Ratiometric temperature sensing with non-thermally coupled levels from Pr–Al co-doped MgGa2O4

Fluorescence intensity ratio (FIR) technique demonstrates significant potential for non-contact temperature sensing with rapid response time, while the design of FIR probes is particularly intriguing. Herein, we report Pr–Al co-doped MgGa 2 O 4 persistent luminescence nanoparticles (PLNPs), as MgAl 0.04 Ga 1.96 O 4 : 0.1 % Pr 3+ (MAGP), for ratiometric temperature sensing application. Pr 3+ ions function as the emission centers for dual-emission at 612 and 494 nm, while Al 3+ ions adjust the lattice environment around Pr 3+ ions to enhance the luminescence. Consequently, 274 nm excitation induces the emissions at 494 and 612 nm, as the transitions of Pr 3+ for 3 P 0 → 3 H 4 and 1 D 2 → 3 H 4 , respectively. The emission mechanism is substantiated by density functional theory calculations, regarding the electronic transitions of Pr 3+ . Ratiometric temperature sensing is achieved over the temperature range of 303–573 K with the thermally non-coupled mechanism of the 3 P 0 / 1 D 2 energy levels by FIR at 612 and 494 nm, respectively. The maximum relative sensitivity was 0.91 %. The mechanism is corroborated as the non-thermally coupled energy levels through intervalence charge transfer. Thus, the reversible and sensitive response was illustrated for temperature measurement and the non-thermally coupled mechanism is efficient for the design of ratiometric temperature sensors.