Chemistry Reference
In-Depth Information
Fig. 1 (a) Monodisperse nanoparticles imaged by TEM; (b) histogram of size distribution
(5
0.3 nm diameter); (c) atomically precise Au
25
(SC
2
H
4
Ph)
18
nanoclusters (1 nm metal core
diameter, -C
2
H
4
Ph groups are omitted, magenta
¼
Au, yellow
¼
S); (d) mass spectrometry
characterization of Au
25
(SC
2
H
4
Ph)
18
nanoclusters
2 Ligand-Protected Gold Nanoclusters
In solution phase, nanoclusters must be protected by ligands or stabilizers; other-
wise, unprotected nanoclusters would immediately aggregate, forming a precipitate
and losing the integrity of individual nanoclusters. For nanochemists, a major task
is to find appropriate ligands for stabilizing nanoclusters and more importantly
enabling controlled synthesis.
The early research on gold nanoclusters involved phosphine as ligand. The gold-
phosphine chemistry was developed as a derivative of the coordination chemistry,
which started in the 1960s. As a spin-off of the research of gold:phosphine complex
compounds, an eleven-gold-atom cluster, Au
11
(PPh
3
)
7
(SCN)
3
, was reported in
1969 [
16
]. The Au
11
structure exhibits an incomplete icosahedral framework.
Mingos and coworkers predicted 13-atom-centered icosahedral cluster and success-
fully synthesized [Au
13
(PR
3
)
10
Cl
2
]
3+
and determined the structure in 1981
[
17
]. Schmid et al. reported Au
55
(PR
3
)
12
Cl
6
, although the structure has not been
attained to date [
18
]. Teo et al.
reported [Au
39
(PR
3
)
14
Cl
6
]
2+
and bimetal
[Au
13
Ag
12
(PR
3
)
10
Br
8
]
+
,[Au
18
Ag
19
(PR
3
)
12
Br
11
]
2+
, and
nanoclusters
such as
