Thermally formation and luminescent performance of silver nanoclusters confined within LTA zeolites

Highlights: • High luminescent silver nanoclusters were formed inside the sodalite cages in LTA zeolites after heat treatment. • The redshifted emission can be attributed to the interaction between Ag₃ⁿ⁺ nanoclusters. • XPS measurement and AP calculation indicated the oxidation of Ag⁰ that constituted Ag₃ⁿ⁺ nanoclusters after exposed in air. -- Abstract: In this research, the Linde Type A (LTA) zeolites were firstly synthesized with hydrothermal method and then the Ag⁺ ions were introduced into LTA through Ag⁺-Na⁺ exchange process, and the luminescent Ag₃ⁿ⁺ nanoclusters can be formed inside the sodalite cages under heat treatment at 300–700 °C, which exhibited yellow-greenish emission under UV excitation. The XRD, SEM and TEM measurements were carried out to study the influence of Ag⁺ loading and heat treatment on the structure of LTA zeolite. The spectral measurement indicated the optimized Ag⁺-exchange level and heat treatment temperature, and the redshift of emission peak with increasing Ag⁺-loading or heat treatment temperature can be attributed to the interaction between Ag₃ⁿ⁺ nanoclusters. When exposing in air, the emission intensity of Ag₃ⁿ⁺ nanocluster was two orders of magnitude decreased while the re-heating can partially recover its emission. According to the XPS measurement and the AP calculation, this reduction in emission intensity can be assigned to the oxidation of silver atoms that constitute Ag₃ⁿ⁺ nanoclusters.