A novel near-infrared LiGaW2O8:Yb3+, Cr3+ up-conversion phosphor with enhanced luminescence intensity based on Ho3+/Er3+ bridges

The development of new luminescent materials with up-conversion (UC) emission falling within the first biological window (650-1000 nm) has drawn extensive attention in biological and medical fields. In this work, LiGaW2O8:Yb3+, Cr3+UC phosphors were prepared for the first time, and the near-infrared (NIR) emission assigned to the(4)T(2)-(4)A(2)transition of Cr(3+)was found to derive from the cooperative sensitization mechanism from Yb(3+)to Cr3+. Moreover, the NIR emission of Cr(3+)in the range of 700-900 nm can be greatly enhanced by the energy transfer (ET) process from Yb(3+)sensitizers to Ho3+/Er(3+)bridging centers and finally to Cr(3+)emitting centers. Such success in LiGaW2O8:Yb3+, Ho3+/Er3+, Cr(3+)provides a new perspective for designing superior UC phosphors with appropriate NIR emission, which could be used in biomedical fields.