Triple-temperature readout in luminescence thermometry with Cr 3+ -doped Mg 2 SiO 4 operating from cryogenic to physiologically relevant temperatures

Cr 3+ -doped Mg 2 SiO 4 orthorhombic nanoparticles are synthesized by a combustion method. The 3d 3 electron configuration of the Cr 3+ ion results in the deep-red emission from optical transitions between d–d orbitals. Two overlapping emissions from the Cr 3+ spin-forbidden 2 E g → 4 A 2g and the spin-allowed 4 T 2g → 4 A 2g electronic transitions are influenced by the strong crystal field in Mg 2 SiO 4 and, thus, are suitable for ratiometric luminescence thermometry. The temperature-induced changes in Cr 3+ -doped Mg 2 SiO 4 emission are tested for use in luminescence thermometry from cryogenic to physiologically relevant temperatures (10–350 K) by three approaches: (a) temperature-induced changes of emission intensity; (b) temperature-dependent luminescence lifetime; and (c) temperature-induced changes of emission band position. The second approach offers applicable thermometry at cryogenic temperatures, starting from temperatures as low as 50 K, while all three approaches offer applicable thermometry at physiologically relevant temperatures with relative sensitivities of 0.7% K −1 for emission intensity, 0.8% K −1 for lifetime and 0.85% K −1 for band position at 310 K.