Enhancing upconversion emissions of NaTm0.02Yb x Y0.98−x F4 nanocrystals through increasing Yb3+ doping

Abstract: By increasing the content of Yb3+ ions from 20% to 98% in NaTm0.02Yb x Y0.98−x F4 (x=0.2−0.98) nanocrystals with size about 10nm, the intensities of near infrared (800nm) and blue (470nm) upconversion (UC) luminescence can be enhanced by orders of 45 and 49 times, respectively, under 970nm diode laser excitation. Pump power dependence illustrated that the 800 and 470nm radiations are still two- and three-photon processes, respectively. TEM imaging showed that the enhancement is not from the change of the crystal size. Steady-state equation and the measured lifetimes indicated that the enhanced 800nm radiations can induce the enhancement of the 470nm emissions, which is in good agreement with the experimental data. [Copyright &y& Elsevier]