Photochemistry in micelles

Turro, Nicholas J.; Cox, Graham; Paczkowski, Mark A.

doi:10.1007/3-540-15141-9_2

Cited by 45 publications

(22 citation statements)

References 105 publications

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“…[1,2] The latter raises a number of fundamental issues, which we will address in this paper for a ketone-amine system. Where are the reactants preferentially located?…”

Section: Introductionmentioning

confidence: 99%

Quenching Mechanisms and Diffusional Pathways in Micellar Systems Unravelled by Time‐Resolved Magnetic‐Field Effects

Goez

Henbest

Windham

et al. 2009

Chemistry A European J

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Magnetic-field effects (MFEs) are used to investigate the photoreaction of xanthone (A) and DABCO (D) in anionic (SDS) or cationic (DTAC) micelles at high pH (DABCO = 1,4-diazabicyclo[2.2.2]octane, SDS = sodium dodecyl sulfate, DTAC = dodecyl trimethyl ammonium chloride). From MFE experiments with nanosecond time resolution, the radical anion A(.)(-) can be observed without any interference from the much more strongly absorbing triplet (3)A*, the different quenching processes can be separated and their rates can be measured. Triplet (3)A* is quenched dynamically both by the SDS micelle (k(1) = 5.0x10(5) s(-1)) and by DABCO approaching from the aqueous phase (k(2) = 2.0x10(9) M(-1) s(-1)). Static quenching by solubilised DABCO (association constant with the SDS micelles, 1.5 M(-1)) also participates at high DABCO concentrations, but is chemically nonproductive and does not lead to MFE generation. The MFEs stemming from the radical ion pairs A(.)(-) D(.)(+) are about 40 times larger in the anionic micelles than in the cationic ones despite a higher yield of free radicals in the latter case. This can be rationalised by different diffusional dynamics: Because of the location of their precursors, A(.)(-) and D(.)(+) are formed at opposite sides of the micelle boundary. Subsequently, the negatively charged Stern layer of the SDS micelle traps the radical cation, which then undergoes surface diffusion, so both the recombination probability and the spin mixing are high; in contrast, the positive surface charge of the DTAC micelle forces the radical cation into the bulk of the solution, thus efficiently blocking a recombination.

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“…[1,2] The latter raises a number of fundamental issues, which we will address in this paper for a ketone-amine system. Where are the reactants preferentially located?…”

Section: Introductionmentioning

confidence: 99%

Quenching Mechanisms and Diffusional Pathways in Micellar Systems Unravelled by Time‐Resolved Magnetic‐Field Effects

Goez

Henbest

Windham

et al. 2009

Chemistry A European J

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“…[1][2][3][4][5][6][7][8]11,12,[49][50][51][52][53][54][55] Steady-state and timeresolved fluorescence spectroscopy is used to investigate the quenching of fluorescent probes solubilized in micelles or microemulsions by quenchers distributed between micelles and the bulk solution (see below). Various kinetic data indicate the absence of a substantial potential barrier for the diffusion of these substances across an interface.…”

Section: Kinetics Of Charge Transfer In Microheterogeneous Systemsmentioning

confidence: 99%

“…Photoinduced charge transfer across a liquid-liquid interface has been thoroughly investigated in micelles, vesicles (liposomes), microemulsions [1][2][3][4][5][6][7][8][9][10] , and bilayer lipid membranes. 11 The processes at the contact of aqueous solutions with organic media being observed in other objects such as proteins, polymers, Langmuir-Blodgett films, conducting organic films etc.…”

Section: Introductionmentioning

confidence: 99%

“…The reactions of photoinduced charge transfer in these systems have been reviewed rather thoroughly by several authors. [2][3][4][5][6][7][8]12,13 However, the effect of the inter- facial potential (∆E o w ) on the path and/or efficiency of photoinduced charge separation in micro-heterogeneous systems, as well as for immiscible liquid phases in general, has not been given necessary attention. This may be largely due to experimental difficulties with measurements and control of the electric potential in those systems.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics of Photoinduced Charge Transfer at Microscopic and Macroscopic Interfaces

1999

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Charge transfer at a liquid-liquid interface is the key process in a variety of chemical and biochemical processes. The kinetics of electron and proton transfer was investigated at micro-and macroscopic interfaces. Experimentally, these techniques are very distinct due to different approaches in measuring the interfacial potential. Nevertheless, three processes, i.e. generation of charge carriers, diffusion and interfacial transfer, constitute three principal steps of charge separation, and are similar regardless of the dimensionality of the system. Differences in (1) the thickness of the double electric layer, (2) span of the photoreaction zone, and (3) relative rate of electron-transfer and phase-transfer reactions enable approximations which are quite unique for a particular system. The mathematical models, corresponding experimental results, and computer-simulation techniques resulting from various descriptions of charge transfer are discussed.

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“…By itself, the microreactor model [89,90] was formulated to explain [91] the extremely high efficiency [92] of the magnetic isotope separation in chemical reactions of geminate radical pairs confined in a micellar phase. Essentially, the model is a synthesis of mathematical formalism [31][32][33] developed to account for the spin dynamics of radical pairs, with a particular model for diffusion-controlled reactions in micellar media [93,94].…”

Section: The Microreactor Model For the Micellized Radical Pairmentioning

confidence: 99%

Investigation of Liquid‐Phase Inhomogeneity on the Nanometer Scale Using Spin‐Polarized Paramagnetic Probes

Tarasov¹,

Forbes²

2017

Properties and Uses of Microemulsions

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The concept, basic physics, and experimental details of time-resolved electron paramagnetic resonance (TREPR) spectroscopy for the study of spin-correlated radical pairs (SCRPs) in heterogeneous media are presented and discussed. The delicate interplay between electron spin wave function evolution (governed by magnetic interactions such as the isotropic electron spin-spin exchange interaction and the electron-nuclear hyperfine interaction) and diffusion (governed by the size and microviscosity of the medium) provides a mechanism for assessing molecular mobility in confined spaces on the nanoscale (e.g., micelles, vesicles, and microemulsions). Experimental examples from micellar SCRPs are used to highlight the dominant features of the TREPR under different degrees of confinement and microviscosity, and spectral simulation methods are described to show how molecular mobility can be quantified.

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Photochemistry in micelles

Cited by 45 publications

References 105 publications

Quenching Mechanisms and Diffusional Pathways in Micellar Systems Unravelled by Time‐Resolved Magnetic‐Field Effects

Quenching Mechanisms and Diffusional Pathways in Micellar Systems Unravelled by Time‐Resolved Magnetic‐Field Effects

Kinetics of Photoinduced Charge Transfer at Microscopic and Macroscopic Interfaces

Investigation of Liquid‐Phase Inhomogeneity on the Nanometer Scale Using Spin‐Polarized Paramagnetic Probes

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