Energy transfer and upconversion emission properties of single NaYF4: Yb3+/Ln3+@NaYF4: Yb3+/Ln3+ core-shell microcrystal

In this work, the energy transfer process and upconversion luminescence properties of NaYF4: Ln3+@NaYF4: Ln3+ (Ln = Yb3+, Er3+, Tm3+) core-shell microcrystals were studied through introducing different Yb3+ ions in core and shell. Compared with Yb3+/Tm3+/Er3+ co-doped NaYF4 microcrystals, the NaYF4:Yb3+/Tm3+@NaYF4: Yb3+/Er3+ core-shell microcrystals displays greater stability spectral characteristics under NIR 980 nm excitation. This is because the core-shell structures can control the excitation energy acquisition channel and avoid interactions between Er3+ and Tm3+ ions. Meanwhile, the luminescence properties of NaYF4@NaYF4 core-shell microcrystals can also be precisely controlled by changing concentrations of Yb3+ ions in the core and shell, respectively. The experimental results further indicate that upconversion emission of microcrystals can also be precisely controlled by constructing core-shell structures. The multicolor emission core-shell microcrystals may have great potential in display, anti-counterfeiting and micro-photoelectric technology applications.