Up-conversion luminescence and photo-thermal effect of KY3F10:Yb3+,Ho3+ nanocrystals

The cubic phase KY3F10:15%Yb3+,1%Ho3+ up-converting nanocrystals are prepared by a simple hydrothermal method. Under 980 nm excitation, strong green and red emissions are produced at the same time. According to a set of steady state rate equations and the power dependence of up-conversion luminescence, it is confirmed that two-step energy transfer from Yb3+ to Ho3+dominates the population of green emission level, while the multi-phonon decay of 5S2/5F4 to 5F5 and promotion from 5I7 to 5F5 are responsible for the red emission. Long-term laser irradiation leads to significant thermal effects. Based on the ratiometric luminescence temperature sensing behavior, the light to heat conversion ability is evaluated. This multi-functional nanocrystal is potentially applicable as the nano-heater for photo-thermal therapy of tumors.