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Luminescence thermometry in the second and third optical windows of biological tissues has gained importance in recent years due to the reduction of both absorption and scattering effects in human tissues, which substantially increase its applicative potential. In this work, we present a luminescent thermometer based on SrTiO 3 :Ni 2+ ,Er 3+ nanocrystals, which is the first reported study of nanothermometry based on Ni 2+ ion luminescence. The SrTiO 3 :Ni 2+ ,Er 3+ nanocrystals were successfully synthesized using the Pechini method. The spectroscopic properties of obtained nanocrystals were investigated in a wide temperature range, namely, between −150 and 210 °C. It was found that Ni 2+ ions in the SrTiO 3 matrix are characterized by broadband emission localized in the II optical window at about 1200 nm, which additionally changes its spectral position toward longer wavelengths with the rise of temperature. Three temperature-dependent parameters were studied for luminescence thermometry: changes in the emission intensity of the Ni 2+ band, the spectral shift of its maximum, and the luminescence intensity ratio of Ni 2+ to Er 3+ ions. The temperature-sensing properties of SrTiO 3 :Ni 2+ ,Er 3+ were investigated as a function of Er 3+ concentration. It was revealed that the increase of thermal sensitivity was associated with the decrease of Er 3+ concentration. The highest value of the relative sensitivity, in the physiological temperature range, was obtained for SrTiO 3 :0.05% Ni 2+ ,0.1% Er 3+ nanocrystals, namely, 0.80%/ °C at 40 °C.

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Ratiometric luminescence thermometry for remote temperature sensing has been constantly gaining an increasing popularity due to its simplicity with yet high precision. Transition metal ions still have an underestimated potential in that area as their luminescence properties can be tuned by targeted modification of the host compound. In this work, we demonstrate that concept in the phosphor LaScO3:Cr 3+ by co-doping with various lanthanide ions that partially substitute the La 3+ ions of the host. It is demonstrated that the incorporated lanthanide ions affect the bond lengths of the [CrO6] 9octahedra in the structure and thus, have a subtle impact on the local crystal field around the Cr 3+ ions. The changes in the crystal field strength lead to a variation in the energy gap between the thermally coupled 2 E(g) and 4 T2(g) states of Cr 3+ . This has an immediate consequence for the potential use of Cr 3+ as a luminescent thermometer and allows to selectively tune the relative thermal sensitivity and performance of this ion by a suitable choice of the co-doped lanthanide ions. 4 T2(g) → 4 A2(g) transition is more prominent in intermediate to weak crystal fields. In contrast to

The Cr3+ doped nanocrystals were examined as a noncontact temperature sensor in the lifetime-based approach. The impact of both the analysis protocol and host material in the lifetime-base has been...