Kinetics of Quenching of Ketone Phosphorescence by Oxygen in a Glassy Matrix

and, John M. Charlesworth; Gan, T.H.

doi:10.1021/jp960325v

Cited by 22 publications

(30 citation statements)

References 26 publications

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“…Considering the measurement conditions used in the references it was found that the drying procedures -if reported -differ from the one used in this work. Jones [13] and Charlesworth and Gan [36] dried their films at temperatures very close to or at the glass transition temperature of PMMA, and Chiou and Paul [31] stored their films even at 130 8C for a week. Therefore, a sample was investigated with and without annealing before measuring the oxygen permeability at 23 8C (Figure 4).…”

Section: Resultsmentioning

confidence: 99%

A Comparative Study of Oxygen Permeabilities of Film‐Forming Polymers by Quenching of Platinum Porphyrin Phosphorescence

Heß¹,

Becker²,

Baluschev³

et al. 2007

Macro Chemistry & Physics

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Oxygen permeabilities of different polymers were determined by using two different methods based on quenching of an excited phosphorescent dye by oxygen. In the first method, the phosphorescent dye platinum octaethylporphyrin is directly dissolved in the polymer film of interest whereas in the second method a sensor film is used which is separated from the film of interest by a spacer. The polymers investigated are PMMA, PVC, PVAc, cellulose acetate, PEMA, and PS. The resulting oxygen permeability coefficients are compared with data reported in the literature. It was found that oxygen permeation strongly depends on the protocol of preparation and thermal history of the films.magnified image

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Section: Resultsmentioning

confidence: 99%

A Comparative Study of Oxygen Permeabilities of Film‐Forming Polymers by Quenching of Platinum Porphyrin Phosphorescence

Heß¹,

Becker²,

Baluschev³

et al. 2007

Macro Chemistry & Physics

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“…The diffusion constant of oxygen in PMMA is 1 order of magnitude smaller than in polystyrene, while the solubility of oxygen is approximately the same [19]. For a single molecule in polystyrene at ambient conditions, the number of oxygen collisions in a 40 ms time interval is of the order of one to ten [19]. To verify if oxygen quenching plays an important role for the t T distribution in polystyrene, we have reduced the oxygen concentration by continuous flushing of the sample with argon.…”

mentioning

confidence: 90%

“…Oxygen is a well-known quencher of the T 1 state of many aromatic dyes [18]. The diffusion constant of oxygen in PMMA is 1 order of magnitude smaller than in polystyrene, while the solubility of oxygen is approximately the same [19]. For a single molecule in polystyrene at ambient conditions, the number of oxygen collisions in a 40 ms time interval is of the order of one to ten [19].…”

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confidence: 99%

Time-Varying Triplet State Lifetimes of Single Molecules

et al. 1999

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It is found that triplet state lifetimes and intersystem crossing yields of individual molecules embedded in a polymer host at room temperature are not constant in time. The range over which the triplet lifetime of a single molecule varies during long observation times shows a strong similarity with the distribution of lifetime values obtained during short observation times of many individual molecules dispersed in space. The similarity is an elegant manifestation of the ergodic principle of statistical physics. 07.79.Fc, Single molecule microscopy and spectroscopy give new and unique insight in the complex behavior of individual emitters on the nanometer scale [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Measurements on individual molecules have two distinct advantages. First, phenomena that are usually hidden due to ensemble averaging can be directly observed, such as spectral and rotational jumps [1][2][3][4][5][6][7][8], photon (anti-)bunching [7,[9][10][11][12][13], and discrete photobleaching. Second, the monitoring of single molecule fluorescence forms a powerful way to probe the dynamics of the local environment on a nanometer scale. Therefore, single molecule detection allows the inhomogeneity of the ensemble to be directly related to the real time dynamics of the heterogeneity of the environment. In contrast, alternative techniques to study the composition of an inhomogeneously broadened ensemble like spectral hole-burning or pump-probe spectroscopies still average over a subset of the ensemble.For the purpose of this Letter, fluorescent molecules are considered as a three-level system. Besides the repetitive transitions between the singlet ground state ͑S 0 ͒ and the lowest singlet excited state ͑S 1 ͒ giving rise to fluorescence, the molecule has a small chance to undergo intersystem crossing (ISC) from S 1 to the lowest excited triplet state ͑T 1 ͒. As long as the T 1 state remains occupied, the S 0 2 S 1 transition does not occur and the fluorescence is interrupted temporarily. After decaying to S 0 the molecule starts fluorescing again. As a result, the fluorescence photons are emitted in bunches separated by dark periods when the molecule is in T 1 . This so-called photon bunching can be investigated in two ways. First, autocorrelation of the time intervals between detected photon counts yields the typical duration of the dark periods and thus the T 1 lifetime [7]. The disadvantage of this indirect method is that it yields only a mean value for the T 1 lifetime. Second, integration of the detected fluorescence photons over time intervals shorter than the duration of the dark periods can identify the time length of each excursion to T 1 in a direct way [11][12][13]. We have used the second method to obtain time-resolved T 1 state dynamics.The first measurements on the T 1 state of individual molecules were performed at cryogenic temperatures [1,[7][8][9]11]. It was found that T 1 lifetimes and intersystem crossing rates could vary among different molecules, which was attributed to loc...

