Praseodymium doped YF3:Pr3+ nanoparticles as optical thermometer based on luminescence intensity ratio (LIR) - Studies in visible and NIR range

Luminescent YF3 nanoparticles doped with Pr(3+ )activator ion have been successfully synthesized via a facile hydrothermal approach for their application as a mull-range optical sensor of temperature. The product synthesized shows intense yellow luminescence at 457 nm laser excitation, and the emission spectra were recorded from 475 to 1650 nm, showing the presence of sharp emission peaks in the measured spectral range. The intensity of the observed emission bands typical of Pr3+ ion changes with temperature significantly. Hence, the intensity ratios of the thermalized emission bands were determined in the temperature range from 293 to 421 K, and they were calibrated for thermal sensing purposes. High relative sensitivity values, ranging from 0.6 to 1.2 % K-1, were found for the emission bands of the thermally-coupled P-3(1) and P-3(0) excited states located around 522-537, 586-603 and 700-723 nm. The temperature calibration based on the thermalized P-3(1) -> F-3(4) and P-3(0) -> F-3(4) bands located in the first biological optical window (650-950 nm), may be especially useful for potential biological applications.