nl9b02144_si_001.pdf (3.99 MB)
Electrochemical Synthesis of Individual Core@Shell and Hollow Ag/Ag2S Nanoparticles
journal contribution
posted on 2019-07-26, 18:38 authored by Donald
A. Robinson, Henry S. WhiteThis
letter presents an electrochemical methodology for structure-tunable
synthesis, characterization, and kinetic monitoring of metal–semiconductor
phase transformations at individual Ag nanoparticles. In the presence
of HS– in aqueous solution, the stochastic collision
and adsorption of Ag nanoparticles at a Au microelectrode initiates
the partial anodic transformation of Ag to Ag2S at each
particle. A single continuous current transient is observed for each
Ag nanoparticle reacted. The characteristic shapes of the transients
are distinct from previously reported amperometric recordings of electrochemical
reactions involving single nanoparticles and are highly uniform at
a constant applied potential. The average maximum current increases
while the event duration decreases as a function of increasing potential.
Independent of applied potential, the electrochemical transformation
event abruptly stops after converting ∼80% of the Ag in the
nanoparticle to Ag2S, a self-terminating process that does
not occur for bulk Ag electrodes under similar conditions. The resulting
products are a mixture of core@shell Ag@Ag2S nanoparticles
with and without voids in the core, as characterized by transmission
electron microscopy (TEM) and energy-dispersive X-ray spectroscopy
(EDX). Both the frequency and size of voids increase at more positive
potentials. The average size of the core@shell nanoparticles determined
by coulometric analysis of the current transients agrees well with
TEM measurements.