ultrafast solvation dynamics of coumarin 153 in imidazolium- based ionic liquids barnhard lang,...
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Ultrafast Solvation Dynamics of Coumarin 153 in Imidazolium-Based Ionic Liquids
Barnhard Lang, Gonzalo Angulo, and Eric VautheyJ.Phys.Chem.A 2006, 110. 7028-7034
Miyasaka Lab.
Masayasu Muramatsu
Contents
Introduction• Room-Temperature Ionic Liquids• Solvation dynamics
Experimental• Fluorescence up-conversion• Three-pulse photon-echo peak-shift
Results & discussion
Summary
N+
N
N
N-
S S
O
OO
O F
F
F
F
F
F
[cnpmim]+
[Tf2N]-
Room-Temperature Ionic Liquids
Room-temperature ionic liquids (RTILs) are organic molten salts
Ultralow volatility: 揮発性
Flameproof
Electrochemical stability
High viscosity
http://www.chem.eng.osaka-u.ac.jp/~elechem/Research.htm http://www.tuat.ac.jp/~ohno/lab/ionic_liquid/IL.html
Application for the Electron Microscope
Star sand SEM imageIonic liquidleft:with RTIL right:bulk
Solvation dynamics
hν
Solvation in conventional liquids
Ener
gy
Solvation Coordinate
S0
S1
hν
Stabilization
Exited state
Ground state
strongly solvated
通常の有機溶媒
Solvation dynamics
○:anion●:cation
Solvation in ionic liquidsDynamic Stokes-shift
Ener
gy
Solvation Coordinate
S0
S1
Solvation
hνemission
Fluorescence up-conversion
Intensity
time
time
time
delay
Excitation pulse : ωe
Fluorescence : ωf
Gate pulse : ωg
Sum frequency : ωs= ωf+ ωg
0
0
0
sample
BBO
ωe
ωf
ωg
ωs
delay
mono
chr.PMT
ω s = ω f+ω gExitationGate
BBO:β-BaB2O4
monochr: モノクロメーター(分光器) PMT: 光電子増倍管
Three-pulse photon-echo peak-shiftpeak-shift τ’
―:-k1+k2+k3
―: k1-k2+k3
T → large
τ’ → small
3PEPS resultsτ’ vs T
pulse1 makes the coherence of polarization.pulse2 interferes with pulse1 indeced polarization.pulse3 is diffracted as the signal.
τ=0 : Transient Grating → no echo
τ 0≫ : decoherent → no echo
T 0≫ : vanish diffraction fringe → no echo干渉縞
Fluorescence up-conversion
Coumarin153 in[cnpmim+][Tf2N-] and[pmim+][BF4
-]
Excitation : 400nmResponse function : 230fs
Dynamic red shift
N+
N
N+
N
N N-
S S
O
OO
O F
F
F
F
F
F
BF4-
[pmim]+
[cnpmim]+ [Tf2N]-
Red : rise Blue : decay
Steady-state absorption and emission spectra
Fluorescence time profiles
× :490nm▼ :540nm● :580nm
× :490nm▼ :540nm● :580nm
Fluorescence up-conversion
Dynamic red shift
Too small peak shift change → ultrafast component?
4600cm-1
600cm-1
500cm-1
Reconstructed time-dependent emission spectra
Time dependence of the emission band maximum
Missing red shift
Three-pulse photon-echo peak-shift
Indocyanine green in[cnpmim+][Tf2N-] and ethanol
Excitation : 800nmPulse duration : 15fs
Differ from Stokes-shift measurements
Inertial part: Signal starts at a higher level and decays slower in ionic liquids
in ionic liquid
in ehtanol
molecular vibration
inertial part
3PEPS results
溶媒の平均自由行程内
分子振動
Summary
The dynamic Stokes shift of coumarin 153 in Room temperature ionic liquids(RTILs) has been measured using fluorescence up-conversion techniques with a response function of 230fs.
Three-pulse photon-echo peak-shift(3PEPS) experiments on indocyanine green in RTILs has been measured.
Ultrafast solvation in RTILs which could not be observed by fluorescence up-conversion was suggested from 3PEPS results. Improved 3PEPS may find farther information.
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