Switching green to red emission in tridoped ZrO2:Yb3+–Er3+–Bi3+ nanocrystals

Abstract Tridoped ZrO 2 :Yb 3 + –Er 3 + –Bi 3+ nanophosphor was synthesized by hydrothermal process and demonstrated the possibility of switching from a strong green–yellow broadband signal to red emission due to Bi 3+ and Er 3+ ion by changing excitation from 350 nm to 970 nm, respectively. The green–yellow band is associated to the transition 3 P 1 → 1 S 0 and was overlapped with the green band associated to the transition 2 H 11/2 + 4 S 3/2 → 4 I 15/2 of Er 3+ as a result of the energy transfer from Bi 3+ to Er 3+ . The strong red band is associated to 4 F 9/2 → 4 I 15/2 transition of Er 3+ and enhanced by a factor of 3 as a result of the forward and backward energy transfer process (Er 3+ → Bi 3+ → Er 3+ ). This sink effect where electrons can be stored temporally and released back can be useful to enhance the emitted signal of other lanthanides.