Controllable Red, Green, Blue (RGB) and Bright White Upconversion Luminescence of Lu2O3:Yb3+/Er3+/Tm3+ Nanocrystals through Single Laser Excitation at 980 nm

Lu2O3:Yb3+/Er3+/Tm3+ nanocrystals have been successfully synthesized by a solvothermal process followed by a subsequent heat treatment at 800 degrees C. Powder X-ray diffraction, transmission electron microscopy, upconversion photoluminescence spectra, and kinetic decay were used to characterize the samples. Under single-wavelength diode laser excitation of 980 nm, the bright blue emissions of Lu2O3:Yb3+, Tm3+ nanocrystals near 477 and 490 nm were observed due to the (1)G(4)-> H-3(6) transition of Tm3+. The bright green UC emissions of Lu2O3:Er3+ nanocrystals appeared near 540 and 565 nm were observed and assigned to the H-2(11/2)-> I-4(15/2) and S-4(3/2)-> I-4(15/2) transitions, respectively, of Er3+. The ratio of the intensity of green luminescence to that of red luminescence decreases with an increase of concentration of Yb3+ in Lu2O3:Er3+ nanocrystals. In Sufficient quantities of Yb3+ with resprct to Er3+, the bright red UC emission of Lu2O3:Yb3+/Er3+ centered at 662 tint was predominant, due to the F-4(9/2)-> I-4(15/2) transition of Er3+. Based on the generation of red, green, and blue emissions in the different doped Lu2O3:RE3+ nanocrystals, it is possible to produce the luminescence with a wide spectrum of colors, including white, by the appropriate doping of Yb3+, Tm3+, and Er3+ in the present Lu2O3 nanocrystals. Namely, Lu2O3:3%Yb3+/0.2% Tm3+/0.4% Er3+ nanocrystals show suitable intensities of blue, green, and red (RGB) emission, resulting in the production of perfect and bright white light with CIE-x=0.3456 and CIE-y=0.3179, which is very close to the standard equal energy white light illuminate (x=0.33, y=0.33). Because of abundant luminescent colors from RGB to white in Lu2O3:Yb3+/Er3+/Tm3+ nanocrystals under 980 nm laser diode (LD) excitation, they can potentially be used as fluorophores in the field of color displays, back light, UC lasers, photonics, and biomedicine.