Photoinduced charge separation in a micelle-induced charge-transfer complex between methylviologen and ethidium ions:  a picosecond absorption spectroscopy study

Atherton, Stephen J.; Hubig, Stephan M.; Callan, Thomas; Duncanson, John A.; Snowden, Paul T.; Rodgers, Michael A. J.

doi:10.1021/j100296a008

Cited by 21 publications

(5 citation statements)

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“…Picosecond absorption measurements as a function of time after the exciting pulse (355 nm) were carried out at The Center for Fast Kinetics Research. The interrogation continuum pulse traverses a variable distance delay line before striking the sample, and this system has been described in detail elsewhere …”

Section: Methodsmentioning

confidence: 99%

Photoinduced Electron Transfer at the Core/Shell Interface of Polystyrene−Anthracene−Poly(methacrylic acid) Diblock Copolymer Micelles in Aqueous Media

1997

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We have characterized the photophysics and excited-state electron transfer reactions of polymer micelles formed from diblock polystyrene-(anthracene)-block-poly(methacrylic acid). In these studies (anthracene) comprises either a single 1-(2-anthryl)-1-phenylethylene (An) or an average of two vinyl-9,10-diphenylanthracene (vDPA). This architecture is expected to place the chromophores in the interfacial region between the polystyrene core and poly(methacrylic acid) corona. Quenching of the anthryl fluorescence by Tl + and two viologens (SPV, 4,4′-bipyridyl-1,1′-bis(propanesulfonate), and MV 2+ , methyl viologen) demonstrated that access to these chromophores was limited at all pHs, and the rate of diffusion of the viologens was relatively slow. Similar conclusions were drawn from quenching of the 3 An* state and the anion radical SPV •-by O 2 . We believe this illustrates that the interfacial region of the micelle is not fully deprotonated even at pH 9. It was observed that the fraction of 3 An* that was quenched by SPV was smaller than 1 An*. This demonstrates the existence of a heterogeneous distribution of anthryl sites such that some 3 An* cannot be quenched, which is not the case for 1 An*. We conclude that the spatial requirements for quenching these two excited states are not equivalent. Electron transfer quenching by SPV produces SPV •-that is very longlived, but some unknown reaction removes the anthryl cation radical. As a consequence, we can build up a concentration of SPV •-under steady-state photolysis. The quantum yield of charge separation per quenching event is similar to previous cases we have studied, ca. 0.5, but unlike linear polyacids, there is very little pH dependence. This is consistent with the idea that there is minimal deprotonation near the core-corona interface of the micelle.

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Section: Methodsmentioning

confidence: 99%

Photoinduced Electron Transfer at the Core/Shell Interface of Polystyrene−Anthracene−Poly(methacrylic acid) Diblock Copolymer Micelles in Aqueous Media

1997

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“…The decay measurements reported were the averages of 20 laser pulses, and transient spectra were obtained as the average of 3 laser pulses at 10 nm intervals. Transient absorption spectra on the picosecond timescale were obtained with a mode-locked Nd:YAG laser using 30 ps wide excitation laser pulses , in a 1 cm cell containing a nitrogen bubble-degassed solution with OD = 0.2−0.4 AU. Transient spectra were obtained as the average of 400 laser pulses at 10 nm intervals.…”

Section: Methodsmentioning

confidence: 99%

Photoinduced Electron Transfer in Donor−Acceptor Aryl Dyads Based on N,N,N‘,N‘-Tetramethyl-p-phenylenediamine as the Donor

Fossum¹,

Fox²,

Gelormini³

et al. 1997

J. Phys. Chem. B

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The solution-phase photophysics of several electron transfer donor−donor−acceptor assemblies (2 and 3) incorporating N,N,N‘,N‘-tetramethyl-p-phenylenediamine (TMPD) derivatized with piperazyl, piperidyl, morpholinyl, and prolinyl groups in the 1- and 4-positions as donors and N,N-dimethyl-4-nitroaniline, anthraquinone, 3,5-dinitrobenzene, and 2,4-dinitrobenzene as acceptors are described. In measurements of the model compounds 1 incorporating only the donor moieties, flash photolysis generated the radical cation and triplet species of TMPD as evidenced by the superposition of their transient absorption spectra. Lifetime measurements reveal, as well, a delayed fluorescence derived from triplet−triplet annihilation. In 2 and 3, electron transfer from the lowest excited singlet state of TMPD to the various acceptors was established by the following: (1) steady-state emission measurements where the fluorescence of TMPD was drastically quenched by the acceptor, (2) the transient absorption spectra of the radical cation and radical anion of the donor and acceptor, and (3) a single-exponential decay profile in 2 and 3, superseding the biexponential decay observed in the model donor.

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“…In comparison, a smaller redshift and decrease in absorbance of the Soret band of [ZnTPPS] 4À was noted when MV 2+ was added to the porphyrin in the absence of liposomes, as shown in Figure 2b. It has been reported that MV 2 + forms a 1:1 complex with a variety of photosensitizers, [16,[44][45][46][47][48] including [ZnTPPS] 4À (K = 1.5 10 3 m À1 ). [41] Under photocatalytic conditions, that is, in the presence of both MV 2+ and positively charged liposomes, both types of electrostatic association might take place.…”

Section: Interaction Of Charged Zinc Porphyrins With Liposomes and Elmentioning

confidence: 99%

Enhanced Photoinduced Electron Transfer at the Surface of Charged Lipid Bilayers

Limburg

Laisné

Bouwman

et al. 2014

Chemistry A European J

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Photocatalytic systems often suffer from poor quantum yields due to fast charge recombination: The energy-wasting annihilation of the photochemically created charge-separated state. In this report, we show that the efficiency of photoinduced electron transfer from a sacrificial electron donor to positively charged methyl viologen, or to negatively charged 5,5'-dithiobis(2-nitrobenzoate), increases dramatically upon addition of charged phospholipid vesicles if the charge of the lipids is of the same sign as that of the electron acceptor. Centrifugation and UV/Vis titration experiments showed that the charged photosensitizers adsorb at the liposome surface, that is, where the photocatalytic reaction takes place. The increased photoelectron transfer efficiency in the presence of charged liposomes has been ascribed to preferential electrostatic interactions between the photosensitizer and the membrane, which prevents the formation of photosensitizer-electron-acceptor complexes that are inactive towards photoreduction. Furthermore, it is shown that the addition of liposomes results in a decrease in photoproduct inhibition, which is caused by repulsion of the reduced electron acceptor by the photocatalytic site. Thus, liposomes can be used as a support to perform efficient photocatalysis; the charged photoproducts are pushed away from the liposomes and represent "soluble electrons" that can be physically separated from the place where they were generated.

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Photoinduced charge separation in a micelle-induced charge-transfer complex between methylviologen and ethidium ions: a picosecond absorption spectroscopy study

Cited by 21 publications

References 0 publications

Photoinduced Electron Transfer at the Core/Shell Interface of Polystyrene−Anthracene−Poly(methacrylic acid) Diblock Copolymer Micelles in Aqueous Media

Photoinduced Electron Transfer at the Core/Shell Interface of Polystyrene−Anthracene−Poly(methacrylic acid) Diblock Copolymer Micelles in Aqueous Media

Photoinduced Electron Transfer in Donor−Acceptor Aryl Dyads Based on N,N,N‘,N‘-Tetramethyl-p-phenylenediamine as the Donor

Enhanced Photoinduced Electron Transfer at the Surface of Charged Lipid Bilayers

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