Chemistry Reference
In-Depth Information
Fig. 10 An overview of the AuPt nanorods showing evolution of morphology. Reproduced
from [
83
]. Copyright 2012 American Institute of Physics
Fig. 11 STEM-HAADF images and EDX elemental maps of AuPt nanorods showing the influ-
ence of CO blocking on Pt overgrowth. (a) Bare Au NRs seed, (b1-4) Au-Pt NRs prepared without
the CO blocking step, and (c1-4) Au-Pt NRs of same composition prepared with the CO blocking
step. Reproduced from [
82
]. Copyright 2013 American Chemical Society
change in morphology is a result of initial Pt clustering growth that leaves part of
the Au surface uncovered especially in the middle of the Au nanorod. The thermo-
dynamic preference for Au-coated Pt probably drives Au to diffuse onto the outside
of the Pt, thinning the centre of the NR until it breaks into two nanoparticles. While
the AuPt nanorods were kept in solution, the samples were stable, suggesting that
the surfactant remaining on the surface may inhibit this diffusion process.
Working on the hypothesis that the incomplete Pt coverage might enable Au
diffusion to the outside of Au
core
Pt
shell
NRs, a selective blocking method was
developed to even out Pt coverage across the surface of Au NRs. The results
from this study are summarised in Fig.
11
[
82
]. The method involved sequential
Pt deposition steps and exploited the difference in binding energies of carbon
monoxide (CO) on Au and Pt surfaces. STEM-HAADF, EDX and electrochemical
