Tailoring the luminescence of Europium ions in mesoporous AlPO₄ monolithic glass

Controllable simultaneous luminescent monolithic mesoporous AlPO ₄ glasses doped with Eu ions were fabricated by dipping into a Eu-containing solution, followed by sintering in air. Reduction of partial Eu³⁺ ions to Eu²⁺ were achieved after annealing Eu ³⁺ ions in AlPO₄ meso-structure, which resulted in simultaneous luminescence of Eu³⁺ (590 and 613 nm) and Eu ²⁺ (450 nm). Controllable luminescence and color tunability from blue to red were liable to obtain, which were characterized by emission spectra and described by CIE diagram. A deliberate tailoring of luminescence of Eu ²⁺ and Eu³⁺ is achieved by controlling the Eu ions concentrations, sintering temperatures, and excitation wavelengths. Reduction and oxidation reactions of Eu ions were investigated by controlling the sintering atmospheres. XRD pattern indicated the typical amorphous glassy phase without obvious phase-separation even in high concentration (0.1 M). The presence of Eu²⁺ ions, which were reduced from Eu³⁺ by hole-electron pairs and diffused into mesoporous structure, was revealed by XPS spectra.