature of the elusive temperature of clusters in molecular beams.
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Affiliation(s)
- Pablo E Videla
- †Departamento de Química Inorgánica Analítica y Química-Física e INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina
| | - Peter J Rossky
- ‡Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712-0165, United States
| | - Daniel Laria
- †Departamento de Química Inorgánica Analítica y Química-Física e INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina
- §Departamento de Física de la Materia Condensada, Comisión Nacional de Energía Atómica, Avenida Libertador 8250, 1429 Buenos Aires, Argentina
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26
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Smith KKG, Poulsen JA, Cunsolo A, Rossky PJ. Refinement of the experimental dynamic structure factor for liquid para-hydrogen and ortho-deuterium using semi-classical quantum simulation. J Chem Phys 2014; 140:034501. [DOI: 10.1063/1.4851997] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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27
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28
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Hu Z, Adachi T, Lee YG, Haws RT, Hanson B, Ono RJ, Bielawski CW, Ganesan V, Rossky PJ, Vanden Bout DA. Effect of the side-chain-distribution density on the single-conjugated-polymer-chain conformation. Chemphyschem 2013; 14:4143-8. [PMID: 24243782 DOI: 10.1002/cphc.201300751] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 10/18/2013] [Indexed: 11/09/2022]
Abstract
The spatial arrangement of the side chains of conjugated polymer backbones has critical effects on the morphology and electronic and photophysical properties of the corresponding bulk films. The effect of the side-chain-distribution density on the conformation at the isolated single-polymer-chain level was investigated with regiorandom (rra-) poly(3-hexylthiophene) (P3HT) and poly(3-hexyl-2,5-thienylene vinylene) (P3HTV). Although pure P3HTV films are known to have low fluorescence quantum efficiencies, we observed a considerable increase in fluorescence intensity by dispersing P3HTV in poly(methyl methacrylate) (PMMA), which enabled a single-molecule spectroscopy investigation. With single-molecule fluorescence excitation polarization spectroscopy, we found that rra-P3HTV single molecules form highly ordered conformations. In contrast, rra-P3HT single molecules, display a wide variety of different conformations from isotropic to highly ordered, were observed. The experimental results are supported by extensive molecular dynamics simulations, which reveal that the reduced side-chain-distribution density, that is, the spaced-out side-chain substitution pattern, in rra-P3HTV favors more ordered conformations compared to rra-P3HT. Our results demonstrate that the distribution of side chains strongly affects the polymer-chain conformation, even at the single-molecule level, an aspect that has important implications when interpreting the macroscopic interchain packing structure exhibited by bulk polymer films.
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Affiliation(s)
- Zhongjian Hu
- Department of Chemistry and Biochemistry, University of Texas at Austin, 1 University Station A5300, Austin TX, 78712 (USA)
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29
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Videla PE, Rossky PJ, Laria D. Nuclear quantum effects on the structure and the dynamics of [H2O]8 at low temperatures. J Chem Phys 2013; 139:174315. [DOI: 10.1063/1.4827935] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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30
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31
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Kapcha LH, Rossky PJ. A simple atomic-level hydrophobicity scale reveals protein interfacial structure. J Mol Biol 2013; 426:484-98. [PMID: 24120937 DOI: 10.1016/j.jmb.2013.09.039] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Accepted: 09/27/2013] [Indexed: 10/26/2022]
Abstract
Many amino acid residue hydrophobicity scales have been created in an effort to better understand and rapidly characterize water-protein interactions based only on protein structure and sequence. There is surprisingly low consistency in the ranking of residue hydrophobicity between scales, and their ability to provide insightful characterization varies substantially across subject proteins. All current scales characterize hydrophobicity based on entire amino acid residue units. We introduce a simple binary but atomic-level hydrophobicity scale that allows for the classification of polar and non-polar moieties within single residues, including backbone atoms. This simple scale is first shown to capture the anticipated hydrophobic character for those whole residues that align in classification among most scales. Examination of a set of protein binding interfaces establishes good agreement between residue-based and atomic-level descriptions of hydrophobicity for five residues, while the remaining residues produce discrepancies. We then show that the atomistic scale properly classifies the hydrophobicity of functionally important regions where residue-based scales fail. To illustrate the utility of the new approach, we show that the atomic-level scale rationalizes the hydration of two hydrophobic pockets and the presence of a void in a third pocket within a single protein and that it appropriately classifies all of the functionally important hydrophilic sites within two otherwise hydrophobic pores. We suggest that an atomic level of detail is, in general, necessary for the reliable depiction of hydrophobicity for all protein surfaces. The present formulation can be implemented simply in a manner no more complex than current residue-based approaches.
