1
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Kumar G, Kellogg M, Dey S, Oliver TAA, Bradforth SE. Unraveling the Photoionization Dynamics of Indole in Aqueous and Ethanol Solutions. J Phys Chem B 2024; 128:4158-4170. [PMID: 38655896 DOI: 10.1021/acs.jpcb.4c01223] [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: 04/26/2024]
Abstract
The photoionization dynamics of indole, the ultraviolet-B chromophore of tryptophan, were explored in water and ethanol using ultrafast transient absorption spectroscopy with 292, 268, and 200 nm excitation. By studying the femtosecond-to-nanosecond dynamics of indole in two different solvents, a new photophysical model has been generated that explains many previously unsolved facets of indole's complex solution phase photochemistry. Photoionization is only an active pathway for indole in aqueous solution, leading to a reduction in the fluorescence quantum yield in water-rich environments, which is frequently used in biophysical experiments as a key signature of the protein-folded state. Photoionization of indole in aqueous solution was observed for all three pump wavelengths but via two different mechanisms. For 200 nm excitation, electrons are ballistically ejected directly into the bulk solvent. Conversely, 292 and 268 nm excitation populates an admixture of two 1ππ* states, which form a dynamic equilibrium with a tightly bound indole cation and electron-ion pair. The ion pair dissociates on a nanosecond time scale, generating separated solvated electrons and indole cations. The charged species serve as important precursors to triplet indole production and greatly enhance the overall intersystem crossing rate. Our proposed photophysical model for indole in aqueous solution is the most appropriate for describing photoinduced dynamics of tryptophan in polypeptide sequences; tryptophan in aqueous pH 7 solution is zwitterionic, unlike in peptides, and resultantly has a competitive excited state proton transfer pathway that quenches the tryptophan fluorescence.
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Affiliation(s)
- Gaurav Kumar
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Michael Kellogg
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Shivalee Dey
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Thomas A A Oliver
- School of Chemistry, Cantock's Close, University of Bristol, Bristol BS8 1TS, U.K
| | - Stephen E Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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2
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Kellogg M, Mencke AR, Muniz CN, Nattikallungal TA, Cardoso-Delgado F, Baluyot-Reyes N, Sewell M, Bird MJ, Bradforth SE, Thompson ME. Intra- and Intermolecular Charge-Transfer Dynamics of Carbene-Metal-Amide Photosensitizers. J Phys Chem C Nanomater Interfaces 2024; 128:6621-6635. [PMID: 38690534 PMCID: PMC11056983 DOI: 10.1021/acs.jpcc.4c01994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Revised: 04/01/2024] [Accepted: 04/02/2024] [Indexed: 05/02/2024]
Abstract
A series of steady-state and time-resolved spectroscopies were performed on a set of eight carbene-metal-amide (cMa) complexes, where M = Cu and Au, that have been used as photosensitizers for photosensitized electrocatalytic reactions. Using ps-to-ns and ns-to-ms transient absorption spectroscopies (psTA and nsTA, respectively), the excited-state kinetics from light absorption, intersystem crossing (ISC), and eventually intermolecular charge transfer were thoroughly characterized. Using time-correlated single photon counting (TCSPC) and psTA with a thermally activated delayed fluorescence (TADF) model, the variation in intersystem crossing (ISC), (S1 → T1) rates (∼3-120 × 109 s-1), and ΔEST values (73-115 meV) for these compounds were fully characterized, reflecting systematic changes to the carbene, carbazole, and metal. The psTA additionally revealed an early time relaxation (rate ∼0.2-0.8 × 1012 s-1) attributed to solvent relaxation and vibrational cooling. The nsTA experiments for a gold-based cMa complex demonstrated efficient intermolecular charge transfer from the excited cMa to an electron acceptor. Pulse radiolysis and bulk electrolysis experiments allowed us to identify the character of the transient excited states as ligand-ligand charge transfer as well as the spectroscopic signature of oxidized and reduced forms of the cMa photosensitizer.
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Affiliation(s)
- Michael
S. Kellogg
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Austin R. Mencke
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Collin N. Muniz
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | | | - Fabiola Cardoso-Delgado
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Nina Baluyot-Reyes
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Marielle Sewell
- Department
of Chemistry, University of California, Riverside, California 92521, United States
| | - Matthew J. Bird
- Chemistry
Division, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Stephen E. Bradforth
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Mark E. Thompson
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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3
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Nemirovich T, Young B, Brezina K, Mason PE, Seidel R, Stemer D, Winter B, Jungwirth P, Bradforth SE, Schewe HC. Stability and Reactivity of Aromatic Radical Anions in Solution with Relevance to Birch Reduction. J Am Chem Soc 2024; 146:8043-8057. [PMID: 38363862 PMCID: PMC10979400 DOI: 10.1021/jacs.3c11655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 01/17/2024] [Accepted: 01/18/2024] [Indexed: 02/18/2024]
Abstract
We investigate the electronic structure of aromatic radical anions in the solution phase employing a combination of liquid-jet (LJ) photoelectron (PE) spectroscopy measurements and electronic structure calculations. By using recently developed protocols, we accurately determine the vertical ionization energies of valence electrons of both the solvent and the solute molecules. In particular, we first characterize the pure solvent of tetrahydrofuran (THF) by LJ-PE measurements in conjunction with ab initio molecular dynamics simulations and G0W0 calculations. Next, we determine the electronic structure of neutral naphthalene (Np) and benzophenone (Bp) as well as their radical anion counterparts Np- and Bp- in THF. Wherever feasible, we performed orbital assignments of the measured PE features of the aromatic radical anions, with comparisons to UV-vis absorption spectra of the corresponding neutral molecules being instrumental in rationalizing the assignments. Analysis of the electronic structure differences between the neutral species and their anionic counterparts provides understanding of the primarily electrostatic stabilization of the radical anions in solution. Finally, we obtain a very good agreement of the reduction potentials extracted from the present LJ-PES measurements of Np- and Bp- in THF with previous electrochemical data from cyclic voltammetry measurements. In this context, we discuss how the choice of solvent holds significant implications for optimizing conditions for the Birch reduction process, wherein aromatic radical anions play crucial roles as reactive intermediates.
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Affiliation(s)
- Tatiana Nemirovich
- Institute
of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
| | - Brandon Young
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Krystof Brezina
- Institute
of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
| | - Philip E. Mason
- Institute
of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
| | - Robert Seidel
- Helmholtz-Zentrum
Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Dominik Stemer
- Fritz-Haber-Institut
der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Bernd Winter
- Fritz-Haber-Institut
der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Pavel Jungwirth
- Institute
of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
| | - Stephen E. Bradforth
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - H. Christian Schewe
- Institute
of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
- J.
Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, 18223 Prague, Czech
Republic
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4
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Bain M, Godínez Castellanos JL, Bradforth SE. High-Throughput Screening for Ultrafast Photochemical Reaction Discovery. J Phys Chem Lett 2023; 14:9864-9871. [PMID: 37890453 DOI: 10.1021/acs.jpclett.3c02389] [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: 10/29/2023]
Abstract
High-repetition-rate lasers present an opportunity to extend ultrafast spectroscopy from a detailed probe of singular model photochemical systems to a routine analysis technique in training machine learning models to aid the design cycle of photochemical syntheses. We bring together innovations in line scan cameras and micro-electro-mechanical grating modulators with sample delivery via high-pressure liquid chromatography pumps to demonstrate a transient absorption spectrometer that can characterize photoreactions initiated with ultrashort ultraviolet pulses in a time scale of minutes. Furthermore, we demonstrate that the ability to rapidly screen an important class of photochemical system, pyrimidine nucleosides, can be used to explore the effect of conformational modification on the evolution of excited-state processes.
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Affiliation(s)
- Matthew Bain
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - José L Godínez Castellanos
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Stephen E Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
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5
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Alfaraidi AM, Schaab J, McClure ET, Kellogg M, Hodgkins TL, Idris M, Bradforth SE, Melot BC, Thompson ME, Djurovich PI. Temperature dependence of radiative and non-radiative decay in the luminescence of one-dimensional pyridinium lead halide hybrids. Phys Chem Chem Phys 2023; 25:21993-22001. [PMID: 37555234 DOI: 10.1039/d3cp02186f] [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
The photoluminescence properties of organic-inorganic pyridinium lead bromide [(pyH)PbBr3] and iodide [(pyH)PbI3] compounds were investigated as a function of temperature. The inorganic substructure consists of face-sharing chains of PbX6 octahedra. Diffuse reflectance spectra of the compounds show low energy absorption features consistent with charge transfer transitions from the PbX3 chains to the pyridinium cations. Both compounds display extremely weak luminescence at room temperature that becomes strongly enhanced upon cooling to 77 K. Broad, featureless low energy emission (λem > 600 nm) in both compounds have large Stokes shifts [1.1 eV for (pyH)PbBr3 and 0.46 eV for (pyH)PbI3] and are assigned to transitions from self-trapped excitons on the inorganic chains whereas emission at higher energy in (pyH)PbBr3 (λem = 450 nm) is assigned to luminescence from a free exciton state. Analysis of data from temperature-dependent luminescence intensity measurements gives activation energies (Ea) for non-radiative decay of the self-trapped excitons in (pyH)PbBr3 and (pyH)PbI3, (Ea = 0.077 eV and 0.103 eV, respectively) and for the free exciton in (pyH)PbBr3 (Ea = 0.010 eV). Analysis of temperature dependent luminescence lifetime data indicates another non-radiative decay process in (pyH)PbI3 at higher temperatures (Ea = 0.17 eV). A large increase in the luminescence lifetime of (pyH)PbI3 below 80 K is consistent with thermalization between triplet sublevels. Analysis of the luminescence power dependence for (pyH)PbI3 shows superlinear response suggestive of quenching by static traps.
