Highly sensitive optical nanothermometry using Er3+-doped GdOF nanoparticles: synthesis, characterization, and temperature sensing applications

The synthesis and characterization of 1 mol% Er3+-doped GdOF nanoparticles for use as optical nanothermometer are presented. The nanoparticles were synthesized using a microwave-assisted solvothermal method, followed by calcination at 700 °C to obtain the oxyfluoride phase. Temperature sensitivity was evaluated using the fluorescence intensity ratio (FIR) method, based on the thermally coupled 2H11/2 and 4S3/2 levels of Er3+ over the 294–423 K range. The results demonstrate a high sensitivity, with an absolute sensitivity of 3.07 × 10−3 K−1 at 423 K and a relative sensitivity of 1.25 % K−1 at 294 K. These competitive values position Er3+-doped GdOF nanoparticles as promising candidates for temperature sensing applications in biomedicine and nanotechnology, offering advantages over other Er3+-based nanothermometers in different host matrices.