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Title: Ag@Au concave cuboctahedra: A unique probe for monitoring Au-catalyzed reduction and oxidation reactions by surface-enhanced Raman spectroscopy

In this paper, we report a facile synthesis of Ag@Au concave cuboctahedra by titrating aqueous HAuCl4 into a suspension of Ag cuboctahedra in the presence of ascorbic acid (AA), NaOH, and poly(vinylpyrrolidone) (PVP) at room temperature. Initially, the Au atoms derived from the reduction of Au 3+ by AA are conformally deposited on the entire surface of a Ag cuboctahedron. Upon the formation of a complete Au shell, however, the subsequently formed Au atoms are preferentially deposited onto the Au{100} facets, resulting in the formation of a Ag@Au cuboctahedron with concave structures at the sites of {111} facets. The concave cuboctahedra embrace excellent SERS activity that is more than 70-fold stronger than that of the original Ag cuboctahedra at an excitation wavelength of 785 nm. The concave cuboctahedra also exhibit remarkable stability in the presence of an oxidant such as H 2O 2 because of the protection by a complete Au shell. These two unique attributes enable in-situ SERS monitoring of the reduction of 4-nitrothiophenol (4-NTP) to 4-aminothiophenol (4-ATP) by NaBH4 through a 4,4'-dimercaptoazobenzene ( trans-DMAB) intermediate and the subsequent oxidation of 4-ATP back to trans-DMAB upon the introduction of H 2O 2.
 [1] ;  [2] ;  [3] ;  [4] ;  [3] ;  [5] ;  [3]
  1. Georgia Institute of Technology, Atlanta, GA (United States); Xiamen Univ., Xiamen (People's Republic of China)
  2. Georgia Institute of Technology, Atlanta, GA (United States); Agnes Scott College, Decatur, GA (United States)
  3. Georgia Institute of Technology, Atlanta, GA (United States)
  4. Brookhaven National Lab. (BNL), Upton, NY (United States)
  5. Xiamen Univ., Xiamen (People's Republic of China)
Publication Date:
Report Number(s):
Journal ID: ISSN 1936-0851; KC0403020
Grant/Contract Number:
Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 10; Journal Issue: 2; Journal ID: ISSN 1936-0851
American Chemical Society
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
29 ENERGY PLANNING, POLICY, AND ECONOMY; seed-mediated growth; surface capping; concave nanocrystal; surface-enhanced Raman spectroscopy; Au-catalyzed reduction and oxidation; Center for Functional Nanomaterials
OSTI Identifier: