jp8b12174_si_001.pdf (429.68 kB)
Halide-Dependent Dealloying of Cux/Auy Core/Shell Nanoparticles for Composition Analysis by Anodic Stripping Voltammetry
journal contribution
posted on 2019-03-11, 00:00 authored by Dhruba
K. Pattadar, Francis P. ZamboriniHere,
we describe the composition analysis of 5–7 nm diameter
citrate-stabilized Cu/Au core/shell nanoparticles with composition
ratios of Cu1/Aux (x = 0.001–2) attached to amine-functionalized glass/indium-tin-oxide
electrodes using anodic stripping voltammetry (ASV) in acidic KBr
or KCl electrolyte solutions. One peak typically appears for Au oxidation,
which is at more positive potential than the peaks for Cu. There are
typically two peaks for Cu oxidation due to different bonding environments
for Cu (Cu–Cu and Cu–Au bonds). The Au and Cu peak positions
and size in the ASVs at different compositions are consistent with
the formation of a Cu/Au core/shell structure. For low quantities
of Au in the alloy (x < 1), the Au oxidation peak
included the oxidation of trapped Cu in KBr solution, but there was
no trapped Cu in the Au oxidation peak in KCl solution, making composition
analysis straightforward in KCl by simply integrating the peaks for
Cu and Au separately. Atomic rearrangement of Au due to strong adsorption
of Br– is likely responsible for the stabilized
Cu in KBr. For larger amounts of Au (x ≥ 2),
most of the Cu is trapped inside the outer Au shell and therefore
oxidizes along with the Au in both KCl and KBr solutions, making direct
composition analysis impossible in both halides for high Au content.