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Affiliation(s)
| | - Jonas Schaab
- Department of Chemistry, University of Southern California, Los Angeles, CA, 90802, USA.
| | - Eric T McClure
- Department of Chemistry, University of Southern California, Los Angeles, CA, 90802, USA.
| | - Michael Kellogg
- Department of Chemistry, University of Southern California, Los Angeles, CA, 90802, USA.
| | - Taylor L Hodgkins
- Department of Chemistry, University of Southern California, Los Angeles, CA, 90802, USA.
| | - Muazzam Idris
- Department of Chemistry, University of Southern California, Los Angeles, CA, 90802, USA.
| | - Stephen E Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, CA, 90802, USA.
| | - Brent C Melot
- Department of Chemistry, University of Southern California, Los Angeles, CA, 90802, USA.
| | - Mark E Thompson
- Department of Chemistry, University of Southern California, Los Angeles, CA, 90802, USA.
| | - Peter I Djurovich
- Department of Chemistry, University of Southern California, Los Angeles, CA, 90802, USA.
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6
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Crans KD, Bain M, Bradforth SE, Oron D, Kazes M, Brutchey RL. The surface chemistry of ionic liquid-treated CsPbBr3 quantum dots. J Chem Phys 2023; 158:2888842. [PMID: 37144713 DOI: 10.1063/5.0147918] [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] [Received: 02/27/2023] [Accepted: 04/19/2023] [Indexed: 05/06/2023] Open
Abstract
The power conversion efficiencies of lead halide perovskite thin film solar cells have surged in the short time since their inception. Compounds, such as ionic liquids (ILs), have been explored as chemical additives and interface modifiers in perovskite solar cells, contributing to the rapid increase in cell efficiencies. However, due to the small surface area-to-volume ratio of the large grained polycrystalline halide perovskite films, an atomistic understanding of the interaction between ILs and perovskite surfaces is limited. Here, we use quantum dots (QDs) to study the coordinative surface interaction between phosphonium-based ILs and CsPbBr3. When native oleylammonium oleate ligands are exchanged off the QD surface with the phosphonium cation as well as the IL anion, a threefold increase in photoluminescent quantum yield of as-synthesized QDs is observed. The CsPbBr3 QD structure, shape, and size remain unchanged after ligand exchange, indicating only a surface ligand interaction at approximately equimolar additions of the IL. Increased concentrations of the IL lead to a disadvantageous phase change and a concomitant decrease in photoluminescent quantum yields. Valuable information regarding the coordinative interaction between certain ILs and lead halide perovskites has been elucidated and can be used for informed pairing of beneficial combinations of IL cations and anions.
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Affiliation(s)
- Kyle D Crans
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Matthew Bain
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Stephen E Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Dan Oron
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Miri Kazes
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Richard L Brutchey
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
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7
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Schaab J, Hamze R, Shi S, Kapper SC, Muthiah Ravinson DS, Estergreen L, Jung MC, Tadle AC, Haiges R, Djurovich PI, Peltier JL, Jazzar R, Bertrand G, Bradforth SE, Thompson ME. Correction to " 'Quick-Silver' from a Systematic Study of Highly Luminescent, Two-Coordinate, d 10 Coinage Metal Complexes. J Am Chem Soc 2023; 145:1470-1471. [PMID: 36576490 DOI: 10.1021/jacs.2c12680] [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: 12/29/2022]
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8
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Estergreen L, Mencke AR, Cotton DE, Korovina NV, Michl J, Roberts ST, Thompson ME, Bradforth SE. Controlling Symmetry Breaking Charge Transfer in BODIPY Pairs. Acc Chem Res 2022; 55:1561-1572. [PMID: 35604637 DOI: 10.1021/acs.accounts.2c00044] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
ConspectusSymmetry breaking charge transfer (SBCT) is a process in which a pair of identical chromophores absorb a photon and use its energy to transfer an electron from one chromophore to the other, breaking the symmetry of the chromophore pair. This excited state phenomenon is observed in photosynthetic organisms where it enables efficient formation of separated charges that ultimately catalyze biosynthesis. SBCT has also been proposed as a means for developing photovoltaics and photocatalytic systems that operate with minimal energy loss. It is known that SBCT in both biological and artificial systems is in part made possible by the local environment in which it occurs, which can move to stabilize the asymmetric SBCT state. However, how environmental degrees of freedom act in concert with steric and structural constraints placed on a chromophore pair to dictate its ability to generate long-lived charge pairs via SBCT remain open topics of investigation.In this Account, we compare a broad series of dipyrrin dimers that are linked by distinct bridging groups to discern how the spatial separation and mutual orientation of linked chromophores and the structural flexibility of their linker each impact SBCT efficiency. Across this material set, we observe a general trend that SBCT is accelerated as the spatial separation between dimer chromophores decreases, consistent with the expectation that the electronic coupling between these units varies exponentially with their separation. However, one key observation is that the rate of charge recombination following SBCT was found to slow with decreasing interchromophore separation, rather than speed up. This stems from an enhancement of the dimer's structural rigidity due to increasing steric repulsion as the length of their linker shrinks. This rigidity further inhibits charge recombination in systems where symmetry has already enforced zero HOMO-LUMO overlap. Additionally, for the forward transfer, the active torsion is shown to increase LUMO-LUMO coupling, allowing for faster SBCT within bridging groups.By understanding trends for how rates of SBCT and charge recombination depend on a dimer's internal structure and its environment, we identify design guidelines for creating artificial systems for driving sustained light-induced charge separation. Such systems can find application in solar energy technologies and photocatalytic applications and can serve as a model for light-induced charge separation in biological systems.
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Affiliation(s)
- Laura Estergreen
- Department of Chemistry, University of Southern California, Los Angeles California 90089, United States
| | - Austin R. Mencke
- Department of Chemistry, University of Southern California, Los Angeles California 90089, United States
| | - Daniel E. Cotton
- Department of Chemistry, University of Texas at Austin, Austin Texas 78712, United States
| | - Nadia V. Korovina
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Josef Michl
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Sean T. Roberts
- Department of Chemistry, University of Texas at Austin, Austin Texas 78712, United States
| | - Mark E. Thompson
- Department of Chemistry, University of Southern California, Los Angeles California 90089, United States
| | - Stephen E. Bradforth
- Department of Chemistry, University of Southern California, Los Angeles California 90089, United States
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9
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Bhattacharyya D, Zhang Y, Elles CG, Bradforth SE. Electronic Structure of Liquid Alkanes: A Representative Case of Liquid Hexanes and Cyclohexane Studied Using Polarization-Dependent Two-Photon Absorption Spectroscopy. J Phys Chem A 2021; 125:7988-7999. [PMID: 34478284 DOI: 10.1021/acs.jpca.1c06230] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Two-photon absorption (2PA) spectra of liquid cyclohexane and hexanes are reported for the energy range 6.4-8.5 eV (177-145 nm), providing detailed information about their electronic structures in bulk liquid. Using a broadband pump-probe fashion, we measured the continuous 2PA spectra by simultaneous absorption of a 266 nm (4.6 eV) pump photon and one UV-vis probe photon from the white-light continuum (1.8-3.9 eV). Theoretical one-photon absorption (1PA) and 2PA cross sections of isolated gas phase molecules are computed by the equation of motion coupled-cluster method with single and double substitutions (EOM-CCSD) to substantiate the assignment of the experimental spectra, and the natural transition orbital (NTO) analysis provides visualization of the participating orbitals in a transition. Our analysis suggests that upon solvation transitions at the lowest excitation energy involving promotion of electron to the 3s Rydberg orbitals are blue-shifted (∼0.55 eV for cyclohexane and ∼0.18 eV for hexanes) to a greater extent as compared to those involving other Rydberg orbitals, which is similar to the behavior observed for water and alcohols. All other transitions experience negligible (cyclohexane) or minor red-shift by ∼0.15-0.2 eV (hexane) upon solvation. In both alkanes, the spectra are entirely dominated by Rydberg transitions: the most intense bands in 1PA and 2PA spectra are due to the excitation of electrons to the Rydberg "p" and "d" type orbitals, respectively, although one transition terminating in the 3s Rydberg has significant 2PA strength. This work demonstrates that the gas phase electronic transition properties in alkanes are not significantly altered upon solvation. In addition, electronic structure calculations using an isolated-molecule framework appear to provide a reasonable starting point for a semiquantitative picture for spectral assignment and also to analyze the solvatochromic shifts for liquid phase absorption spectra.
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Affiliation(s)
- Dhritiman Bhattacharyya
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Yuyuan Zhang
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Christopher G Elles
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Stephen E Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
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10
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Mason PE, Schewe HC, Buttersack T, Kostal V, Vitek M, McMullen RS, Ali H, Trinter F, Lee C, Neumark DM, Thürmer S, Seidel R, Winter B, Bradforth SE, Jungwirth P. Spectroscopic evidence for a gold-coloured metallic water solution. Nature 2021; 595:673-676. [PMID: 34321671 DOI: 10.1038/s41586-021-03646-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 05/14/2021] [Indexed: 02/04/2023]
Abstract
Insulating materials can in principle be made metallic by applying pressure. In the case of pure water, this is estimated1 to require a pressure of 48 megabar, which is beyond current experimental capabilities and may only exist in the interior of large planets or stars2-4. Indeed, recent estimates and experiments indicate that water at pressures accessible in the laboratory will at best be superionic with high protonic conductivity5, but not metallic with conductive electrons1. Here we show that a metallic water solution can be prepared by massive doping with electrons upon reacting water with alkali metals. Although analogous metallic solutions of liquid ammonia with high concentrations of solvated electrons have long been known and characterized6-9, the explosive interaction between alkali metals and water10,11 has so far only permitted the preparation of aqueous solutions with low, submetallic electron concentrations12-14. We found that the explosive behaviour of the water-alkali metal reaction can be suppressed by adsorbing water vapour at a low pressure of about 10-4 millibar onto liquid sodium-potassium alloy drops ejected into a vacuum chamber. This set-up leads to the formation of a transient gold-coloured layer of a metallic water solution covering the metal alloy drops. The metallic character of this layer, doped with around 5 × 1021 electrons per cubic centimetre, is confirmed using optical reflection and synchrotron X-ray photoelectron spectroscopies.
