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

Here, we report the synthesis of bifunctional Ag@SiO 2/Au nanoparticles with an “islands in the sea” configuration by titrating HAuCl 4 solution into an aqueous suspension of Ag@SiO 2 core–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 SiO 2 shell in 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 SiO 2 sea. Furthermore, by controlling the amount of HAuCl 4 titrated into the reaction system, the Au islands can be made to pass through and protrude from the SiO 2 shell, embracing catalytic activity toward the reduction of 4-nitrophenol to 4-aminophenol by NaBH4. And while the Ag in the core provides a strong surface-enhanced Raman scattering activity, the SiO 2 sea helps maintain the Au component as compact, isolated, and stabilized islands. The Ag@SiO 2/Au nanoparticles can serve as a bifunctional probe to monitor the stepwise Au-catalyzed reduction of 4-nitrothiophenol to 4-aminothiophenol by NaBH 4 and Ag-catalyzed oxidation of 4-aminothiophenol to trans-4,4'-dimercaptoazobenzene by the O 2 from air in themore » same reaction system.« less
 [1] ;  [2] ; ORCiD logo [1]
  1. School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta Georgia 30332 United States
  2. Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton New York 11973 United States
Publication Date:
Report Number(s):
Journal ID: ISSN 2199-692X; R&D Project: 16060; 16060; KC0403020
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Additional Journal Information:
Journal Volume: 3; Journal Issue: 4; Journal ID: ISSN 2199-692X
Research Org:
Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Au nanoparticles; Ag@SiO2 nanocrystals; surface-enhanced Raman scattering; Au-catalyzed reduction; Ag-catalyzed oxidation; Center for Functional Nanomaterials
OSTI Identifier: