We studied the relation between structure of the Ag clusters produced in Ag-type zeolite-A and properties of photo luminescence (PL) by use of in-situ X-ray absorption fine structure (XAFS). Ag clusters are generated in the cavity of Ag-type zeolite-A which is cooled to room temperature after heated at 500°C for 24 hours under vacuum or atmosphere. We investigated the change of the Ag clusters in the zeolite cavity when various gases are introduced:oxygen, nitrogen, water vapor, and their mixture. The Ag clusters were breakdown when H_2O gas was introduced and the fact of the breakdown of the cluster is necessary for appearing the strong PL band. It was suggested that the structural change in the zeolite induced by the formation and breakdown of the Ag clusters is key point of the PL mechanism.
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