Luminescence investigation of red-emitting Sr₂MgMoO₆:Eu³⁺ phosphor for visualization of latent fingerprint

Fingerprints are widely studied due to their unique shape and lifelong properties. The latent fingerprint (LFP) visualization is critical in identifying crime scenes and personal information. At present, the powder dusting method for LFP detection is favored due to its environmental friendliness and nontoxicity. However, this method has low resolution, low sensitivity, and large background interference. To address these shortcomings, the red-emitting Sr₂MgMoO₆:xEu³⁺ (x = 0-0.50) phosphors were synthesized using the solid-state reaction process. The products were systematically studied through the structural phase, luminescent property, decay curve, and color purity. Sr₂MgMoO₆:xEu³⁺ phosphors were monitored at 596 nm and exhibited a commendable broad excitation band between 250 and 475 nm. This result indicated that the disadvantage of the poor absorption of commercial red phosphors (Y₂O₂S:Eu³⁺) in the near-ultraviolet region was overcome. Under excitation at 393 nm, the synthesized Sr₂MgMoO₆:Eu³⁺ phosphor exhibited intense red light at 596 and 616 nm, due to the ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ transitions of Eu³⁺ ions. The optimal concentration for the Sr₂MgMoO₆:xEu³⁺ phosphor was x = 20 mol%, and the concentration quenching effect was ascribed to the dipole-dipole interaction. The Commission International del'Eclairage (CIE) chromaticity coordinates of Sr₂MgMoO₆:Eu³⁺ were (0.643, 0.356), and the color purity was 99.8%. Furthermore, the fluorescent LFP images developed by Sr₂MgMoO₆:0.20Eu³⁺ phosphors were well visualized, and level 1-3 details were well identified with high resolution, contrast, sensitivity, and selectivity. The obtained results suggested that the Sr₂MgMoO₆:Eu³⁺ phosphor can be applied for LFP detection.