Surface Plasmon Resonance. General Introduction презентация

Surface Plasmon Resonance
General Introduction
Steffen Jockusch
07/15/07
Plasmons:
- collective oscillations of the “free electron gas” density, often at optical frequencies.
Surface Plasmons:
- plasmons confined to surface (interface) and interact with light resulting in polaritons.
- propagating electron density waves occurring at the interface between metal and dielectric.

Surface Plasmon Resonance
General Introduction
Steffen Jockusch
07/15/07
Plasmons:
- collective oscillations of the “free electron gas” density, often at optical frequencies.
Surface Plasmons:
- plasmons confined to surface (interface) and interact with light resulting in polaritons.
- propagating electron density waves occurring at the interface between metal and dielectric.
Surface Plasmon Resonance:
- light (λ) in resonance with surface plasmon oscillation

Requirements:
- Material with free electrons:
Pb, In, Hg, Sn, Cd
Cu, Ag, Au
plasma frequency
UV
VIS
Metals
2

Requirements:
- Material with free electrons:
Pb, In, Hg, Sn, Cd
Cu, Ag, Au
plasma frequency
UV
VIS
Metals
- Surface (interface):
flat surfaces
nanoparticles
50 nm
Au
2

Requirements:
- Material with free electrons:
Pb, In, Hg, Sn, Cd
Cu, Ag, Au
plasma frequency
UV
VIS
Metals
- Surface (interface):
flat surfaces
nanoparticles
50 nm
Au
2
- Light: How to couple the photons to the surface?

Total reflection on a prism
θ
prism
0
reflectance
1
angle
θc
θ
prism
3

Evanescent Wave
θ
prism
evanescent field
evanescent wave: - nearfield standing wave,
- extends about 1/2 λ,
- decays exponentially with the distance
0
reflectance
1
angle
θc
4

Surface Plasmon Resonance
θ
detector
50 nm
Au
0
reflectance
1
angle
θc
θo
5
(Kretschmann)

Surface Plasmon Resonance Spectroscopy
θ
detector
Au
analyte
0
reflectance
1
angle
θc
θo
θ1
To measure: - thickness changes,
- density fluctuation,
- molecular adsorption
6

Knoll, et.al. Biosensors & Bioelectronics, 1995, 10, 903
Surface Plasmon Resonance Spectroscopy in Sensors
7

(Kretschmann)
Waveguide coupler
Grating coupler
Prism coupler
Homola, Chem. Rev. 2008, 108, 462
Coupling of Light to Surface Plasmon
8

Nanoparticle Surface Plasmon
d
λ
λ
d <<
Nanoparticle
9

Eustis and El-Sayed, Chem. Soc. Rev., 2006, 35, 209
Nanoparticle Surface Plasmon
d
λ
λ
d <<
Nanoparticle
Light resonance with the surface plasmon oscillation
causes the free electrons in the metal to oscillate.
9