Monodisperse Gd2O3:Ln (Ln = Eu3+, Tb3+, Dy3+, Sm3+, Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) nanocrystals with tunable size and multicolor luminescent properties

Multicolor and monodisperse Gd2O3: Ln (Ln = Eu3+, Tb3+, Dy3+, Sm3+, Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) nanocrystals (NCs) with narrow size distribution were prepared by a homogeneous precipitation method followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), photoluminescence (PL) spectra, cathodoluminescence (CL) spectra, and kinetic decays were employed to characterize the samples. The results show that the Gd2O3: Ln NCs can be directly indexed to cubic Gd2O3 phase with high purity. And the possible formation mechanism and the chemical reaction of each step to form spherical Gd2O3: Ln NCs are proposed according to the concerned analysis. Upon ultraviolet and low-voltage electron beams excitation, Gd2O3:Ln (Ln = Eu3+, Tb3+, Dy3+, and Sm3+) NCs exhibit respective bright red (Eu3+, D-5(0) -> F-7(2)), green (Tb3+, D-5(4) -> F-gamma(5)), blue (Dy3+, F-4(9/2) -> H-6(13/2)) and yellow (Sm3+, (4)G(5/2) -> H-6(7/2)) down-conversion (DC) emissions. Under 980 nm NIR irradiation, Gd2O3: Ln (Ln Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+) exhibit characteristic up-conversion (UC) emissions of Er3+, Tm3+, and Ho3+, respectively.