Aryldiazonium
ions are widely used reagents for surface modification.
Attractive aspects of their use include wide substrate compatibility
(ranging from plastics to carbons to metals and metal oxides), formation
of stable covalent bonding to the substrate, simplicity of modification
methods that are compatible with organic and aqueous solvents, and
the commercial availability of many aniline precursors with a straightforward
conversion to the active reagent. Importantly, the strong bonding
of the modifying layer to the surface makes the method ideally suited
to further on-surface (postfunctionalization) chemistry. After an
initial grafting from a suitable aryldiazonium ion to give an anchor
layer, a target species can be coupled to the layer, hugely expanding
the range of species that can be immobilized. This strategy has been
widely employed to prepare materials for numerous applications including
chemical sensors, biosensors, catalysis, optoelectronics, composite
materials, and energy conversion and storage. In this Review our goal
is first to summarize how a target species with a particular functional
group may be covalently coupled to an appropriate anchor layer. We
then review applications of the resulting materials.