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Affiliation(s)
- Lauren H Kapcha
- Department of Chemistry and Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin, TX 78712-1167, USA
| | - Peter J Rossky
- Department of Chemistry and Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin, TX 78712-1167, USA.
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32
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Dowdle JR, Buldyrev SV, Stanley HE, Debenedetti PG, Rossky PJ. Temperature and length scale dependence of solvophobic solvation in a single-site water-like liquid. J Chem Phys 2013; 138:064506. [DOI: 10.1063/1.4789981] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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33
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Ha TJ, Lee J, Chowdhury SF, Akinwande D, Rossky PJ, Dodabalapur A. Transformation of the electrical characteristics of graphene field-effect transistors with fluoropolymer. ACS Appl Mater Interfaces 2013; 5:16-20. [PMID: 23252452 DOI: 10.1021/am3025323] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report on the improvement of the electronic characteristics of monolayer graphene field-effect transistors (FETs) by an interacting capping layer of a suitable fluoropolymer. Capping of monolayer graphene FETs with CYTOP improved the on-off current ratio from 5 to 10 as well as increased the field-effect mobility by as much as a factor of 2 compared to plain graphene FETs. Favorable shifts in the Dirac voltage toward zero with shift magnitudes in excess of 60 V are observed. The residual carrier concentration is reduced to ~2.8 × 10(11) cm(-2). Removal of the fluoropolymer from graphene FETs results in a return to the initial electronic properties before depositing CYTOP. This suggests that weak, reversible electronic perturbation of graphene by the fluoropolymer favorably tune the electrical characteristics of graphene, and we hypothesize that the origin of this improvement is in the strongly polar nature of the C-F chemical bonds that self-organize upon heat treatment. We demonstrate a general method to favorably restore or transform the electrical characteristics of graphene FETs, which will open up new applications.
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34
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Jailaubekov AE, Willard AP, Tritsch JR, Chan WL, Sai N, Gearba R, Kaake LG, Williams KJ, Leung K, Rossky PJ, Zhu XY. Hot charge-transfer excitons set the time limit for charge separation at donor/acceptor interfaces in organic photovoltaics. Nat Mater 2013; 12:66-73. [PMID: 23223125 DOI: 10.1038/nmat3500] [Citation(s) in RCA: 313] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 10/24/2012] [Indexed: 05/13/2023]
Abstract
Photocurrent generation in organic photovoltaics (OPVs) relies on the dissociation of excitons into free electrons and holes at donor/acceptor heterointerfaces. The low dielectric constant of organic semiconductors leads to strong Coulomb interactions between electron-hole pairs that should in principle oppose the generation of free charges. The exact mechanism by which electrons and holes overcome this Coulomb trapping is still unsolved, but increasing evidence points to the critical role of hot charge-transfer (CT) excitons in assisting this process. Here we provide a real-time view of hot CT exciton formation and relaxation using femtosecond nonlinear optical spectroscopies and non-adiabatic mixed quantum mechanics/molecular mechanics simulations in the phthalocyanine-fullerene model OPV system. For initial excitation on phthalocyanine, hot CT excitons are formed in 10(-13) s, followed by relaxation to lower energies and shorter electron-hole distances on a 10(-12) s timescale. This hot CT exciton cooling process and collapse of charge separation sets the fundamental time limit for competitive charge separation channels that lead to efficient photocurrent generation.
