A method of forming CuFeS2 chalcopyrite nanoparticles. The method includes, in the presence of one or more ligands, reacting an iron-containing compound, a copper-containing compound and a sulfur-containing compound to form CuFeS2 chalcopyrite nanoparticles; and wherein at least one of the ligands forms a coordination complex with copper, and at least one of the ligands forms a coordination complex with iron. Also a method of forming metal-doped CuFeS2 chalcopyrite nanoparticles such as Zn-doped CuFeS2 chalcopyrite nanoparticles. Also, a CuFeS2 chalcopyrite nanoparticle layer on a substrate. Also, a composition of matter including Zn-doped CuFeS2 chalcopyrite nanoparticles. Also, a Zn-doped CuFeS2 chalcopyrite nanoparticle layer on a substrate.