Mechanism of Shape Evolution in Ag Nanoprisms Stabilized
by Thiol-Terminated Poly(ethylene glycol): An in Situ Kinetic Study
- Publication date
- Publisher
Abstract
Silver
nanoprisms are found to undergo a shape transformation from
triangular to disk-like upon functionalization with thiol-terminated
poly(ethylene glycol) (PEG-SH). The shape transformation starts with
a rounding of the nanoprism tips followed by a reduction in the overall
particle size. The changes in nanoparticle morphology and surface
chemistry during the PEGylation process are investigated by a combination
of transmission electron microscopy, in situ UV–vis spectroscopy,
and in situ solution-phase X-ray absorption near-edge structure at
the Ag <i>L</i><sub>3</sub>- and the S <i>K</i>-edge. We found that PEG-SH etches the Ag surface through a catalytic
redox process, whereby oxidized surface atoms are first removed from
the nanoprism tips (likely as the silver(I) thiolate complex) and
then reduced back to elemental silver (in the form of small clusters)
in the solution along with oxidation of the thiolate to the disulfide.
The effect of PEG-SH concentration and molecular weight are investigated,
along with the role of ambient oxygen in the etching process. The
results have implications for the behavior of silver nanoprisms in
various plasmonic applications (e.g., surface-enhanced Raman scattering
and metal-enhanced fluorescence) and also provide insights into the
degradation mechanism of silver nanomaterials in the environment
