Near-infrared rechargeable glass-based composites for green persistent luminescence

Abstract

<p>The fabrication of Yb³⁺, Tm³⁺ co-doped oxyfluorophosphate glass-based composites, with green persistent luminescence after being charged with near-infrared light, is demonstrated. The mechanism responsible for the green afterglow after near-infrared illumination is unveiled. The composite is prepared using a modified melting process to limit the evaporation of fluorine during melting. Intense (blue and ultraviolet) up-conversion emission is obtained by optimizing the Yb₂O₃ and Tm₂O₃ concentrations. A heat treatment promotes volume precipitation of Yb³⁺, Tm³⁺ co-doped CaF₂ crystals. Although the intensity of the blue up-conversion emission from the Tm^{3+ 1}G₄ level is lower in the highly Yb³⁺-concentrated glass-ceramic due to reverse energy transfer from Tm³⁺ to Yb³⁺, the heat treatment leads to an increase of the intensity of the emissions around 346 nm, 361 nm nm and 450 nm coming from the Tm^{3+ 1}I₆ and ¹D₂ levels. By combining the Yb³⁺ and Tm³⁺ ions with SrAl₂O₄:Eu²⁺,Dy³⁺crystals, green afterglow can be obtained after charging with near-infrared light.</p>