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Affiliation(s)
- Philip E Mason
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague, Czech Republic
| | - H Christian Schewe
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague, Czech Republic.,Molecular Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
| | - Tillmann Buttersack
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague, Czech Republic.,Molecular Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany.,Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Vojtech Kostal
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague, Czech Republic
| | - Marco Vitek
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague, Czech Republic
| | - Ryan S McMullen
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Hebatallah Ali
- Molecular Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany.,Department of Physics, Faculty of Women for Art, Science and Education, Ain Shams University, Cairo, Egypt
| | - Florian Trinter
- Molecular Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany.,Photon Science, Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany.,Institut für Kernphysik, Goethe-Universität Frankfurt, Frankfurt am Main, Germany
| | - Chin Lee
- Molecular Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany.,Department of Chemistry, University of California, Berkeley, CA, USA.,Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Daniel M Neumark
- Department of Chemistry, University of California, Berkeley, CA, USA.,Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Stephan Thürmer
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Robert Seidel
- Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany.,Department of Chemistry, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Bernd Winter
- Molecular Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
| | - Stephen E Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, CA, USA
| | - Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague, Czech Republic.
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11
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Cox JM, Bain M, Kellogg M, Bradforth SE, Lopez SA. Role of the Perfluoro Effect in the Selective Photochemical Isomerization of Hexafluorobenzene. J Am Chem Soc 2021; 143:7002-7012. [PMID: 33938749 DOI: 10.1021/jacs.1c01506] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Hexafluorobenzene and many of its derivatives exhibit a chemoselective photochemical isomerization, resulting in highly strained, Dewar-type bicyclohexenes. While the changes in absorption and emission associated with benzene hexafluorination have been attributed to the so-called "perfluoro effect", the resulting electronic structure and photochemical reactivity of hexafluorobenzene is still unclear. We now use a combination of ultrafast time-resolved spectroscopy, multiconfigurational computations, and non-adiabatic dynamics simulations to develop a holistic description of the absorption, emission, and photochemical dynamics of the 4π-electrocyclic ring-closing of hexafluorobenzene and the fluorination effect along the reaction coordinate. Our calculations suggest that the electron-withdrawing fluorine substituents induce a vibronic coupling between the lowest-energy 1B2u (ππ*) and 1E1g (πσ*) excited states by selectively stabilizing the σ-type states. The vibronic coupling occurs along vibrational modes of e2u symmetry which distorts the excited-state minimum geometry resulting in the experimentally broad, featureless absorption bands, and a ∼100 nm Stokes shift in fluorescence-in stark contrast to benzene. Finally, the vibronic coupling is shown to simultaneously destabilize the reaction pathway toward hexafluoro-benzvalene and promote molecular vibrations along the 4π ring-closing pathway, resulting in the chemoselectivity for hexafluoro-Dewar-benzene.
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Affiliation(s)
- Jordan M Cox
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts 02115, United States
| | - Matthew Bain
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Michael Kellogg
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Stephen E Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Steven A Lopez
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts 02115, United States
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12
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Gozem S, Seidel R, Hergenhahn U, Lugovoy E, Abel B, Winter B, Krylov AI, Bradforth SE. Probing the Electronic Structure of Bulk Water at the Molecular Length Scale with Angle-Resolved Photoelectron Spectroscopy. J Phys Chem Lett 2020; 11:5162-5170. [PMID: 32479725 DOI: 10.1021/acs.jpclett.0c00968] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We report a combined experimental and theoretical study of bulk water photoionization. Angular distributions of photoelectrons produced by ionizing the valence bands of neat water using X-ray radiation (250-750 eV) show a limited (∼20%) decrease in the β anisotropy parameter compared to the gas phase, indicating that the electronic structure of the individual water molecules can be probed. We show that, in the high-energy regime, photoionization of bulk can be described using an incoherent superposition of individual molecules, in contrast to a low-energy regime where photoionization probes delocalized entangled states of molecular aggregates. The two regimes-low versus high energy-are limiting cases where the de Broglie wavelength of the photoelectron is larger or smaller than the intermolecular distance between water molecules, respectively. The comparison of measured and computed anisotropies reveals that the reduction in β at high kinetic energies is mostly due to scattering rather than rehybridization due to solvation.
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Affiliation(s)
- Samer Gozem
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30303, United States
| | - Robert Seidel
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Straße 15, 12489 Berlin, Germany
- Humboldt-Universität zu Berlin, Department of Chemistry, Brook-Taylor-Strasse 2, D-12489 Berlin, Germany
| | - Uwe Hergenhahn
- Leibniz Institute of Surface Engineering (IOM), Department of Functional Surfaces, Permoserstrasse 15, 04318 Leipzig, Germany
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Evgeny Lugovoy
- Leibniz Institute of Surface Engineering (IOM), Department of Functional Surfaces, Permoserstrasse 15, 04318 Leipzig, Germany
- University of Leipzig, Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry, Linnéstrasse 3, 04318 Leipzig, Germany
| | - Bernd Abel
- Leibniz Institute of Surface Engineering (IOM), Department of Functional Surfaces, Permoserstrasse 15, 04318 Leipzig, Germany
- University of Leipzig, Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry, Linnéstrasse 3, 04318 Leipzig, Germany
| | - Bernd Winter
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Anna I Krylov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
- The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22671 Hamburg, Germany
| | - Stephen E Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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13
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Buttersack T, Mason PE, McMullen RS, Schewe HC, Martinek T, Brezina K, Crhan M, Gomez A, Hein D, Wartner G, Seidel R, Ali H, Thürmer S, Marsalek O, Winter B, Bradforth SE, Jungwirth P. Photoelectron spectra of alkali metal–ammonia microjets: From blue electrolyte to bronze metal. Science 2020; 368:1086-1091. [DOI: 10.1126/science.aaz7607] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 02/25/2020] [Accepted: 04/03/2020] [Indexed: 11/02/2022]
Affiliation(s)
- Tillmann Buttersack
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089-0482, USA
| | - Philip E. Mason
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
| | - Ryan S. McMullen
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089-0482, USA
| | - H. Christian Schewe
- Molecular Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Tomas Martinek
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
| | - Krystof Brezina
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
- Charles University, Faculty of Mathematics and Physics, Ke Karlovu 3, 121 16 Prague 2, Czech Republic
| | - Martin Crhan
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
| | - Axel Gomez
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
- Département de Chimie, École Normale Supérieure, PSL University, 75005 Paris, France
| | - Dennis Hein
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, D-12489 Berlin, Germany
| | - Garlef Wartner
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, D-12489 Berlin, Germany
| | - Robert Seidel
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, D-12489 Berlin, Germany
| | - Hebatallah Ali
- Molecular Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Stephan Thürmer
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto 606-8502, Japan
| | - Ondrej Marsalek
- Charles University, Faculty of Mathematics and Physics, Ke Karlovu 3, 121 16 Prague 2, Czech Republic
| | - Bernd Winter
- Molecular Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
| | - Stephen E. Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089-0482, USA
| | - Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
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14
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Buttersack T, Mason PE, Jungwirth P, Schewe HC, Winter B, Seidel R, McMullen RS, Bradforth SE. Deeply cooled and temperature controlled microjets: Liquid ammonia solutions released into vacuum for analysis by photoelectron spectroscopy. Rev Sci Instrum 2020; 91:043101. [PMID: 32357686 DOI: 10.1063/1.5141359] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 03/17/2020] [Indexed: 06/11/2023]
Abstract
A versatile, temperature controlled apparatus is presented, which generates deeply cooled liquid microjets of condensed gases, expelling them via a small aperture into vacuum for use in photoelectron spectroscopy (PES). The functionality of the design is demonstrated by temperature- and concentration-dependent PES measurements of liquid ammonia and solutions of KI and NH4I in liquid ammonia. The experimental setup is not limited to the usage of liquid ammonia solutions solely.
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Affiliation(s)
- Tillmann Buttersack
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nam. 2, 16610 Prague 6, Czech Republic
| | - Philip E Mason
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nam. 2, 16610 Prague 6, Czech Republic
| | - Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nam. 2, 16610 Prague 6, Czech Republic
| | - H Christian Schewe
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Molekülphysik, Faradayweg 4-6, 14195 Berlin, Germany
| | - Bernd Winter
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Molekülphysik, Faradayweg 4-6, 14195 Berlin, Germany
| | - Robert Seidel
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Straße 15, 12489 Berlin, Germany and Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany
| | - Ryan S McMullen
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, USA
| | - Stephen E Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, USA
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15
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Bhattacharyya D, Mizuno H, Rizzuto AM, Zhang Y, Saykally RJ, Bradforth SE. New Insights into the Charge-Transfer-to-Solvent Spectrum of Aqueous Iodide: Surface versus Bulk. J Phys Chem Lett 2020; 11:1656-1661. [PMID: 32040333 DOI: 10.1021/acs.jpclett.9b03857] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Liquid phase charge-transfer-to-solvent (CTTS) transitions are important, as they serve as photochemical routes to solvated electrons. In this work, broadband deep-ultraviolet electronic sum frequency generation (DUV-ESFG) and two-photon absorption (2PA) spectroscopic techniques were used to assign and compare the nature of the aqueous iodide CTTS excitations at the air/water interface and in bulk solution. In the one-photon absorption (1PA) spectrum, excitation to the 6s Rydberg-like orbital (5p → 6s) gives rise to a pair of spin-orbit split iodine states, 2P3/2 and 2P1/2. In the 2PA spectra, the lower-energy 2P3/2 peak is absent and the observed 2PA peak, which is ∼0.14 eV blue-shifted relative to the upper 2P1/2 CTTS peak seen in 1PA, arises from 5p → 6p electronic promotion. The band observed in the ESFG spectrum is attributed to mixing of excited states involving 5p → 6p and 5p → 6s promotions caused by both vibronic coupling and the external electric field generated by asymmetric interfacial solvation.
