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Title: How Ag Nanospheres Are Transformed into AgAu Nanocages

Bimetallic hollow, porous noble metal nanoparticles are of broad interest for biomedical, optical and catalytic applications. The most straightforward method for preparing such structures involves the reaction between HAuCl 4 and well-formed Ag particles, typically spheres, cubes, or triangular prisms, yet the mechanism underlying their formation is poorly understood at the atomic scale. By combining in situ nanoscopic and atomic-scale characterization techniques (XAFS, SAXS, XRF, and electron microscopy) to follow the process, we elucidate a plausible reaction pathway for the conversion of citrate-capped Ag nanospheres to AgAu nanocages; importantly, the hollowing event cannot be explained by the nanoscale Kirkendall effect, nor by Galvanic exchange alone, two processes that have been previously proposed. We propose a modification of the bulk Galvanic exchange process that takes into account considerations that can only occur with nanoscale particles. In conclusion, this nanoscale Galvanic exchange process explains the novel morphological and chemical changes associated with the typically observed hollowing process.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ; ORCiD logo [1] ; ORCiD logo [1]
  1. Northwestern Univ., Evanston, IL (United States)
Publication Date:
Grant/Contract Number:
FG02-08ER46539
Type:
Published Article
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 139; Journal Issue: 35; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
ENGLISH
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1393316
Alternate Identifier(s):
OSTI ID: 1408113