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Affiliation(s)
- Askat E Jailaubekov
- Energy Frontier Research Center (EFRC: CST), University of Texas, Austin, Texas 78712, USA
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35
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Ferguson AL, Giovambattista N, Rossky PJ, Panagiotopoulos AZ, Debenedetti PG. A computational investigation of the phase behavior and capillary sublimation of water confined between nanoscale hydrophobic plates. J Chem Phys 2012; 137:144501. [DOI: 10.1063/1.4755750] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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36
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Affiliation(s)
- László Turi
- Department of Physical Chemistry, Eötvös Loránd University, Budapest, Hungary.
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37
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Romero-Vargas Castrillón S, Matysiak S, Stillinger FH, Rossky PJ, Debenedetti PG. Thermal stability of hydrophobic helical oligomers: a lattice simulation study in explicit water. J Phys Chem B 2012; 116:9963-70. [PMID: 22877080 DOI: 10.1021/jp305134w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We investigate the thermal stability of helical hydrophobic oligomers using a three-dimensional, water-explicit lattice model and the Wang-Landau Monte Carlo method. The degree of oligomer helicity is controlled by the parameter ε(mm) < 0, which mimics monomer-monomer hydrogen bond interactions leading to the formation of helical turns in atomistic proteins. We vary |ε(mm)| between 0 and 4.5 kcal/mol and therefore investigate systems ranging from flexible homopolymers (i.e., those with no secondary structure) to helical oligomers that are stable over a broad range of temperatures. We find that systems with |ε(mm)| ≤ 2.0 kcal/mol exhibit a broad thermal unfolding transition at high temperature, leading to an ensemble of random coils. In contrast, the structure of conformations involved in a second, low-temperature, transition is strongly dependent on |ε(mm)|. Weakly helical oligomers are observed when |ε(mm)| ≤ 1.0 kcal/mol and exhibit a low-temperature, cold-unfolding-like transition to an ensemble of strongly water-penetrated globular conformations. For higher |ε(mm)| (1.7 kcal/mol ≤ |ε(mm)| ≤ 2.0 kcal/mol), cold unfolding is suppressed, and the low-temperature conformational transition becomes a "crystallization", in which a "molten" helix is transformed into a defect-free helix. The molten helix preserves ≥50% of the helical contacts observed in the "crystal" at a lower temperature. When |ε(mm)| = 4.5 kcal/mol, we find that conformational transitions are largely suppressed within the range of temperatures investigated.
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Romero-Vargas Castrillón S, Matysiak S, Stillinger FH, Rossky PJ, Debenedetti PG. Phase Behavior of a Lattice Hydrophobic Oligomer in Explicit Water. J Phys Chem B 2012; 116:9540-8. [DOI: 10.1021/jp3039237] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Silvina Matysiak
- Fischell Department of Bioengineering, University of Maryland, College Park, Maryland 20742,
United States
| | - Frank H. Stillinger
- Department
of Chemistry, Princeton University, Princeton,
New Jersey 08544,
United States
| | - Peter J. Rossky
- Institute for Computational Engineering & Sciences and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Pablo G. Debenedetti
- Department of Chemical and Biological
Engineering, Princeton University, Princeton,
New Jersey 08544, United States
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Matysiak S, Debenedetti PG, Rossky PJ. Role of hydrophobic hydration in protein stability: a 3D water-explicit protein model exhibiting cold and heat denaturation. J Phys Chem B 2012; 116:8095-104. [PMID: 22725973 DOI: 10.1021/jp3039175] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We investigate the microscopic mechanism of cold and heat denaturation using a 3D lattice model of a hydrated protein in which water is represented explicitly. The water model, which incorporates directional bonding and tetrahedral geometry, captures many aspects of water thermodynamics and properly describes hydrophobic hydration around apolar solutes because the hydrogen bonding rules in the model were gleaned from off-lattice atomistic simulations of water around representative protein structures. By incorporating local chain stiffness in the protein model, a homopolymer can fold into a β-hairpin. It is shown that the homopolymer can be folded by either attractive interactions between the monomers or as a direct consequence of the entropic cost of forming interfacial hydrogen bonds in the solvent. However, cold denaturation is not observed if the collapse transition is induced by intramolecular attractions. We further find that it is the changes in hydrophobic hydration with decreasing temperature that drive cold unfolding and that the overall process is enthalpically driven, whereas heat denaturation is entropically driven.
