Lifetime of the 3H4 Electronic State in Tm3+-Doped Upconverting Nanoparticles for NIR Nanothermometry.

Emission bands from thermally coupled states in lanthanide-doped nanoparticles have been studied for ratiometric nanothermometry in biological applications. Unfortunately certain factors such as water absorption distort the intensity, limiting the accuracy of ratiometric nanothermometry. However, the decay time of such states does not suffer from such distortions. We introduce the decay time of the 3H4 state in Yb3+, Tm3+-doped nanoparticles for improved nanothermometry. The strong 800 nm upconversion emission exists in the first biological transparency window. This is the first use of a single upconversion band for lifetime nanothermometry.