Document

Ultrafast Solvation Dynamics of
Coumarin 153 in ImidazoliumBased Ionic Liquids
Barnhard Lang, Gonzalo Angulo, and Eric Vauthey
J.Phys.Chem.A 2006, 110. 7028-7034
Miyasaka Lab.
Masayasu Muramatsu
Contents
Introduction
•
•
Room-Temperature Ionic Liquids
Solvation dynamics
[cnpmim]+
Experimental
•
•
Fluorescence up-conversion
Three-pulse photon-echo peak-shift
Results & discussion
Summary
[Tf2N]-
Room-Temperature Ionic Liquids
Room-temperature ionic liquids (RTILs) are organic molten salts
Ultralow volatility:揮発性
Flameproof
Electrochemical stability
High viscosity
Application for the Electron Microscope
Ionic liquid
http://www.tuat.ac.jp/~ohno/lab/ionic_liquid/IL.html
Star sand SEM image
left:with RTIL
right:bulk
http://www.chem.eng.osaka-u.ac.jp/~elechem/Research.htm
Solvation dynamics
Solvation in conventional liquids
通常の有機溶媒
S1
Exited state
Energy
Stabilization
S0
hν
Ground state
hν
Solvation Coordinate
strongly solvated
Solvation dynamics
Dynamic Stokes-shift
Solvation in ionic liquids
S1
Energy
Solvation
S0
hν
emission
○:anion
●:cation
Solvation Coordinate
Fluorescence up-conversion
delay
sample
Fluorescence : ωf
ωs
ωf
ωe
Excitation pulse : ωe
Intensity
BBO
0
ωg
Exitation
Gate
delay
Gate pulse : ωg
time
ωｓ= ωｆ＋ωｇ
0
BBO:β-BaB2O4
monochr:モノクロメーター（分光器）
PMT:光電子増倍管
0
Sum frequency : ωs= ωf+ ωg
time
time
Three-pulse photon-echo peak-shift
peak-shift τ’
―:-k1+k2+k3
―: k1-k2+k3
T → large
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
τ’ → small
3PEPS results
τ’ vs T
Fluorescence up-conversion
[pmim]+
[cnpmim]+
Steady-state absorption and emission spectra
Coumarin153 in[cnpmim+][Tf2N-]
and[pmim+][BF4-]
Excitation : 400nm
Response function : 230fs
×:490nm
▼:540nm
●:580nm
Fluorescence time profiles
Dynamic red shift
Red : rise
Blue : decay
[Tf2N]-
Fluorescence up-conversion
Dynamic red shift
Missing red shift
Reconstructed time-dependent emission spectra
500cm-1
4600cm-1
600cm-1
Time dependence of the emission band maximum
Too small peak shift change
→ ultrafast component?
Three-pulse photon-echo peak-shift
in ionic liquid
molecular vibration
分子振動
Indocyanine green in[cnpmim+][Tf2N-]
and ethanol
inertial part
溶媒の平均自由行程内
in ehtanol
Excitation : 800nm
Pulse duration : 15fs
Differ from Stokes-shift measurements
Inertial part: Signal starts at a higher level
and decays slower in ionic liquids
3PEPS results
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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