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Affiliation(s)
- Dhritiman Bhattacharyya
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Hikaru Mizuno
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Anthony M Rizzuto
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Yuyuan Zhang
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Richard J Saykally
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Stephen E Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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16
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Greaney MJ, Joy J, Combs BA, Das S, Buckley JJ, Bradforth SE, Brutchey RL. Effects of interfacial ligand type on hybrid P3HT:CdSe quantum dot solar cell device parameters. J Chem Phys 2019; 151:074704. [DOI: 10.1063/1.5114932] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Affiliation(s)
- Matthew J. Greaney
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Jimmy Joy
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Blair A. Combs
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Saptaparna Das
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Jannise J. Buckley
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Stephen E. Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Richard L. Brutchey
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
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17
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Hamze R, Shi S, Kapper SC, Muthiah Ravinson DS, Estergreen L, Jung MC, Tadle AC, Haiges R, Djurovich PI, Peltier JL, Jazzar R, Bertrand G, Bradforth SE, Thompson ME. Correction to “ ‘Quick-Silver’ from a Systematic Study of Highly Luminescent, Two-Coordinate, d 10 Coinage Metal Complexes”. J Am Chem Soc 2019; 141:10118. [DOI: 10.1021/jacs.9b06147] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [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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18
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Bhattacharyya D, Zhang Y, Elles CG, Bradforth SE. Electronic Structure of Liquid Methanol and Ethanol from Polarization-Dependent Two-Photon Absorption Spectroscopy. J Phys Chem A 2019; 123:5789-5804. [DOI: 10.1021/acs.jpca.9b04040] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Dhritiman Bhattacharyya
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Yuyuan Zhang
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Christopher G. Elles
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Stephen E. Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
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19
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Hamze R, Shi S, Kapper SC, Muthiah Ravinson DS, Estergreen L, Jung MC, Tadle AC, Haiges R, Djurovich PI, Peltier JL, Jazzar R, Bertrand G, Bradforth SE, Thompson ME. "Quick-Silver" from a Systematic Study of Highly Luminescent, Two-Coordinate, d 10 Coinage Metal Complexes. J Am Chem Soc 2019; 141:8616-8626. [PMID: 31062972 DOI: 10.1021/jacs.9b03657] [Citation(s) in RCA: 130] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A systematic study is presented on the physical and photophysical properties of isoelectronic and isostructural Cu, Ag, and Au complexes with a common amide (N-carbazolyl) and two different carbene ligands (i.e., CAAC = (5 R,6 S)-2-(2,6-diisopropylphenyl)-6-isopropyl-3,3,9-trimethyl-2-azaspiro[4.5]decan-2-ylidene, MAC = 1,3-bis(2,6-diisopropylphenyl)-5,5-dimethyl-4-keto-tetrahydropyridylidene). The crystal structures of the (carbene)M(I)(N-carbazolyl) (MCAAC) and (MAC)M(I)(N-carbazolyl) (MMAC) complexes show coplanar carbene and carbzole ligands and C-M-N bond angles of ∼180°. The electrochemical properties and energies for charge transfer (CT) absorption and emission compounds are not significantly affected by the choice of metal ion. All six of the (carbene)M(Cz) complexes examined here display high photoluminescence quantum yields of 0.8-1.0. The compounds have short emission lifetimes (τ = 0.33-2.8 μs) that fall in the order Ag < Au < Cu, with the lifetimes of (carbene)Ag(Cz) roughly a factor of 10 shorter than for (carbene)Cu(Cz) complexes. Detailed temperature-dependent photophysical measurements (5-325 K) were carried out to determine the singlet and triplet emission lifetimes (τfl and τph, respectively) and the energy difference between the singlet and triplet excited state, Δ ES1-T1. The τfl values range between 20 and 85 ns, and the τph values are in the 50-200 μs regime. The emission at room temperature is due exclusively to E-type delayed fluorescence or TADF (i.e., T1→ΔS1→S0+hν ). The emission rate at room temperature is fully governed by Δ ES1-T1, with the silver complexes giving Δ ES1-T1 values of 150-180 cm-1 (18-23 meV), whereas the gold and copper complexes give values of 570-590 cm-1 (70-73 meV).
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Affiliation(s)
- Rasha Hamze
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Shuyang Shi
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Savannah C Kapper
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | | | - Laura Estergreen
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Moon-Chul Jung
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Abegail C Tadle
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Ralf Haiges
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Peter I Djurovich
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Jesse L Peltier
- UCSD-CNRS Joint Research Laboratory (UMI 3555), Department of Chemistry and Biochemistry , University of California, San Diego , La Jolla , California 92093-0358 , United States
| | - Rodolphe Jazzar
- UCSD-CNRS Joint Research Laboratory (UMI 3555), Department of Chemistry and Biochemistry , University of California, San Diego , La Jolla , California 92093-0358 , United States
| | - Guy Bertrand
- UCSD-CNRS Joint Research Laboratory (UMI 3555), Department of Chemistry and Biochemistry , University of California, San Diego , La Jolla , California 92093-0358 , United States
| | - Stephen E Bradforth
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Mark E Thompson
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
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20
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Buttersack T, Mason PE, McMullen RS, Martinek T, Brezina K, Hein D, Ali H, Kolbeck C, Schewe C, Malerz S, Winter B, Seidel R, Marsalek O, Jungwirth P, Bradforth SE. Valence and Core-Level X-ray Photoelectron Spectroscopy of a Liquid Ammonia Microjet. J Am Chem Soc 2019; 141:1838-1841. [PMID: 30673221 PMCID: PMC6728086 DOI: 10.1021/jacs.8b10942] [Citation(s) in RCA: 23] [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] [Indexed: 11/28/2022]
Abstract
![]()
Photoelectron
spectroscopy of microjets expanded into vacuum allows
access to orbital energies for solute or solvent molecules in the
liquid phase. Microjets of water, acetonitrile and alcohols have previously
been studied; however, it has been unclear whether jets of low temperature
molecular solvents could be realized. Here we demonstrate a stable
20 μm jet of liquid ammonia (−60 °C) in a vacuum,
which we use to record both valence and core-level band photoelectron
spectra using soft X-ray synchrotron radiation. Significant shifts
from isolated ammonia in the gas-phase are observed, as is the liquid-phase
photoelectron angular anisotropy. Comparisons with spectra of ammonia
in clusters and the solid phase, as well as spectra for water in various
phases potentially reveal how hydrogen bonding is reflected in the
condensed phase electronic structure.
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Affiliation(s)
- Tillmann Buttersack
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences , Flemingovo nam. 2 , 16610 Prague 6 , Czech Republic
| | - Philip E Mason
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences , Flemingovo nam. 2 , 16610 Prague 6 , Czech Republic
| | - Ryan S McMullen
- Department of Chemistry , University of Southern California , Los Angeles , California 90089-0482 , United States
| | - Tomas Martinek
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences , Flemingovo nam. 2 , 16610 Prague 6 , Czech Republic
| | - Krystof Brezina
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences , Flemingovo nam. 2 , 16610 Prague 6 , Czech Republic
| | - Dennis Hein
- Helmholtz-Zentrum Berlin für Materialien und Energie , D-14109 Berlin , Germany
| | - Hebatallah Ali
- Fritz-Haber-Institut der Max-Planck-Gesellschaft , D-14195 Berlin , Germany
| | - Claudia Kolbeck
- Fritz-Haber-Institut der Max-Planck-Gesellschaft , D-14195 Berlin , Germany
| | - Christian Schewe
- Fritz-Haber-Institut der Max-Planck-Gesellschaft , D-14195 Berlin , Germany
| | - Sebastian Malerz
- Fritz-Haber-Institut der Max-Planck-Gesellschaft , D-14195 Berlin , Germany
| | - Bernd Winter
- Fritz-Haber-Institut der Max-Planck-Gesellschaft , D-14195 Berlin , Germany
| | - Robert Seidel
- Helmholtz-Zentrum Berlin für Materialien und Energie , D-14109 Berlin , Germany
| | - Ondrej Marsalek
- Faculty of Mathematics and Physics , Charles University , Ke Karlovu 3 , 121 16 Prague 2 , Czech Republic
| | - Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences , Flemingovo nam. 2 , 16610 Prague 6 , Czech Republic
| | - Stephen E Bradforth
- Department of Chemistry , University of Southern California , Los Angeles , California 90089-0482 , United States
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21
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Kellogg M, Akil A, Muthiah Ravinson DS, Estergreen L, Bradforth SE, Thompson ME. Symmetry breaking charge transfer as a means to study electron transfer with no driving force. Faraday Discuss 2019; 216:379-394. [DOI: 10.1039/c8fd00201k] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Herein we explore the symmetry breaking charge transfer process in two dipyrrin-based bichromophoric systems.