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Affiliation(s)
- Silvina Matysiak
- Fischell Department of Bioengineering, University of Maryland, College Park, Maryland 20742, United States.
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Head-Gordon T, Lynden-Bell RM, Dowdle JR, Rossky PJ. Predicting cavity formation free energy: how far is the Gaussian approximation valid? Phys Chem Chem Phys 2012; 14:6996-7004. [PMID: 22495173 DOI: 10.1039/c2cp00046f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We examine the range of validity of the Gaussian model for various water-like liquids whose intermolecular potentials differ from SPC/E water, to provide insight into the temperature dependence of the hydrophobic effect for small hard sphere solutes. We find that low compressibility liquids that have more close-packed network structures show much larger deviations from Gaussian fluctuations for low or zero occupancies relative to more compressible fluids with more open networks. Water appears to be a unique molecular fluid in possessing equilibrium density fluctuations that are faithfully described by the Gaussian theory. We ascribe this success to the fact, shown here, that the orientational correlations near a small hard sphere solute involve remarkably little reorganization from the bulk, which is a consequence of water's low solvent reorganization enthalpy and entropy.
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Affiliation(s)
- T Head-Gordon
- Department of Bioengineering, University of California, Berkeley, California 94720, USA
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Su Z, Buldyrev SV, Debenedetti PG, Rossky PJ, Eugene Stanley H. Modeling simple amphiphilic solutes in a Jagla solvent. J Chem Phys 2012; 136:044511. [DOI: 10.1063/1.3677185] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Affiliation(s)
- Silvina Matysiak
- Institute for Computational Engineering and Sciences and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas, 78712 United States
- Fischell Department of Bioengineering, University of Maryland, College Park, Maryland, 20742 United States
| | - Pablo G. Debenedetti
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey, 08544 United States
| | - Peter J. Rossky
- Institute for Computational Engineering and Sciences and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas, 78712 United States
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Mones L, Rossky PJ, Turi L. Quantum-classical simulation of electron localization in negatively charged methanol clusters. J Chem Phys 2011; 135:084501. [PMID: 21895193 DOI: 10.1063/1.3624366] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Affiliation(s)
- Letif Mones
- Department of Physical Chemistry, Eötvös Loránd University, P. O. Box 32, H-1518, Budapest 112, Hungary.
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Stirnemann G, Castrillón SRV, Hynes JT, Rossky PJ, Debenedetti PG, Laage D. Non-monotonic dependence of water reorientation dynamics on surface hydrophilicity: competing effects of the hydration structure and hydrogen-bond strength. Phys Chem Chem Phys 2011; 13:19911-7. [DOI: 10.1039/c1cp21916b] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Rossky PJ, Walker GC. Paul F. Barbara (1953–2010). Science 2010; 330:1191. [DOI: 10.1126/science.1199894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
A chemical physicist who developed methods to study elementary reactions also explored the dynamics of complex polymers and biomolecules.
