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rotational movement of anisotropic nanoparticles with a subdegree
uncertainty.106–108 By combination of defocused imaging and the rota
tion of the polarization direction of light incident upon the sample,
the 3D orientation of stationary AuNPs was resolved with a higher
precision in TIR scattering microscope. In another work, a dual color
TIR scattering microscope was used to track the orientation change
of AuNRs when interacting with synthetic lipid membranes by analyz
ing orientationdependent intensity fluctuations of surface plasmon
resonance enhancement along the long and short axis simultane
ously.^108 AuNR orientation changes in the sample plane can be tracked
in details using polarized light that propagates parallel to the prism
surface, while outofplane orientation changes can be tracked utiliz
ing the long axis of the AuNR and its interaction with polarized light
propagating perpendicularly to the prism surface.
5. Application based on Localized Surface
Plasmon Resonance
The typical LSPR sensing application of plasmonic nanoparticles is to
detect changes of their surrounding environment through shifts of
scattering profile.^109 This kind of a sensor has been designed to detect
bimolecular binding events110,111 close to the surface and molecular
adsorb on the surface,^112 to characterize carbohydrate–protein interac
tions^113 and measure the binding of a protein to DNA.^114 For instant,
a sensor^115 was designed to detect conformational changes in a surface
bound construct of the calciumsensitive protein calmodulin. Increases
in calcium concentration induce a 0.96 nm redshift in the spectral
position of the LSPR extinction maximum (λ max). Addition of a
calciumchelating agent forces the protein to return to its original
conformation and is detected as a reversal of the λ maxshift.
5.1. Localized Surface Plasmon Resonance Change to
Sensor Catalytic Reaction
Due to the quantum effects and free electrons on their surface,
AuNPs of small scale exhibit catalytic activity and attract many scien
tists to study its mechanism. It’s discovered that catalytic reactions
