Synthesis, Tunable Multicolor Output, and High Pure Red Upconversion Emission of Lanthanide-Doped Lu<sub>2</sub>O<sub>3</sub> Nanosheets

<table>Schematic energy level diagrams of Yb<sup>3+</sup>, Er<sup>3+</sup>, and Ho<sup>3+</sup> ions and proposed upconversion mechanism.</table>

Advances in Condensed Matter Physics

Figure 4: Synthesis, Tunable Multicolor Output, and High Pure Red Upconversion Emission of Lanthanide-Doped Lu<sub>2</sub>O<sub>3</sub> Nanosheets 