Structures of polymers used for stabilization of metal clusters: (a) poly(N-vinyl-2-pyrrolidone) (PVP); (b) poly(allylamine) (PAA); (c) poly(2-vinylpyridine) (P2VP); (d) poly(4-vinylpyridine) (P4VP); (e) cyclodextrin derivatives (X-(α, β or γ)-CD) with X = OH, SH or NH₂ (n = 6, 7, and 8 for α, β, and γ); (f) OH-terminated poly(amidoamine) dendrimer of generation 2 (PAMAM-G2).