Quantum-Sized Silver Sulfide Clusters in Zeolite A

The reaction of H2S with activated Ag+-loaded zeolite A leads to silver sulfide zeolite A composites. The optical absorption spectra of samples with different loading densities of silver sulfide suggest the formation of small silver sulfide clusters which are stable under ambient conditions. To our knowledge, this is the first report on the preparation and the optical absorption and emission spectra of silver sulfide clusters in the cavities of a zeolite in the size regime below 15 A. The loading densities of the investigated silver sulfide zeolite A composites are 0.05, 0.10, 0.25, 0.50, 1.00, 1.25, 1.50, 1.75, and 2.00 silver ions per pseudo unit cell of zeolite A. The samples are colorless (low loading density) or yellow-green (high loading density). The luminescence is blue-green for samples with low silver sulfide content, yellow or orange at medium silver sulfide content, and red at high silver sulfide content.