Controlled synthesis and temperature-dependent spectra of NaYF4:Yb3+, Re3+@NaYF4@SiO2 (RE = Er, Tm) core–shell–shell nanophosphors

Abstract

The NaYF4 Yb3+, Re3+@NaYF4@SiO2 (RE = Er, Tm) core–shell–shell nanophosphors were synthesized by thermal decomposition of lanthanide trifluoroacetate precursors and subsequent hydrolysis coating process. Structures of resulting nanophosphors are studied by the X-ray diffraction and high-resolution transmission electron microscopy. Temperature-dependent photoluminescence spectra, thermal quenching ratios, fluorescence intensity ratios, and temperature sensitivity of resulting nanoparticles are studied in the temperature range from 298 to 623 K. The results suggest that the NaYF4:Yb3+, Er3+@NaYF4@SiO2 is a suitable candidate for making a low temperature sensor up to 450 K with a maximum sensitivity of 24 × 10−4 K−1, and the NaYF4:Yb3+, Tm3+@NaYF4@SiO2 is an excellent candidate for temperature sensors at high temperature. This work presents a new method to use the fluoride nanocrystals as the optical thermometry at high temperature.