The orange–red persistent luminescence of Ba_1−xCa_xS: Yb²⁺

A series of Ba_1−xCa_xS: 2%Yb²⁺ (x=0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) persistence phosphors were prepared via a conventional solid state reaction method under H₂ reducing atmosphere. Fluorescence, phosphorescent and near-infrared photo-stimulated spectra were presented at room temperature. The obtained data indicated that the red persistent luminescence can be lengthened by introducing impurity metal cation. Moreover, the persistent luminescence can be effectively released under the excitation of 980 nm LED. In consideration of the high transmittance of red light as well as near-infrared lights in the organism, Ba_1−xCa_xS: 2%Yb²⁺ phosphors have potential application in fluorescence bio-imaging.