Tailored Engineering of Bimetallic Plasmonic Au@Ag Core@Shell Nanoparticles

Abstract

A distinctive synthetic method for the efficient synthesis of multifunctional bimetallic plasmonic Au@Ag core@shell nanoparticles (NPs) with tunable size, morphology, and localized surface plasmon resonance (LSPR) using Triton X-100/hexanol-1/deionized water/cyclohexane-based water-in-oil (W/O) microemulsion (ME) is described. The W/O ME acted as a “true nanoreactor” for the synthesis of Au@Ag core@shell NPs by providing a confined and controlled environment and suppressing the nucleation, growth, agglomeration, and aggregation of the NPs. High-resolution transmission electron microscopic analysis of the synthesized Au@Ag core@shell NPs revealed an “unusual core@shell” contrast, and the selected area electron diffraction and Moiré patterns showed that Au layers are paralleled to Ag layers, thus indicating the formation of Au@Ag core@shell NPs. Interestingly, the UV–visible spectrum of the Au@Ag core@shell NPs exhibited enthralling plasmonic properties by introducing a high-frequency quadrupolar LSPR mode originated from the isolated Au@Ag NPs along with a low-frequency dipolar LSPR mode originated from the coupled Au@Ag NPs. The effective plasmonic enhancement of the Au@Ag core@shell NPs is attributed to the extreme enhancement of the localized electromagnetic field by coupling of the localized surface plasmons of the Au core and Ag shell. The mechanisms for the nucleation and growth of Au@Ag core@shell NPs in W/O ME have been proposed. A unique electron transfer phenomenon between the Au core and Ag shell is elucidated for better understanding and manipulation of the electronic properties, which evinced the development of Au@Ag core@shell NPs through suppression of the galvanic replacement reaction.

Recent advances of Au@Ag core–shell SERS‐based biosensors

“…It makes Au/Ag alloys the optimum platform for high low-frequency performance and low high-frequency performance. [81] The Au/Ag alloys possess low density and allow for a significant increase in material sensitivity. [82] As a result, the background noise is reduced, and the signal-to-noise ratio is improved.…”

Hybrid Nanomaterials: Historical Developments, Classification and Biomedical Applications

“…Their advanced characteristics, task specificity, and miniaturization quality have made them distinct from other materials bringing about a rapid rise in their growth and demand. The multidisciplinary of this scientific trend, as well as the integration of the advantageous and superior properties of both organic and inorganic materials, is pivotal to developing multifunctional materials based on building blocks [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”

Formation of Au@Ag Bimetallic Nanoparticles via Ion Implantation and Its Effects on Boosting the Near-Infrared Emission of Er3+ Ions in Germanate Glass for Applications in Optical Amplifiers

“…In fact, the quenching of the NIR emission of Er 3+ of the transition in 1.53 μm has been observed, related to the incorporation of Au and Ag MNPs . This limitation could be overcome by the synthesis of Au@Ag bimetallic NPs due to the possibility of optimizing the plasmon absorption energy to enhance the luminescence by boosting the suitable synergistic phenomenon. , …”

“…35 This limitation could be overcome by the synthesis of Au@Ag bimetallic NPs due to the possibility of optimizing the plasmon absorption energy to enhance the luminescence by boosting the suitable synergistic phenomenon. 35,36 The formation of Au@Ag NPs via ion implantation has been investigated, 37,38 but little attention has been given to their plasmonic effect on the spectroscopic properties of RE ions. In this work, the plasmonic effects of Au@Ag NPs in a Er 3+ -doped GeO 2 -PbO glass were investigated, which promoted considerable boosting for the emission at 1.53 μm (NIR).…”