LiAlO:Fe and LiAlO:Fe, Nd as a New Luminescent Nanothermometer Operating in 1st Biological Optical Window.

New types of contactless luminescence nanothermometers, namely, LiAlO:Fe and LiAlO:Fe, Nd are presented for the first time, revealing the potential for applications in biological systems. The temperature-sensing capability of the nanocrystals was analyzed in wide range of temperature (-150 to 300 °C). The emission intensity of the Fe ions is affected by the change in temperature, which induces quenching of the T (G) → A (S) Fe transition situated in the 1 biological window. The highest relative sensitivity in the temperature range (0 to 50 °C) was found to be 0.82% °C (at 26 °C) for LiAlO: 0.05% Fe nanoparticles that are characterized by long luminescent lifetime of 5.64 ms. In the range of low and high temperatures the S was calculated for LiAlO:0.5% Fe to be 0.92% °C at -100 °C and for LiAlO:0.01% Fe to be 0.79% °C at 150 °C. The cytotoxicity assessment carried out on the LiAlO:Fe nanocrystals, demonstrated that they are biocompatible and may be utilized for in vivo temperature sensing. The ratiometric luminescent nanothermometer, LiAlO:Fe, Nd, which was used as a reference, possesses an S = 0.56%/°C at -80 °C, upon separate excitation of Fe and Nd ions using 266 nm and 808 nm light, respectively.