Reduction of ions which are fixed on the clusters favours to cluster growth rather than formation of newisolated atoms. The bonding between clusters with unreduced ions or two charged clusters is also strong and these association processes are fast:
where m, n and p represent the nuclearities, and x, y and z, symbolize the number of associated ions. The control of the final size depends on the limitation applied to the coalescence beyond certain nuclearity. For free clusters such as nanocolloids in solution, the coalescence may be limited by a polymeric molecule acting as a cluster stabilizer