Thermal Effects in Up-Conversion Luminescence NaYF 4 : Tm 3+ , Yb 3+ Core-Shell Nanoparticles in the Temperature Range of 18–312 K

This work demonstrates the temperature (18–312 K) impact on Tm 3+ up-conversion luminescence in core-shell structured NaYF 4 :Tm 3+ , Yb 3+ nanoparticles excited at 976 nm. As the temperature decreases from room temperature to 18 K, Tm 3+ up-conversion luminescence bands intensities greatly increase, an average of 60-fold, emitting intense blue and ultraviolet radiation. Tm 3+ up-conversion luminescence spectra measurements at different temperatures reveal that three thermal quenching mechanisms are responsible for observed variations in Tm 3+ up-conversion luminescence spectra. These three quenching mechanisms are related to the excitation radiation absorption, Stark sublevel population, and energy transfer from Yb 3+ to Tm 3+ .