Chemistry Reference
In-Depth Information
Fig. 3 Schematic
illustration of the biphasic
Brust-Schiffrin synthesis of
gold colloids
Aqueous layer
Organic layer
H[AuCl
4
]
HS
N(oc
tyl)
4
+
B
r
-
NaBH
4
gold
particle
= S
Brust-Schiffrin methods have been developed for the synthesis of gold nanoclusters
with different core sizes. Wu et al. [
81
] have introduced a facile, single-phase THF
procedure that produced monodispersed Au
25
nanoclusters via a “size-focusing”
process.
One great advantage of the thiolato-colloids prepared in organic solvents is that
it is possible to undergo substitution chemistry akin to that which has been
developed for co-ordination compounds. Murray et al. [
82
,
83
] have studied
exchange of some of the alkane thiolato ligands by polyfunctionalised thiolato
ligands (see Fig.
4
) and this has led for example to a range of ferrocenyl-
functionalised derivatives. Some basic inorganic reactions, e.g. oxidation and
reduction, have also been studied. In these syntheses, different types of organic
compounds have been used as capping ligands to protect gold nano-clusters,
e.g. thiolate, phosphine, selenolate, carbonyl, alkyne, DNA and protein cages.
In addition other sulphur-containing ligands, e.g. xanthanates, di- and tri-thiols,
disulfides and polythioethers, have been utilised as stabilising ligands [
82
,
83
].
Heating these colloidal sols near the boiling point of the solvent, i.e. at approx-
imately 140
C for a few minutes followed by a longer period of heating at approx-
imately 110
C, leads to smaller average particle sizes and smaller polydispersities.
This procedure has also led to the formation of 2D and 3D superlattices, which have
been investigated extensively by Klabunde et al. [
84
]. The availability of nano-sized
