Luminescence properties of Ag2S and Ag4S2 in zeolite A
Silver sulfide particles of different size are synthesized in the cavities of zeolites A and ZK-4 by exposing the Ag+-exchanged dehydrated zeolites to H2S. The two smallest stable particles synthesized by this method are the Ag2S molecule and the Ag4S2 cluster. Both show photoluminescence in the visible region. The luminescence properties of the samples are studied as a function of temperature, of the silver sulfide content, and of the co-cations. By using the Ca2+-exchanged form of zeolite A it is possible to synthesize silver sulfide–zeolite systems which contain Ag2S and Ag4S2 in the same zeolite crystal. After excitation with UV light energy transfer from the excited Ag2S to Ag4S2 most probably occurs. These systems are potential materials for thermometry because their luminescence properties strongly depend on the temperature.