Sho Narita

In-situ XAFS study of Ag clusters in Ag-type zeolite-A

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 H2O 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.

XAFS and IR Studies on Luminescent Silver Zeolites

In this chapter, studies of structures and optical properties of Ag-zeolite A by means of X-ray absorption fine structure (XAFS) and infrared (IR) spectra are presented. XAFS is a powerful tool to study the local structure of Ag nanoclusters in the zeolite cavity and IR spectra are quite sensitive to the change in zeolite lattice affected by the production of Ag clusters. First, we focus on the creation of Ag clusters in zeolite A by heat treatment under atmosphere and vacuum. Second, we discuss the mechanism of photolumines‐ cence for Ag-zeolite composite. It is widely believed that the emitting point is Ag clusters in the Ag zeolite; on the other hand, our recent result is contradicted that Ag clusters are broken down in the strongly emitting species.

IR and XAFS studies of photoluminescent Ag-type zeolite-A

We examined the relation between the zeolite framework, Ag clusters, and properties of photoluminescence (PL) using in-situ infrared spectroscopy (IR) and X-ray absorption fine structure (XAFS). The Ag clusters are generated in the cavity of Ag-type zeolite-A that is cooled to room temperature after heating at 500°C for 24 hour under vacuum or in atmosphere. The Ag clusters in the zeolite cavity break down when air is introduced. According to the formation and breakdown of the Ag cluster, the infrared spectrum of the zeolite framework changed slightly. Then, this change was compensated by irradiation of the excitation light. Results suggest that the structural change in the zeolite induced by the formation and breakdown of the Ag clusters is a key point of the PL mechanism.