Origin of Simultaneous Donor- Acceptor Emission in Single Molecule of Peryleneimide- Terrylenediimide Labeled Polyphenylene Dendrimers Sergey M.Melnikov.

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.

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Contents

● Background　　 about dendrimers and its application

● Introduction　　 Energy transfer process ● Experimental Confocal Single Molecule Spectroscopy Wide-field Spectroscopy (defocused imaging)

● Conclusion

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Background

T1P4

T2P8

:Perylenemonoimide unit

:Terylenediimide unit

Potential application to new photonic device

core

interior

surface

3

single photon source artificial light-harvesting system

lightpulse

Singlephoton

light

energy

J.P.C.B.2004,108,16686-16696 J.A.C.S.2007,129,3539-3544

R

Example of photonic devices

4

R

RR

Evaluation and understanding of the dendrimers

Ensemble measurements Single molecule measurements

• Energy transfer• Electron transfer• Emission lifetime etc.

Dynamics, Efficiency of

• Ultra-high temporal resolution• Reliable average values

• Emission dynamics of individual molecular systems

• Photon antibunching

Enables us to evaluate single nanoscale dendrimers

Complementary use of both measuring methods can give us comprehensive understanding of the dendrimers.

Introduction

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Introduction - Energy transfer processes

transition probability ω is

Förster theoryFörster theory

D* + A → D + A*

ω ＝（ 1/τ0 ）・（ R0/ R ） 6

R : distance between molecules

R0 : critical transfer distance

τ0 : lifetime of donor

S1-S1 annihilationS1-S1 annihilation

HoppingHopping

S1* + S1* 　　→　　 So + S1* 　

S1* + S0 　　→　　 S0 + S1*

S ０

S １

S ０

S １

AcceptorDonor

S ０

S １

S ０

S １

S ｎ

AcceptorDonorOrientation of dipole moment

Fluorescence of donor

Absorption of acceptor

Spectral overlap6

Important factors in R06Important factors in R06

( R06 ∝ D J

The purpose of this research

hν0

PI unit

Exciton blockade 7

hν2

T1P4

hν2

hν1

hν0

Energy transfer processes

Directional FRETHopping

S1(PI)-S1(TDI) annihilation S1(PI)-S1(PI) annihilation

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Sample preparation

Spin-coat methodSpin-coat method

Well cleaned cover glass

Zeonex film (thickness = 100~200nm)

single molecule

② Spin-coat on cover glass ① T1P4 and T2P8 in chloroform ( ＋ Zeonex(Polynorbornene) )

2000 rpm

Cover glass

Concentration is 10-10M

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Experimental Setup

Fluorescence from PDI unit

Fluorescence from PI unit

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Typical fluorescence transients of single molecules.(Parts A and B display T1P4 molecules, and parts Cand D,T2P8. Parts A and C correspond to pulse excitation, and parts B and D, to CW excitation.

T1P4

A:pulse B:CW

T2P8

C:pulse D:CW

Fluorescence from TDI

Fluorescence from PI

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

T1P4

A:pulse B:CW

T2P8

C:pulse D:CW

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Pulse T1P412(11 ％)

27(25 ％)

71(64 ％)

T2P851(15 ％)

81(24 ％)

207(61 ％ )

CW T1P47(11 ％ ) 16(24 ％

)43(65 ％)

T2P811(11%) 14(25 ％

)70(74 ％)

Occurrence of three different modes of behavior for single molecules

Discussion

Excitationtype compound

Dual-coloremission

Only redemission

Red followedby green emission

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Discussion

Probability of excitation

T2PT2P88P8

2

P81

= 0.421

T1PT1P44P4

2

P41

= 0.177

Number of chromophores(PI)

Number of chromophore(s) excited

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Pij

chromophore compound r [nm]

PI - PDI T1P4 2.3

T2P8 3.1

PI - PI T1P4 0.5 - 4.0

T2P8 0.5 - 5.5

Intramolecular distances

Fluorescence decay time and time constant of annihilation

Dual-color fluorescence cannot be solely explained by exciton blockade.

PI

emission

PI-TDI

annihilation

(T1P4)

PI-TDI

annihilation

(T2P8)

4 ns 220 ps 1 ns

Directional FRET 5.9 nmEnergy hopping 4.8 nmS1-S1 annihilation

(between PI and PI) 5.3 nmS1-S1 annihilation

(between PI and PDI) 3.7 nm

Forster Radii (critical transfer distance)Forster Radii (critical transfer distance)

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Dipole moment

The pattern of radiation

defocus

①②

① ②

Orientation of dipole moment

Ref. J. Enderlein et al 　J.Opt.Soc.Am.B,2003,20,554-559Polymer,2006,47,2511-2518

Wide-field Imaging (defocused imaging)

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Optical Setup （ Wide-field Spectroscopy ）

Defocus

Fluorescence detection from PI unit

Fluorescence detectionfrom TDI unit

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Typical example of emission of T1P4 and T2P8

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

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T1P4

T2P8

Fluorescence from TDI Fluorescence from PI

Orientation of dipole

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Possible explanation of these results

Annihilation and hopping

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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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