MgTiO 3 :Mn 4+ a multi-reading temperature nanoprobe.

MgTiO 3 nanoparticles doped with Mn 4+ , with homogeneous size ranging about 63.1 ± 9.8 nm, were synthesized by a molten salt assisted sol gel method. These nanoparticles have been investigated as optical thermal sensors. The luminescence of tetravalent manganese ion in octahedral environment within the perovskite host presents drastic variations with temperature. Three different thermometry approaches have been proposed and characterized. Two luminescence intensity ratios are studied. Firstly between the two R-lines of Mn 4+ emission at low temperature (-250 °C and -90 °C) with a maximal sensitivity of 0.9% °C -1 , but also secondly between 2 E → 4 A 2 (R-line) and the 4 T 2 → 4 A 2 transitions. This allows studying the temperature variation within a larger temperature range (-200 °C to 50 °C) with a sensitivity between 0.6% °C -1 and 1.2% °C -1 over this range. The last proposed method is the study of the lifetime variation versus temperature. The effective lifetime value corresponds to a combination of transitions from two excited energy levels of the tetravalent manganese ( 2 E and 4 T 2 ) in thermal equilibrium toward the fundamental 4 A 2 state. Since the more energetic transition ( 4 T 2 → 4 A 2 ) is spin-allowed, contrary to the 2 E → 4 A 2 one, the lifetime drastically decreases with the increase in temperature leading to an impressive high sensitivity value of 4.1% °C -1 at 4 °C and an exceptional temperature resolution of 0.025 °C. According to their optical features, MgTiO 3 :Mn 4+ nanoparticles are indeed suitable candidates for the luminescence temperature probes at the nanoscale over several temperature ranges.