Single molecule

Single Molecule Spectroscopy
(SMS)
2010/6/9
Miyasaka Lab.
Iida Atsushi
Contents
•
•
•
•
Introduction
-History of Single Molecule Spectroscopy (SMS)
-Difference between ensemble and single-molecule measurement
-Information obtained only by SMS
Measurement
-Principle
-Single-molecule detection
 Confocal Microscope
 Wide-Field Mycroscope
Representative results of SMS
-Blinking
-Spectral jump
-Photon antibunching
My work
History of Single Molecule
Spectroscopy
• 1989 W. E. Moerner et al.
First detection of single-molecule
with FM spectroscopy
• 1990 M. Orrit et al.
Fluorescence excitation spectra
of single molecules
• 1992 T. Basche et al.
Blinking, Spectral jump
Difference between ensemble and
single-molecule measurements
The result of ensemble measurement
Ensemble
An emission spectrum of a single molecule
“Single molecule”
Information obtained only by SMS
FRET : 励起エネルギー移動
SMS
Ensemble measurement
Intensity of
red light
Direct observation of
dynamical state changes
The signal is averaged.
Information obtained only by SMS
• Evaluation of nano-scale heterogeneity
Fluorescent molecule
Polymer
Properties of a molecule depend on
its microscopic environment .
• Energy level
• Life-time
• Diffusion
Principle
Absorption
I0
I
I0
I
Fluorescence
Quite sensitive detector
Single fluorescence molecules in dark space
can be detected optically.
Key : Reduction of the noise from the background
Confocal Microscope
Intensity trajectory
Sample
Life-time
Objective lens
Coincidence
Pinhole
Detector
3-dimentianal resolution
Small background
High temporal resolution
Wide-field Microscope
2-dimentioanl resolution
Objective lens
・translational diffusion coefficient
High sensitivity camera
・rotational motion
・Many molecules can be observed at a time.
Blinking
Dye molecules in a polymer film (PMMA)
non-luminescent
Each molecule emits light frequently.
Non-luminescent process, for example photo-ionization,
relates with this phenomena.
Spectral jump
Host molecule
p-terphenyl
Guest molecule
pentacene
M. Oritt, J. Bernard, Phys. Rev. Lett., 65, 2716 (1990).
Photon antibunching
Beam splitter (50:50)
Detector 1
A molecule emits one photon
from its one excited state.
Detector 2
Photons can not be
divided.
If you detect photons from a
single molecule, there is no
possibility to detect two
photons by the detector 1 and
2 at the same time.
Phenomenon that multiple photons do not exist at the same time.
12
Light pulse
125ns
Interphoton arrival time
Photon
Photodetector 1
Photodetector 2
Events
Photon antibunching
-125
0
125
Delay /ns
Ensemble
Events
Single molecule
Coincidence
-125
0
125
Delay /ns
The coincidence event is not observed for single molecule system.
13
My Work
water
-
octane
Droplet is very small.
specific surface area(比表面積)
surface area
volume
Influence of surface is
very big in ultrasmall droplet.
-
-
-
-
-
The surface is anionic.
The interaction between surface and a solute
depends on the size and the surface charge.
My Work
Transmission
Fluorescence
Dye molecule is moving in the droplet,
and absorbs to the surface.
Only one dye molecule exists in the droplet.
My work
surfactant ; triton x-100 (non-ionic)
SDS (anionic)
Triton x-100
The nano-scale environment
around a solute is similar to
that in the bulk octane.
Triton x-100
A solute is diffusing center of the droplet.
SDS
SDS
A solute exists in the different
environment from the bulk octane.
Life-time
SDS<Triton x-100
(3.6ns)
A solute is diffusing near the surface.
(6.2ns)
Life-time of the dye molecules in bulk octane is 6.4ns.

Download Report