Synthesis and Characteristics of Sr₃La(PO₄)₃:Eu³⁺ Phosphor with Luminescence in NIR Biological Window

The Sr₃La(PO₄)₃:Eu³⁺ (SLP:Eu³⁺) phosphor was prepared with the coprecipitation method, which emited red visible-light along with a near-infrared (NIR) luminescence in the biological window region. The influence of synthesis temperature and Eu³⁺ doping concentration on the characteristics of the phosphor was discussed. The optimal crystallinity was obtained when the phosphor was doped with 0.7 mol% of Eu³⁺ and annealed at 1200 °C for 2 h. The particle size was approximately 1 μm. As compared with the SLP:0.01 Eu³⁺, the photoluminescence intensity of the SLP:0.07 Eu³⁺ increased by 4.95-fold at wavelength of 615 nm and 3.97-fold at 705 nm. The red SLP:Eu³⁺ phosphor with a high NIR emission is a potential candidate material for bio-image and bio-sensor applications.