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Affiliation(s)
- Michael Kellogg
- Department of Chemistry
- University of Southern California
- Los Angeles
- USA
| | - Ali Akil
- Department of Chemistry
- University of Southern California
- Los Angeles
- USA
| | | | - Laura Estergreen
- Department of Chemistry
- University of Southern California
- Los Angeles
- USA
| | | | - Mark E. Thompson
- Department of Chemistry
- University of Southern California
- Los Angeles
- USA
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22
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Korovina NV, Joy J, Feng X, Feltenberger C, Krylov AI, Bradforth SE, Thompson ME. Linker-Dependent Singlet Fission in Tetracene Dimers. J Am Chem Soc 2018; 140:10179-10190. [PMID: 30016102 DOI: 10.1021/jacs.8b04401] [Citation(s) in RCA: 96] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Separation of triplet excitons produced by singlet fission is crucial for efficient application of singlet fission materials. While earlier works explored the first step of singlet fission, the formation of the correlated triplet pair state, the focus of recent studies has been on understanding the second step of singlet fission, the formation of independent triplets from the correlated pair state. We present the synthesis and excited-state dynamics of meta- and para-bis(ethynyltetracenyl)benzene dimers that are analogues to the ortho-bis(ethynyltetracenyl)benzene dimer reported by our groups previously. A comparison of the excited-state properties of these dimers allows us to investigate the effects of electronic conjugation and coupling on singlet fission between the ethynyltetracene units within a dimer. In the para isomer, in which the two chromophores are conjugated, the singlet exciton yields the correlated triplet pair state, from which the triplet excitons can decouple via molecular rotations. In contrast, the meta isomer in which the two chromophores are cross-coupled predominantly relaxes via radiative decay. We also report the synthesis and excited-state dynamics of two para dimers with different bridging units joining the ethynyltetracenes. The rate of singlet fission is found to be faster in the dimer with the bridging unit that has orbitals closer in energy to that of the ethynyltetracene chromophores.
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Affiliation(s)
- Nadezhda V Korovina
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Jimmy Joy
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Xintian Feng
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Cassidy Feltenberger
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Anna I Krylov
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Stephen E Bradforth
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Mark E Thompson
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
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23
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Das S, Thornbury WG, Bartynski AN, Thompson ME, Bradforth SE. Manipulating Triplet Yield through Control of Symmetry-Breaking Charge Transfer. J Phys Chem Lett 2018; 9:3264-3270. [PMID: 29847949 DOI: 10.1021/acs.jpclett.8b01237] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The efficiency of an organic solar cell depends on the efficacy of exciton diffusion and dissociation processes, and this can be enhanced by reducing the exciton binding energy and increasing the exciton lifetime. Zinc chlorodipyrrin (ZCl) complexes exhibit reduced exciton binding energy due to ultrafast generation of intramolecular charge transfer (ICT) states via symmetry-breaking charge transfer in polar media. This Letter explores the fate of the ICT states using nanosecond transient absorption. In cyclohexane, ZCl undergoes intersystem crossing to produce triplets with ∼8 ns time constant (∼30% yield), and no ICT states are generated. However, in more polar solvents, triplets are generated within 1 ns via ICT state recombination with ∼3 times higher yield than produced via ISC. This high triplet yield in toluene (89%) and acetonitrile (76%) via ICT state recombination is a beneficial pathway to spin-protect the excited-state decay for additional charge generation from triplet excited states.
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Affiliation(s)
- Saptaparna Das
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - William G Thornbury
- Department of Chemical Engineering , University of Southern California , Los Angeles , California 90089 , United States
| | - Andrew N Bartynski
- Department of Chemical Engineering , University of Southern California , Los Angeles , California 90089 , United States
| | - Mark E Thompson
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
| | - Stephen E Bradforth
- Department of Chemistry , University of Southern California , Los Angeles , California 90089 , United States
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24
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Kudinov KA, Cooper DR, Ha JK, Hill CK, Nadeau JL, Seuntjens JP, Bradforth SE. Scintillation Yield Estimates of Colloidal Cerium-Doped LaF 3 Nanoparticles and Potential for "Deep PDT". Radiat Res 2018; 190:28-36. [PMID: 29672241 DOI: 10.1667/rr14944.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
A hybrid of radiotherapy and photodynamic therapy (PDT) has been proposed in previously reported studies. This approach utilizes scintillating nanoparticles to transfer energy to attached photosensitizers, thus generating singlet oxygen for local killing of malignant cells. Its effectiveness strongly depends upon the scintillation yield of the nanoparticles. Using a liquid scintillator as a reference standard, we estimated the scintillation yield of Ce0.1La0.9F3/LaF3 core/shell nanoparticles at 28.9 mg/ml in water to be 350 photons/MeV under orthovoltage X-ray irradiation. The subsequent singlet oxygen production for a 60 Gy cumulative dose to cells was estimated to be four orders of magnitude lower than the "Niedre killing dose," used as a target value for effective cell killing. Without significant improvements in the radioluminescence properties of the nanoparticles, this approach to "deep PDT" is likely to be ineffective. Additional considerations and alternatives to singlet oxygen are discussed.
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Affiliation(s)
| | - Daniel R Cooper
- c Medical Physics Unit, Faculty of Medicine, McGill University, Montreal, Canada
| | - Jonathan K Ha
- b Department of Radiation Oncology, Keck Medical School, University of Southern California, Los Angeles, California
| | - Colin K Hill
- b Department of Radiation Oncology, Keck Medical School, University of Southern California, Los Angeles, California
| | - Jay L Nadeau
- d Graduate Aerospace Laboratories, Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, California
| | - Jan P Seuntjens
- c Medical Physics Unit, Faculty of Medicine, McGill University, Montreal, Canada
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25
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Roy A, Seidel R, Kumar G, Bradforth SE. Exploring Redox Properties of Aromatic Amino Acids in Water: Contrasting Single Photon vs Resonant Multiphoton Ionization in Aqueous Solutions. J Phys Chem B 2018. [DOI: 10.1021/acs.jpcb.7b11762] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anirban Roy
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Robert Seidel
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - Gaurav Kumar
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Stephen E. Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
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26
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Kumar G, Roy A, McMullen RS, Kutagulla S, Bradforth SE. The influence of aqueous solvent on the electronic structure and non-adiabatic dynamics of indole explored by liquid-jet photoelectron spectroscopy. Faraday Discuss 2018; 212:359-381. [DOI: 10.1039/c8fd00123e] [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: 11/21/2022]
Abstract
Time-resolved photoelectron spectroscopy (TRPES) in a liquid micro-jet is implemented here to investigate the influence of water on the electronic structure and dynamics of indole, the chromophore of the amino acid tryptophan.
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Affiliation(s)
- Gaurav Kumar
- Department of Chemistry
- University of Southern California
- Los Angeles
- USA
| | - Anirban Roy
- Department of Chemistry
- University of Southern California
- Los Angeles
- USA
| | - Ryan S. McMullen
- Department of Chemistry
- University of Southern California
- Los Angeles
- USA
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27
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McAnally RE, Bender JA, Estergreen L, Haiges R, Bradforth SE, Dawlaty JM, Roberts ST, Rury AS. Defects Cause Subgap Luminescence from a Crystalline Tetracene Derivative. J Phys Chem Lett 2017; 8:5993-6001. [PMID: 29185754 DOI: 10.1021/acs.jpclett.7b02718] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We use steady-state and ultrafast nonlinear spectroscopies in combination with density functional theory calculations to explain light emission below the optical gap energy (Eo) of crystalline samples of 5,12-diphenyl tetracene (DPT). In particular, the properties of vibrational coherences imprinted on a probe pulse transmitted through a DPT single crystal indicate discrete electronic transitions below Eo of this organic semiconductor. Analysis of coherence spectra leads us to propose structural defect states give rise to these discrete transitions and subgap light emission. We use the polarization dependence of vibrational coherence spectra to tentatively assign these defects in our DPT samples. Our results provide fundamental insights into the properties of midgap states in organic materials important for their application in next-generation photonics and optoelectronics technologies.
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Affiliation(s)
- R Eric McAnally
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Jon A Bender
- Department of Chemistry, University of Texas at Austin , Austin, Texas 78712, United States
| | - Laura Estergreen
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Ralf Haiges
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Stephen E Bradforth
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Jahan M Dawlaty
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Sean T Roberts
- Department of Chemistry, University of Texas at Austin , Austin, Texas 78712, United States
| | - Aaron S Rury
- Department of Chemistry, Wayne State University , Detroit, Michigan 48202, United States
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28
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Pham TA, Govoni M, Seidel R, Bradforth SE, Schwegler E, Galli G. Electronic structure of aqueous solutions: Bridging the gap between theory and experiments. Sci Adv 2017; 3:e1603210. [PMID: 28691091 PMCID: PMC5482551 DOI: 10.1126/sciadv.1603210] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 04/28/2017] [Indexed: 05/31/2023]
Abstract
Predicting the electronic properties of aqueous liquids has been a long-standing challenge for quantum mechanical methods. However, it is a crucial step in understanding and predicting the key role played by aqueous solutions and electrolytes in a wide variety of emerging energy and environmental technologies, including battery and photoelectrochemical cell design. We propose an efficient and accurate approach to predict the electronic properties of aqueous solutions, on the basis of the combination of first-principles methods and experimental validation using state-of-the-art spectroscopic measurements. We present results of the photoelectron spectra of a broad range of solvated ions, showing that first-principles molecular dynamics simulations and electronic structure calculations using dielectric hybrid functionals provide a quantitative description of the electronic properties of the solvent and solutes, including excitation energies. The proposed computational framework is general and applicable to other liquids, thereby offering great promise in understanding and engineering solutions and liquid electrolytes for a variety of important energy technologies.
