Chemistry Reference
In-Depth Information
Scheme 3 Schematic illustration of the synthesis of gold clusters templated with dendrimers.
Reprinted from [
103
] with permission by the American Chemical Society
et al. [
101
] for the first time demonstrated the synthesis of Au
55
:SC
x
clusters
(
x
12, 18) by high-resolution chromatographic fractionation of Au:SC
x
clusters
prepared by thiolation of PVP-stabilized Au clusters and subsequent incubation in
neat C
x
SH. In this method, Au:PVP clusters were initially prepared by chemical
reduction and the toluene solution of C
x
SH was added into the hydrosol of Au:PVP
cluster under vigorous stirring to generate Au:SC
x
clusters. The prepared Au:SC
x
clusters were then incubated at 80
C for 24 h in neat C
x
SH liquid. Subsequently, the
resulting clusters were successfully fractionated by recycling gel permeation chro-
matography (GPC) into Au
38
:SC
x
and Au
55
:SC
x
compositions.
Another facile synthesis of Au
55
nanoclusters was achieved by using dendrimer
(usually poly(amidoamine), PAMAM) as template [
102
,
103
]. As shown in the
Scheme
3
, the synthesis follows the three-step process. Firstly, metal ions are extracted
from solution into the dendrimer interior by taking advantage of the complexation
reaction with the internal tertiary amines. Secondly, the metal ions are reduced by
BH
4
, and the resultant atoms subsequently aggregate to form zero-valent nanoclusters
within the dendrimer templates. By controlling the ratio of AuCl
4
to dendrimer, Au
55
nanoclusters could be obtained. Moreover, when the dendrimer-encapsuled clusters
are treated with a toluene solution of an
n
-alkanethiol,
n
-alkanethiol could presumably
self-assemble onto the cluster surface and the resulting thiolate-capped clusters can be
extracted from the dendrimers to toluene phase [
103
].
ΒΌ
