Efficient dual‐mode up‐conversion and down‐shifting emission in β‐NaYF4:Yb3+,Er3+ microcrystals via ion exchange
We report efficient dual‐mode up‐conversion (UC) and down‐shifting (DS) emission in a single Yb3+/Er3+‐co‐doped β‐NaYF4 microcrystals with controlled morphology and size via a simple Na+ ion‐exchange modification (IEM) method. IEM well preserves the crystal structure and monodispersed morphology of hydrothermal‐synthesized β‐NaYF4. Meanwhile, IEM gives rise to the significant enhancement of UC emission intensity up to 3800 times and strongly enhanced DS emission intensity of Er3+ and Yb3+ by several times in β‐NaYF4:Yb3+,Er3+ microcrystals. IEM also strongly prolongs the DS emission lifetimes of Er3+ and Yb3+ in visible and near‐infrared region. The enhanced UC and DS emission intensities and prolonged lifetimes in β‐NaYF4:Yb3+,Er3+ are mainly ascribed to the dispersing of localized Yb3+ and Er3+ clusters during IEM.
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