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 NPs through suppression of the galvanic replacement reaction. The mechanisms for the nucleation and growth of NPs in W/O ME have been proposed.
The effective plasmonic enhancement of the 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. Interestingly, the UV–visible spectrum of the NPs exhibited enthralling plasmonic properties by introducing a high-frequency quadrupolar LSPR mode originated from the isolated NPs along with a low-frequency dipolar LSPR mode originated from the coupled NPs. High-resolution transmission electron microscopic analysis of the synthesized NPs revealed an “unusual ” contrast, and the selected area electron diffraction and Moiré patterns showed that Au layers are paralleled to Ag layers, thus indicating the formation of NPs. The W/O ME acted as a “true nanoreactor” for the synthesis of NPs by providing a confined and controlled environment and suppressing the nucleation, growth, agglomeration, and aggregation of the NPs. A distinctive synthetic method for the efficient synthesis of multifunctional bimetallic plasmonic 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.
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