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Title: Bifunctional Ag@SiO 2 /Au Nanoparticles for Probing Sequential Catalytic Reactions by Surface‐Enhanced Raman Spectroscopy

We report the synthesis of bifunctional Ag@SiO2/Au nanoparticles with an “islands in the sea” configuration by titrating HAuCl4solution into an aqueous suspension of Ag@SiO2core–shell nanocubes in the presence of NaOH, ascorbic acid, and poly(vinyl pyrrolidone) at pH 11.9. The NaOH plays an essential role in generating small pores in the SiO2shellin situ, followed by the epitaxial deposition of Au from the Ag surface through the pores, leading to the formation of Au islands (6–12 nm in size) immersed in a SiO2sea. By controlling the amount of HAuCl4titrated into the reaction system, the Au islands can be made to pass through and protrude from the SiO2shell, embracing catalytic activity toward the reduction of 4‐nitrophenol to 4‐aminophenol by NaBH4. While the Ag in the core provides a strong surface‐enhanced Raman scattering activity, the SiO2sea helps maintain the Au component as compact, isolated, and stabilized islands. The Ag@SiO2/Au nanoparticles can serve as a bifunctional probe to monitor the stepwise Au‐catalyzed reduction of 4‐nitrothiophenol to 4‐aminothiophenol by NaBH4and Ag‐catalyzed oxidation of 4‐aminothiophenol totrans‐4,4′‐dimercaptoazobenzene by the O2from air in the same reaction system.

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Author(s) / Creator(s):
 ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Page Range / eLocation ID:
p. 245-251
Medium: X
Sponsoring Org:
National Science Foundation
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