b2815 Tissue Engineering and Nanotheranostics “9.61x6.69”158 Tissue Engineering and Nanotheranostics
other, their enhanced electric field will overlap and induce more com
plex phenomenon,6–9 that is hot spot, Fano resonance and so on.
Nordlander et al. developed a theory to explain Fano resonance,
analogous to hybridization model in atom bonding.10–13 Take Dimer
system as example, briefly, when the polarizer is oriented perfectly
along the interparticle axis, only the σmode is seen in the scattering
spectrum. As σmode is formed by headon hybridizing, charge with
the opposite sign is accumulated on opposite sides of the gap to
decrease frequency, and its net charge is high to increase intensity,
whereas only the p*mode contributes when the polarizer is oriented
perfectly perpendicular to the interparticle axis. Contrast to σmode,
p*mode is slightly blueshifted relative to the single particle reso
nance and is lower in intensity. For complicate systems, it is necessary
to reduce the system to a simple system.
In the experiment, Reinhard B.M group found that the ratio of
spectral shift of particles (with diameters in the range of 20–70 nm)
is a first approximation, independent of the nanoparticles diameter
and follows a universal scaling relationship to individual nanoparticles
resonance wavelength. For AuNPs, the universal scaling relationship
as a function of interparticle separations, S, and particle diameter, D,
was determined as follows14,15:
plas 0.23
00.18
S
De
λ
λ
−