Controlled synthesis of sponge-like porous Au–Ag alloy nanocubes for surface-enhanced Raman scattering properties

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Abstract
We develop an interesting route to prepare new sponge-like Au–Ag alloy nanocubes (NCs) with controlled porosity and atomic percentage through an interparticle alloying and dealloying process. Au@Ag NCs were first synthesized using Au nanooctahedra as initial seeds. Then, the Au@Ag NCs were covered with SiO2 and thermally annealed, forming solid Au–Ag alloy NCs with a SiO2 layer. After removing the majority of the SiO2 layer and leaching less-stable Ag from solid Au–Ag alloy NCs, uniform sponge-like porous Au–Ag alloy NCs were obtained. In this process, SiO2 not only prevents fusion between adjacent Au@Ag NPs under thermal annealing, but also directs the final shape of sponge-like Au–Ag alloy NPs with a cubic shape as a template. Thanks to the high-density “hotspots” in nanopores, sharp corners and edges, and a synergistic effect between Au and Ag species, such sponge-like Au–Ag alloy NCs showed excellent SERS performance with an enhancement factor of ∼108, which can effectively detect 4-aminothiophenol (4-ATP) at a concentration as low as 1 × 10−10 M. This strategy is universal and it can be extended to prepare sponge-like Au–Ag alloy NPs with different accurate shapes. Such sponge-like nanoporous alloy NPs have many potential applications such as in plasmonics, SERS, drug delivery, photothermal therapy, and catalysis systems.
Funding Information
  • National Natural Science Foundation of China (51371165)
  • National Natural Science Foundation of China (51571189)
  • National Natural Science Foundation of China (51771188)
  • Chinese Academy of Sciences
  • CAS-SAFEA International Partnership Program for Creative Research Teams

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