Optical thermometry and fingerprint detection applications of La2MgTiO6: Bi3 + , Eu3+ phosphors

A series of Bi 3+ /Eu 3+ single-doped and co-doped La 2 MgTiO 6 phosphors were synthesized by the high-temperature solid-state method. Their crystal structure, micromorphology and luminescent properties were systematically studied. The luminescence characteristics of the La 2 MgTiO 6 : Bi 3+ , Eu 3+ phosphors could be effectively tailored by modulating the Eu 3+ doping concentration. Under 340 nm excitation, characteristic emission peaks originating from the 3 P 1 → 1 S 0 transition of Bi 3+ at 415 nm and the 5 D 0 → 7 F 2 transition of Eu 3+ at 613 nm were simultaneously observed. In the La 2 MgTiO 6 : Bi 3+ , Eu 3+ phosphor, energy transfer from Bi 3+ to Eu 3+ is primarily mediated by electric dipole-dipole interactions. Leveraging the distinct thermal quenching behaviors of Bi 3+ and Eu 3+ , a high-sensitivity, triple-mode fluorescence thermometer was developed based on the temperature dependence of Bi 3+ fluorescence intensity (FI), the fluorescence intensity ratio (FIR) between Bi 3+ and Eu 3+ , and the temperature-induced shift in CIE chromaticity coordinates. The maximum relative sensitivities (Sᵣ) of these three modes reached 2.52% K −1 at 408 K, 2.10% K −1 at 368 K, and 0.60% K −1 at 348 K, respectively. The La 2 MgTiO 6 : Bi 3+ , Eu 3+ phosphor demonstrates excellent thermometric performance, positioning it as a promising candidate for temperature monitoring applications. Furthermore, the La 2 MgTiO 6 : Bi 3+ , Eu 3+ phosphor has been successfully applied to latent fingerprint detection, exhibiting distinct purplish-red emission under ultraviolet irradiation, which significantly enhances the visual contrast. These experimental results demonstrate that the La 2 MgTiO 6 : Bi 3+ , Eu 3+ phosphor holds great potential for dual-function applications in optical thermometry and forensic detection.