The crystallographic features of the as-prepared UCNPs were examined by an X-ray diffractometer (XRD) with Cu K radiation at 40 kV and 40 mA (Bruke D8 Advance, Hangzhou, China). The morphology and size of the Y
2O
3:Er
3+/Tm
3+ UCNPs were characterized by transmission electron microscopy (TEM;
Tecnai G2 F20, FEI, Changsha, China). The compositional elements of the UCNPs were measured by an energy dispersive spectrometer (EDS). For photoluminescence experiments, the 808 and 980 nm fiber coupled diode lasers (BWT K808DAHFN-25.00W, BWT K976DA3RN-30.00W, Changsha, China) were used as the excitation sources. Additionally, the generated UCL was collected and detected by a monochromator (Zolix
Omni-λ300i, Changsha, China) and a photomultiplier (PMT). The photos of the UCL color were taken by a Complementary Metal Oxide Semiconductor (CMOS) sensor (Sony IMX519, Changsha, China). All the above photoluminescence measurements were performed at room temperature, and the test samples were prepared by dissolving the UCNPs in ethanol solution with a mass concentration of 0.5 mg mL
−1.
Zhao X., Wu Z., Yang Z., Yang X., Zhang Y., Yuan M., Han K., Song C., Jiang Z., Wang H., Li S, & Xu X. (2020). Dual-Wavelength Excited Intense Red Upconversion Luminescence from Er3+-Sensitized Y2O3 Nanocrystals Fabricated by Spray Flame Synthesis. Nanomaterials, 10(8), 1475.