Biomedical Engineering Reference
In-Depth Information
Figure 1.14
Results for the CD response for various types of chiral Au NCs.
(a) Right-handed twister and anti-twister with
δ
R
=
1.5 and
−
0.8 nm. (b)
Asymmetric pyramid with
α
=
1. (c) Chiral tetrahedral structure with
a
0
=
2 nm. In all cases,
R
0
7 nm. Adapted with permission from Ref. [20].
Copyright 2012, American Chemical Society.
=
distortion. The function describes a perturbation in geometry
created to a sphere. Perturbation can be modulated by a parameter
δ
R
, seen in the SI of Ref. [20]. The formalism can be applied
to generally all kinds of distortions described by such functions.
In our study, we are interested in helical twisters, pyramid-like
NPs, and tetrahedron-like NPs, on which four bumps of different
sizes are created at the vertices to mimic a tetrahedral framework.
Coincidently, the helical structure again demonstrated the strongest
potential in plasmonic CD generation, though we have discussed
in the last paragraph that the mechanism is essentially different
from helical AuNP chains. This suggested an interesting connection
between chiral plasmon excitationsand chiral geometries.
1.6 Experimental Measurements of Plasmonic Circular
Dichroism
Chiral plasmonic NC assemblies so far involved spherical NPs,
nanorods, nanofibers, chiral mesoporous films, chiral inorganic
molecules, biomolecules, and so on [1, 25, 26, 35, 36, 42, 48, 56, 66,
67, 72]. In this section, we will give a few examples of experimental
works on chiral nanoscalesystems.
InthefieldofplasmonicCDresearchofNPs,apioneerstudywas
carried out on chiral silver NPs assembly by Shemer et al. [65]. In
