Chemistry Reference
In-Depth Information
Fig. 8
Left
: ESI mass spectra of the 22 kDa nanoclusters in 50:50 toluene:CH
3
CN mixture
with addition of metal acetates. (a) ESI spectra in the full mass range with KOAc and (b)
expansion of 3+ molecular ion peaks showing the presence of Au
103
(SR)
45
,Au
104
(SR)
45
,
Au
104
(SR)
46
,Au
105
(SR)
46
.
Right
: expansion of 2+ molecular ion peaks using rubidium(Rb),
potassium(K), and sodium(Na) acetate salts, respectively, confirming the presence of the same
set of peaks as in 3+ region. The peaks marked by one and two
asterisks
represent nanoclusters
with one and two cationic adducts, respectively, the mass difference corresponding to the cations.
Notably Au
102
(SR)
44
is not detected. Reproduced from [
51
] with permission from The Royal
Society of Chemistry
with -SCH
2
CH
2
Ph. Previously we showed that using
SPh in the synthesis leads to
the formation of the 36-atom species instead of Au
38
[
52
]. This clearly shows
that using an aromatic ligand alters the core size in some cases when compared
with -SCH
2
CH
2
Ph or -SC
6
H
13
ligands.
5 Synthesis Through Core-Size Conversion
In this section, the synthesis of Au
38
(SR)
24
,Au
40
(SR)
24
, and Au
130
(SR)
50
through
core-size conversion synthesis is discussed. Firstly, in Sect.
5.1
, the core-size
conversion syntheses of Au
38
and Au
40
are discussed. This involves the use of
nanoclusters smaller than 120 metal atoms [
53
]. Secondly, in Sect.
5.2
, core-size
conversion synthesis of Au
130
nanomolecules using nanoclusters larger than
200 metal atoms is discussed [
54
].
The two-phase Brust-Schiffrin synthesis is typically used to synthesize organo
thiolated gold nanoclusters [
5
]. The product obtained from this synthesis is a
polydispersed mixture of gold nanoclusters with several sizes present in the reac-
tion mixture [
2
]. After the report on Brust-Schiffrin synthesis, several other syn-
thetic protocols with increased yields and different synthetic approaches have been
reported in the literature for several sizes of gold nanomolecules [
2
,
46
,
52
,
55
-
57
]. To narrow down the size distribution of the polydisperse products obtained
after synthesis, the products are etched with excess ligand at elevated temperatures.
Etching
of thiolated gold nanoclusters was first introduced by Whetten and
coworkers [
7
]. The etching procedures for phosphine-protected clusters were well
