Biomedical Engineering Reference
In-Depth Information
Figure 1.12
Schematics of chiral objects generated by various equations
r
). Adapted with permission from Ref. [20]. Copyright 2012,
American Chemical Society.
=
R
NC
(
θ
,
ϕ
InasmallNC,theCDsignalcanbeexpandedasapowerseriesof
k
, using a long waveapproximation [20]:
CD
=
ak
2
+
bk
4
+
. . . ,
(1.46)
where
a
and
b
arecoe
cientsrelatedtothedielectricfunctionsand
the geometric parameters. Leading by
k
2
, CD is much smaller than
absorption, as absorption is of the power of
k
.Onthecontrary,CDis
much stronger than scattering of
k
4
.
The chiral shape of an NC is defined using equations
r
=
).Itwillbemorestraightforwardtojustlisttheseexamples
at the beginning of the section. The plots of these objects are shown
inFig.1.12,whilethefunctionsdescribingtheseobjectsareavailable
in the SI of Ref. [20]
R
NC
(
θ
,
ϕ
1.5.2
Origins of Plasmonic CD: Mode Mixing
In order to learn more about the physical process underlying the
interactions between plasmon modes of a chiral NC and incident
light, we now use a modal analysis and an artificial dielectric
constant from the Drude model. The Drude model parameters are
selected to provide a very narrow absorption peak so that we can
