Bimetallic
Ag@Au nanoparticles (NPs) have received significant
research interest because of their unique optical properties and molecular
sensing ability through surface-enhanced Raman scattering (SERS).
However, the synthesis of Ag@Au core–shell plasmonic nanostructures
with precisely controlled size and shape remained a great challenge.
Here, we report a simple approach for the synthesis of bimetallic
Ag@Au nanodisks of about 13.5 nm thickness and different diameters
through a seed-mediated growth process. The synthesis involves the
conformal deposition of Au atoms at the corner sites of Ag nanoplate
(AgNPL) seeds coupled with site-selective oxidative etching of AgNPL
edges to generate Ag@Au nanodisks. The resultant Ag@Au nanodisks manifest
significantly improved chemical stability and tunable localized surface
plasmon resonance from the visible to the near-infrared spectral range.
Moreover, in comparison to AgNPLs, the Ag@Au nanodisks showed greatly
enhanced SERS performance with an enhancement factor up to 0.47 ×
10
5
, which is nearly 3-fold higher than that of the original
AgNPLs (0.18 × 10
5
). Furthermore, the Ag@Au nanodisks
show a high sensitivity for detecting probe molecules such as crystal
violet of concentration as low as 10
–9
M and excellent
reproducibility, with the SERS intensity fluctuation less than 12.5%.
The synthesis route adapted for the controlled fabrication of Ag@Au
nanodisks can be a potential platform for maneuvering other bimetallic
plasmonic nanostructures useful for plasmonics and sensing applications.
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