Isomérisation photochimique de l'azobenzène en solution. I

1974 ◽  
Vol 52 (10) ◽  
pp. 1848-1857 ◽  
Author(s):  
Jacques Ronayette ◽  
René Arnaud ◽  
Philippe Lebourgeois ◽  
Jacques Lemaire
Keyword(s):  
Internal Conversion ◽  
Quantum Yields ◽  
Nonradiative Transition ◽  
Triplet Level ◽  
Trans Form ◽  
Triplet Energy ◽  
Diffusion Controlled ◽  
Photochemical Isomerization ◽  
Low Probability ◽  
Triplet Energy Transfer

The photochemical isomerization of azobenzene can be sensitized by aromatic compounds (chrysene, phenanthrene, naphthalene) or by carbonyls (benzil, biacetyl). Comparison of the photostationary states and the initial quantum yields of isomerization leads to the deduction of a mechanism for this sensitization. The triplet levels Tβt and Tβc of the trans and cis forms are populated by diffusion-controlled, triplet–triplet energy transfer. These levels are deactivated nonradiatively without giving rise to isomerization. The Tβc level of the cis form undergoes a quantitative internal conversion to another triplet level Tαc, while the Tβt level of the trans form undergoes a nonradiative transition to the ground state. The internal conversion Tβt → Tαt in the trans isomer occurs with low probability (0.04 to 0.06). The levels Tαt and Tαc are the intermediates in the isomerization; they are deactivated to the two isomeric forms of azobenzene with equal probability. [Journal translation]

Un exemple d'isomérisation radicalaire en chaînes: la photoinduction de l'isomérisation cis–trans de la pentène-3 one-2

1977 ◽  
Vol 55 (22) ◽  
pp. 3915-3926 ◽  
Author(s):  
Armel Rioual ◽  
André Deflandre ◽  
Jacques Lemaire
Keyword(s):  
Energy Transfer ◽  
Quantum Yields ◽  
Unsaturated Ketone ◽  
Chain Process ◽  
Triplet Energy ◽  
Low Concentrations ◽  
Energy Transfers ◽  
Donor And Acceptor ◽  
A Chain ◽  
Triplet Energy Transfer

Mechanisms of the photosensitized cis–trans photoisomerization of 3-penten-2-one which do not imply only classical triplet–triplet energy transfer are proposed; they are based upon measurements of the variations of initial quantum yields of isomerization with the initial donor and acceptor concentrations, the wavelength of excitation, and the nature of the donor and of the solvent. Carbonyl donors (acetophenone, benzophenone, acetone) induce a radical isomerization by a chain process in reducing solvents; the example of acetophenone is specially interesting. In solvents in which the donor is not photoreduced (as benzene or CCl4) classical triplet–triplet energy transfers occur. Sensitization with aromatic donors (benzene, mesitylene) proceeds through triplet–triplet energy transfer at low concentrations of the acceptor. At higher concentrations of acceptor, an exciplex is formed between the ketone and the aromatic in its singlet excited state; this exciplex is deactivated by dissociation and by causing the isomerization of the α,β-unsaturated ketone.

H2O2-activated triplet–triplet annihilation upconversion via modulation of the fluorescence quantum yields of the triplet acceptor and the triplet–triplet-energy-transfer efficiency

2015 ◽  
Vol 51 (62) ◽  
pp. 12403-12406 ◽  
Author(s):  
Renjie Tao ◽  
Jianzhang Zhao ◽  
Fangfang Zhong ◽  
Caishun Zhang ◽  
Wenbo Yang ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Energy Transfer Efficiency ◽  
Transfer Efficiency ◽  
Quantum Yields ◽  
Fluorescent Product ◽  
Triplet Energy ◽  
Fluorescence Quantum Yields ◽  
Triplet Energy Transfer ◽  
Triplet Triplet Annihilation

H2O2-activatable TTA upconversion was achieved with non-fluorescent 9,10-bis(diphenylphosphino)anthracene as a triplet acceptor/emitter, which can be oxidized to a fluorescent product by H2O2.

scholarly journals Green-to-Blue Triplet Fusion Upconversion Sensitized by Anisotropic CdSe Nanoplatelets

2020 ◽  
Author(s):  
Zachary A. VanOrman ◽  
Alexander S. Bieber ◽  
Sarah Wieghold ◽  
Lea Nienhaus
Keyword(s):  
Energy Transfer ◽  
Quantum Confinement ◽  
Quantum Yields ◽  
Cdse Nanocrystals ◽  
Triplet Energy ◽  
Tunneling Barrier ◽  
Low Efficiency ◽  
Back Transfer ◽  
Triplet Energy Transfer ◽  
Photocatalytic Applications

