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Kou ITOH MIYASAKA Lab.

Origin of Simultaneous Donor- Acceptor Emission in Single Molecule of Peryleneimide-Terrylenediimide Labeled Polyphenylene Dendrimers. Sergey M.Melnikov Edwin K.L.Yeow,Hiroshi Uji-I,Mircea Cotlet Klaus Mullen, Frans C De Schryver Jorg Enderlein, and Johan Hofkens

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Kou ITOH MIYASAKA Lab.

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  1. Origin of Simultaneous Donor-Acceptor Emission in Single Molecule of Peryleneimide-Terrylenediimide Labeled Polyphenylene Dendrimers Sergey M.Melnikov Edwin K.L.Yeow,Hiroshi Uji-I,Mircea Cotlet Klaus Mullen, Frans C De Schryver Jorg Enderlein, and Johan Hofkens J.Phys.Chem.C. 2007, 111, 708-719 Kou ITOHMIYASAKA Lab.

  2. Contents ●Background about dendrimers and its application ● Introduction Energy transfer process ● Experimental Confocal Single Molecule Spectroscopy Wide-field Spectroscopy (defocused imaging) ● Conclusion

  3. Background surface core T1P4 interior T2P8 :Perylenemonoimide unit :Terylenediimide unit Potential application to new photonic device

  4. light light pulse Example of photonic devices single photon source artificial light-harvesting system R R R Single photon energy R J.P.C.B.2004,108,16686-16696 J.A.C.S.2007,129,3539-3544

  5. Introduction Evaluation and understanding of the dendrimers Ensemble measurements Single molecule measurements Dynamics, Efficiency of • Emission dynamics of individual molecular systems • Photon antibunching • Energy transfer • Electron transfer • Emission lifetime etc. • Ultra-high temporal resolution • Reliable average values Enables us to evaluate single nanoscale dendrimers Complementary use of both measuring methods can give us comprehensive understanding of the dendrimers.

  6. Introduction-Energy transfer processes Förster theory Hopping D*+A→D+A* S1*+S0→S0+S1* transition probability ω is ω＝（1/τ0）・（R0/ R）6 S１ S１ ( R06 ∝ c2FD J ) S０ S０ τ0 : lifetime of donor Donor Acceptor R0 : critical transfer distance R : distance between molecules S1-S1 annihilation Important factors in R06 S1*+S1*→So+S1* Fluorescence of donor Sｎ Absorption of acceptor S１ S１ S０ S０ Spectral overlap Donor Acceptor Orientation of dipole moment

  7. The purpose of this research hν2 hν0 PI unit TDI unit T1P4 hν2 hν0 hν1 Exciton blockade

  8. Energy transfer processes Directional FRET Hopping S1(PI)-S1(TDI) annihilation S1(PI)-S1(PI) annihilation

  9. 2000 rpm Cover glass Sample preparation Spin-coat method Concentration is 10-10M ② Spin-coat on cover glass ① T1P4 and T2P8 in chloroform (＋Zeonex(Polynorbornene) ) single molecule Zeonex film (thickness = 100~200nm) Well cleaned cover glass

  10. Experimental Setup Fluorescence from PI unit Fluorescence from PDI unit

  11. Fluorescence from TDI Fluorescence from PI T1P4 A:pulse B:CW T2P8 C:pulse D:CW Typical fluorescence transients of single molecules. (Parts A and B display T1P4 molecules, and parts C and D,T2P8. Parts A and C correspond to pulse excitation, and parts B and D, to CW excitation.

  12. T1P4 A:pulse B:CW T2P8 C:pulse D:CW Two-colar fluorescence transients of single molecules. (Parts A and B display T1P4 molecules, and parts C and D,T2P8. Parts A and C correspond to pulse excitation, and parts B and D, to CW excitation.

  13. Discussion Occurrence of three different modes of behavior for single molecules Excitation type Red followed by green emission Dual-color emission Only red emission compound

  14. Discussion Number of chromophores(PI) Pij Probability of excitation Number of chromophore(s) excited T2P8 T1P4 P82 P42 = 0.421 = 0.177 P81 P41 Intramolecular distances

  15. Fluorescence decay time and time constant of annihilation Forster Radii (critical transfer distance) Dual-color fluorescence cannot be solely explained by exciton blockade.

  16. Wide-field Imaging (defocused imaging) ② ① defocus Dipole moment ② ① The pattern of radiation Orientation of dipole moment Ref. J. Enderlein et al J.Opt.Soc.Am.B,2003,20,554-559 Polymer,2006,47,2511-2518

  17. Defocus Optical Setup（Wide-field Spectroscopy） Fluorescence detection from TDI unit Fluorescence detection from PI unit

  18. Typical example of emission of T1P4 and T2P8 T1P4 T2P8 Fluorescence from PI Fluorescence from TDI Defocused images of single molecule embedded in a polymer film. Parts A and B correspond to T1P4 molecules, and parts C and D, to T2P8

  19. Orientation of dipole

  20. Possible explanation of these results Annihilation and hopping

  21. Conclusion • The authors have investigated a fundamentally photochemical process (energy transfer) in dendrimers, T1P4 and T2P8. • Single molecule detection by confocal microscopy and wide-field imaging revealed that the two-color emission from the dendrimers cannot be explained only by the exciton blockade.

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