Chemistry Reference
In-Depth Information
become to control the size and shape of these cluster materials so that their
properties can be controlled for novel material and catalytic applications.
1.2 Why Are Gold Clusters Interesting?
There are at least two reasons why there has been intense interest in gold clusters:
(1) they serve as models for structure and bonding of cluster compounds [
4
-
9
], a
topic further elaborated in [
10
] ('Theoretical studies on gold clusters and
nanoparticles'). (2) Seminal work by Bond [
11
], Hutchings [
12
], Haruta [
13
] and
others [
14
-
16
] in the 1970s and 1980s in the field of heterogeneous catalysis led to a
paradigm shift by showing that gold, the noblest of all metals, can be turned into a
highly active catalyst simply by reducing its dimensions to a few nanometres
[
13
]. Examples of catalytic reactions that were discovered include hydrogenation
of alkenes (Eq. (
1
)) [
11
], hydrochlorination of acetylene (Eq. (
2
)) [
12
] and oxi-
dation of CO (Eq. (
3
)) [
13
]. Finally, it has been recognised for some time that
homogenous catalysis may give rise to nanoparticles that maybe the actual catalysts
[
17
]. Indeed a recent report by Corma et al. [
18
] has highlighted that such
nanoclusters can be highly reactive catalysts for the ester-assisted addition of
water to alkynes (Eq. (
4
)), with turnover numbers of ten million [
19
].
ð
1
Þ
ð
2
Þ
ð
3
Þ
ð
4
Þ
1.3 Definition of a Gold Cluster Ion
A diverse range of scientists have been involved in the study of clusters, which has
given rise to a 'Tower of Babel' of other terms for clusters, including colloids,
Q-particles, quantum dots, nanoparticles, grains, aerosols, hydrosols, dust, foam,
non-covalent complexes, supramolecular complexes, protein assemblies, etc. John-
ston [
20
] suggests that the earliest scientific reference to clusters may have been
made by Robert Boyle in 1661, when he wrote of '
minute masses or clusters
...
as were not easily dissipable into such particles as compos'd them' [
21
]. Since then,
the word 'cluster' has been commonly used by physicists, chemists and mass
...
