Nonstoichiometry of nanocrystalline monoclinic silver sulfide.

Powders of silver sulfide have been synthesized by chemical bath deposition from aqueous solutions of silver nitrate and sodium sulfide in the presence of sodium citrate or EDTA-H2Na2. Colloid solutions have been prepared by a chemical condensation method from the same aqueous solutions. Synthesized silver sulfide nanopowders have a monoclinic (space group P21/c) acanthite-type structure but the occupancy of the metal sublattice sites by Ag atoms is smaller than 1. Unlike coarse-crystalline silver sulfide Ag2S, silver sulfide nanopowders with particles sizes of less than ∼50 nm are nonstoichiometric, contain vacant sites in the metal sublattice and have a composition of ∼Ag1.93S.