Study of photoluminescence sites in Ag-loaded Na–Y type zeolite

The origin of photoluminescence (PL) was identified as Ag-loaded Na-type Y-type zeolites. To clarify the origin of PL, identifying the luminescent sites of Ag in the zeolite is important. Therefore, we studied the Ag coordination sites when PL development occurs with reduced Ag loading in the zeolite. Using aqueous AgNO3 solutions adjusted to 0.3–1.0 mol/L, we manipulated Ag loading. Quantitative measurements taken using electron probe microanalysis (EPMA) indicated the amounts of Ag atoms per unit cell of the zeolite as 1.3–4.9. The PL measurement results indicated that the PL intensity increased as the Ag loading increased up to 2.0. Furthermore, PL intensity decreased as Ag loading exceeded 2.0. X-ray absorption fine structure (XAFS) measurements showed that up to 2.0 Ag is preferentially coordinated to the center of the hexagonal prisms (Site I) in the zeolite framework. Furthermore, findings indicate that Ag coordinates to the 6-ring (sites I′, II’) in addition to Site I when the number of Ag is greater than 2.0. These results revealed Site I as the luminescence site and sites I′ and II’ as luminescence inhibition sites.