Chemistry Reference
In-Depth Information
with near-monodisperse size distributions (
15%), while colloids are often
>
10 nm with much broader size distributions' [
27
].
Since there are limits on many mass analysers used in mass spectrometry-based
approaches to the study of gold cluster ions, in this chapter we take as our definition
of a gold cluster ion:
A cluster containing 2 or more gold atoms and up to 1,000 atoms that has an overall
negative or positive charge. The cluster can be either a 'bare gold cluster' or a 'ligated gold
cluster'.
1.4 Scope of the Review
There have been a number of general reviews on gas-phase cluster ions [
28
-
32
]as
well as reviews on gold cluster ions [
33
,
34
]. This review focuses on literature
reports that utilise mass spectrometry (MS): (1) as a key analytical tool to examine
the formation and reactions of gold clusters; (2) as basic methods to study the
structure, properties and reactivity of gold cluster ions in the gas phase and (3) as a
way of soft landing gold cluster ions onto surfaces to generate catalysts.
All mass spectrometers consist of: (1) an ionisation source to generate ions in or
to transfer ions to the gas phase, (2) a mass analyser to separate ions according to
their mass to charge ratio (
m/z
), (3) a detector to 'count' the number of ions at each
m/z
value and (4) a data processor/recorder [
35
]. The development of matrix-
assisted laser desorption (MALDI) and electrospray ionisation (ESI) has
revolutionised the analysis and study of inorganic and organometallic complexes
and nanoclusters via mass spectrometry [
36
]. MALDI and ESI have been coupled to
a range of mass analysers, and the resultant mass spectrometers are commonly used
in the analysis of metal clusters. The mode of operation and the 'figures of merit' of
the various types of mass analysers available are not discussed here - readers are
referred to an excellent review [
37
].
There are many potential combinations of ionisation source and mass analyser
that can be used for fundamental studies, but these are not discussed in any detail
here. The most widely used mass spectrometers in gold cluster ion studies over the
past decades have been ion cyclotron resonance (ICR) mass spectrometers (includ-
ing their Fourier transform variants) [
38
-
40
], triple quadrupole mass spectrometers
[
41
,
42
], flowing afterglow reactors [
43
] and ion-trap mass spectrometers [
44
].
While computational chemistry plays a key role in supporting many experimen-
tal studies on the structure and reactivity of gold clusters, papers solely dealing with
theoretical calculations are largely neglected except where they shed important
insights into prior experimental work.
The structure and reactivity of neutral gold clusters have also been studied in the
gas phase (see Sect.
3.3
). Readers interested in this topic should also refer to recent
work on the absorption of CO onto silver-doped gold clusters [
45
] and the oxidation