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“…Previous studies have examined the potential of the use of phosphorescence quenching by oxygen in glassy polymers (Charlesworth, 1996;Korolev et al, 1999).…”

Section: Measurements Of Oxygen Permeabilitymentioning

confidence: 99%

“…Oxygen is a powerful quencher of both fluorescence and phosphorescence and luminescence quenching has been used as an effective method for probing the presence of molecular oxygen in polymeric media (Charlesworth & Gan, 1996;Guillet & Andrews, 1992;Jones, 1968;Masoumi et al, 1996) following the initial study showing that comparison of the triplet lifetime of a probe in the presence and absence of oxygen provided a facile and rapid indicator of oxygen quenching in the gelatin matrix . We have recently used phosphorescence quenching of Ery B to correlate the dynamic properties of the gelatin matrix with the oxygen diffusion rate while other studies have shown the potential of Ery B as an oxygen sensor in sol-gel silica (Lam, Chan, & Lo, 2001).…”

Section: Oxygen Permeabilitymentioning

confidence: 99%

Molecular mobility and oxygen permeability in amorphous β-lactoglobulin films

Sundaresan

Ludescher

2008

Food Hydrocolloids

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OF THE DISSERTATIONOur overall objective is to understand how molecular mobility modulates diffusion rates and thus chemical reactivity in films made from amorphous β-lactoglobulin. The phosphorescence emission spectra and lifetimes of the triplet probe erythrosin B embedded in the β-Lg films provide measures of the modes, rates, and distribution of molecular mobility in the film, providing the molecular detail necessary to connect food quality and stability to molecular structure and mobility. The mobility contours generated from this research provided us with information about the onset temperature and level of molecular mobility required to support permeability of atmospheric oxygen. In β-Lgbased binary matrices, sugars (sucrose, trehalose, maltose), plasticizers (glycerol, sorbitol, maltitol and PEG-400), fatty acids (palmitic acid, caprylic acid) and protein (BSA) were selected to investigate how variations in composition influence the molecular mobility and oxygen permeability in amorphous β-Lg matrix. Further more complicated β-Lg -based ternary matrices (maltose and maltitol) and (PEG and sucrose) were generated inorder to gain a deeper understanding of edible films.iii In pure β-Lg films there was linear correlation between molecular mobility and oxygen permeability. Various additives showed different results with respect to mobility and permeability. The addition of sucrose, maltose, maltitol and trehalose greatly reduced the mobility and the permeability of the β-Lg matrix. Glycerol exhibited an antiplasticization effect and showed decreased mobility at a molar ratio of 1:1 glycerol/ β-Lg.PEG greatly enhanced the permeability of β-Lg matrix. Fatty acids palmitic acid and caprylic acid had a rigidification effect on the matrix with no change in permeability. We were able to detect dynamic synergies in β-Lg maltose and maltitol mixtures, whereby these sugar-polyol mixtures at equal ratios anti-plasticized the β-Lg matrix and at unequal ratios plasticized the matrix. The tertiary matrix comprising of β-Lg, PEG 400and sucrose brought about a substantial reduction in the permeability. A better understanding of the mobility in these complex matrices will help improve the effectiveness of β-Lg in barrier applications in real food systems.

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Kinetics of Quenching of Ketone Phosphorescence by Oxygen in a Glassy Matrix

Cited by 22 publications

References 26 publications

A Comparative Study of Oxygen Permeabilities of Film‐Forming Polymers by Quenching of Platinum Porphyrin Phosphorescence

A Comparative Study of Oxygen Permeabilities of Film‐Forming Polymers by Quenching of Platinum Porphyrin Phosphorescence

Time-Varying Triplet State Lifetimes of Single Molecules

Molecular mobility and oxygen permeability in amorphous β-lactoglobulin films

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