Luminescence Lifetime Distributions Analysis in Heterogeneous Systems by the Use of Excel's Solver

Branco, T. J. F.; Rego, A.M. Botelho do; Machado, I. Ferreira; Ferreira, L.F. Vieira

doi:10.1021/jp0520087

Cited by 39 publications

(59 citation statements)

References 37 publications

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“…These results also agree with previous studies of pyrene adsorbed onto calix [4]arene, 28 where the presence of pyrene microcrystals was confirmed, but no evidence for the presence of other ground state dimers was found. At the observation wavelength of 470 nm the lifetime distribution analysis (data not shown) also confirmed the absence of the dimer for the calix [4]arene.…”

Section: -12supporting

confidence: 92%

“…In the case of calix [8]arene, this emission, although visible in air equilibrated samples, became slightly stronger with the argon purging. The lifetime distribution analysis at the observation wavelength of the monomer phosphorescence, 600 nm, revealed, as for calix [4]arene, 28 the presence of both the delayed excimer fluorescence and monomer phosphorescence. The lifetimes obtained for the delayed excimer fluorescence and for the monomer phosphorescence were 71 ls and 2.5 ms, respectively for calix [6]arene and 240 ls and 11 ms, respectively for calix [8]arene (data not shown).…”

Section: -12mentioning

confidence: 87%

“…In this analysis we studied the prompt emissions of pyrene using the same method previously used by our group to study the triplet emissions of pyrene in calix [4]arene. 28 The mathematical details of this approach are given in ref. 28 Lifetime distribution analysis is needed for studying pyrene included within calixarene's nanocavities since these molecules present different conformations and even different possible adsorption sites.…”

Section: Time Resolved Luminescence and Lifetime Distribution Analysimentioning

confidence: 99%

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Pyrene—p-tert-butylcalixarenes inclusion complexes formation: a surface photochemistry study

Branco

Ferreira

Rego

et al. 2006

Photochem Photobiol Sci

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Diffuse reflectance and luminescence techniques were used to study the photophysics and photochemistry of pyrene within p-tert-butylcalix [n]arenes with n = 4, 6, and 8, and to study their ability to form inclusion complexes in heterogeneous media. Evidences for inclusion complex formation were found for the three hosts under study. [8]arene. This feature is particularly relevant for calix [6]arene, suggesting a very favourable situation for the hydrogen atom abstraction to occur. The analysis of the degradation products revealed the presence of hydroxypyrene as a major photodegradation product for the three hosts. Dihydro-hydroxypyrene was also formed in the case of calix[6]arene and calix [8]arene. The formation of the calixarene's phenoxyl radical and subsequent hydrogen abstraction is consistent with the formation of dihydro-dihydroxypyrene.

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Section: -12supporting

confidence: 92%

Section: -12mentioning

confidence: 87%

Section: Time Resolved Luminescence and Lifetime Distribution Analysimentioning

confidence: 99%

See 1 more Smart Citation

Pyrene—p-tert-butylcalixarenes inclusion complexes formation: a surface photochemistry study

Branco

Ferreira

Rego

et al. 2006

Photochem Photobiol Sci

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“…25 This new methodology allows for asymmetric distributions and uses Voigt profiles (Gaussian-Lorentzian product) instead of pure Gaussian or Lorentzian distributions. A very simple and widely available tool for fitting has been used, the Microsoft Excel Solver.…”

Section: Room Temperature Laser Induced Phosphorescencementioning

confidence: 99%

“…25 The use of the sum of a few exponentials to analyse the decay of probes onto heterogeneous surfaces is a description without physical meaning, 25,26 and the best tool to study decays of a probe onto heterogeneous surfaces is a lifetime distribution analysis (as Scaiano and co-workers did recently, e.g. ref.…”

Section: Room Temperature Laser Induced Phosphorescencementioning

confidence: 99%

Surface photochemistry: benzophenone as a probe for the study of silica and reversed-phase silica surfaces