<p>Green-to-blue photon upconversion bears great potential in photocatalytic applications. However, current hybrid inorganic-organic upconversion schemes utilizing spherical CdSe nanocrystals are often limited by energetic polydispersity, low quantum yields and an additional tunneling barrier resulting from the necessity of surface-passivating inorganic shells. In this contribution, we introduce anisotropic CdSe nanoplatelets as triplet sensitizers. Here, quantum confinement occurs in only one direction, erasing effects stemming from energetic polydispersity. We investigate the triplet energy transfer from the CdSe nanoplatelets to the surface-bound triplet acceptor 9-anthracene carboxylic acid. We further focus on the influence of nanoplatelet stacking and singlet back transfer on the observed upconversion efficiency. We obtain an upconversion quantum yield of 5.4% at a power density of 11 W/cm<sup>2­</sup> using the annihilator 9,10-diphenylanthracene, and a low efficiency threshold <i>I</i><sub>th</sub> of 237 mW/cm<sup>2</sup>. </p>

scholarly journals Steric shielding vs. σ–π orbital interactions in triplet–triplet energy transfer

2015 ◽  
Vol 6 (7) ◽  
pp. 4035-4041 ◽  
Author(s):  
Inmaculada Andreu ◽  
Isabel Morera ◽  
Fabrizio Palumbo ◽  
German Sastre ◽  
Francisco Bosca ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Rate Constants ◽  
Transfer Rate ◽  
Fine Tuning ◽  
Triplet Level ◽  
Energy Transfer Rate ◽  
Triplet Energy ◽  
Orbital Interactions ◽  
Triplet Energy Transfer

Fine tuning of the benzoylthiophene triplet level through σ–π orbital interactions modifies the energy transfer rate constants to appropriate acceptors.

scholarly journals Green-to-Blue Triplet Fusion Upconversion Sensitized by Anisotropic CdSe Nanoplatelets

2020 ◽  
Author(s):  
Zachary A. VanOrman ◽  
Alexander S. Bieber ◽  
Sarah Wieghold ◽  
Lea Nienhaus
Keyword(s):  
Energy Transfer ◽  
Quantum Confinement ◽  
Quantum Yields ◽  
Cdse Nanocrystals ◽  
Triplet Energy ◽  
Tunneling Barrier ◽  
Low Efficiency ◽  
Back Transfer ◽  
Triplet Energy Transfer ◽  
Photocatalytic Applications

<p>Green-to-blue photon upconversion bears great potential in photocatalytic applications. However, current hybrid inorganic-organic upconversion schemes utilizing spherical CdSe nanocrystals are often limited by energetic polydispersity, low quantum yields and an additional tunneling barrier resulting from the necessity of surface-passivating inorganic shells. In this contribution, we introduce anisotropic CdSe nanoplatelets as triplet sensitizers. Here, quantum confinement occurs in only one direction, erasing effects stemming from energetic polydispersity. We investigate the triplet energy transfer from the CdSe nanoplatelets to the surface-bound triplet acceptor 9-anthracene carboxylic acid. We further focus on the influence of nanoplatelet stacking and singlet back transfer on the observed upconversion efficiency. We obtain an upconversion quantum yield of 5.4% at a power density of 11 W/cm<sup>2­</sup> using the annihilator 9,10-diphenylanthracene, and a low efficiency threshold <i>I</i><sub>th</sub> of 237 mW/cm<sup>2</sup>. </p>

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.

Why Triage the Materials with Low Luminescence Quantum Efficiency: The Use of 35Cbz4BzCN as a Universal Host for Organic Light Emitting Diode through Effective Triplet Energy Transfer

2021 ◽  
Author(s):  
Yi-Mei Huang ◽  
Tse-Ying Chen ◽  
Deng-Gao Chen ◽  
Hsuan-Chi Liang ◽  
Cheng-Ham Wu ◽  
...  
Keyword(s):  
Light Emitting Diode ◽  
Delayed Fluorescence ◽  
Triplet Energy ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Thermally Activated ◽  
Triplet Energy Transfer ◽  
Triplet Lifetime ◽  
Triplet Excitons

35Cbz4BzCN, a novel universal host with long triplet lifetime, has been developed. The triplet excitons in 35Cbz4BzCN can be effectively harvested by phosphorescence and thermally activated delayed fluorescence emitters. In...

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