2 research outputs found
[Ag<sub>25</sub>(SR)<sub>18</sub>]<sup>−</sup>: The “Golden” Silver Nanoparticle
Silver
nanoparticles with an atomically precise molecular formula
[Ag<sub>25</sub>(SR)<sub>18</sub>]<sup>−</sup> (−SR:
thiolate) are synthesized, and their single-crystal structure is determined.
This synthesized nanocluster is the only silver nanoparticle that
has a virtually identical analogue in gold, i.e., [Au<sub>25</sub>(SR)<sub>18</sub>]<sup>−</sup>, in terms of number of metal
atoms, ligand count, superatom electronic configuration, and atomic
arrangement. Furthermore, both [Ag<sub>25</sub>(SR)<sub>18</sub>]<sup>−</sup> and its gold analogue share a number of features in
their optical absorption spectra. This unprecedented molecular analogue
in silver to mimic gold offers the first model nanoparticle platform
to investigate the centuries-old problem of understanding the fundamental
differences between silver and gold in terms of nobility, catalytic
activity, and optical property
Switching a Nanocluster Core from Hollow to Nonhollow
Modulating the structure–property
relationship in atomically
precise nanoclusters (NCs) is vital for developing novel NC materials
and advancing their applications. While promising biphasic ligand-exchange
(LE) strategies have been developed primarily to attain novel NCs,
understanding the mechanistic aspects involved in tuning the core
and the ligand-shell of NCs in such biphasic processes is challenging.
Here, we design a single phase LE process that enabled us to elucidate
the mechanism of how a hollow NC (e.g., [Ag<sub>44</sub>(SR)<sub>30</sub>]<sup>4–</sup>, SR: thiolate) converts into a nonhollow NC
(e.g., [Ag<sub>25</sub>(SR)<sub>18</sub>]<sup>−</sup>) and
vice versa. Our study reveals that the complete LE of the hollow [Ag<sub>44</sub>(SPhF)<sub>30</sub>]<sup>4–</sup> NCs (SPhF: 4-fluorobenzenethiolate)
with incoming 2,4-dimethylbenzenethiol (HSPhMe<sub>2</sub>) induced
distortions in the Ag<sub>44</sub> structure forming the nonhollow
[Ag<sub>25</sub>(SPhMe<sub>2</sub>)<sub>18</sub>]<sup>−</sup> by a disproportionation mechanism, while the reverse reaction of
[Ag<sub>25</sub>(SPhMe<sub>2</sub>)<sub>18</sub>]<sup>−</sup> with HSPhF prompted an unusual dimerization of Ag<sub>25</sub>,
followed by a rearrangement step that reproduces the original [Ag<sub>44</sub>(SPhF)<sub>30</sub>]<sup>4–</sup>. Remarkably, both
the forward and the backward reactions proceed through similar size
intermediates that seem to be governed by the boundary conditions
set by the thermodynamic and electronic stability of the hollow and
nonhollow metal cores. Furthermore, the resizing of NCs highlights
the surprisingly long-range effect of the ligands which are felt by
atoms far deep in the metal core, thus opening a new path for controlling
the structural evolution of nanoparticles