Ferreira¹,

Machado²,

Silva

et al. 2006

Photochem Photobiol Sci

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This work reports the use of benzophenone, a very well characterized probe, to study new hosts: two reversed-phase silicas. Laser-induced room temperature luminescence of argon purged solid powdered samples of benzophenone adsorbed onto the two different reversed-phase silicas, RP-18 and RP-8, revealed the existence of a low energy emission band in contrast with the benzophenone adsorbed on 60 Å pore silica, where only triplet benzophenone emits. This low energy emission band was identified as the fluorescence of the ketyl radical of benzophenone, which is formed as the result of a hydrogen atom abstraction reaction of the triplet excited benzophenone from the alkyl groups of the surface of the reversed silicas. Such emission does not exist for benzophenone adsorbed onto 60 Å pore silica. Room temperature phosphorescence was obtained in argon purged samples for all the surfaces under use. The decay times of the benzophenone emission vary greatly with the alkylation of the silica surface when compared with "normal" silica surface. A lifetime distributions analysis has shown that the shortest lifetimes for the benzophenone emission exist in the former case. Triplet-triplet absorption of benzophenone was detected in all cases and is the predominant absorption in the case of 60 Å pore silica, while benzophenone ketyl radical formation occurs in the case of the reversed silicas. Diffuse reflectance laser flash photolysis and gas chromatography-mass spectrometry techniques provided complementary information, the former about transient species and the latter regarding the final products formed after laser irradiation, both at 266 nm or 355 nm. Product analysis and identification show that the degradation photoproducts are dependent on the excitation wavelength, the photochemistry being much more rich and complex in the 266 nm excitation case, where an a-cleavage reaction occurs. A detailed mechanistic analysis is proposed.

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A remote photochemical reaction for surface modification of polymeric substrate

Zhao

Zhang

Yang

2012

J. Polym. Sci. A Polym. Chem.

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BACKGROUND: Enhancer of zeste homolog 2 (EZH2), a member of polycomb group proteins, is involved in the regulation of cell cycle progression and has been implicated in various human malignancies, including breast cancer, and also has been associated with aggressive tumor behavior. However, the clinical significance of EZH2 expression in inflammatory breast cancer (IBC), a rare but aggressive type of breast carcinoma, has not been explored. In this retrospective study, the authors examined EZH2 expression in IBC tumors and evaluated the relation between EZH2 expression and patient survival. METHODS: Tissue microarrays of 88 surgically resected IBC tumors were stained immunohistochemically for EZH2, and the authors evaluated the association of EZH2 expression status with clinicopathologic factors and clinical outcome. RESULTS: The median follow‐up for the entire cohort was 45.7 months, and the 5‐year overall survival (OS) rate was 45%. EZH2 was expressed frequently in IBC tumors (75.7%) and was associated significantly with unfavorable prognostic factors, such as higher tumor grade, negative estrogen receptor status, and triple‐negative status (ie, negative for the estrogen, progesterone, and human epidermal growth factor 2 receptors). Univariate survival analysis indicated that patients who had EZH2‐positive IBC had a significantly lower 5‐year OS rate than patients who had EZH2‐negative IBC (P = .01). In multivariate analysis, only positive EZH2 status remained an independent predictor of worse OS. CONCLUSIONS: EZH2 was expressed frequently in IBC tumors. The current results indicated that EZH2 expression status may be used to identify a subset of patients with IBC who have a relatively worse prognosis. Targeting EZH2 also may provide a novel strategy for improving the clinical outcome of patients with IBC. Cancer 2011;. © 2011 American Cancer Society.

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Luminescence Lifetime Distributions Analysis in Heterogeneous Systems by the Use of Excel's Solver

Cited by 39 publications

References 37 publications

Pyrene—p-tert-butylcalixarenes inclusion complexes formation: a surface photochemistry study

Pyrene—p-tert-butylcalixarenes inclusion complexes formation: a surface photochemistry study

Surface photochemistry: benzophenone as a probe for the study of silica and reversed-phase silica surfaces

A remote photochemical reaction for surface modification of polymeric substrate

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