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 SiO2shell
Aromatic azo compounds are high‐value chemicals extensively used as pigments, drugs, and food additives, but their production typically requires stoichiometric amounts of environmentally unfriendly metals or nitrites. There is an urgent need to develop a dual catalytic system capable of reducing nitroaromatics to aromatic amines, followed by their oxidation to azo compounds. Here we report such a dual catalyst based on Ag@Pd‐Ag core‐frame nanocubes for the stepwise conversion of 4‐nitrothiophenol to
- NSF-PAR ID:
- 10235787
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemNanoMat
- Volume:
- 2
- Issue:
- 8
- ISSN:
- 2199-692X
- Page Range / eLocation ID:
- p. 786-790
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract 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 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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