Thermally activated LTA(Li)-Ag zeolites with water-responsive photoluminescence properties

Silver-zeolite composites are interesting materials with unique optical properties such as high external quantum efficiencies and large Stokes shifts. The selective formation of luminescent silver clusters within zeolite scaffolds can be achieved by varying silver guest and zeolite host conditions. Nevertheless, at present, the controlled synthesis of Ag-zeolite composites with responsive optical properties remains a challenge. In this report, silver-zeolite composites displaying a dynamical emission color change with respect to their water content were synthesized using LTA zeolites containing lithium cations as counter-balancing agents. An intense blue emission was encountered in partially hydrated LTA(Li)-Ag composites, at low silver loadings, whereas a green/yellow emission was observed in their fully hydrated state. The materials synthesized in this report possess high external quantum efficiencies, up to 62%, compared to their close analogues having Na, K, and Ca as counter-balancing ions. Due to the remarkable dynamical change in emission color depending on the hydration level of LTA(Li)-Ag composites, the use of these materials as luminescence-based humidity sensors is suggested.