Topic
Excimer
About: Excimer is a research topic. Over the lifetime, 3725 publications have been published within this topic receiving 75104 citations.
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TL;DR: The fluorescence excitation spectra of L showed a fluorescent "turn-on" probe for Fe(3+) with 30-fold enhancement in excitation band intensity of excimer.
Abstract: A highly selective and sensitive ratiometric and “turn-on” fluorescent probe for Fe3+, 2-(1-pyrenyl) benzimidazole (L), was synthesized by a one-step process. In emission spectra, the relative intensity ratio of excimer to monomer fluorescence (IE450/IM387) of L increased 510-fold upon the addition of 30 equiv. of Fe3+ with a detection limit of 0.2 μM (11.2 ppb) in aqueous solution. Meanwhile, the fluorescence excitation spectra of L showed a fluorescent “turn-on” probe for Fe3+ with 30-fold enhancement in excitation band intensity of excimer.
35 citations
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TL;DR: The kinetics of the fluorescence self-quenching of pyrene in multilamellar vesicles of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) in the fluid phase are studied and it is concluded that the primary step of the diffusion of the pyrene-labeled phospholipid involves the simultaneous jump of phospholIPid and fluorophore moieties.
35 citations
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TL;DR: In this article, the photophysical properties of 4-alkyl- and 4alkoxy-4′-cyanobiphenyls with different chain lengths were compared in the dilute solution phase and bulk phases with respect to Stokes shifts and decay times.
Abstract: The photophysical properties of 4-alkyl- and 4-alkoxy-4′-cyanobiphenyls with different chain lengths were compared in the dilute solution phase and bulk phases (crystalline, liquid-crystalline and isotropic) with respect to Stokes shifts and decay times. In solution, highly polar states are formed with decay times around 1 ns and subnanosecond rise times indicative of a molecular rearrangement occurring prior to emission. In the bulk phase, the major proportion of the emission derives from an excimer-type state with a red-shifted spectrum and very long decay time (10–25 ns depending on temperature and chain length). Possible excimer conformations are discussed. An excimer with a twisted geometry (twisted intramolecular charge transfer (TICT) excimer) is excluded by comparison with a bridged biphenyl system (fluorene derivative). The same compound also demonstrates that excited state intramolecular relaxation towards a 90° twist angle is unlikely. In polar solvents, relaxation occurs towards an increased planarity in accordance with the Rapp model. This conclusion is discussed in relation to results from quantum chemical calculations.
35 citations
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TL;DR: In this article, the state selective photodissociation of acetylene, C2H2/C2D2, was studied in the wavelength range 121.2-132.2 nm by high resolution Rydberg atom time-of-flight measurements on the atomic fragment, H/D.
Abstract: The state selective photodissociation of acetylene, C2H2/C2D2, was studied in the wavelength range 121.2–132.2 nm by high resolution Rydberg atom time-of-flight measurements on the atomic fragment, H/D. In the wavelength region studied members of all four Rydberg series and the highly excited Ẽ valence state were state selectively excited using tunable vacuum-ultraviolet laser radiation. The lifetime of the excited states which were studied varied from 58 fs to more than 2 ps. Formation of the ethynyl radical in its X electronic ground state and its first electronically excited A state is observed with practically no indication of B state fragments. Two decay channels with different dissociation dynamics were also observed. In both channels the observed decay dynamics depended strongly on the excited state of the parent molecule. Further there are major differences between these two dissociation pathways with respect to the measured internal energy and angular distributions. In one channel the dissociat...
35 citations
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TL;DR: The fluorescence decays of pyrene in small and large unilamellar L,α-dipalmitoylphosphatidylcholine vesicles have been investigated as a function of probe concentration and temperature and the fluorescence decay kinetics are compatible with the excimer formation scheme which is valid in an isotropic medium.
Abstract: The fluorescence decays of pyrene in small and large unilamellar L, alpha-dipalmitoylphosphatidylcholine vesicles have been investigated as a function of probe concentration and temperature. When the molar ratio of pyrene to phospholipid equals 1:3000, no excimer emission is observed and the fluorescence decays are mono-exponential. When this ratio is equal to or higher than 1:120, excimer formation is observed. Above the phase transition temperature the observed fluorescence decays of monomer and excimer can be adequately described by a bi-exponential function. The monomer decays can be equally well fitted to a decay law which takes into account a time-dependence in the probe diffusion rate constant. The fluorescence decay kinetics are compatible with the excimer formation scheme which is valid in an isotropic medium. The excimer lifetime and the (apparent) rate constant of excimer formation have been determined as a function of probe concentration at different temperatures above the phase transition temperature. The activation energy of excimer formation is found to be 29.4 +/- 1.3 kJ/mol. In small unilamellar vesicles the diffusion constant associated with the pyrene excimer formation process varies from 8.0 X 10(-7) cm2/s at 40 degrees C to 2.2 X 10(-6) cm2/s at 70 degrees C. Below the phase transition temperature the monomer decays can be described by a decay law which takes into account a time dependence of the rate constant of excimer formation. The lateral diffusion coefficient of pyrene calculated from the decay fitting parameters of the monomer region varies from 4.0 X 10(-9) cm2/s at 20 degrees C to 7.9 X 10(-8) cm2/s at 35 degrees C. No significant difference could be observed between the pyrene fluorescence decay kinetics in small and large unilamellar vesicles.
35 citations