Two-photon absorption spectrum of poly(fluorene)

Najechalski, P.; Morel, Yannick; Stéphan, Olivier; Baldeck, Patrice L.

doi:10.1016/s0009-2614(01)00649-2

Cited by 78 publications

(56 citation statements)

References 14 publications

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“…The former is attributable to the π-π * transition along the conjugated diphenylpyridine-fluorene backbone. The observed red shift of the peak in the solid state (compared to that in the dilute solution) is consistent with the increase in effective conjugation (Najechalski et al 2001). After switching the polymer film to the on-2 state, the broad peak (CT band) at 400-700 nm is substantially enhanced, with the peak position remaining unchanged.…”

Section: Resultssupporting

confidence: 72%

Tristable electrical conductivity switching in a polyfluorene–diphenylpyridine copolymer with pendant carbazole groups

Liu

Liaw

Lee

et al. 2009

Phil. Trans. R. Soc. A.

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Tristable electrical conductivity switching and non-volatile memory effects are demonstrated in a conjugated copolymer of poly(2,6-diphenyl-4-((9-ethyl)-9H -carbazole)-pyridinyl-alt-2,7-(9,9-didodecyl)-9H -fluorenyl) (PPCzPF). The indium-tin oxide (ITO)/PPCzPF/Al device can be switched from the low-conductivity (off) state to the first high-conductivity (on-1) state at 1.8 V, with an on/off current ratio of approximately 100. The device can be further switched from the on-1 state to the next higher conductivity (on-2) state at 2.4 V, with an on-2/on-1 current ratio of approximately 20. All the three conductivity states are accessible, stable and nonerasable. The tri-level conductance switching can be explained in terms of field-induced conformational ordering of the polymer chains and enhanced charge-transfer interaction at the PPCzPF/ITO interface.

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Section: Resultssupporting

confidence: 72%

Tristable electrical conductivity switching in a polyfluorene–diphenylpyridine copolymer with pendant carbazole groups

Liu

Liaw

Lee

et al. 2009

Phil. Trans. R. Soc. A.

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“…It was expected that the oligofluorene arms could transfer the absorbed energy to the porphyrin core by not only through-space energy transfer (Förster) but also through-bond energy transfer because of the conjugated chemical connection [43,44] . Since fluorene derivatives have large two-photon absorption cross sectionns [45][46][47][48] , the porphyrin-cored star polymer was expected to be a suitable photosensitizer to efficiently generate singlet oxygen by two-photon excitation. To confirm that the conjugated chemical connection in porphyrin-cored star polymer TPA-FxP could help enhance largely the generation of singlet oxygen, the triplet-triplet absorption dynamics, the two-photon absorption, and enhancement of the production of singlet oxygen under two-photon excitation conditions were investigated with tetraphenylporphyrin (TPP) as a reference substance.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of two-photon absorption cross section and singlet-oxygen generation in porphyrin-cored star polymers

Yan

Jia

et al. 2009

Sci. China Ser. B-Chem.

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We report a newly synthesized polymer of a star-shaped porphyrin compound (TPA-FxP) with four oligofluorene arms at its meso positions with the pronounced enhancement of the two-photon properties and the generation of singlet oxygen by utilizing the two-photon excited fluorescence resonance energy transfer. The steady-state spectra and transient triplet-triplet absorption spectra give evidence that the enhanced two-photon absorption cross section results from not only the through-space energy transfer (Förster) but also the through-bond energy transfer between conjugated peripheral oligofluorene arms and the porphyrin core. The two-photon absorption cross section at 780 nm up to 3360 GM (1 GM = 10 −50 cm 4 ⋅s/photon) of TPA-FxP was obtained, which is comparable to the highest values reported from other similar chemically modified porphyrin core compounds. Furthermore, the enhanced production of singlet oxygen under two-photon absorption conditions is also reported.porphyrin-cored star polymer, two-photon excitation, energy transfer

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“…Thus, the absorption caused only by two-photon transitions in a nanosecondpulse-excited medium (C = 2⋅10 -2 mol/l, L = 1 cm) can be observed only at TPA cross-sections of the order of 100 GM and more. For the greatest TPA cross-sections obtained in practice [12][13][14][15], nonlinear absorption can be observed at lower excitation power densities. Thus, we have W thr ~ 20-30 MW/cm 2 for δ (2) = 1000 GM and only 2-3 MW/cm 2 for δ (2) = 10 000 GM.…”

Section: Resultsmentioning

confidence: 91%

Effect of excited state absorption on the transmissivity of organic-dye-based media under two-photon excitation

Svetlichnyi

2009

Russ Phys J

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535:37Nonlinear absorption in a medium (organic dye solution) subject to two-photon excitation by laser pulses of duration ranging from femtoseconds to nanoseconds has been simulated. The effect of the absorption from excited singlet and triplet states on the transmissivity of the medium under two-photon excitation has been investigated. It has been shown that in a medium excited by monopulses, the S 1 → S n and T 1 → T m absorption makes a considerable contribution to the total nonlinear absorption of the medium only for nanosecond pulse durations. When a medium is excited by a sequence of femtosecond pulses with a repetition frequency of some tens of megahertz, significant additional nonlinear absorption can arise only due to T 1 →T m transitions that occur due to accumulation of molecules in triplet states. This effect should be taken into account in determining the cross-section for two-photon absorption in dyes and also in developing radiation intensity limiters for femtosecond lasers.

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Two-photon absorption spectrum of poly(fluorene)

Cited by 78 publications

References 14 publications

Tristable electrical conductivity switching in a polyfluorene–diphenylpyridine copolymer with pendant carbazole groups

Tristable electrical conductivity switching in a polyfluorene–diphenylpyridine copolymer with pendant carbazole groups

Enhancement of two-photon absorption cross section and singlet-oxygen generation in porphyrin-cored star polymers

Effect of excited state absorption on the transmissivity of organic-dye-based media under two-photon excitation

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