Yb/Er/Tm tri-doped Na3ZrF7 upconversion nanocrystals for high performance temperature sensing

Non-contact optical thermometry based on fluorescence intensity ratio (FIR) technique has been widely researched over the past few decades. However, the reported systems exhibit two important shortcomings including the existence of a few interferential signals in addition to the required spectral bands for FIR and the absence of internal standard for reference signal. Herein, only two emission bands of Er3+:F-4(9/2) -> I-4(15/2) (similar to 673 nm) and Tm3+:H-3(4) -> H-3(6) (similar to 800 nm) are achieved in Yb/Er/Tm tri-doped Na3ZrF7 nano-system. Moreover, the upconversion (UC) emission intensity of Er3+ keeps unchanged with the rising of temperature, which is applied as reference signal; while that of Tm3+ enhances evidently, which is applied as temperature signal. The calculated maximum absolute temperature sensitivity (S-a) and relative temperature sensitivity (S-r) are 0.17 K-1 at 393 K and 1.76%K-1 at 313 K, respectively.