α-NaYF4:Yb3+-Tm3+@CaF2 nanocrystals for NIR-to-NIR temperature sensing

The approach of lanthanides doping upconversion temperature sensing exhibits high superiority in bioscience. However, most of the upconversion nanothermometers show their fluorescences temperature sensing beyond biological transparent window (650-950 nm) while suffering from the interference of surrounding environment. Here we report a nanoprobe with ultrasmall size, i.e. alpha-NaYF4:Yb-Tm@CaF2 nanocrystal, which has a sensitive capability to realize NIR-to-NIR temperature sensing. Temperature sensing sensitivities through 3H(4) -> 3H(6) and 1G(4) -> 3H(6) transitions of Tm3+ ions are evaluated in temperature region of 313-373 K. The results indicate that alpha-NaYF4:Yb-Tm@CaF2 nanocrystal is a promising candidate for biological temperature sensing. (C) 2016 Published by Elsevier B.V.