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

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 100mL of AgNO 3 aqueous solutions of 2.0 to 50mmol / L. The mixtures were shaken for 24h, 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 0.5mmol / g or higher. These products showed yellow luminescence under UV light excitations of 254 and 312nm. The luminescent products showed two excitation bands with peak maxima at 271 and 311nm, and a single emission band at 550nm. The luminescence intensity was low for the 0.5mmol / g Ag loaded sample, but it signi fi cantly increased with the increasing amounts of Ag + up to a 1.0mmol / 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 1.0mmol / g, along with a measured internal quantum ef fi ciency of 20.8 % ( ­ ex. =