Single-Molecule Kinetics of Interfacial Electron Transfer

Lu, Hsueh-Pei; Xie, Xiaohui

doi:10.1021/jp9634518

Cited by 131 publications

(165 citation statements)

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“…The decays, histogrammed by using all of the detected photons from a single molecule, are multiexponential, similar to the ensemble-averaged decays in toluene, and carry decay time components as large as several tens of nanoseconds. Multiexponential single-molecule fluorescence decays have been reported for both biological and synthetic molecules and were related to fluctuating decay times during the measurement (10,13,14), contrary to the single-exponential decays of single dye molecules (refs. 20-22 and as seen here for single PN16 and PN8 molecules in ZE).…”

Section: Methodsmentioning

confidence: 99%

“…However, whereas highly efficient FRET results in fluorescence emitted mainly from the acceptor fluorophore, highly efficient ET usually leads to a strong quenching of the fluorescence of the emitting chromophore. Thus, reports on single-molecule photoinduced ET are rather limited (10)(11)(12)(13)(14), in contrast to reports on singlemolecule FRET. A particular situation of ET refers to the case in which the locally excited state (LES) and the charge-separated state (CSS) are relatively close in energy (Fig.…”

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confidence: 98%

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Probing conformational dynamics in single donor-acceptor synthetic molecules by means of photoinduced reversible electron transfer

Cotlet

Masuo

Luo

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

110

102

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S ingle-molecule detection (SMD) has been extensively used to answer questions of both biophysical chemistry and chemical physics relevance (1-5). An elegant way to probe conformational changes is to take advantage of distance-dependent processes involving pairs of fluorophores. Förster resonant energy transfer (FRET) between two fluorophores has gained popularity as a sensitive tool to probe distance changes in the nanometer range (5-8). With an efficiency scaling with the inverse of the 6th power of the interchromophore distance, FRET can be used to track distance changes in the 2-to 8-nm range in various biological structures (5). The distance scale can be downsized to the ångstrom scale if one uses photoinduced electron transfer (ET). ET usually involves a pair of electron donor (D) and acceptor (A) chromophores spatially separated by an edge-toedge distance of Ϸ1 nm or less (9). Because the efficiency scales exponentially with the D-A distance, ET can probe distance changes with subångstrom resolution. However, whereas highly efficient FRET results in fluorescence emitted mainly from the acceptor fluorophore, highly efficient ET usually leads to a strong quenching of the fluorescence of the emitting chromophore. Thus, reports on single-molecule photoinduced ET are rather limited (10-14), in contrast to reports on singlemolecule FRET. A particular situation of ET refers to the case in which the locally excited state (LES) and the charge-separated state (CSS) are relatively close in energy (Fig. 1A, with CSS in position 2). In this case, upon optical excitation, the LES deactivates mainly by forward ET to the CSS and, if the radiationless deactivation of the CSS to the ground state (GS) is inefficient (see below), the CSS is forced to decay through the LES by reverse ET (14, 15). The fluorescence is delayed but can retain a high quantum yield. If present, reversible ET can be probed by SMD if the excited chromophore shows bright fluorescence and high photostability. In some cases, competition between the deactivation of the CSS to the LES or to the GS may be influenced by molecular oxygen (15).Here we use single-molecule fluorescence decay times to probe the dynamics of reversible ET between an excited perylenediimide (acceptor, P) and triphenylamine (donor, N) as parts in a dendritic structure. Triphenylamines are attached to the core perylenediimide by means of a polyphenylene skeleton that imposes some rigidity on the whole structure. The D-A distance is thus modified, in a controlled way, from the first (PN8, Fig. 1B with R ϭ R1) to the second (PN16, Fig. 1B with R ϭ R2) generation; hence, we expected that the parameters of the ET change as well. Materials and MethodsEnsemble stationary and time-resolved fluorescence spectroscopy was performed on 10 Ϫ6 M solutions of PN8 and PN16 (16) in solvents of different polarity: methylcyclohexane, toluene, and ethyl acetate, all of spectral-grade purity. Before measurements, solutions were degassed by freeze-pump-thaw cycling. Fluorescence decays were recorded at 5...

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 98%

Probing conformational dynamics in single donor-acceptor synthetic molecules by means of photoinduced reversible electron transfer

Cotlet

Masuo

Luo

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

110

102

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“…Lu & Xie demonstrated single-molecule measurement of photoinduced electron transfer from a sensitizing dye molecule (cresyl violet) to a semiconductor surface (indium-tin-oxide) using repetitive excitation with a picoseond pulse train (81). The fluorescence decay of a single dye molecule reflects the temporal survival probability of the excited state, which, in this case, is dominated by the fast electron transfer from the dye molecule to the conduction band of the semiconductor surface.…”

Section: Chemical Activitiesmentioning

confidence: 99%

Optical Studies of Single Molecules at Room Temperature

Xie

Trautman²

1998

Annu. Rev. Phys. Chem.

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641

551

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Recent developments in optical studies of single molecules at room temperature are reviewed, with an emphasis on the underlying principles and the potential of single-molecule experiments. Examples of single-molecule studies are given, including photophysics and photochemistry pertinent to single-molecule measurements, spectral fluctuations, Raman spectroscopy, diffusional motions, conformational dynamics, fluorescence resonant energy transfer, exciton dynamics, and enzymatic turnovers. These studies illustrate the information obtainable with the single-molecule approach that is hidden in ensemble-averaged measurements.

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“…T he experimental and theoretical study of single-molecule kinetics is a subject of topical interest in chemical kinetics (1)(2)(3)(4)(5)(6)(7)(8). where P u (t) is the probability that the molecule is in the chemical state u at time t and k uuЈ (t) is the transition rate from the state u to the state uЈ at time t.…”

Section: Introductionmentioning

confidence: 99%