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

Abstract

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 ⁴T₂–⁴A₂ transition of Cr³⁺ was found to derive from the cooperative sensitization mechanism from Yb³⁺ to Cr³⁺. Moreover, the NIR emission of Cr³⁺ in the range of 700–900 nm can be greatly enhanced by the energy transfer (ET) process from Yb³⁺ sensitizers to Ho³⁺/Er³⁺ bridging centers and finally to Cr³⁺ emitting centers. Such success in LiGaW₂O₈:Yb³⁺, Ho³⁺/Er³⁺, Cr³⁺ provides a new perspective for designing superior UC phosphors with appropriate NIR emission, which could be used in biomedical fields.