Preparation and Characterization of Silver Sulfide Nanocrystals Generated from Silver(I)-Thiolate Polymers

Silver sulfide nanocrystals have been formed by the conversion of silver thiolate polymers with sodium sulfide in a dual-phase solution preparation. From transmission electron microscopy and laser desorption ionization mass spectrometry, the mean nanocrystalline diameter is estimated to be 5.4 nm. Large-angle X-ray diffraction is qualitatively consistent with the rhombic phase (acanthite) of Ag2S. The removal of the silver thiolate polymer is confirmed by mass spectrometry, and initial results indicate that fractional crystallization may be utilized to separate these large nanocrystalline compounds by their respective core sizes. Optical absorption spectroscopy indicates a band gap of 1.1 eV, which is not shifted appreciably from the bulk value for this direct band gap semiconductor.