Visible emission from Ag+ exchanged SOD zeolites

Abstract

Broad visible emissions dominant at green or red have been observed for the thermally-treated Ag⁺ exchanged SOD zeolites, determined by the Ag⁺ loading contents and the excitation wavelengths. Contrary to the notable reversible green/red dominant emission evolution in the Ag⁺ exchanged LTA zeolites upon hydration/dehydration in air (or water vapor)/vacuum, emission spectra of the Ag⁺ exchanged SOD zeolites are insensitive to the environmental change. This is most probably due to the difficult H₂O permeation in SOD zeolites in comparison with LTA zeolites. By combining the environment dependent emission spectra of the Ag⁺ exchanged LTA and SOD zeolites, we proposed the following emission mechanisms for Ag⁺ exchanged LTA and SOD zeolites: the green emission is due to the transition from ligand-to-metal (framework O²⁻ → Ag⁺) charge transfer state to the ground state and the red emission is due to the transition from the metal–metal (Ag⁺–Ag⁺) charge transfer state to the ground state. The insensitive environment dependent emission characteristics of Ag⁺ exchanged SOD zeolites may have potential applications as robust phosphors.