scholarly journals Chlorophyll-Carotenoid Excitation Energy Transfer in High-Light-Exposed Thylakoid Membranes Investigated by Snapshot Transient Absorption Spectroscopy

2018 ◽  
Vol 140 (38) ◽  
pp. 11965-11973 ◽  
Author(s):  
Soomin Park ◽  
Alexandra L. Fischer ◽  
Collin J. Steen ◽  
Masakazu Iwai ◽  
Jonathan M. Morris ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Excitation Energy Transfer ◽  
Thylakoid Membranes ◽  
High Light ◽  
Transient Absorption Spectroscopy

scholarly journals Snapshot Transient Absorption Spectroscopy of Carotenoid Radical Cations in High-Light-Acclimating Thylakoid Membranes

2017 ◽  
Vol 8 (22) ◽  
pp. 5548-5554 ◽  
Author(s):  
Soomin Park ◽  
Alexandra L. Fischer ◽  
Zhirong Li ◽  
Roberto Bassi ◽  
Krishna K. Niyogi ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Radical Cations ◽  
Thylakoid Membranes ◽  
High Light ◽  
Transient Absorption Spectroscopy

scholarly journals Beads on a Chain (BoC) Fluorescent Oligomeric Materials: Interactions of Conjugated Organic Cross-Linkers with Silsesquioxane Cages

2021 ◽  
Author(s):  
Shahrea Mahbub ◽  
Sukanya Saha ◽  
Ramakrishna Guda ◽  
Joseph Furgal
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Transient Absorption ◽  
Electronic Materials ◽  
Field Effect Transistors ◽  
Single Photon ◽  
Photophysical Properties ◽  
Excitation Energy Transfer ◽  
Transient Absorption Spectroscopy ◽  
Gravimetric Analysis

<div> <div> <div> <p>Organic electronic materials have advantages over inorganics in terms of versatility, cost and processability. Recent advancements in organic materials for light emitting diodes (OLED), field effect transistors (OFET), and photovoltaics have engendered extensive innovation potential on this field. In this research, we focus on synthesizing SQ (silsesquioxane) based oligomers cross- linked by di-bromo-aromatic linkers and explore how the cross-linker and oligomer length influence their photophysical properties. Bis-tri-alkoxy silyl (linker) model compounds were synthesized to compare non-cage photophysical properties with the oligomers. Several techniques such as UV/Vis, fluorescence, FTIR, thermal gravimetric analysis (TGA) have been used to characterize the systems. Time-resolved fluorescence and femtosecond transient absorption spectroscopy are used to understand the excited state dynamics of these materials. Studies are carried out to understand the differences between monomers and oligomers and potential energy transfer and charge transfer between the cages and cross-linking chromophores. Transient absorption showed lower energy absorption from the excited states, suggesting short range communication between moieties. Single photon counting studies have shown distinct lifetime differences between most linkers and cages showing possible excitation energy transfer through these materials. Transient absorption anisotropy measurements have shown signatures for excitation energy transfer between linker chromophores for oligomeric compounds. The silsesquioxane (SQ) backbone of the oligomers gives substantial thermal stability as well as solution processability, giving better flexibility for achieving energy transfer between linking chromophores. </p> </div> </div> </div>

scholarly journals Beads on a Chain (BoC) Fluorescent Oligomeric Materials: Interactions of Conjugated Organic Cross-Linkers with Silsesquioxane Cages

2021 ◽  
Author(s):  
Shahrea Mahbub ◽  
Sukanya Saha ◽  
Ramakrishna Guda ◽  
Joseph Furgal
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Transient Absorption ◽  
Electronic Materials ◽  
Field Effect Transistors ◽  
Single Photon ◽  
Photophysical Properties ◽  
Excitation Energy Transfer ◽  
Transient Absorption Spectroscopy ◽  
Gravimetric Analysis

<div> <div> <div> <p>Organic electronic materials have advantages over inorganics in terms of versatility, cost and processability. Recent advancements in organic materials for light emitting diodes (OLED), field effect transistors (OFET), and photovoltaics have engendered extensive innovation potential on this field. In this research, we focus on synthesizing SQ (silsesquioxane) based oligomers cross- linked by di-bromo-aromatic linkers and explore how the cross-linker and oligomer length influence their photophysical properties. Bis-tri-alkoxy silyl (linker) model compounds were synthesized to compare non-cage photophysical properties with the oligomers. Several techniques such as UV/Vis, fluorescence, FTIR, thermal gravimetric analysis (TGA) have been used to characterize the systems. Time-resolved fluorescence and femtosecond transient absorption spectroscopy are used to understand the excited state dynamics of these materials. Studies are carried out to understand the differences between monomers and oligomers and potential energy transfer and charge transfer between the cages and cross-linking chromophores. Transient absorption showed lower energy absorption from the excited states, suggesting short range communication between moieties. Single photon counting studies have shown distinct lifetime differences between most linkers and cages showing possible excitation energy transfer through these materials. Transient absorption anisotropy measurements have shown signatures for excitation energy transfer between linker chromophores for oligomeric compounds. The silsesquioxane (SQ) backbone of the oligomers gives substantial thermal stability as well as solution processability, giving better flexibility for achieving energy transfer between linking chromophores. </p> </div> </div> </div>

