| Powders of silver sulfide Ag2S 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 chemical condensation method from the same aqueous solutions. Synthesized Ag2S powder with particle size ~500 nm have monoclinic (space group P21/c) acanthite-type crystal structure. Silver sulfide nanopowders have the same monoclinic acanthite-type structure but the occupancy of the metal sublattice sites by silver atoms is smaller than 1. Unlike coarse-crystalline silver sulfide Ag2S, silver sulphide nanopowders with the size of particles less than ~50 nm are nonstoichiometric, contain vacant sites in metal sublattice and have a composition ~Ag1.93S. It is shown that by varying the ratio between the concentrations of reagents in the initial reaction mixture it is possible to deposit Ag2S nanoparticles with preassigned average size ranging in the interval from about 500 nm down to about 30 nm. The average size of silver sulfide Ag2S nanoparticles in stable colloid solutions is equal 10-20 nm. |
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