Excited state quenching kinetics of zinc meso-tetrakis (N-methylpyridinium-4-yl) porphyrin by methyl viologen in AOT reverse micelles

Togashi, Denísio M.; Costa, Sı́lvia M. B.

doi:10.1039/b109960b

Cited by 26 publications

(9 citation statements)

References 75 publications

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“…This goal can be achieved either by synthesis or by entrapment of the donor or acceptor in organized assemblies. The encapsulation effect of organized assemblies can bring the donor and the acceptor together and thus facilitate the forward electron transfer whereas their hydrophobic and hydrophilic microenvironments can provide differential solubilization to the ion pair formed, in case one of the products is more hydrophobic than the other, leading to the formation of solvent separated ion pairs and consequent suppression of the back electron transfer [11,12]. In the present study, we have investigated the effect of micelles on photoinduced electron transfer between chlorin p 6 and methyl viologen dication (MV 2+ ) ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced electron transfer from chlorin p6 to methyl viologen in aqueous micelles

Mukherjee

Mishra

Datta

2005

Chemical Physics Letters

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Section: Introductionmentioning

confidence: 99%

Photoinduced electron transfer from chlorin p6 to methyl viologen in aqueous micelles

Mukherjee

Mishra

Datta

2005

Chemical Physics Letters

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“…[8][9] Fluorescence quenching associated with photoinduced electron transfer has also been extensively studied in such molecular organizates. [10][11][12] These studies involve probes linked to different locations and can provide information regarding the distribution of the donor and the quencher and/ or the rate of access of the quencher to the different sub-regions of the microheterogeneous solution. Acridine Orange (AO), a fluorescent dye utilized in photodynamic therapy 13 and as a possible type II photosensitizer in solar energy conversion, 14 was used to investigate the aqueous interior of two microemulsions formed by (i) the well-known anionic surfactant AOT [sodium bis (2-ethylhexyl) sulfosuccinate] and (ii) the nonionic surfactant Triton X-100 (Trx-100).…”

Section: Introductionmentioning

confidence: 99%

Fluorescence quenching of Acridine Orange in microemulsions induced by the non-steroidal anti-inflammatory drug Piroxicam

Andrade

Costa

2003

Photochem Photobiol Sci

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The singlet excited-state quenching of Acridine Orange (AO) by methyl viologen (MV2+) and the non-steroidal anti-inflammatory drug Piroxicam (Prx), incorporated in sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane/water and Triton X-100 (Trx-100)/cyclohexane-hexanol/water (w/o) microemulsions, was followed by steady- and transient-state fluorescence. The water content was varied by using different values of omega 0 (omega 0 = [H2O]/[S]) at fixed AOT (0.1 M) and Trx-100 (0.2 M) concentrations. In AOT, MV2+ resides at the interface, while Prx partitions between the interface and bulk water, but considerably biased towards the latter compared to AO. The quenching process efficiency increases with increasing omega 0, but reaches a diffusional value similar to that of free water only for the case of Prx, underlining the electrostatic effect of the AOT interface. The quenching process in Trx-100 microemulsions is more efficient for Prx than for MV2+, pointing to a similar polyoxyethylene intra-chain location for the former and AO. In both cases, data obtained allowed the microviscosity of the aqueous interior at different omega 0 to be extrapolated and indicate an increase in eta w values with water content, reflecting changes in the shape of Trx-100 microemulsions, which occur at omega 0 = 8.

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“…This interpretation of the quenching mechanism, k q = k ex , is further confirmed by the value we find for k q , which is of the same order of those reported in the literature for the exchange rate constant between AOT reverse micelles in heptane 26 and isooctane. 27 The quenching by TBA was also investigated. In homogeneous media this amine behaves as a better quencher of the dye triplet state than TEOA.…”

Section: Triplet Quenching By Aminesmentioning

confidence: 99%

Quenching of the triplet state of safranine-O by aliphatic amines in AOT reverse micelles studied by transient absorption spectroscopy

Porcal

Chesta

Biasutti

et al. 2012

Photochem Photobiol Sci

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The photophysics of Safranine-O (3,6-diamino-2,7-dimethyl-5 phenyl phenazinium chloride) (SfH(+)Cl(-)) was investigated in reverse micelles (RMs) of AOT (sodium bis(2-ethylhexyl)sulfosuccinate) with special emphasis on the triplet state processes. The triplet is formed in its monoprotonated form, independently of the pH of the water used to prepare the RMs. While the intersystem crossing quantum yields in RMs are similar to those in organic solvents, the triplet lifetime is much longer. Since the pH in the water pool of AOT RMs is close to 5 and the triplet state of the dye is subjected to proton quenching, the long lifetime indicates that the dye resides in a region where it cannot be reached by protons during its lifetime. All the measurements indicate that the dye is localized in the interface, sensing a medium of micropolarity similar to EtOH : water (3:1) mixtures. The quenching by aliphatic amines was also investigated. While the quenching by the hydrophobic tributylamine is similar to that in methanol, the hydro-soluble triethanolamine is one order of magnitude more effective in RMs than in homogeneous solution. In the latter case the quenching process is interpreted by a very fast intramicellar quenching, the overall kinetics being controlled by the exchange of amine molecules between RMs. Semireduced dye is formed in the quenching process in RMs in the di-protonated state with a comparable quantum yield to the monoprotonated state formed in homogeneous solvents. The results point to the advantage of the reverse micellar system for the generation of active radicals for the initiation of vinyl polymerization, since a much lower concentration of amine can be employed with similar quantum yields.

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Excited state quenching kinetics of zinc meso-tetrakis (N-methylpyridinium-4-yl) porphyrin by methyl viologen in AOT reverse micelles

Cited by 26 publications

References 75 publications

Photoinduced electron transfer from chlorin p6 to methyl viologen in aqueous micelles

Photoinduced electron transfer from chlorin p6 to methyl viologen in aqueous micelles

Fluorescence quenching of Acridine Orange in microemulsions induced by the non-steroidal anti-inflammatory drug Piroxicam

Quenching of the triplet state of safranine-O by aliphatic amines in AOT reverse micelles studied by transient absorption spectroscopy

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