Thymine Dimerization Induced by Oxidative DNA Lesions and Epigenetic Intermediates via Triplet-Triplet Energy Transfer

2020 ◽  
Author(s):  
Mauricio Lineros-Rosa ◽  
Antonio Francés-Monerris ◽  
Antonio Monari ◽  
Miguel Angél Miranda ◽  
Virginie Lhiaubet-Vallet
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Transient Absorption ◽  
Theoretical Calculations ◽  
Dna Lesions ◽  
Transient Absorption Spectroscopy ◽  
Triplet Energy ◽  
Pyrimidine Dimers ◽  
Triplet Energy Transfer ◽  
Dna Nucleobases

Interaction of nucleic acids with light is a scientific question of paramount relevance not only in the understanding of life functioning and evolution, but also in the insurgence of diseases such as malignant skin cancer and in the development of biomarkers and novel light-assisted therapeutic tools. This work shows that the UVA portion of sunlight, not absorbed by canonical DNA nucleobases, can be absorbed by 5-formyluracil (ForU) and 5-formylcytosine (ForC), two ubiquitous oxidative lesions and epigenetic intermediates present in living beings in natural conditions. We measure the strong propensity of these molecules to populate triplet excited states able to transfer the excitation energy to thymine-thymine dyads, inducing the formation of the highly toxic and mutagenic cyclobutane pyrimidine dimers (CPDs). By using steady-state and transient absorption spectroscopy, NMR, HPLC, and theoretical calculations, we quantify the differences in the triplet-triplet energy transfer mediated by ForU and ForC, revealing that the former is much more efficient in delivering the excitation energy and producing the CPD photoproduct. Although significantly slower than ForU, ForC is also able to harm DNA nucleobases and therefore this process has to be taken into account as a viable photosensitization mechanism. The present findings evidence a rich photochemistry crucial to understand DNA photodamage and of potential use in the development of biomarkers and non-conventional photodynamic therapy agents.

Decoupling the artificial special pair to slow down the rate of singlet energy transfer

2012 ◽  
Vol 16 (05n06) ◽  
pp. 685-694 ◽  
Author(s):  
Pierre D. Harvey ◽  
Adam Langlois ◽  
Mikhail Filatov ◽  
Daniel Fortin ◽  
Kei Ohkubo ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Absorption Spectroscopy ◽  
Density Functional ◽  
Transient Absorption ◽  
Geometry Optimization ◽  
Transient Absorption Spectroscopy ◽  
Free Base ◽  
Functional Theory ◽  
Time Resolved ◽  
Slow Rise

Trimer 2, composed of a cofacial heterobismacrocycle, octamethyl-porphyrin zinc(II) and bisarylporphyrin zinc(II) held by an anthracenyl spacer, and a flanking acceptor, bisarylporphyrin free-base ( Ar = -3,5-(t Bu )2 C 6 H 3), has been studied by means of absorption spectroscopy, "steady state and time-resolved fluorescence" and fs transient absorption spectroscopy, and density functional theory (DFT) in order to assess the effect of decoupling the chromophores' low energy MOs on the rate of the singlet, S1, energy transfer, k ET , compared to a recently reported work on a heavily coupled trimeric system, Trimer 1, [biphenylenebis(n-nonyl)porphyrin zinc(II)]-bisarylporphyrin free-base ( Ar = -3,5-(t Bu )2 C 6 H 3). The position of the 0–0 peaks of the absorption and fluorescence spectra of Trimer 2 indicates that these porphyrin units are respectively energy donor 1, donor 2, and acceptor. The DFT computations confirm that the MOs of the cofacial donor 1-donor 2 dyad are decoupled, but significant MO coupling between donor 2 and acceptor 1 is still present despite the strong dihedral angle between their respective average planes (77.5°: geometry optimization by DFT). The fs transient absorption spectra exhibit a clear S1–Sn fingerprint of the bisarylporphyrin zinc(II) chromophore and the kinetic trace exhibits a slow rise time of 87 ps, due to a S1 donor 1 → donor 2 ET. The transient species donor 2 and acceptor decay respectively in the short (~1.5) ns and 6 ns time scale.

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