Photophysics of polycyclic aromatic hydrocarbons adsorbed on silica gel surfaces. 1. Fluorescence lifetime distribution analysis: an ill-conditioned problem

Liu, Yuan S.; Ware, William R.

doi:10.1021/j100124a033

Cited by 82 publications

(44 citation statements)

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“…An optically thick (ϳ0.5 mm) polymer film prepared from the same dye solution was used as a reference sample. The resulting concentration of NBIA in PMMA was about 10 25 M. The polymer provides a reasonably high dielectric contrast between the filler and silica globules (refractive index of 1.490 for PMMA versus ϳ1.3 for opal silica clusters [12,13]), and makes it possible to avoid undesirable interactions of dye molecules with the silica surface [16]. In nonpolar solvents, the NBIA dye has a high quantum yield [17] and a substantial Stokes loss that provides a weak reabsorption of fluorescence.…”

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confidence: 99%

Spontaneous Emission of Organic Molecules Embedded in a Photonic Crystal

et al. 1998

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We report on modification of the spontaneous emission of dye molecules embedded in a threedimensional solid-state photonic crystal exhibiting a stop band in the visible range. Molecules embedded in artificial opal filled with a polymer show a dip in the fluorescence spectrum and nonexponential spontaneous decay kinetics containing both accelerated and inhibited components compared to the dye fluorescence in a reference polymer matrix. Results are interpreted in terms of redistribution of the photon density of states in the photonic crystal. [S0031-9007(98)06494-1] PACS numbers: 42.50. -p

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confidence: 99%

Spontaneous Emission of Organic Molecules Embedded in a Photonic Crystal

et al. 1998

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“…Data of the sample signal over the instrumental response were deconvoluted and analyzed by the exponential series method. 35 Ludox® (Sigma-Aldrich) was used as scatterer. Experimental data correspond to expected theoretical values when χ 2 is close to 1.…”

Section: Time-resolved Emission Spectroscopy (Tres)mentioning

confidence: 99%

Photoluminescence of Solvent-Selected Fluorescent Moieties in MEH-PPV Solutions and Films

Ribeiro¹,

Camargo²,

Pereira³

et al. 2017

J. Braz. Chem. Soc.

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In this work, we examined how photoluminescence in poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) is affected by morphology, dictated by the mode of preparation. For that, MEH-PPV dilute solutions in good and non-solvents, thick cast films with poly[methylmethacrylate] (PMMA) as inert matrix and spin-coated thin films were prepared. These systems were studied by steady-state and time-dependent fluorescence spectroscopy and electronic microscopy. Unexpected photoluminescent behavior was detected in solutions and films and it was related to different excitons modulated by MEH-PPV conformation. By semi empirical calculations we obtained the singlet and triplet state energies of an MEH-PPV model system and, from time-resolved fluorescence spectroscopy, the existence of short-lived excited states was revealed, enabling us to infer on possible singlet fission in MEH-PPV-based systems.Keywords: photoluminescence, morphology, thin films, time-resolved fluorescence, computational calculations IntroductionSince poly(phenylene-vinylene) (PPV) derivatives were found to be electroluminescent, 1 the search for a systematic method to determine their applications has been of great interest. Their mechanical, morphological and optical properties have been widely discussed and findings related these properties to preparation methods. Although there are many aspects regarding the effects of preparation methods on optical response, authors seem to agree that preparation method influences molecular conformation, enabling or inhibiting aggregation and, consequently, affecting inter and intrachain interactions. Processing parameters are believed to modify the conformation and assembling mechanisms of polymeric materials, resulting in a memory effect of the structural information that is replicated from solutions to solid films. Therefore, to understand the role of chain conformation in solution is of major importance for applications such as device fabrication, since properties can be tuned, enhancing the desired characteristics and suppressing the undesired ones. 2,3 For instance, it is well known that photoluminescence of PPV derivatives show prominent red-shift due to the enhancement of energy transfer as the π-electron delocalization increases. 4 As pointed out in an earlier work, 5 this red-shift indicates aggregation driven by π-π interactions as the conjugation length increases.In polymeric systems, several occurrences are responsible for chain torsions that impose limits to the length of conjugated segments, affecting the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps. They are interpreted as stabilization and/or destabilization of HOMO and LUMO levels. 6 These occurrences may be related to the presence of impurities, molecules of solvent that strongly interact with the polymer chains and a distribution of torsion angles promoted by molecular interactions of any nature. 6 In this situation, the densities of excited states (DOS) available for electronic chan...

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“…A number of linear and nonlinear regularization methods are known (36,37) that provide stable solutions to ill-posed inverse problems. Of these, the ones used in the analysis of fluorescence decay data are the Maximum Entropy Method (32), an iterative regularization approach known as the Exponential Series Method (33), regularization based on the truncated singular-value decomposition (34) and a method based on Tikhonov-Philips regularization (35). In our case, we employed the Tikhonov regularization approach (36,37), so that the regularized solution f, is computed as:…”

Section: (4)mentioning

confidence: 99%

Investigation of Tetherable Distilbazolium Compounds as Fluorescent Probes in Nanostructured Silica Sol‐gel Materials^¶

Petrov¹,

Clchos²,

Wagner³

et al. 2005

Photochem & Photobiology

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Distibazolium dyes are investigated by steady‐state and time‐resolved fluorescence techniques in a series of low‐ and highviscosity polar solvents and in a silica sol‐gel matrix. In all solvents and the sol‐gel matrix, an interplay of photoinduced switching between different cis‐trans isomers and solvation dynamics is observed. Even in a viscous solution (glycerol) and in silica gel, cis‐trans isomerization is solvent‐controlled. Whereas in glycerol the solvation results in a time‐dependent fluorescence Stokes shift, the solvation‐induced spectral heterogeneity in silica gel is mostly static, possibly due to a close proximity of dye molecules to the silica surfaces of the nanopores. Compared to low‐viscosity solvents, where the cis‐trans isomerization process takes place with a solvent‐dependent rate on the timescale of about 120–150 ps, it slows down to about 1100–1400 ps in glycerol and about 1500 ps in a sol‐gel matrix. Additionally, fluorescence kinetics of the dyes in the sol‐gel reveals the presence of a range of different “frozen‐in” conformers exhibiting a broad spectrum of lifetimes from 20 to 300 ps.

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Photophysics of polycyclic aromatic hydrocarbons adsorbed on silica gel surfaces. 1. Fluorescence lifetime distribution analysis: an ill-conditioned problem

Cited by 82 publications

References 3 publications

Spontaneous Emission of Organic Molecules Embedded in a Photonic Crystal

Spontaneous Emission of Organic Molecules Embedded in a Photonic Crystal

Photoluminescence of Solvent-Selected Fluorescent Moieties in MEH-PPV Solutions and Films

Investigation of Tetherable Distilbazolium Compounds as Fluorescent Probes in Nanostructured Silica Sol‐gel Materials^¶

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Photophysics of polycyclic aromatic hydrocarbons adsorbed on silica gel surfaces. 1. Fluorescence lifetime distribution analysis: an ill-conditioned problem

Cited by 82 publications

References 3 publications

Spontaneous Emission of Organic Molecules Embedded in a Photonic Crystal

Spontaneous Emission of Organic Molecules Embedded in a Photonic Crystal

Photoluminescence of Solvent-Selected Fluorescent Moieties in MEH-PPV Solutions and Films

Investigation of Tetherable Distilbazolium Compounds as Fluorescent Probes in Nanostructured Silica Sol‐gel Materials¶

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Investigation of Tetherable Distilbazolium Compounds as Fluorescent Probes in Nanostructured Silica Sol‐gel Materials^¶