Sensitizer-dependent up-conversion of Ho3+ in nanocrystalline Y2O3

Ho3+-Yb3+ co-doped Y2O3 nanocrystals were synthesized by firing hydroxy carbonate precursors. Yb3+-concentration-dependent up-conversion properties of Ho3+ in Y2O3 nanocrystals have been investigated. The relative intensity of up-converted red emission increases more quickly than that of the green and the near-infrared ones with the enhancement of the concentration of Yb3+. It is believed that the energy process S-5(2) (5F4) (Ho) + I-5(7) (Ho) -> I-5(6) (Ho)+ F-5(5) ( Ho) plays an important role in the population of the F-5(5) level of Ho3+. The result indicates that the intensity ratio of the green emission to the red one can be tuned by changing the sensitizer concentration.