Seed-Mediated Growth of Ag@Au Nanodisks with Improved Chemical Stability and Surface-Enhanced Raman Scattering

Abstract

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.

Template-Assisted in Situ Synthesis of Ag@Au Bimetallic Nanostructures Employing Liquid-Phase Transmission Electron Microscopy

“…The MD trajectories under thermodynamic conditions in absence of additives show a considerable increase of the {111} facets, because the diffusion from this surface is the fastest (associated to the lowest potential energy barrier) among all the inter-facets diffusion processes 10 . As a consequence, in the case of the cubic seed the {110} facets progressively disappear and the NP becomes a truncated octahedron, exposing mainly {100} and {111} facets, in agreement with previous studies.…”

“…16,17 Despite of these difficulties several groups have been able to synthesize galvanic replacement-free Ag@Au nanostructures with morphologies such as nanorods, cubes and nanodisks. 10,18,19 A major challenge is to develop a mechanistic understanding of the growth of these complicated nanostructures, because physical properties, e.g. the optical response, the catalytic activity and the magnetic behaviour, are highly dependent on the detailed composition and morphology.…”

DNA‐Origami‐Based Assembly of Au@Ag Nanostar Dimer Nanoantennas for Label‐Free Sensing of Pyocyanin

“…It is well established that on‐resonance measurements result in higher EFs than normal SERS [35] . In view of the multifunctional properties of bimetallic Au−Ag nanostructures, considerable efforts have been dedicated to explore their potential for SERS based applications [36–38] . In particular, anisotropic shaped nanostructures are of great interest owing to the presence of multiple intrinsic hotspots and broadly tunable plasmonic resonances [28] .…”

In Situ Creation of Surface-Enhanced Raman Scattering Active Au–AuOx Nanostructures through Electrochemical Process for Pigment Detection

“…37 Thus, the SPE-Au25 exhibited the superior SERS performance of EF compared to the literature. 19−22 The SPE-Au25 sample possessed a higher performance of SERS than SPE-Au50 because of a stronger peak intensity of AuO x , which corresponds to the amount of produced AuO x on the surface. Additionally, the lowest SERS performance of SPE-Au5 sample among SPE-Au50, SPE-Au25, and SPE-Au5 substrates could be caused by the formation of bulk Au.…”