Nanoscale thermometry with fluorescent yttrium-based Er/Yb-doped fluoride nanocrystals

- Erbium and ytterbium doped fluorescent sensors of various sizes are synthesized.
- The nanocrystals are embedded in fluoride matrices to favor radiative recombinations.
- Erbium and Ytterbium-doped nanocrystals are excitable from blue to near-infrared.
- Fluorescence intensity ratio is a robust technique to monitor temperature.

We have synthesized fluorescent yttrium-based fluoride nanoparticles doped with Er3+ and Yb3+ ions. The nanocrystals, whose size can be adjusted from a few tens to a few hundreds of nanometers, exhibit a strong temperature-dependent fluorescence that makes them excellent candidates for nanoscale thermometry in the (25-100 °C) range. The temperature is determined by monitoring the intensity ratio of two visible fluorescence lines that are in thermal equilibrium. We discuss the thermal sensitivity of such probes and show that they can be indifferently excited at several wavelengths from the blue to the near-infrared part of the electromagnetic spectrum which makes them candidates of high potentials in many experimental environments.