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Affiliation(s)
- Tuan Anh Pham
- Quantum Simulations Group, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | - Marco Govoni
- Institute for Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Robert Seidel
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089–0482, USA
| | - Stephen E. Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089–0482, USA
| | - Eric Schwegler
- Quantum Simulations Group, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
| | - Giulia Galli
- Institute for Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
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29
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Bass KK, Estergreen L, Savory CN, Buckeridge J, Scanlon DO, Djurovich PI, Bradforth SE, Thompson ME, Melot BC. Vibronic Structure in Room Temperature Photoluminescence of the Halide Perovskite Cs3Bi2Br9. Inorg Chem 2016; 56:42-45. [DOI: 10.1021/acs.inorgchem.6b01571] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kelsey K. Bass
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Laura Estergreen
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Christopher N. Savory
- Kathleen Lonsdale Materials Chemistry, University College London (UCL), 20 Gordon Street, London WC1H 0AJ, United Kingdom
| | - John Buckeridge
- Kathleen Lonsdale Materials Chemistry, University College London (UCL), 20 Gordon Street, London WC1H 0AJ, United Kingdom
| | - David O. Scanlon
- Kathleen Lonsdale Materials Chemistry, University College London (UCL), 20 Gordon Street, London WC1H 0AJ, United Kingdom
- Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - Peter I. Djurovich
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Stephen E. Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Mark E. Thompson
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Brent C. Melot
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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30
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Abstract
The valence orbital electron binding energies of water and of embedded solutes are crucial quantities for understanding chemical reactions taking place in aqueous solution, including oxidation/reduction, transition-metal coordination, and radiation chemistry. Their experimental determination based on liquid-photoelectron spectroscopy using soft X-rays is described, and we provide an overview of valence photoelectron spectroscopy studies reported to date. We discuss principal experimental aspects and several theoretical approaches to compute the measured binding energies of the least tightly bound molecular orbitals. Solutes studied are presented chronologically, from simple electrolytes, via transition-metal ion solutions and several organic and inorganic molecules, to biologically relevant molecules, including aqueous nucleotides and their components. In addition to the lowest vertical ionization energies, the measured valence photoelectron spectra also provide information on adiabatic ionization energies and reorganization energies for the oxidation (ionization) half-reaction. For solutes with low solubility, resonantly enhanced ionization provides a promising alternative pathway.
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Affiliation(s)
- Robert Seidel
- Institute of Methods for Material Development, Helmholtz-Zentrum Berlin, D-12489 Berlin, Germany; ,
| | - Bernd Winter
- Institute of Methods for Material Development, Helmholtz-Zentrum Berlin, D-12489 Berlin, Germany; ,
| | - Stephen E Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482;
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31
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Bradforth SE, Miller ER, Dichtel WR, Leibovich AK, Feig AL, Martin JD, Bjorkman KS, Schultz ZD, Smith TL. University learning: Improve undergraduate science education. Nature 2016; 523:282-4. [PMID: 26178951 DOI: 10.1038/523282a] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Stephen E Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California, USA
| | - Emily R Miller
- AAU Undergraduate STEM Education Initiative at the Association of American Universities, Washington DC, USA
| | | | | | | | - James D Martin
- North Carolina State University, Raleigh, North Carolina, USA
| | - Karen S Bjorkman
- Department of Physics and Astronomy, University of Toledo, Ohio, USA
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32
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Korovina NV, Das S, Nett Z, Feng X, Joy J, Haiges R, Krylov AI, Bradforth SE, Thompson ME. Singlet Fission in a Covalently Linked Cofacial Alkynyltetracene Dimer. J Am Chem Soc 2016; 138:617-27. [PMID: 26693957 DOI: 10.1021/jacs.5b10550] [Citation(s) in RCA: 185] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Singlet fission is a process in which a singlet exciton converts into two triplet excitons. To investigate this phenomenon, we synthesized two covalently linked 5-ethynyl-tetracene (ET) dimers with differing degrees of intertetracene overlap: BET-X, with large, cofacial overlap of tetracene π-orbitals, and BET-B, with twisted arrangement between tetracenes exhibits less overlap between the tetracene π-orbitals. The two compounds were crystallographically characterized and studied by absorption and emission spectroscopy in solution, in PMMA and neat thin films. The results show that singlet fission occurs within 1 ps in an amorphous thin film of BET-B with high efficiency (triplet yield: 154%). In solution and the PMMA matrix the S1 of BET-B relaxes to a correlated triplet pair (1)(T1T1) on a time scale of 2 ps, which decays to the ground state without forming separated triplets, suggesting that triplet energy transfer from (1)(T1T1) to a nearby chromophore is essential for producing free triplets. In support of this hypothesis, selective excitation of BET-B doped into a thin film of diphenyltetracene (DPT) leads to formation of the (1)(T1T1) state of BET-B, followed by generation of both DPT and BET-B triplets. For the structurally cofacial BET-X, an intermediate forms in <180 fs and returns to the ground state more rapidly than BET-B. First-principles calculations predict a 2 orders of magnitude faster rate of singlet fission to the (1)(T1T1) state in BET-B relative to that of crystalline tetracene, attributing the rate increase to greater coupling between the S1 and (1)(T1T1) states and favorable energetics for formation of the separated triplets.
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Affiliation(s)
- Nadezhda V Korovina
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Saptaparna Das
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Zachary Nett
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Xintian Feng
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Jimmy Joy
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Ralf Haiges
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Anna I Krylov
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Stephen E Bradforth
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
| | - Mark E Thompson
- Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States
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33
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Oliver TAA, Zhang Y, Roy A, Ashfold MNR, Bradforth SE. Exploring Autoionization and Photoinduced Proton-Coupled Electron Transfer Pathways of Phenol in Aqueous Solution. J Phys Chem Lett 2015; 6:4159-4164. [PMID: 26722792 DOI: 10.1021/acs.jpclett.5b01861] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The excited state dynamics of phenol in water have been investigated using transient absorption spectroscopy. Solvated electrons and vibrationally cold phenoxyl radicals are observed upon 200 and 267 nm excitation, but with formation time scales that differ by more than 4 orders of magnitude. The impact of these findings is assessed in terms of the relative importance of autoionization versus proton-coupled electron transfer mechanisms in this computationally tractable model system.
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Affiliation(s)
- Thomas A A Oliver
- School of Chemistry, University of Bristol , Bristol, BS8 1TS, United Kingdom
| | - Yuyuan Zhang
- University of Southern California , Los Angeles, California 90089, United States
| | - Anirban Roy
- University of Southern California , Los Angeles, California 90089, United States
| | - Michael N R Ashfold
- School of Chemistry, University of Bristol , Bristol, BS8 1TS, United Kingdom
| | - Stephen E Bradforth
- University of Southern California , Los Angeles, California 90089, United States
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34
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Bartynski AN, Gruber M, Das S, Rangan S, Mollinger S, Trinh C, Bradforth SE, Vandewal K, Salleo A, Bartynski RA, Bruetting W, Thompson ME. Symmetry-Breaking Charge Transfer in a Zinc Chlorodipyrrin Acceptor for High Open Circuit Voltage Organic Photovoltaics. J Am Chem Soc 2015; 137:5397-405. [DOI: 10.1021/jacs.5b00146] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Mark Gruber
- Institute
for Physics, Augsburg University, 86135 Augsburg, Germany
| | | | - Sylvie Rangan
- Department
of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, United States
| | - Sonya Mollinger
- Department
of Materials Science and Engineering, Stanford University, Palo Alto, California 94305, United States
| | | | | | - Koen Vandewal
- Department
of Materials Science and Engineering, Stanford University, Palo Alto, California 94305, United States
| | - Alberto Salleo
- Department
of Materials Science and Engineering, Stanford University, Palo Alto, California 94305, United States
| | - Robert A. Bartynski
- Department
of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, United States
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35
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Zhang X, Shastry S, Bradforth SE, Nadeau JL. Nuclear uptake of ultrasmall gold-doxorubicin conjugates imaged by fluorescence lifetime imaging microscopy (FLIM) and electron microscopy. Nanoscale 2015; 7:240-51. [PMID: 25407725 DOI: 10.1039/c4nr04707a] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Fluorescence lifetime imaging microscopy (FLIM) has been used to image free and encapsulated doxorubicin (Dox) uptake into cells, since interaction of Dox with DNA leads to a characteristic lifetime change. However, none of the reported Dox conjugates were able to enter cell nuclei. In this work, we use FLIM to show nuclear uptake of 2.7 nm mean diameter Au nanoparticles conjugated to Dox. The pattern of labelling differed substantially from what was seen with free Dox, with slower nuclear entry and stronger cytoplasmic labelling at all time points. As the cells died, the pattern of labelling changed further as intracellular structures disintegrated, consistent with association of Au-Dox to membranes. The patterns of Au distribution and intracellular structure changes were confirmed using electron microscopy, and indicate different mechanisms of cytotoxicity with stable Au-Dox conjugates compared to Dox alone. Such conjugates are promising tools for overcoming resistance in Dox-resistant cancers.
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Affiliation(s)
- Xuan Zhang
- Department of Biomedical Engineering, McGill University, 3775 University Street, Montreal, QC H3A 2B4, Canada.
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36
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Schroeder CA, Pluhařová E, Seidel R, Schroeder WP, Faubel M, Slavíček P, Winter B, Jungwirth P, Bradforth SE. Oxidation half-reaction of aqueous nucleosides and nucleotides via photoelectron spectroscopy augmented by ab initio calculations. J Am Chem Soc 2014; 137:201-9. [PMID: 25551179 DOI: 10.1021/ja508149e] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Oxidative damage to DNA and hole transport between nucleobases in oxidized DNA are important processes in lesion formation for which surprisingly poor thermodynamic data exist, the relative ease of oxidizing the four nucleobases being one such example. Theoretical simulations of radiation damage and charge transport in DNA depend on accurate values for vertical ionization energies (VIEs), reorganization energies, and standard reduction potentials. Liquid-jet photoelectron spectroscopy can be used to directly study the oxidation half-reaction. The VIEs of nucleic acid building blocks are measured in their native buffered aqueous environment. The experimental investigation of purine and pyrimidine nucleotides, nucleosides, pentose sugars, and inorganic phosphate demonstrates that photoelectron spectra of nucleotides arise as a spectral sum over their individual chemical components; that is, the electronic interactions between each component are effectively screened from one another by water. Electronic structure theory affords the assignment of the lowest energy photoelectron band in all investigated nucleosides and nucleotides to a single ionizing transition centered solely on the nucleobase. Thus, combining the measured VIEs with theoretically determined reorganization energies allows for the spectroscopic determination of the one-electron redox potentials that have been difficult to establish via electrochemistry.
