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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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Journal ArticleDOI
TL;DR: In this paper, the kinetics of intermolecular excimer formation are reported for a polystyrene sample containing one pyrene end group (PS-Py), which serves as a model for the termination process in free-radical polymerization.
Abstract: The kinetics of intermolecular excimer formation are reported for a polystyrene sample containing one pyrene end group (PS-Py). This reaction serves as a model for the termination process in free-radical polymerization. Fluorescence decay profiles were measured for both monomer and excimer emissions, and from these, the transient contribution to the diffusion-controlled reaction was evaluated. In this way, the mutual diffusion coefficients characteristic of the reaction could be determined. These values (Do = 1.4 X 104 cm2 a-1, toluene 20 "C; 1.2 X lP cm2 s-l, cyclohexane, 34.5 "C) for the polymer of M, = 10 400 (M, f M, = 1.05) are remarkably close to values reported for polystyrene ihelf (M, = 10 700) as determined by quasielastic light scattering (Do = 1.57 x lo+, toluene 20 OC; 1.23 X lP, cyclohexane, 34.5 "C). This close correspondence between the two seta of values implies that, in this concentration region, excimer formation (and the termination reaction for polymers of this length) is controlled by center-of-mass diffusion of the polymer.

30 citations

Journal ArticleDOI
TL;DR: The results give the spectral and dynamical properties of a Zr-NDC MOF in solvent suspensions, opening the way to further studies of these kinds of MOFs interacting with fluorescent dyes for possible photonic applications.
Abstract: We report on the spectra and dynamics of a Zr-naphthalene dicarboxylic acid (Zr-NDC) MOF in different diluted solvent suspensions and in a concentrated tetrahydrofuran (THF) one. In a diluted diethyl ether (DE) suspension, we observed intraparticle excimer formation between neighboring naphthalene organic linkers, leading to a red-shifted broad band in the emission spectrum and to a dynamics composed of three components τ1 = 650 ps, τ2 = 3.7 ns and τ3 = 13.9 ns, assigned to the excimer photoproduction, monomer and excimer lifetimes, respectively. Furthermore, both absorption and emission spectra show a blue shift in more polar solvents characterized by the solvent polarity function f(e,n). We also observed changes in the excimer formation time (490-840 ps) probably due to a variation in the MOF structural fluctuation induced by solvent filling. The global fluorescence quantum yield of these suspensions is around 0.30 ± 0.05. At higher concentrations of the MOF particles, we observed the absorption and emission signals of aggregates having an intercrystal excimer formation in ∼ 5 ps in a THF suspension, ∼ 100 times shorter than that observed in a diluted one. Our results give the spectral and dynamical properties of a Zr-NDC MOF in solvent suspensions, opening the way to further studies of these kinds of MOFs interacting with fluorescent dyes for possible photonic applications.

30 citations

Journal ArticleDOI
TL;DR: Photophysical investigations are reported for two arene-derivatized zirconium phosphonates (layered solids) and the chromophore groups that are attached within the interlayer region of these materials are seen to form excimer pairs.
Abstract: Photophysical investigations are reported for two arene-derivatized zirconium phosphonates (layered solids). The chromophore groups that are attached within the interlayer region of these materials are seen to form excimer pairs. Whereas the naphthalene-containing system exhibits both monomer and excimer fluorescence, the potentially greater overlap of chromophores for the system containing anthracene-pendant groups causes that compound to only show excimer fluorescence.

30 citations

Journal ArticleDOI
TL;DR: The galleries of an Mg-Al layered double hydroxide have been functionalized by intercalation of carboxymethyl beta-cyclodextrin cavities and two types of included naphthalene molecules have been identified: a preformed excimer-like species characterized by the absence of rise time in decay measurements and a monomeric species that is incapable of excimer formation due to the presence of suitably located includednaphthalenes in its proximity.
Abstract: The galleries of an Mg-Al layered double hydroxide have been functionalized by intercalation of carboxymethyl, \beta -cyclodextrin cavities. The anchored cavities form a random array of identical-sized hydrophobic nanopockets arranged in a bilayer fashion in the interlamellar space of the layered solid. Naphthalene molecules have been included within these cavities by partitioning from a polar solvent. The fluorescence from the included naphthalene shows an unusual behaviorsthe excimer to monomer emission intensity decreases with increasing concentration of included naphthalene. This is shown to be a consequence of the absence of translational mobility of the naphthalene-cyclodextrin adduct in the functionalized solid. Two types of included naphthalene have been identified: a preformed excimer-like species characterized by the absence of rise time in decay measurements and a monomeric species that is incapable of excimer formation due to the absence of suitably located included naphthalenes in its proximity. The concentration of each species and the enthalpy for excimer formation have been determined from the temperature variation of fluorescence intensities.

30 citations

Journal ArticleDOI
W. Stampor1
TL;DR: In this article, electric field and excitation wavelength dependence of TPD and TAPC were measured in films of N,N′-diphenyl-N,N, N′-bis(3-methylphenyl)-1,1′-biphenymyl-4,4′ -diamine (TPD) and 1, 1.1′ -bis(di-4-tolylaminophenyl) cyclohexane (TAPC), the diamine compounds commonly used as hole-transporting materials in organic

30 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023106
2022253
202142
202045
201959
201847