  Inorganic nanocrystal gels retain distinct properties of individual
nanocrystals while offering tunable, network structure-dependent
characteristics. We review different mechanisms for assembling gels from
colloidal nanocrystals including (1) controlled destabilization, (2) direct
bridging, (3) depletion, as well as linking mediated by (4) coordination
bonding or (5) dynamic covalent bonding, and we highlight how each impacts gel
properties. These approaches use nanocrystal surface chemistry or the addition
of small molecules to mediate inter-nanocrystal attractions. Each method offers
advantages in terms of gel stability, reversibility, or tunability and presents
new opportunities for design of reconfigurable materials and fueled assemblies.
