Chemistry Reference
In-Depth Information
Fig. 2 Example of a neutral AuNC that has been analysed via MS: (a) ESI-MS Cs
+
adduct of
Au
36
(SPh-
t
Bu)
34
;(b) crystal structure highlighting the Au
36
S
24
framework. Figure reproduced
from [
61
]
as highlighted for glutathione ligands, which produce anionic NCs; (2) ESI-MS of
caesium acetate-doped solutions of Au
36
(SPh-
t
Bu)
24
give rise to cationic caesium
adducts (Fig.
2a
)[
61
].
The recent gold cluster literature can largely be divided into two classes based on
the capping ligands used:
1.
Thiolate ligands
: these anionic ligands often produce neutral clusters that make
them challenging to analyse via mass spectrometry. Nonetheless, there are quite
a few examples of MALDI/MS and ESI-MS being used to examine their
formation and size distributions. Since this area has been reviewed in 2010
[
33
], only subsequent work is briefly described below.
2.
Phosphine ligands
: these neutral ligands allow the ready identification of
charged cationic gold nanoclusters via ESI-MS. Clusters capped by either
monophosphines or bisphosphines (monodentate or bidentate phosphine
ligands) have been studied. The latter exhibit interesting size-selectivity effects,
as discussed in detail in the following sections.
2.2 Top-Down and Bottom-Up Approaches for the Synthesis
of Gas-Phase Gold Nanoclusters
The techniques developed to study bare and ligated gold cluster ions in the gas
phase fall into the same two categories, Fig.
3
, as identified by Ott and Finke [
27
]
for solution phase studies of clusters:
