Chemistry Reference
In-Depth Information
Fig. 13 UV-Vis absorption spectra of Au
67
(SR)
35
(
red
), Au
38
(SR)
24
(
dotted
), and a larger
~Au
300
, 76.3 kDa (
dashed
) nanoclusters in toluene. Reprinted from [
107
] with permission by
the American Chemical Society
of thiolate to gold, NaBH
4
to gold, and water to methanol), especially 36 water-
soluble organothiolates on the formation of gold nanoclusters. However, the yields
of the Au
102
nanoclusters synthesized from the reported methods are very low. To
obtain pure Au
102
nanoclusters in high purity, Kornberg and coworkers [
110
]
developed an improved strategy for synthesizing Au
102
(
p
-MBA)
44
nanoclusters
in abundant, essentially pure form. In the synthesis, two steps were used. First,
p
-MBA and HAuCl
4
(3:1 ratio of
p
-MBA: gold) were dissolved in water and 47%
methanol, followed by the reduction of NaBH
4
at room temperature. After a series
of careful fractional precipitation with methanol, highly monodispersed, atomically
precise Au
102
(
p
-MBA)
44
cluster was finally obtained. From the ESI-MS of
the isolated nanoclusters shown in Fig.
14a
, it can be seen that a series of peaks
with mass-to-charge ratios corresponding to partially deprotonated states of
Au
102
(
p
-MBA)
44
can be observed. The breadth of the peaks could suggest slight
contamination by clusters of different compositions. The MALDI-TOF mass gave a
broad peak centered at 22 kDa (Fig.
14b
), consisting with 102 gold atoms and
44 sulfur atoms. These mass characterizations indicated the successful synthesis of
highly monodispersed Au
102
nanoclusters with high yield and purity. In recent
years, the mechanism of the ligand exchange reaction of Au
102
(
p
-MBA)
44
was also
