The present invention provides a two-dimensional double perovskite nanomaterial represented by the formula Cs.sub.2ABX.sub.6 or L.sub.4[Cs.sub.2ABX.sub.6].sub.n-1ABX.sub.8, wherein A is a metal ion selected from Ag(I), Au(I), and Cu(I); B is a metal ion selected from In(III), Bi(III), Sb(III), Fe(III), and Tl(III); X is a halogen; L is a ligand; and n represents the number of metal-halide octahedral layers present in said nanomaterial. The invention further provides a light emitting material and electronic-, optic-, or optoelectronic device comprising said nanomaterial; as well as methods for the preparation of said nanomaterial.