Metal nanoclusters have physical properties differing significantly from their bulk counterparts.
Metallic properties such as delocalization of electrons in bulk metals which imbue them with high
electrical and thermal conductivity, light reflectivity and mechanical ductility may be wholly or
partially absent in metal nanoclusters, while new properties develop. We review modern synthetic
methods used to form metal nanoclusters. The focus of this critical review is solution based
chemical synthesis methods which produce fully dispersed clusters. Control of cluster size and
surface chemistry using inverse micelles is emphasized. Two classes of metals are discussed,
transition metals such as Au and Pt, and base metals such as Co, Fe and Ni. The optical and
catalytic properties of the former are discussed and the magnetic properties of the latter are given
as examples of unexpected new size-dependent properties of nanoclusters. We show how classical
surface science methods of characterization augmented by chemical analysis methods such as
liquid chromatography can be used to provide feedback for improvements in synthetic protocols.
Characterization of metal clusters by their optical, catalytic, or magnetic behavior also provides
insights leading to improvements in synthetic methods. The collective physical properties of
closely interacting clusters are reviewed followed by speculation on future technical applications
of clusters.
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