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Affiliation(s)
- Christi A Schroeder
- Department of Chemistry, University of Southern California , Los Angeles, California 90089-0482, United States
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37
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Trinh C, Kirlikovali K, Das S, Ener M, Gray HB, Djurovich P, Bradforth SE, Thompson ME. Symmetry-Breaking Charge Transfer of Visible Light Absorbing Systems: Zinc Dipyrrins. J Phys Chem C Nanomater Interfaces 2014; 118:21834-21845. [PMID: 25270268 PMCID: PMC4174994 DOI: 10.1021/jp506855t] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 08/27/2014] [Indexed: 05/12/2023]
Abstract
Zinc dipyrrin complexes with two identical dipyrrin ligands absorb strongly at 450-550 nm and exhibit high fluorescence quantum yields in nonpolar solvents (e.g., 0.16-0.66 in cyclohexane) and weak to nonexistent emission in polar solvents (i.e., <10-3, in acetonitrile). The low quantum efficiencies in polar solvents are attributed to the formation of a nonemissive symmetry-breaking charge transfer (SBCT) state, which is not formed in nonpolar solvents. Analysis using ultrafast spectroscopy shows that in polar solvents the singlet excited state relaxes to the SBCT state in 1.0-5.5 ps and then decays via recombination to the triplet or ground states in 0.9-3.3 ns. In the weakly polar solvent toluene, the equilibrium between a localized excited state and the charge transfer state is established in 11-22 ps.
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Affiliation(s)
- Cong Trinh
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Kent Kirlikovali
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Saptaparna Das
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Maraia
E. Ener
- California
Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
| | - Harry B. Gray
- California
Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
| | - Peter Djurovich
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Stephen E. Bradforth
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Mark E. Thompson
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089, United States
- E-mail:
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38
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Buckley JJ, Couderc E, Greaney MJ, Munteanu J, Riche CT, Bradforth SE, Brutchey RL. Chalcogenol ligand toolbox for CdSe nanocrystals and their influence on exciton relaxation pathways. ACS Nano 2014; 8:2512-21. [PMID: 24499409 DOI: 10.1021/nn406109v] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
We have employed a simple modular approach to install small chalcogenol ligands on the surface of CdSe nanocrystals. This versatile modification strategy provides access to thiol, selenol, and tellurol ligand sets via the in situ reduction of R2E2 (R=tBu, Bn, Ph; E=S, Se, Te) by diphenylphosphine (Ph2PH). The ligand exchange chemistry was analyzed by solution NMR spectroscopy, which reveals that reduction of the R2E2 precursors by Ph2PH directly yields active chalcogenol ligands that subsequently bind to the surface of the CdSe nanocrystals. Thermogravimetric analysis, FT-IR spectroscopy, and energy dispersive X-ray spectroscopy provide further evidence for chalcogenol addition to the CdSe surface with a concomitant reduction in overall organic content from the displacement of native ligands. Time-resolved and low temperature photoluminescence measurements showed that all of the phenylchalcogenol ligands rapidly quench the photoluminescence by hole localization onto the ligand. Selenol and tellurol ligands exhibit a larger driving force for hole transfer than thiol ligands and therefore quench the photoluminescence more efficiently. The hole transfer process could lead to engineering long-lived, partially separated excited states.
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Affiliation(s)
- Jannise J Buckley
- Department of Chemistry and the Center for Energy Nanoscience, University of Southern California , Los Angeles, California 90089, United States
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39
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Cooper DR, Kudinov K, Tyagi P, Hill CK, Bradforth SE, Nadeau JL. Photoluminescence of cerium fluoride and cerium-doped lanthanum fluoride nanoparticles and investigation of energy transfer to photosensitizer molecules. Phys Chem Chem Phys 2014; 16:12441-53. [DOI: 10.1039/c4cp01044b] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
CexLa1−xF3 nanoparticles have been proposed for use in nanoscintillator–photosensitizer systems, aiming to combine the effects of radiotherapy and photodynamic therapy.
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Affiliation(s)
- Daniel R. Cooper
- Department of Biomedical Engineering
- McGill University
- 3775 Rue University
- Montreal, Canada
| | - Konstantin Kudinov
- Department of Chemistry
- University of Southern California
- Los Angeles, USA
| | - Pooja Tyagi
- Department of Chemistry
- McGill University
- 3775 Rue University
- Montreal, Canada
| | - Colin K. Hill
- Department of Radiation Oncology
- Keck School of Medicine
- University of Southern California
- Los Angeles, USA
| | | | - Jay L. Nadeau
- Department of Biomedical Engineering
- McGill University
- 3775 Rue University
- Montreal, Canada
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40
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Couderc E, Greaney MJ, Brutchey RL, Bradforth SE. Direct Spectroscopic Evidence of Ultrafast Electron Transfer from a Low Band Gap Polymer to CdSe Quantum Dots in Hybrid Photovoltaic Thin Films. J Am Chem Soc 2013; 135:18418-26. [DOI: 10.1021/ja406884h] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Elsa Couderc
- Department of Chemistry and
the Center for Energy Nanoscience, University of Southern California, Los Angeles, California 90089, United States
| | - Matthew J. Greaney
- Department of Chemistry and
the Center for Energy Nanoscience, University of Southern California, Los Angeles, California 90089, United States
| | - Richard L. Brutchey
- Department of Chemistry and
the Center for Energy Nanoscience, University of Southern California, Los Angeles, California 90089, United States
| | - Stephen E. Bradforth
- Department of Chemistry and
the Center for Energy Nanoscience, University of Southern California, Los Angeles, California 90089, United States
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41
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Thürmer S, Seidel R, Faubel M, Eberhardt W, Hemminger JC, Bradforth SE, Winter B. Photoelectron angular distributions from liquid water: effects of electron scattering. Phys Rev Lett 2013; 111:173005. [PMID: 24206487 DOI: 10.1103/physrevlett.111.173005] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Indexed: 05/03/2023]
Abstract
Photoelectron angular distributions (PADs) from the liquid-water surface and from bulk liquid water are reported for water oxygen-1s ionization. Although less so than for the gas phase, the measured PADs from the liquid are remarkably anisotropic, even at electron kinetic energies lower than 100 eV, when elastic scattering cross sections for the outgoing electrons with other water molecules are large. The PADs reveal that theoretical estimates of the inelastic mean free path are likely too long at low kinetic energies, and hence the electron probing depth in water, near threshold ionization, appears to be considerably smaller than so far assumed.
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Affiliation(s)
- Stephan Thürmer
- Joint Laboratory for Ultrafast Dynamics in Solutions and at Interfaces, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
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42
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Zhang Y, Oliver TAA, Das S, Roy A, Ashfold MNR, Bradforth SE. Exploring the Energy Disposal Immediately After Bond-Breaking in Solution: The Wavelength-Dependent Excited State Dissociation Pathways of para-Methylthiophenol. J Phys Chem A 2013; 117:12125-37. [DOI: 10.1021/jp405160n] [Citation(s) in RCA: 14] [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: 11/28/2022]
Affiliation(s)
- Yuyuan Zhang
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Thomas A. A. Oliver
- School of Chemistry, Cantocks Close, University of Bristol, Bristol BS8 1TS, U.K
| | - Saptaparna Das
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Anirban Roy
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | | | - Stephen E. Bradforth
- Department
of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
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43
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Mastron JN, Roberts ST, McAnally RE, Thompson ME, Bradforth SE. Aqueous Colloidal Acene Nanoparticles: A New Platform for Studying Singlet Fission. J Phys Chem B 2013; 117:15519-26. [DOI: 10.1021/jp4057972] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Joseph N. Mastron
- Department of Chemistry
and the Center for Energy Nanoscience, University of Southern California, Los Angeles, California
90089, United States
| | - Sean T. Roberts
- Department of Chemistry
and the Center for Energy Nanoscience, University of Southern California, Los Angeles, California
90089, United States
| | - R. Eric McAnally
- Department of Chemistry
and the Center for Energy Nanoscience, University of Southern California, Los Angeles, California
90089, United States
| | - Mark E. Thompson
- Department of Chemistry
and the Center for Energy Nanoscience, University of Southern California, Los Angeles, California
90089, United States
| | - Stephen E. Bradforth
- Department of Chemistry
and the Center for Energy Nanoscience, University of Southern California, Los Angeles, California
90089, United States
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44
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Thürmer S, Ončák M, Ottosson N, Seidel R, Hergenhahn U, Bradforth SE, Slavíček P, Winter B. On the nature and origin of dicationic, charge-separated species formed in liquid water on X-ray irradiation. Nat Chem 2013; 5:590-6. [DOI: 10.1038/nchem.1680] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Accepted: 05/03/2013] [Indexed: 12/22/2022]
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45
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Zhang Y, Oliver TAA, Ashfold MNR, Bradforth SE. Contrasting the excited state reaction pathways of phenol and para-methylthiophenol in the gas and liquid phases. Faraday Discuss 2013; 157:141-63; discussion 243-84. [PMID: 23230767 DOI: 10.1039/c2fd20043k] [Citation(s) in RCA: 68] [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: 11/21/2022]
Abstract
To explore how the solvent influences primary aspects of bond breaking, the gas and solution phase photochemistries of phenol and ofpara-methylthiophenol are directly compared using, respectively, H (Rydberg) atom photofragment translation spectroscopy and femtosecond transient absorption spectroscopy. Approaches are demonstrated that allow explicit comparisons of the nascent product energy disposals and dissociation mechanisms in the two phases. It is found, at least for the case of the weakly perturbing cyclohexane environment, that most aspects of the primary reaction dynamics of the isolated molecule are reproduced in solution. Specifically, in the gas phase, both molecules can undergo fast X-H (X = O, S) bond dissociation upon excitation with short wavelengths (193 < lambda(pump) < 216 nm), following population of the dissociative S2 (1 1(pi sigma*)) state. Product electronic branching, vibrational and translational energy disposals are determined. Photolysis of phenol and para-methylthiophenol in solution at 200 nm results in formation of vibrationally excited radicals on a timescale shorter than 200 fs. Excitation of para-methylthiophenol at 267 nm reaches close to the S1 (1 1(pipi*))/S2 (11(pi sigma*)) conical intersection (CI): ultrafast dissociation is observed in both the isolated and solution systems-again indicating direct dissociation on the S2 potential energy surface. Comparing results for this precursor at different excitation energies, the extent of geminate recombination and the derived H-atom ejection lengths in the condensed phase photolyses are in qualitative agreement with the translational energy release measured in the gas phase studies. Conversely, excitation of phenol at 267 nm prepares the system in its S1 state at an energy well below its S1/S2 CI; the slow O-H bond fission inferred in the gas phase experiments is observed directly in the time-resolved studies in cyclohexane solution via the appearance of phenoxyl radical absorption after -1 ns, with only S1 excited state absorption discernible at earlier delay times. The slow O-H bond fission in solution provides additional evidence for a tunnelling dissociation mechanism, where the H atom tunnels beneath the lower diabats of the S2/S1 CI. Finally, the photodissociation of phenol clusters in solution is considered, where evidence is presented that the O-H dissociation coordinate is impeded in H-bonded dimers.