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Affiliation(s)
- Peter J. Rossky
- Department of Chemistry and Biochemistry, University of Texas, 1 University Station, A5300, Austin, TX 78712-0165, USA
| | - Gilbert C. Walker
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S3H6, Canada
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Nepomnyashchii AB, Cho S, Rossky PJ, Bard AJ. Dependence of electrochemical and electrogenerated chemiluminescence properties on the structure of BODIPY dyes. Unusually large separation between sequential electron transfers. J Am Chem Soc 2010; 132:17550-9. [PMID: 21090724 DOI: 10.1021/ja108108d] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Electrochemistry and electrogenerated chemiluminescence (ECL) of selected substituted BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) dyes have been studied. The location and nature of substituents on positions 1-8 are important in predicting the behavior, and especially the stability, of the radical ions formed on electron transfer. Dyes with unsubstituted positions 2, 6, and 8 show a kinetic contribution to both oxidation and reduction. Dyes with only unsubstituted positions 2 and 6 and a substituted 8 position show chemically reversible reduction but irreversible oxidation. Unsubstituted positions 2 and 6 tend to show dimer formation on oxidation. Completely substituted dyes show nernstian oxidation and reduction. Oxidation and reduction studies of simple BODIPY dyes show an unusually large separation between the first and second reduction peaks and also the first and second oxidation peaks, of about 1.1 V, which is very different from that observed for polycyclic hydrocarbons and other heteroaromatic compounds, where the spacing is usually about 0.5 V. Electronic structure calculations confirmed this behavior, and this effect is attributed to a greater electronic energy required to withdraw or add a second electron and a lower relative solvation energy for the dianion or dication compared with those of the polycyclic hydrocarbons. ECL was generated for all compounds either by annihilation or by using a co-reactant.
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Affiliation(s)
- Alexander B Nepomnyashchii
- Center for Electrochemistry and Chemistry and Biochemistry Department, The University of Texas at Austin, Austin, Texas 78712, USA
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Mones L, Rossky PJ, Turi L. Analysis of localization sites for an excess electron in neutral methanol clusters using approximate pseudopotential quantum-mechanical calculations. J Chem Phys 2010; 133:144510. [PMID: 20950020 DOI: 10.1063/1.3503506] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Affiliation(s)
- Letif Mones
- Department of Physical Chemistry, Eötvös Loránd University, Budapest 112, P. O. Box 32, H-1518, Hungary.
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Abstract
We have undertaken atomistic molecular simulations to systematically determine the structural contributions to the hydrophobicity of fluorinated solutes and surfaces compared to the corresponding hydrocarbon, yielding a unified explanation for these phenomena. We have transformed a short chain alkane, n-octane, to n-perfluorooctane in stages. The free-energy changes and the entropic components calculated for each transformation stage yield considerable insight into the relevant physics. To evaluate the effect of a surface, we have also conducted contact-angle simulations of water on self-assembled monolayers of hydrocarbon and fluorocarbon thiols. Our results, which are consistent with experimental observations, indicate that the hydrophobicity of the fluorocarbon, whether the interaction with water is as solute or as surface, is due to its "fatness." In solution, the extra work of cavity formation to accommodate a fluorocarbon, compared to a hydrocarbon, is not offset by enhanced energetic interactions with water. The enhanced hydrophobicity of fluorinated surfaces arises because fluorocarbons pack less densely on surfaces leading to poorer van der Waals interactions with water. We find that interaction of water with a hydrophobic solute/surface is primarily a function of van der Waals interactions and is substantially independent of electrostatic interactions. This independence is primarily due to the strong tendency of water at room temperature to maintain its hydrogen bonding network structure at an interface lacking hydrophilic sites.
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Affiliation(s)
| | - Peter J. Rossky
- Departments of Chemical Engineering and
- Chemistry and Biochemistry and Institute for Computational Engineering and Sciences, University of Texas, Austin, TX 78712
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Bedard-Hearn MJ, Sterpone F, Rossky PJ. Nonadiabatic Simulations of Exciton Dissociation in Poly-p-phenylenevinylene Oligomers. J Phys Chem A 2010; 114:7661-70. [DOI: 10.1021/jp103446z] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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