Kinetics of the Photochemical Charge Separation in Micellar Solutions

Kuz'min, M.G.; Zaitsev, N. K.

doi:10.1007/978-3-642-71881-6_10

Cited by 6 publications

(13 citation statements)

References 126 publications

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“…For the reactions in water, a = log(M k REC / k SEP ) and d = log( k SEP /s -1 ). Experimental data obtained in this work and found in the literature ,,− ,,− for water, cationic micelles (CTAB, tetradecyltrimethylammonium bromide, and dodecylpyridinium chloride), and nonionic micelles (Brij 35, 56, and 58) are presented in Figure . It should be emphasized that experimental data both for the ground-state and excited-state reactions were used in the same plots.…”

Section: Discussionmentioning

confidence: 81%

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Protolytic Photodissociation and Proton-Induced Quenching of 1-Naphthol and 2-Octadecyl-1-Naphthol in Micelles

et al. 2004

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Kinetics of excited-state proton-transfer reactions and proton-induced fluorescence quenching of 1-naphthol (1N) and 2-octadecyl-1-naphthol (2O1N) in micellar solutions of cetyltrimethylammonium bromide (CTAB), polyoxyethylene(23) lauryl ether (Brij 35), and sodium dodecyl sulfate (SDS) was studied by using stationary and time-resolved fluorescence techniques. The ground-state acidity constant of 2O1N in cationic micelles of CTAB was found to be significantly smaller than that of the parent compound (ΔpK = 0.5). However, similar rate and equilibrium constants of the protolytic dissociation were obtained for 1N and 2O1N in the singlet excited state. Effects of nonionic micelles of Brij 35 closely resemble those of CTAB. In anionic micelles of SDS, the protolytic photodissociation was much slower for 2O1N than for 1N. The protonation rate for the excited anions in micellar solutions increases by approximately 2 orders of magnitude in the series CTAB, Brij 35, SDS. Excited-state kinetics was rationalized within the framework of a pseudophase model, which included micellar effects on the proton-transfer equilibrium and interfacial diffusion of hydronium ions. The electrostatic surface potential of charged micelles was estimated from the acidity constants of naphthols.

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Section: Discussionmentioning

confidence: 81%

“…1-Naphthol derivatives provide an opportunity to probe protolytic reactions in a variety of microheterogeneous systems as well as in mixed homogeneous solutions. Pronounced photodissociation of 1N has been observed in micelles of anionic and nonionic surfactants, in lipid bilayers, and in negatively charged microemulsions. ,,,− …”

Section: Introductionmentioning

confidence: 99%

Protolytic Photodissociation and Proton-Induced Quenching of 1-Naphthol and 2-Octadecyl-1-Naphthol in Micelles

et al. 2004

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“…The parameters A 2 − A 4 will under these circumstances approximately be given as and eq 10 takes the form of a monoexponential decay function with τ = ( k 0 + 〈 n 〉 k qm ) -1 . Under such conditions, a different approach can be used to describe the reaction kinetics, the so-called pseudophase model. , In this model, the micelles are considered to form one homogeneous pseudophase. The reactants are assumed to be distributed over the micellar pseudophase and the bulk phase, this distribution being described by their distribution coefficients, i.e., their equilibrium distribution.…”

Section: Theorymentioning

confidence: 99%

“…Micellar systems also offer convenient model systems for the investigation of the effects of the binding and the local microenvironment on the reactivity. For instance, the effects of the microenvironment on the excited-state acidity of a molecule − and on the excited-state electron transfer − has been studied in restricted systems. The difference in shifts of p K a found for positively charged and uncharged micelles indicates a difference of the interfacial potential between cationic and anionic micelles of about 100 mV .…”

Section: Introductionmentioning

confidence: 99%

“…Excited-state proton transfer is generally found to be slower in nonionic and anionic micelles than in homogeneous solution 30-32,36 and of about the same rate in cationic micelles . Moreover, compartmentalization in micelles, leading to a change in the local environment, is known to strongly influence excited-state electron transfer. − , …”

Section: Introductionmentioning

confidence: 99%

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Electron-Transfer Reactions in SDS Micelles: Reactivity of Pyrene and Tris(2,2‘-bipyridyl)ruthenium(II) Excited States Investigated by Time-Resolved Luminescence Quenching

et al. 1999

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The effects of micellization on the rate constants and Gibbs energy of electron transfer (ΔG et) are studied by time-resolved luminescence quenching of tris(2,2‘-bipyridyl)ruthenium(II) (RUBIPY) and pyrene (PY) by electron acceptors and donors in sodium dodecylsulfate (SDS) micelles. For RUBIPY, which is bound to the SDS micelles and accessible to water, ΔG et is considerably smaller than what is found in organic solutions, though the spectral properties of RUBIPY and the value of diffusion-controlled quenching rate constant are typical for the micellar interior. For this system, dissolution in micelles enables a change of the local reactant concentration and mobility, retaining their higher reactivity in aqueous solution. In contrast, for PY, which is known to be localized in the palisade layer of an SDS micelle, the quenching rate constants coincide well with those found in acetonitrile.

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Fluorescence in Organized Assemblies

Hinze¹

2000

Encyclopedia of Analytical Chemistry

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This article provides an overview of the general properties of organized assembly (ordered media) systems such as aqueous surfactant and bile salt micelles, lipid and surfactant vesicles (liposomes) and cyclodextrins (CDs) and summarizes their utilization to enhance the performance of analytical fluorescence measurements. In many instances, organic molecules and metal complex species, when included within a CD cavity or solubilized and bound to surfactant aggregates, exhibit enhanced fluorescence. This gives rise to improved detectability of such analytes. The altered microenvironment within the organized medium is capable of impeding the interfering action of other species (inorganic or organic) present in the sample matrix. This often can improve the selectivity of the analytical method. These benefits of improved sensitivity and selectivity arise from the compartmentalization, isolation and shielding of the excited singlet state of the guest analyte from quenching and nonradiative decay processes as well as prevent side reactions that otherwise can occur in bulk solution (or sample matrix). In addition, organic solvents or time‐consuming extraction steps can be avoided owing to the increased solubility of the nonpolar organic or inorganic reagents and/or analyte molecules in water in the presence of the organized medium; allowing for the use of an aqueous medium to perform the procedure. The possibility of conducting reactions and forming fluorescent organic or metal chelates in micellar (or other organized) media that are not observed in a bulk homogeneous solvent system serves to expand the scope of chemistries that one can consider using to design/develop new, unique and improved fluorescent assays. Numerous representative examples of fluorescent methods for determination of both organic and inorganic analytes are provided which serve to illustrate the advantages and benefits accrued from the use of the micelles, vesicles, liposomes or CDs in such procedures. Some experimental considerations and cautions to keep in mind when utilizing organized media are also delineated. An extensive reference section is provided so that the interested reader can easily refer to such for more detailed information on these systems and topics.

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Kinetics of the Photochemical Charge Separation in Micellar Solutions

Cited by 6 publications

References 126 publications

Protolytic Photodissociation and Proton-Induced Quenching of 1-Naphthol and 2-Octadecyl-1-Naphthol in Micelles

Protolytic Photodissociation and Proton-Induced Quenching of 1-Naphthol and 2-Octadecyl-1-Naphthol in Micelles

Electron-Transfer Reactions in SDS Micelles: Reactivity of Pyrene and Tris(2,2‘-bipyridyl)ruthenium(II) Excited States Investigated by Time-Resolved Luminescence Quenching

Fluorescence in Organized Assemblies

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