Chemistry Reference
In-Depth Information
Fig. 18 Structural evolution of Au
n
(SR)
m
nanoclusters
constitute the four faces of the truncated tetrahedral Au
28
kernel, and six {100}
facets on the six edges of the tetrahedron.
The Au
28
kernel is protected by four dimeric staples (-SR-Au-SR-Au-SR-) and
twelve bridging thiolates (-SR-). Each of the four dimeric staples protects one
{111} facet (Fig.
17b
). On each {100} facet (comprising two squares), two bridging
thiolates can be identified (Fig.
17b
). The Au
36
S
24
framework has an overall
D
2h
symmetry and is
achiral
. With the above analysis, the formula of Au
36
(SR)
24
may
be represented as Au
28
[Au
2
(SR)
3
]
4
(SR)
12
to illustrate the partition of gold atoms in
the kernel and surface of the cluster.
6 Summary
The above discussed nanocluster structures are summarized in Fig.
18
, in which one
can see the evolution or general trend of structural features with increasing size.
Particularly interesting questions are: what structures in terms of kernel and staple
motifs would be adopted in smaller nanoclusters (
n
25)? What structures would
<
the intermediate-size (38
102) exhibit?
Future work is expected to reveal more structures and systematic structural rules
may be formulated.
Other than the structures of nanoclusters, the electronic and optical properties of
such nanoclusters remain to pursue in future work. For example, Au
n
(SR)
m
nanoclusters are found to be fluorescent but the quantum yields are quite low
(up to a few percent). What factors govern the photoluminescence properties?
Is it possible to largely enhance the luminescence?
n
102) and larger nanoclusters (
n
<
<
>
