Yb3+/Tm3+/Ho3+ tri-doped YPO4 submicroplates: A promising optical thermometer operating in the first biological window

Currently, real-time and accurate temperature monitoring of biological tissues and cells is of significance for many biological applications. Here, a new type of optical thermometer have been designed based on the thermo-responsive fluorescence intensity ratio (FIR) of Ho3+ (5F5 → 5I8) to Tm3+ (3F3 → 3H6) emission. To explore the possible application in optical thermometry, Yb3+/Ho3+/Tm3+ tri-doped YPO4 submicroplates have been successfully synthesized via a facile hydrothermal route. Interestingly, the as-designed UC thermometer (operating in the first biological window) exhibits high temperature sensitivity (∼8.85% K−1) and good signal discriminability, which may be expected to find promising potential application for accurately detecting temperature of biological tissues.