Origin of Simultaneous Donor- Acceptor Emission in Single Molecule of Peryleneimide-...
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Transcript of Origin of Simultaneous Donor- Acceptor Emission in Single Molecule of Peryleneimide-...
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.
1
Contents
● Background about dendrimers and its application
● Introduction Energy transfer process ● Experimental Confocal Single Molecule Spectroscopy Wide-field Spectroscopy (defocused imaging)
● Conclusion
2
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
5
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
8
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
9
Experimental Setup
Fluorescence from PDI unit
Fluorescence from PI unit
10
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
11
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
12
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)
15
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)
16
Optical Setup ( Wide-field Spectroscopy )
Defocus
Fluorescence detection from PI unit
Fluorescence detectionfrom TDI unit
17
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
18
T1P4
T2P8
Fluorescence from TDI Fluorescence from PI
Orientation of dipole
19
Possible explanation of these results
Annihilation and hopping
20
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.
21