Preparation of rare-earth-free luminescent material from partially Ag+-exchanged zeolite X

摘要

A luminescent material free of rare earth elements was prepared from a partially Ag+ exchanged zeolite X. One gram of a commercially available zeolite X (Na+ form) was mixed with 100 mL of AgNO₃ aqueous solutions of 2.0 to 50 mmol/L. The mixtures were shaken for 24 h, then the solid products were separated and dried at 50°C. Some of the products were heated at 100 to 800°C in atmospheric air. Luminescence was observed from the products with Ag loadings of 0.5 mmol/g or higher. These products showed yellow luminescence under UV light excitations of 254 and 312 nm. The luminescent products showed two excitation bands with peak maxima at 271 and 311 nm, and a single emission band at 550 nm. The luminescence intensity was low for the 0.5 mmol/g Ag loaded sample, but it significantly increased with the increasing amounts of Ag+ up to a 1.0 mmol/g loading, then a quenching occurred with a further increased Ag+ loading. Heating of the Ag-loaded zeolite X decreased the luminescence intensity. Heating the Ag loaded zeolite X at 800°C resulted in a low blue luminescence intensity due to collapsing the zeolite X structure into an amorphous phase. This study suggested that a luminescent material free of rare earth elements can be fabricated from Ag-exchanged zeolite X without any heat treatment. The highest luminescence intensity was attained at the Ag loading of 1.0 mmol/g, along with a measured internal quantum efficiency of 20.8% (λ ex. = 311 nm).