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Title: Ultrafast excited-state dynamics in shape- and composition-controlled gold–silver bimetallic nanostructures

Journal Article · · Journal of Physical Chemistry. C
 [1];  [2];  [1];  [2];  [2];  [1]
  1. Vanderbilt Univ., Nashville, TN (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

In this paper, we have examined the ultrafast dynamics of shape- and composition-controlled bimetallic Au/Ag core/shell nanostructures with transient absorption spectroscopy (TAS) as a function of Ag layer thickness (0–15 nm) and pump excitation fluence (50–500 nJ/pulse). Our synthesis approach generated both bimetallic nanocubes and nanopyramids with distinct dipolar plasmon resonances and plasmon dephasing behavior at the resonance. Lifetimes obtained from TAS at low powers (50 nJ/pulse) demonstrated minimal dependence on the Ag layer thickness, whereas at high power (500 nJ/pulse) a rise in electron–phonon coupling lifetime (τ1) was observed with increasing Ag shell thickness for both nanocubes and nanopyramids. This is attributable to the stronger absorption of the 400 nm pump pulse with higher Ag content, which induced higher electron temperatures. The phonon–phonon scattering lifetime (τ2) also rises with increasing Ag layer, contributed both by the increasing size of the Au/Ag nanostructures as well as by surface chemistry effects. Further, we observed that even the thinnest, 2 nm, Ag shell strongly impacts both τ1 and τ2 at high power despite minimal change in overall size, indicating that the nanostructure composition also strongly impacts the thermalization temperature following absorption of 400 nm light. We also observed a shape-dependent trend at high power, where τ2 increased for the nanopyramids with increasing Ag shell thickness and nanostructure size, but bimetallic nanocubes demonstrated an unexpected decrease in τ2 for the thickest, 15 nm, Ag shell. This was attributed to the larger number of corners and edges in the nanocubes relative to the nanopyramids.

Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Science (SC)
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1350925
Journal Information:
Journal of Physical Chemistry. C, Vol. 121, Issue 8; ISSN 1932-7447
Publisher:
American Chemical SocietyCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 10 works
Citation information provided by
Web of Science

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Cited By (2)

Ag-Based nanocomposites: synthesis and applications in catalysis journal January 2019
Monitoring the growth dynamics of colloidal gold-silver core-shell nanoparticles using in situ second harmonic generation and extinction spectroscopy journal December 2019