Ultrafast Excited-State Dynamics of Oxazole Yellow DNA Intercalators

Fürstenberg, Alexandre; Vauthey, Eric

doi:10.1021/jp073182t

Cited by 38 publications

(52 citation statements)

References 51 publications

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“…In order to reconstruct time-resolved emission spectra, a global analysis was undertaken, as described in detail elsewhere. 54,56 In brief, for each sample the normalized fluorescence time profiles at various emission wavelengths were analyzed globally using the convolution of a Gaussian-shaped IRF with the sum of exponential terms. The width of the IRF was typically around 140 fs for solution measurements with the 0.25 mm cell.…”

Section: Fluorescence Up-conversion Spectroscopymentioning

confidence: 99%

Ultrafast spectroscopic investigation of a fullerene poly(3-hexylthiophene) dyad

et al. 2011

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We present the femtosecond spectroscopic investigation of a covalently linked dyad, PCB-P3HT, formed by a segment of the conjugated polymer P3HT (regioregular poly(3-hexylthiophene) that is end-capped with the fullerene derivative PCB ([6,6]-phenyl-C 61 -butyric acid ester), adapted from PCBM. The fluorescence of the P3HT segment in tetrahydrofuran (THF) solution is reduced by 64% in the dyad compared to a control compound without attached fullerene (P3HT-OH). Fluorescence upconversion measurements reveal that the partial fluorescence quenching of PCB-P3HT in THF is multiphasic and occurs on an average time scale of 100 ps, in parallel to excited-state relaxation processes. Judging from ultrafast transient absorption experiments, the origin of the quenching is excitation energy transfer from the P3HT donor to the PCB acceptor. Due to the much higher solubility of P3HT compared to PCB in THF, the PCB-P3HT dyad molecules self-assemble into micelles. When pure C 60 is added to the solution, it is incorporated into the fullerene-rich center of the micelles. This dramatically increases the solubility of C 60 , but does not lead to significant additional quenching of the P3HT fluorescence by the C 60 contained in the micelles. In PCB-P3HT thin films drop-cast from THF, the micelle structure is conserved. In contrast to solution, quantitative and ultrafast (<150 fs) charge separation occurs in the solid-state films and leads to the formation of long-lived mobile charge carriers with characteristic transient absorption signatures similar to those that have been observed in P3HT:PCBM bulk heterojunction blends. While π-stacking interactions between neighboring P3HT chains are weak in the micelles, they are strong in thin films drop-cast from ortho-dichlorobenzene (DCB). Here, PCB-P3HT self-assembles into a network of long fibers, clearly seen in AFM images.Ultrafast charge separation occurs also for the fibrous morphology, but the transient absorption experiments show fast loss of part of the charge carriers due to intensity-induced 2 recombination/annihilation processes and monomolecular interfacial trap-mediated or geminate recombination. The yield of the long-lived charge carriers in the highly organized fibers is however comparable to that obtained with annealed P3HT:PCBM blends. PCB-P3HT can therefore be considered as an active material in organic photovoltaic devices.

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Section: Fluorescence Up-conversion Spectroscopymentioning

confidence: 99%

Ultrafast spectroscopic investigation of a fullerene poly(3-hexylthiophene) dyad

et al. 2011

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“…The origin of this component is not absolutely clear, but has already been observed when excitation is performed far from the 0-0 transition. [44,45] Therefore, this Gaussian component can be possibly associated with vibrational relaxation processes taking place from the initially Franck- Condon region of the excited state down to the equilibrium. [46,47] A Gaussian component was also found in all the other systems investigated herein.…”

Section: Ultrafast Fluorescence Dynamicsmentioning

confidence: 99%

Site‐Dependent Excited‐State Dynamics of a Fluorescent Probe Bound to Avidin and Streptavidin

et al. 2009

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Sensing protein environment: The femtosecond fluorescence dynamics of a molecular probe attached to avidin and streptavidin (see figure) depends markedly on the location of the probe and on the protein. These differences reflect not only the protein primary and tertiary structures but also the effect of the surrounding water molecules. The excited‐state dynamics of biotin–spacer–Lucifer‐Yellow (LY) constructs bound to avidin (Avi) and streptavidin (Sav) was investigated using femtosecond spectroscopy. Two different locations in the proteins, identified by molecular dynamics simulations of Sav, namely the entrance of the binding pocket and the protein surface, were probed by varying the length of the spacer. A reduction of the excited‐state lifetime, stronger in Sav than in Avi, was observed with the long spacer construct. Transient absorption measurements show that this effect originates from an electron transfer quenching of LY, most probably by a nearby tryptophan residue. The local environment of the LY chromophore could be probed by measuring the time‐dependent polarisation anisotropy and Stokes shift of the fluorescence. Substantial differences in both dynamics were observed. The fluorescence anisotropy decays analysed by using the wobbling‐in‐a‐cone model reveal a much more constrained environment of the chromophore with the short spacer. Moreover, the dynamic Stokes shift is multiphasic in all cases, with a ∼1 ps component that can be ascribed to diffusive motion of bulk‐like water molecules, and with slower components with time constants varying not only with the spacer, but with the protein as well. These slow components, which depend strongly on the local environment of the probe, are ascribed to the motion of the hydration layer coupled to the conformational dynamics of the protein.

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“…with much lower amplitude than with YOYO-1 and with time constants of 2.3 and 41 ps. [15] YO-PRO-1 intercalates between two base pairs and is thus expected to impose less pronounced geometrical constraints on the double helix and could therefore be more shielded from bulk water than the bisintercalator YOYO-1. Such slowing down of TDSS dynamics at biomolecular interfaces had previously been observed by others [5] but its origin is still debated.…”

Section: Solvation Dynamicsmentioning

confidence: 99%

“…[15] However, the amplitudes of the decay components strongly depend on the DNA:dye ratio since the energy hopping is intermolecular: the higher the loading in dye molecules of the DNA strand, the shorter the average dye − dye distance and the more efficient the energy hopping. [15] …”

Section: Introductionmentioning

confidence: 99%