CaGdF based heterogeneous core@shell upconversion nanoparticles for sensitive temperature measurement.

Lanthanide-doped upconversion nanoparticles (UCNPs) have attracted great attention in temperature sensing because of their widespread thermal quenching effect (TQE), a phenomenon in which luminescence intensity decreases as the temperature increases. However, enhancing the TQE of activated ions without changing the dopants or the host is still challenging. Herein, Yb and Er codoped UCNPs in a cubic CaGdF host were synthesized by a coprecipitation method for optical temperature sensing.