Quantum-sized silver sulfide clusters in zeolite A

The reaction of H2S with activated Ag+-loaded zeolite A leads to silver sul fide zeolite A composites. The optical absorption spectra of samples with d ifferent 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 abso rption and emission spectra of silver sulfide clusters in the cavities of a zeolite in the size regime below 15 Angstrom. The loading densities of the investigated silver sulfide zeolite A composites are 0.05, 0.10, 0.25, 0.5 0, 1.00, 1.25, 1.50, 1.75, and 2.00 silver ions per pseudo unit cell of zeo lite A. The samples are colorless (low loading density) or yellow-green (hi gh loading density). The luminescence is blue-green for samples with low si lver sulfide content, yellow or orange at medium silver sulfide content, an d red at high silver sulfide content.