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Affiliation(s)
- Yuyuan Zhang
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA
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46
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Zhong Q, Diev VV, Roberts ST, Antunez PD, Brutchey RL, Bradforth SE, Thompson ME. Fused porphyrin-single-walled carbon nanotube hybrids: efficient formation and photophysical characterization. ACS Nano 2013; 7:3466-3475. [PMID: 23477287 DOI: 10.1021/nn400362e] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A systematic study of the interaction between π-extended porphyrins and single-walled carbon nanotubes (SWNTs) is reported here. Zinc porphyrins with 1-pyrenyl groups in the 5,15-meso positions, 1, as well as compounds where one or both of the pyrene groups have been fused at the meso and β positions of the porphyrin core, 2 and 3, respectively, have been examined. The strongest binding to SWNTs is observed for porphyrin 3, leading to debundling of the nanotubes and formation of stable suspensions of 3-SWNT hybrids in a range of common organic solvents. Absorption spectra of 3-SWNT suspensions are broad and continuous (λ=400-1400 nm), and the Q-band of 3 displays a significant bathochromic shift of 33 nm. The surface coverage of the SWNTs in the nanohybrids was estimated by spectroscopic and analytical methods and found to reach 64% for (7,6) nanotubes. The size and shape of π-conjugated porphyrins were found to be important factors in determining the strength of the π-π interactions, as the linear anti-3 isomer displays more than 90% binding selectivity compared to the bent syn-3 isomer. Steady-state photoluminescence measurements show quenching of porphyrin emission from the nanohybrids. Femtosecond transient absorption spectroscopy reveals that this quenching results from ultrafast electron transfer from the photoexcited porphyrin to the SWNT (1/kCT=260 fs) followed by rapid charge recombination on a picosecond time scale. Overall, our data demonstrate that direct π-π interaction between fused porphyrins and SWNTs leads to electronically coupled stable nanohybrids.
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Affiliation(s)
- Qiwen Zhong
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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47
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Harris SJ, Murdock D, Zhang Y, Oliver TAA, Grubb MP, Orr-Ewing AJ, Greetham GM, Clark IP, Towrie M, Bradforth SE, Ashfold MNR. Comparing molecular photofragmentation dynamics in the gas and liquid phases. Phys Chem Chem Phys 2013; 15:6567-82. [PMID: 23552482 DOI: 10.1039/c3cp50756d] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [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
This article explores the extent to which insights gleaned from detailed studies of molecular photodissociations in the gas phase (i.e. under isolated molecule conditions) can inform our understanding of the corresponding photofragmentation processes in solution. Systems selected for comparison include a thiophenol (p-methylthiophenol), a thioanisole (p-methylthioanisole) and phenol, in vacuum and in cyclohexane solution. UV excitation in the gas phase results in RX-Y (X = O, S; Y = H, CH3) bond fission in all cases, but over timescales that vary by ~4 orders of magnitude - all of which behaviours can be rationalised on the basis of the relevant bound and dissociative excited state potential energy surfaces (PESs) accessed by UV photoexcitation, and of the conical intersections that facilitate radiationless transfer between these PESs. Time-resolved UV pump-broadband UV/visible probe and/or UV pump-broadband IR probe studies of the corresponding systems in cyclohexane solution reveal additional processes that are unique to the condensed phase. Thus, for example, the data clearly reveal evidence of (i) vibrational relaxation of the photoexcited molecules prior to their dissociation and of the radical fragments formed upon X-Y bond fission, and (ii) geminate recombination of the RX and Y products (leading to reformation of the ground state parent and/or isomeric adducts). Nonetheless, the data also show that, in each case, the characteristics (and the timescale) of the initial bond fission process that occurs under isolated molecule conditions are barely changed by the presence of a weakly interacting solvent like cyclohexane. These condensed phase studies are then extended to an ether analogue of phenol (allyl phenyl ether), wherein UV photo-induced RO-allyl bond fission constitutes the first step of a photo-Claisen rearrangement.
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Affiliation(s)
- Stephanie J Harris
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK
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48
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Georgin M, Carlini L, Cooper D, Bradforth SE, Nadeau JL. Differential effects of β-mercaptoethanol on CdSe/ZnS and InP/ZnS quantum dots. Phys Chem Chem Phys 2013; 15:10418-28. [PMID: 23681155 DOI: 10.1039/c3cp50311a] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Marcel Georgin
- Department of Biomedical Engineering, McGill University, Montreal, QC H3A 2B4, Canada
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49
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Pluhařová E, Ončák M, Seidel R, Schroeder C, Schroeder W, Winter B, Bradforth SE, Jungwirth P, Slavíček P. Transforming Anion Instability into Stability: Contrasting Photoionization of Three Protonation Forms of the Phosphate Ion upon Moving into Water. J Phys Chem B 2012; 116:13254-64. [DOI: 10.1021/jp306348b] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [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)
- Eva Pluhařová
- Institute
of Organic Chemistry
and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
- Department of Physical Chemistry, Institute of Chemical Technology, Technická
5, 16628 Prague 6, Czech Republic
| | - Milan Ončák
- Department of Physical Chemistry, Institute of Chemical Technology, Technická
5, 16628 Prague 6, Czech Republic
| | - Robert Seidel
- Helmholtz-Zentrum Berlin für Materialien und Energie, and BESSY, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
- Department of Chemistry, University of Southern California, Los Angeles, California
90089-0482, United States
| | - Christi Schroeder
- Department of Chemistry, University of Southern California, Los Angeles, California
90089-0482, United States
| | - William Schroeder
- Department of Chemistry, University of Southern California, Los Angeles, California
90089-0482, United States
| | - Bernd Winter
- Helmholtz-Zentrum Berlin für Materialien und Energie, and BESSY, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
| | - Stephen E. Bradforth
- Department of Chemistry, University of Southern California, Los Angeles, California
90089-0482, United States
| | - Pavel Jungwirth
- Institute
of Organic Chemistry
and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
| | - Petr Slavíček
- Department of Physical Chemistry, Institute of Chemical Technology, Technická
5, 16628 Prague 6, Czech Republic
- J. Heyrovský Institute of Physical Chemistry, Dolejškova 3,
18223 Prague 8, Czech Republic
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50
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Greaney MJ, Das S, Webber DH, Bradforth SE, Brutchey RL. Improving open circuit potential in hybrid P3HT:CdSe bulk heterojunction solar cells via colloidal tert-butylthiol ligand exchange. ACS Nano 2012; 6:4222-30. [PMID: 22537193 DOI: 10.1021/nn3007509] [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] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Organic ligands have the potential to contribute to the reduction potential, or lowest unoccupied molecular orbital (LUMO) energy, of semiconductor nanocrystals. Rationally introducing small, strongly binding, electron-donating ligands should enable improvement in the open circuit potential of hybrid organic/inorganic solar cells by raising the LUMO energy level of the nanocrystal acceptor phase and thereby increasing the energy offset from the polymer highest occupied molecular orbital (HOMO). Hybrid organic/inorganic solar cells fabricated from blends of tert-butylthiol-treated CdSe nanocrystals and poly(3-hexylthiophene) (P3HT) achieved power conversion efficiencies of 1.9%. Compared to devices made from pyridine-treated and nonligand exchanged CdSe, the thiol-treated CdSe nanocrystals are found to consistently exhibit the highest open circuit potentials with V(OC) = 0.80 V. Electrochemical determination of LUMO levels using cyclic voltammetry and spectroelectrochemistry suggest that the thiol-treated CdSe nanocrystals possess the highest lying LUMO of the three, which translates to the highest open circuit potential. Steady-state and time-resolved photoluminescence quenching experiments on P3HT:CdSe films provide insight into how the thiol-treated CdSe nanocrystals also achieve greater current densities in devices relative to pyridine-treated nanocrystals, which are thought to contain a higher density of surface traps.
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Affiliation(s)
- Matthew J Greaney
- Department of Chemistry and the Center for Energy Nanoscience, University of Southern California, Los Angeles, California 90089-0744, USA
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