Single cell temperature probed by Eu +3 doped TiO 2 nanoparticles luminescence

Temperature is a critical parameter in biology, affecting the speed of reactions that occur in living systems. Nevertheless, measuring temperature with subcellular resolution (micrometric scale) and reliability remains a challenge to overcome. In this perspective, luminescence nanothermometry is a non‐contact technique which aims to measure temperature with a sub‐micrometric spatial resolution through the use of nanomaterials whose luminescence is affected solely by changes in temperature. Here, TiO 2 nanoparticles doped with Eu +3 ions (Eu +3 ‐TiO 2 ) are used for sensing temperature differences within single living cells. XRD, XPS, SEM, TEM and NEXAFS analysis allow the determination of the physicochemical characteristics of the Eu +3 ‐TiO 2 nanoparticles and, the variation of the luminescence intensity of the Eu +3 ‐TiO 2 nanoparticles with their temperature is investigated. The successful internalization of Eu +3 ‐TiO 2 nanoparticles in different types of cells is observed. The luminescence of nanoparticles internalized in L929 fibroblast cells is measured when the system is heated in a biological relevant temperature range. Making use of an appropriate calibration curve the temperature variation inside the cells is determined with sensitivity of 0.5 K per 1% of luminosity change when heated.