Chiral
growth and chirality transfer associated with plasmonic
nanostructures have rejuvenated the field of chirality. As the precise
regioselective growth of inorganic crystals into chiral shapes at
the nanoscale is extremely challenging, “bottom-up”
synthesis of intrinsically chiral nanoparticles with structural stability
is obviously attractive and important. With the thiolated bimolecular
cosurfactants, we demonstrated a chemical strategy for the synthesis
of intrinsically helical plasmonic nanorods (HPNRs) with strong and
tailorable plasmonic circular dichroism (PCD) responses, deriving
from the zwitterionic interactions between the −NH3
+ and −COO– groups of the cysteine
molecules (Cys). The influence of structural parameters of HPNRs on
PCD responses was analyzed systematically by theoretical simulations.
Among the different structural parameters, the pitch depth was found
to have the greatest impact on the PCD signals, in agreement with
the experimental results. Moreover, the obtained HPNRs with the strong,
tunable, and stable chiroptical properties were found to be able to
induce circularly polarized luminescence of achiral luminophores.
Due to the generality of this effect, this chiral plasmonic nanostructure
may have great potential for use in the fields of chiral sensors,
chiral catalysis, and displays.
Local surface plasmon resonance (LSPR)-enhanced catalysis has attracted much attention recently. Palladium nanoparticles have been reported to have various nanozyme activities and exhibit promising potentials for biomedical applications. However, as Pd is a poor plasmonic metal, little attention has been paid to its LSPR-regulated nanozyme activity. Herein, by using Au nanorods (AuNRs) as a strong plasmonic core, we coated a thin layer Pd to form a rod-shaped core−shell structure. The obtained Au@PdNRs showed tunable LSPR bands in the near-infrared (NIR) spectral range inheriting from the Au core and yet an exposed Pd surface for catalysis. The oxidase-like activity was investigated in the dark and upon SPR excitation. The plasmon-enhanced activity was observed and was mainly ascribed to the local photothermal effect. Finally, to enhance biocompatibility, mesoporous silica-coated nanorods were used to detect the oxidase-like activity in cells. After being endocytosed by cells, upon plasmon excitation, the oxidase activity of Au@PdNRs could be manifested and lead to higher cytotoxicity and depolarization of mitochondrial membrane potential. Our studies highlight the feasibility of regulating the nanozyme activity of plasmonic nanostructures using their unique NIR plasmonic features with spatiotemporal control.
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