Effect of SiO2 and zeolite surfaces on the excited triplet state of benzophenone, BT; a spectroscopic and kinetic study

Thomas, J. K.

doi:10.1039/b316945f

Cited by 13 publications

(8 citation statements)

References 30 publications

(19 reference statements)

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“…T generally has a long lifetime, on the order of ms. 20,21 But, from the calculation results based on the flow rate in the circulation flow system, the lifetime of BP T could extend to the order of 10 1 s. This value differs significantly from the widely accepted result. However, it should be noted that the lifetime of BP T given by literature usually corresponded to the peak value (with highest relative abundances) of a distribution, which means that there is still certain amount (though few) of BP T having a longer lifetime than others.…”

Section: Bpcontrasting

confidence: 49%

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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Section: Bpcontrasting

confidence: 49%

A remote photochemical reaction for surface modification of polymeric substrate

Zhao

Zhang

Yang

2012

J. Polym. Sci. A Polym. Chem.

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“…Time resolved laser-induced luminescence (LIL), diffuse reflectance laser flash-photolysis (DRLFP) and ground-state diffuse reflectance absorption spectroscopy (GSDR) are techniques that have been successfully applied to photodegradation studies of opaque systems of probes included into nanochannels or nanocavities. [1][2][3][4][5][6] These solid state photochemical methods have been applied by our group to study several organic compounds adsorbed onto different hosts such as microcrystalline cellulose, 7 p-tert-butylcalix[n]arenes (n = 4, 6 and 8) and derivatives, [8][9][10] silicalite, cyclodextrins and silica 1,8,11 among others.…”

Section: Introductionmentioning

confidence: 99%

Surface photochemistry: alloxazine within nanochannels of Na+ and H+ ZSM-5 zeolites

Ferreira¹,

Costa

Machado

et al. 2009

Phys. Chem. Chem. Phys.

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This work reports the surface photochemistry study of alloxazine adsorbed within nanochannels of MFI zeolites, namely in a series of Na+ and H+ ZSM-5 zeolites where the hydrophobic and hydrophilic character of the host varies systematically. Laser-induced room temperature and 77 K luminescence of air-equilibrated solid powdered samples of alloxazine adsorbed onto the two sets of zeolites, which we will name NaZSM-5 and HZSM-5, revealed the existence of a single emission of alloxazine as a broad band centred at about 450 nm in some cases, while in others an emission with a maximum at about 510 nm was detected. The decay times of the alloxazine emission vary greatly going from solution to entrapment within the nanochannels of the ZSM-5 zeolites. In the latter case a lifetime distribution analysis has shown that the longest lifetime for the alloxazine fluorescence emission exists in the case where an isoalloxazine-type emission was detected, i.e. whenever the hydrophobic character of the host increases. Alloxazine entrapped in the more acidic zeolites exists in the form of emissive monomers. However, alloxazine emits both from monomeric and aggregated emissive forms in the case of the hydrophobic zeolites. These data indicate the formation of planar dimers of alloxazine whenever the number of active sites in the zeolite decreases. These dimers have to be formed at the intersections of the zig-zag and linear nanochannels of the zeolite since there is no space available for their formation inside the zeolite channels. The isoalloxazine tautomers are formed due to the existence of alloxazine dimers which may undergo double proton transfer in the excited state, following laser excitation. Delayed fluorescence of alloxazine was also detected for the HZSM-5 and NaZSM-5 entrapment both at room temperature and at 77 K. The present study is paradigmatic as regards the host influence on the photochemistry of the guest.

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“…1-8 These solid state photochemical methods have been recently applied by our group to study several organic compounds adsorbed onto different hosts such as p-tert-butylcalix [4], [6] and [8]arenes and derivatives, 9-11 microcrystalline cellulose, 12-14 silicalite and cyclodextrins, 15-17 silica 18 and resorcinarene frameworks, 19 among others.…”

Section: Introductionmentioning

confidence: 99%

“…Time resolved laser induced luminescence, diffuse reflectance laser flash-photolysis and ground state diffuse reflectance absorption spectroscopy are relatively new techniques that can be applied to study opaque and crystalline systems. [1][2][3][4][5][6][7][8] These solid state photochemical methods have been recently applied by our group to study several organic compounds adsorbed onto different hosts such as p-tert-butylcalix [4], [6] and [8]arenes and derivatives, 9-11 microcrystalline cellulose, 12-14 silicalite and cyclodextrins, 15-17 silica 18 and resorcinarene frameworks, 19 among others.…”

Section: Introductionmentioning

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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Effect of SiO2 and zeolite surfaces on the excited triplet state of benzophenone, BT; a spectroscopic and kinetic study

Cited by 13 publications

References 30 publications

A remote photochemical reaction for surface modification of polymeric substrate

A remote photochemical reaction for surface modification of polymeric substrate

Surface photochemistry: alloxazine within nanochannels of Na+ and H+ ZSM-5 zeolites

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

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