High-performance of optical thermometry based on the non-thermally coupled levels in YVO4: Yb3+/Er3+/Tm3+ nanocrystals

Hydrothermally fabricated nanocrystals YVO4: Yb3+/Er3+/Tm3+ were investigated for up-conversion (UC) luminescence and optical temperature sensing performance. Upon 980 nm excitation, the luminescence intensity firstly increases and then decreases with raising Yb3+ doping content and reaches the maximum at 15 mol%. Considering the strong UC emission, the temperature sensing behavior was investigated based on the fluorescence intensity ratio (FIR) technique in temperature range of 293–573 K. The study was focused on the non-thermally coupled levels (NTCLs) including transitions 3F2,3 → 3H6 and 1G4→3H6 of Tm3+, transitions from the 4S3/2, stark sublevel 4S3/2(2), and 4F9/2 to the ground state 4I15/2 of Er3+ owing to their various temperature-dependent behaviors. Through using the stark sublevel 4S3/2(2) of Er3+, the maximum absolute sensitivity (SA) of 0.0563 K-1, relative sensitivity (SR) of 2.334 %K−1 and the minimum temperature resolution of 0.0058 K was achieved with good repeatability. The experimental results indicate that the as-obtained YVO4: 15%Yb3+/1%Er3+/1%Tm3+ nanocrystals can be potential candidates for nano-dimensional optical thermometry applications.