1. Empirical design for gold nanoparticle
arrays for nano-biosensor
Maher Z. Ahmed
Department of Physics & Astronomy
The University of Western Ontario
ES 530b
2. Glass substrate
Choosing the substrate for nano gold particles
Absorption Characterization for the glass substrate
Absorption peak @ 379 nm
Typical LSPR peak and sensing
shift
Flat is the most suitable
3. Electrodynamics calculations
E extinction coefficient of metal nanoparticle
εr real components of the metal dielectric function
εi imaginary components of the metal dielectric function
εout dielectric constant of the external environment.
χ shape paramter, 2 for sphere -> 20 spheroids
a radius of spherical nanoparticle
N areal density of the nanoparticles
discrete dipole approximation (DDA) for other shapes
Plasmonic Materials for Surface-Enhanced Sensing and Spectroscopy
Amanda J. Haes, Christy L.Haynes et al. MRS Bulletin 30 (2005) 368-375
Material
Environment
shape
Size
Mie theory for spherical
Resonance condition
εr = - x εout
4. A. J. Haes et al. MRS Bulletin 30 (2005) 368-375
LSPR for Ag nanoparticles (labeled A–H) fabricated by Nanosphere Lithography (NSL)
in-plane width a out-of-plane height b
Effect of size the LSPR peak wavelength
5. K.-H. Su, et al. Nano Lett., Vol. 3, No. 8, 2003 p. 1087-1090
(a) Scattering spectra of elliptical Au
particles fabricated by E-beam
lithography (EBL)
short axis lengths of 84, 91, 96,
102, and 104 nm.
The long/short axis aspect ratio is
kept at about 1.55.
(b) Measured plasmon resonant
wavelength as a function of the
particle short-axis length.
6. 3.7% shift for cylinder
Effect of shape on the LSPR peak wavelength
(a) Extinction efficiency (ratio of
cross section to effective area)
of silver nanoparticles in
vacuum. Each particle has the
same volume of a sphere with
a radius of 50 nm.
|E|2 contours (E is electric field) for
a (b) sphere, cube, and (d)
pyramid, plotted for
wavelengths corresponding to
the plasmon peak in (a)
A. J. Haes et al. MRS Bulletin 30 (2005) 368-375
7. K.-H. Su, et al. Nano Lett., Vol. 3, No. 8, 2003 p. 1087-1090
Comparison of computer-simulated (□, O) and experimentally (∆)
measured resonant wavelength shifts as a function of the gap
between two particles.
Effect of interparticle distance on the LSPR peak
wavelength
0.016
8. sphere of diameter 30 nm
5.13 maximum absorption
@ λ= 356.51 n m
NanoSphere Optics Lab Field Simulator
Using Mie theory for nano spherical particle in air
simplification
interparticle distance 30 nm
the shift in peak 0.015 for one direction
for 4
4 x 0.015 x 356.5
= 21
expected peak
λ= 377 n m + cylindrical shift 15nm
= 392
www.nanohub.org
9. Absorption
0.047% @ λ=
377 n m
Absorption 0.042%
@ λ= 392 n m
Absorption peak @ 379 nm
Absorption 0.042%
@ λ= 392 n m
10. max
max max
max
, ,
( , )
V
V
d dV d
V χ ε ε
λ λ χ
λ λ
λ χ
χ
=
∂ ∂
= + ÷ ÷∂ ∂
11.
12. Simulation using Mie Theory
to LSPR wavelength nano gold spheres of different volumes
